No full-text available
To read the full-text of this research,
you can request a copy directly from the authors.
Supported Cu(II) polymer catalysts for aqueous phenol oxidation
Abstract
Supported Cu(II) polymer catalysts were used for the catalytic oxidation of phenol at 30 degrees C and atmospheric pressure using air and H(2)O(2) as oxidants. Heterogenisation of homogeneous Cu(II) catalysts was achieved by adsorption of Cu(II) salts onto polymeric matrices (poly(4-vinylpyridine), Chitosan). The catalytic active sites were represented by Cu(II) ions and showed to conserve their oxidative activity in heterogeneous catalysis as well as in homogeneous systems. The catalytic deactivation was evaluated by quantifying released Cu(II) ions in solution during oxidation, from where Cu-PVP(25) showed the best leaching levels no more than 5 mg L(-1). Results also indicated that Cu-PVP(25) had a catalytic activity (56% of phenol conversion when initial Cu(II) catalytic content was 200 mg L(Reaction)(-1)) comparable to that of commercial catalysts (59% of phenol conversion). Finally, the balance between activity and copper leaching was better represented by Cu-PVP(25) due to the heterogeneous catalytic activity had 86% performance in the heterogeneous phase, and the rest on the homogeneous phase, while Cu-PVP(2) had 59% and CuO/gamma-Al(2)O(3) 68%.
... В качестве активных катализаторов пероксидного окисления были протестированы Cu, Fe, Mn, Zn, Ni в виде массивных и смешанных оксидов и гидроксидов [Botas et al., 2010;Chou, Huang, 1999;Liu, Sun, 2007a;Massa et al., 2008;Oliveirо et al., 2007;Таблица 1.1 Катализаторы, используемые для пероксидного и аэробного окисления органических веществ в водных растворах Катализаторы для пероксидного окисления Катализаторы для аэробного окисления Гомогенные катализаторы (соли и комплексы Fe, Cu, Mn) [Сычев, Исак, 1995;Andreozzi et al., 1999;Busca et al., 2008;Neyens, Baeyens, 2003;Salem et al., 2000] [ Luck, 1996Luck, , 1999Pintar et al., 2004a] Оксидные катализаторы на основе переходных металлов (Fe, Cu, Mn, Co, Ni) в форме оксидов и смешанных оксидов [Busca et al., 2008;Garrido-Ramirez, 2010] [ Bhargava et al., 2006;Jing et al., 2012;Kim, Ihm, 2011;Levec, Pintar, 2007;Pintar et al., 2004a] Благородные металлы (Pt, Ru, Pd, Au), закрепленные на стабильных оксидных (CeO 2 , TiO 2 , ZrO 2 , Al 2 O 3 ) либо углеродных носителях [Bhargava et al., 2006] Pestunova et al., 2002;Qiu et al., 2005], полиоксометаллатов [Gao, Hua, 2006;Nardello et al., 2006] и перовскитоподобных оксидов [Sotelo et al., 2004]. Были предприняты попытки закрепить каталитически активный металл на слоистых глинах Barrault et al., 2000;Caudo et al., 2007;Guo, Al-Dahhan, 2003;Kim, Lee, 2004;Mei et al., 2004;Mojovic et al., 2009;Molina et al., 2006;Timofeeva et al., 2009], цеолитах [Centi et al., 2000;Dukkanci et al., 2010;Kondru et al., 2009;Parkhomchuk et al., 2008;Phu et al., 2001], полимерной [Castro et al., 2009;Liou et al., 2005], силикатной [Crowther, Larachi, 2003] или углеродной [Bautista et al., 2010;Dhaouadi, Adhoum, 2010;Li et al., 2010;Liou, Chen, 2009;Lücking et al., 1998;Ramirez et al., 2007a;Rey et al., 2009;Zazo et al., 2006] матрице. Наиболее перспективными для практического использования считаются железосодержащие гетерогенные катализаторы, ввиду их высокой эффективности, низкой токсичности и невысокой стоимости железа по сравнению с другими активными металлами. ...
... В качестве катализаторов тестировали каталитически активные металлы, их массивные и смешанные оксиды и гидроксиды [Botas et al., 2010;Cuzzola et al., 2002;Liou, Chen, 2009;Liu, Sun, 2007а;Massa et al., 2008;Pestunova et al., 2002], слоистые глины [Barrault et al., 2000;Ben Achama et al., 2008;Kim, Lee, 2004;Mei, Yu, 2004;Mojovic et al., 2009;Timofeeva et al., 2009] и перовскитоподобные оксиды, содержащие переходные металлы [Sotelo et al., 2004]. Предпринимались попытки закрепить каталитически актив-ный металл на полимерной [Castro et al., 2009], силикатной [Crowther, Larachi, 2003] или углеродной [Botas et al., 2010;Rey et al., 2009;Yuranova et al., 2004] матрице. Однако высокая активность и достаточная стабильность в водной среде наблюдалась не для всех катализаторов [Castro et al., 2009;Kim, Lee, 2004;Pestunova et al., 2002]. ...
... Предпринимались попытки закрепить каталитически актив-ный металл на полимерной [Castro et al., 2009], силикатной [Crowther, Larachi, 2003] или углеродной [Botas et al., 2010;Rey et al., 2009;Yuranova et al., 2004] матрице. Однако высокая активность и достаточная стабильность в водной среде наблюдалась не для всех катализаторов [Castro et al., 2009;Kim, Lee, 2004;Pestunova et al., 2002]. Так, например, металлическое железо проявляет активность в пероксидном окислении только после окисления металла и вымывания ионов железа в раствор. ...
В монографии рассмотрены общие проблемы защиты окружающей среды (почв, грунтов и вод) от опасных и устойчивых к разложению химических веществ и приведены результаты собственных исследований, направленных на разработку химических, в частности, каталитических и сорбционных методов обезвреживания опасных химических веществ (гептил, полихлорированные углеводороды, тяжелые металлы), микробиологических и интегрированных методов ремедиации нефтезагрязненных природных сред. Рассмотрены вопросы эффективного контроля очистки методом биологического тестирования, а также геохимическими методами по результатам изучения избирательности и стадийности процессов трансформации нефтяных УВ.
Для научных работников, преподавателей вузов, аспирантов, студентов, специализирующихся в области экологической химии, геохимии и микробиологии, решающих задачи охраны окружающей среды, устойчивого развития и рационального природопользования.
... Porous copolymers of 2-VP and 4-VP crosslinked with divinyl benzene (DVB) were used for Cu(II), Ni(II) and Co(II) sorption 11. Castro el al. used P4VPD as supported Cu(II) polymer catalysts for the catalytic oxidation of phenol at 303 K and atmospheric pressure using air and H 2 O 2 as oxidants [12]. ...
... In the past decade, the PSO kinetic model has been widely applied to the pollutants sorption from aqueous solutions [30]. 12 The Elovich equation, also successfully employed to describe second order kinetics is based on the supposition that the actual sorbent surface is energetically heterogeneous and that neither desorption nor interactions between the sorbed species could considerably influence the sorption kinetics at low surface coverage [33]. This equation does not propose any definite mechanism for sorbate-sorbent reaction, but it has been broadly used in sorption kinetics to describe chemisorption through mechanisms which are chemical reactions by nature [34]. ...
... Positively charged Cu(II) cations form coordination complexes with the nitrogen atom of the pyridine group due to the strong affinity of pyridyl group to metals and its ability to undergo hydrogen bonding, as was established in some previously published studies of P4VPD [12]. ...
Synthesis of an unconventional resin based on 4-vinylpyridine (4-VP) and its Cu(II) sorption behavior were studied. Three samples of macroporous crosslinked poly(4-vinylpyridine-co-ethylene glycol dimethacrylate) (P4VPE) with different porosity parameters were prepared by suspension copolymerization by varying the n-heptane amount in the inert component. The samples were characterized by mercury porosimetry, elemental analysis and X-ray photoelectron spectroscopy (XPS). The sorption of P4VPE for Cu(II) ions, determined under non-competitive conditions, was relatively rapid, i.e., the maximum capacity was reached within 30 min. The maximum experimental sorption capacity for the sample with the highest values of pore diameter and specific pore volume (sample 3, Q(eq) = 89 mg g(-1)) was 17.5 times higher than for the sample with the lowest values of pore diameter and specific pore volume (sample 1, Q(eq) = 5.1 mg g(-1)). Since the values for pyridine content in all P4VPE samples were almost the same, it was concluded that the porosity parameters have predominant influence on Cu(II) sorption rates on P4VPE. The sorption behavior and the rate-controlling mechanisms were analyzed using six kinetic models (pseudo-first order, pseudo-second order, Elovich, intraparticle diffusion, Bangham and Boyd models). XPS study clarified the nature of the formed P4VPE-Cu(II) species.
... CWPO of phenol wastewater can be performed at mild operating conditions, and it can not only obviate limitations of liquid-gas mass transfer, but also reduce the costs of investment [7]. The catalysts utilized in CWPO method can be categorized as heterogeneous catalysts and homogeneous catalysts [8][9][10][11]. ...
... The major aim of installing baffles in batch reactor is to prevent the swirling flows, to decrease the impeller viscous dissipation, to create and enhance the stability of required power and thus promoting the performance of mixing [32,33]. Titanium dioxide (TiO 2 ) is one of the most appropriate semiconductor materials for industrial processes based on its attractive activity, high physical and chemical stability, minimum cost, noncorrosive property and widespread availability [10,11]. ...
... higher in Cu(II) than in Fe(III)-based systems for the nitrobenzene oxidation by hydrogen peroxide in homogeneous systems. Castro et al. [9] demonstrated that at 30°C, Cu(II) was active to the oxidation of phenol; even at low copper concentrations (5 mg/L) and using the stoichiometric amount of H 2 O 2 (14 mol/mol) those authors obtained a 15% conversion of phenol in 2 h. Prasad et al. [10] successfully used copper salts in homogeneous reaction with H 2 O 2 and O 2 as oxidizing agents for the treatment of petrochemical wastewaters. ...
... Up to the present, only few publications deal with homogeneous Fenton processes with copper as catalyst, and only one reports specifically the application of this system to the degradation of phenol [9]. For this reason, the objective of this study was to investigate the capability of Cu(II) as a Fenton-like catalyst for the oxidation of phenol as a model pollutant. ...
... Phenol conversion was calculated by measuring the phenol concentration using HPLC (Agilent Technologies, model 1100) with a C18 reverse phase column (Agilent Technologies, Hypersil ODS), the method used is fully described elsewhere [12]. The total organic carbon (TOC) values were collected from a TOC Analyser (Analytic Jena, model NC 2100). ...
... Knowing that P-I-Cua and PBI-Cus yielded promising phenol and TOC conversions, it is important to know the activity of the leached Cu(II) in the homogeneous phase. Data and trends from a previous catalytic phenol oxidation report [12] were employed here. Thus, Cu(II) leaching from P-I- Cua (6.2 mg L −1 ) promoted approximately 32% phenol conversion and represented 13% of catalyst deactivation, while Cu(II) leaching from PBI-Cus (2.7 mg L −1 ) yielded 21% phenol conversion with 6% catalytic deactivation. ...
Polymer-supported metal complexes have been used as catalysts for the catalytic wet hydrogen peroxide oxidation (CWPO) of phenol. The synthesis of six catalysts derived from three polymer-supports (a polybenzimidazole resin and two poly(styrene-divinylbenzene) resins) and two Cu(II) salts. The catalytic oxidation of phenol with initial phenol concentration of 1 g L−1 was performed in a 200 mL batch stirred tank reactor at 30 °C and atmospheric pressure. Under these conditions, phenol conversion and total organic carbon conversion were evaluated. The highest phenol conversion was 93% obtained for poly(DVB-co-VBC) functionalised with iminodiacetic acid (IMDA) and loaded with copper acetylacetonate, however metal leaching was very unsatisfactory. If metal leaching was taken into consideration, it was found that polybenzimidazole loaded with copper sulphate appeared to be the most stable yielding 54% of mineralisation and 0.75 TOC/phenol conversion efficiency with simultaneously low release of metal during the oxidation.
... These processes have as main advantages the ability to degrade a toxic substance or convert it into a biodegradable form, due to the generation of hydroxyl radicals (•OH), species capable of attacking the majority of organic molecules [30]. Phenol catalytic oxidation has been applied with a heterogeneous Cu(II) onto Chitosan and poly(4-vinylpyridine) (PVP) catalysts in a reactor for municipal wastewater treatment using air and H 2 O 2 as oxidants [31]. The stage of phenol photodegradation and formation of organic intermediates and •OH radicals were studied by UV/TiO 2 and Vis/N, C-TiO 2 processes [32]. ...
The actual work evaluated the effect of initial phenol concentration (CPh0) of 500, 1000 and 1500 mg.L-1, the molar stoichiometric ratio of Phenol/Hydrogen peroxide (RP/H) of 25, 50 and 75 % and time (t) of 30, 90 and 150 min on the oxidation of phenolic effluents by called Direct Contact Thermal Treatment (DiCTT). This process provides a novel means to induce degradation and mineralization of organic pollutants in water. The experimental studies were carried out at semi-industrial plant. The organic pollutant was degraded with a conversion higher than 99% and a Total Organic Carbon (TOC) mineralization exceeding 40%, to a (RP/H) of 75%, independent of the CPh0, that was identified as the optimal condition by thermochemical process. The initial phenol concentration was quantified and identified by the High Performance Liquid Chromatography (HPLC) technique followed by statistical design tools to optimization using Response Surface Methodology (RSM) and an analytical mathematical modelling via Artificial Neural Networks (ANNs). The results also showed the dynamic concentration evolution of the intermediates formed (catechol, hydroquinone and para-benzoquinone). Artificial Neural Networks were applied to model the step experimental of Phenol Degradation (PD) and Total Organic Carbon (TOC) conversion by DiCTT thermochemical process. For the ANN modelling, “statistic 8.0” software was used with a Multi-Layer Perceptron (MLP) feed-forward networks by input-output data using a back-propagation algorithm. The correlation coefficients R2 between the network predictions and the experimental results were in the range of 0.95–0.99.
... A disadvantage of using iron precursors is that the reaction should be carried out at pH values around 3. In turn, copper has a similar role as iron in catalysing hydrogen peroxide to produce hydroxyl radical, with the advantage that this reaction still retains a high efficiency at a higher pH range [8][9][10]. However, Catalytic wet peroxide oxidation of reactive dyes could be successfully carried out with Cu-based catalysts. ...
In this work, the decolorization of Methyl Orange was conducted using catalysts prepared by impregnation of copper on natural clay in the presence of H 2 O 2. The catalysts Cu-clay, prepared from the concentrated metal precursor of (impregnation ratio, W(Cu(NO 3) 2)/W(clay) = 1,5%-7,5%) were characterized by several methods such as X-ray diffraction (XRD), electronic scan microscopy (SEM), x-ray fluorescence (FX), and Brunauer-Emmett-Teller (BET). Important factors affecting catalyst activity and methyl orange removal efficiencies were studied: the effects of temperature, oxidant concentration, and catalyst dosage. The results showed, a very significant activation of hydrogen peroxide by the catalyst, the Methyl Orange depletion percentage reaching 94 % after 2 h, and very stability of the catalyst. It was also observed that the best catalyst, at a reaction temperature of 25°C. 2,5ml of H 2 O 2 and 4.0 g/L of 5% Cu-clay, 94% decolorization was achieved within 120 min treatment. Although the Cu show high activity, their stability and reusability still need improvement.
... In addition, by immobilization onto easily removable support, the catalyst can be removed from the solution without any special equipment and reused multiple times, and the catalytic activity can be readily initiated or terminated upon insertion or removal of the catalyst in solution (Karuppusamy et al., 2020). In this regard, several researchers have reported the application of a polymer-supported copper catalyst to the oxidative decomposition of contaminants in solution (Castro et al., 2009;Haider et al., 2016). ...
This study investigated the applicability of waste antivirus copper film (CF) as a Fenton-like catalyst. The reaction activity of H2O2 and CF in combination was significantly enhanced by ultrasound (US) irradiation, and the synergy factor calculated from bisphenol A (BPA) degradation using CF-H2O2-US was 9.64 compare to that of dual factors. Photoluminescence analyses were conducted to compare the generation of hydroxyl radicals during both processes. In this sono-Fenton-like process, BPA degradation was affected by solution pH, temperature, ultrasound power, CF size, H2O2 dose, and initial BPA concentration. The BPA degradation curves showed an induction period (first stage) and a rapid degradation period (second stage). Process efficiency was totally and partially enhanced in the presence of chloride and carbonate ions, respectively. Chemical scavenger tests showed that both free and surface-bound hydroxyl radicals participate in BPA degradation under the sono-Fenton-like process using CF. The functional groups and copper crystals on the CF surface remained unchanged after five consecutive reuses, and the BPA degradation efficiency of CF was maintained over 80% during the reuse processes as a sono-Fenton-like catalyst.
... Under the optimized conditions about 42% of phenol conversion was obtained. Castro et al. (2008) used home made supported Cu(II)/polymer catalysts and commercial CuO/Al 2 O 3 catalyst for phenol degradation with air or hydrogen peroxide at 303K and atmosferic pressure. Phenol conversions varied from 56 to 68% depending on catalyst nature. ...
The catalytic oxidation of phenol solutions using H2O2 as oxidizing agent and a home-made CuO/Al2O3 catalyst was studied in a laboratory batch reactor. Experiments were performed at temperatures between 293 and 353K. Phenol conversion and hydrogen peroxide decomposition increased with increasing temperatures. Complete phenol conversion and 80% TOC removal was achieved at temperatures above 323K.
... Active alumina has also been used as an excellent host for assorted guest of biological and medical molecules, such as its application for controlled drug delivery system (DDS) (Shyamal et al., 2009). The material is also known for other wide varieties of industrial applications such as its used as adsorbent in gas purification (Kim et al., 2007), liquid filteration and purification (Rahmani et al., 2010), it is used as catalyst support in heterogeneous catalysis, it is also used in ionic exchange processes (Castro et al., 2009). This work is aimed at synthesizing microporous activated alumina using kaolin as starting material by employing a three step method: (i) Dealumination of kaolin to produce aluminum sulfate solution (alum), (ii) precipitation of aluminum hydroxide from the aluminum sulfate obtained using caustic soda solution and (iii) calcination of the aluminum hydroxide obtained at a specific temperatures to produce mesoporous activated alumina. ...
Activated alumina was synthesized from Kankara kaolin using a novel three steps; dealumination, precipitation and calcination methods. The shows activated alumina synthesized was characterized using XRF, XRD, FTIR, BET, TEM, SEM and TGA/DTG techniques. The XRF of the product shows that it contained aluminum oxide of 83.47 wt%., the XRD showed the presence of the characteristic peaks of alumina. The FTIR showed typical spectra of alumina. The BET analysis showed that the material was microporous material having pore diameter of 1.212 nm, pore volume of 0.0613 cm3/g and high surface area of 202.3 m2/g. The SEM micrograph showed structural morphology of gglomerated particles with hollow structural arrangement. The TEM showed that the crystals were in nano size, the average crystal size was estimated as 12.5 nm.
... Nickel (II) complexes bearing N, O-chelate ligand activation for MMA polymerization yielded poly (methyl methacrylate) (PMMA) with rich syndiotacticity microstructure [4][5][6][7][8][9][10]. The chelating polymers find applications in bioinorganic industry [11], wastewater treatment [12,13], pollution control [14], hydrometallurgy [15], preconcentration [16], anionic polyelectrolyte hydrogels [17], cation-exchange resins [18] , showed potential applications in material science as conductive [19], luminescent [20], magnetic, porous, chiral or non-linear optical materials [21], catalytic [22,23,24,25],organic synthesis [26], polymer drug graft, recovery of trace metal ions [13] and antimicrobial activities [27,28]. ...
4-vinyl pyridine nickel complex containing polymerizable vinyl group, prepared by condensing (4:1 molar ratio) of 4-vinyl
pyridine with Nickel chloride, then polymerized with methyl methacrylate at 70 °C using AIBN as initiator. Metal complex
and polymer metal complex have been characterized by elemental analyses, molar conductance, IR, 1H-NMR , Mass
spectra and thermal analyses (DTA and TGA). Conductivity measurement reveals the nonelectrolytic nature of the
complex. This confirms that, the anion is coordinated to the metal ion. The IR reveal the metal ion is coordinated via the
nitrogen atom of 4-VP. Nickel complex and polymer nickel complex have been tested invitro against number of tumor and
number of microorganisms in order to assess their anti tumor and antimicrobial properties. The antimicrobial activity was
observed by compounds VP-Ni and MMA-VP-Ni under the screening conditions. The activity against HCT-116 cells was
detected for compound VP-Ni (with IC50 value 9.8±0.6 μg/ml), compared with reference standard (24.6±0.3 μg/ml) followed
by MMA-VP-Ni (48.3±1.5). In conclusion, this study highlighted the synthesis of polymer nickel complex, and proved the
promising biological activity of the synthesized compounds.
... The process is known as catalytic wet peroxide oxidation (CWPO) (Gomes et al., 2010). Immobilization of metallic ions, mainly iron and copper, over different supports, such as polymers (Castro et al., 2009(Castro et al., , 2010, activated carbons (Zazo et al., 2006;Taran et al., 2010;Santos et al., 2009), zeolites (Kondru et al., 2009;Aravindhan et al., 2006), pillared clays (Carriazo et al., 2003;Galeanoa et al., 2011;Jagtap and Ramaswamy, 2006), resins (Liou et al., 2005) and silica (Xiang et al., 2009) has been described in the literature for application in CWPO processes. Heterogeneous catalysis eliminates the need of treating the resultant sludge formed by the dissolved iron in the effluent and its precipitation (Bautista et al., 2010). ...
The aim of this work is to study the heterogeneous oxidative degradation of ofloxacin antibiotic using a composite material prepared from sodium alginate and cyclohexane dinitrilo tetraacetic acid (CDTA). The characterization tests indicated the successful incorporation of metal chelator and iron. It was also demonstrated that the synthesized beads are mesoporous. The influence of several experimental parameters (i.e.: H2O2 dose, working temperature, beads loading and initial drug concentration) on the process performances was evaluated. The reaction temperature significantly affects the drug conversion efficiency. It was also observed that the synthesized material was efficient toward the target antibiotic degradation in the presence of small quantities of hydrogen peroxide. Under optimum conditions (0.05 g of granules, initial drug concentration = 10 mg/L, 25 μL of 10 mmol/L H2O2), conducted in a batch reaction, 94% degradation of ofloxacin was reached. The results also indicate that the composite material showed a reasonable stability; a relatively low decrease of activity after four successive runs (only 9%) and a negligible iron leaching (0.8%) have been observed. The synthesized composite material offered interesting advantages in terms of simplicity, good stability, ease of recovery from the liquid medium after use and its efficiency in the presence of low quantities of oxidant. It constitutes a good candidate in the water treatment area.
... Recently, copolymer supported materials such as catalysts, reagents, and substrates are employed in high temperature reactions. Consequently, thermostability evaluation of the synthesized copolymer is essential for application perspectives [40,41]. Differential thermal analysis of copolymer microspheres of differing CLDs were performed by simultaneous thermal analysis (Perkin Elmer) in the temperature range of 50e800 C under nitrogen atmosphere using a heating rate of 10 C/min. ...
Megaporous spherical acrylate copolymer beads were synthesized by suspension polymerization using non-solvating porogens. Non-solvating porogens with higher aliphatic hydrocarbon content generated megaporous morphology with lower surface area. Surface area increased and inversely megaporosity was mitigated with decrease in the aliphatic hydrocarbon content of porogen. Megaporosity (5.47 μm) and pore volume of 5.52 cm3/g was obtained with n-decanol Thermal property of copolymer is a function of type (rigidity/flexibility/elemental composition) and concentration (cross-link density) of monomer and cross-linker. Copolymer containing rigid cross-linker (divinylbenzene) had better thermal stability over copolymer with flexible cross-linker (ethylene dimethacrylate). Further, higher concentration of rigid cross-linker or lower concentration of flexible cross-linker enhanced the thermal stability. Porous polymers are potentially recognized as a solid support for adsorption and entrapment technology.
... A disadvantage of using iron precursors is that the reaction should be carried out at pH values around 3. In turn, copper has a similar role as iron in catalysing hydrogen peroxide to produce hydroxyl radical, with the advantage that this reaction still retains a high efficiency at a higher pH range [8][9][10]. However, Catalytic wet peroxide oxidation of reactive dyes could be successfully carried out with Cu-based catalysts. ...
... To overcome these problems, the degradation process by H 2 O 2 /Cu (II) system has been chosen. The latter, unlike the H 2 O 2 /Fe(II) system, gives good results in a wide pH range [9]. ...
The degradation of olive mill wastewater was investigated by a Fenton-like process using Cu (II) as a catalyst and hydrogen peroxide as an oxidant. Phenolic compounds degradation increased from 43% at 30°C to 62% at 50°C after 65 min treatment. Nonlinear regression methods allowed to accurately describe the experimental results and among the tested models, namely Lewis, Page-modified, Henderson/Pabis, and diffusion models, the most appropriate was found to be the Lewis model. The degradation was found to follow a first-order kinetic and the activation energy was 21 kJ/mol.
... Thus, proposed recovery and reuse system needs high site area availability. Supporting metal ions onto a solid matrix has been used to confine them in Fenton and Fenton-like reactors (Al-Hayek and Doré 1990;Liou et al. 2005;Dantas et al. 2006;Makhotkina et al. 2006;Castro et al. 2009;Liotta et al. 2009). However, supported metals have shown to decrease their catalytic activity when compared to their homogeneous state (Cuzzola et al. 2002). ...
... Esplugas et al. [16] studied and compared the effectiveness of different advanced oxidation processes (ozone and its combination, photolysis and UV/H 2 O 2 , Fenton and photocatalysis) for phenol degradation and showed that the Fenton process has the fastest degradation rate. Furthermore, several research studies have been carried out to investigate the use of different transition metals in homogeneous and heterogeneous form in conjunction with hydrogen per- oxide212223242526272829. Many works demonstrated that the use of Fenton's processes as a primary treatment of OMW enhances the efficiency of anaerobic digestion because the pre-treated effluent is more readily degradable than the original untreated effluent. ...
Olive mill wastewaters, due to a low biodegradability, acidic pH, high salinity, lack of nutrients and elevated amounts of polyphenols, are hard to treat using conventional biological processes. In recent years, several pre-treatments of these by-products have been developed to increase their anaerobic biodegradability and to exploit them for biogas production. However, these processes are often expensive and hard to carry out. This paper presents a process, easy to manage, that involves the use of hydrogen peroxide under alkaline conditions without the addition of catalysts. This process is able to efficiently increase the anaerobic biodegradability of olive mill wastewaters. In fact, with mild treatment conditions, it is possible to obtain polyphenols abatements of 78%, increases of 48% in the volatile fatty acids content and only a restricted reduction in the organic matter content. By conducting many digestion tests, it was verified that this process permits high biogas production by olive oil by-products. Indeed, with properly prepared samples, after a negligible acclimation period, methane yields of approximately 0.37 LCH4/gCODremoved were detected.
... The water in the ocean constitutes 97% of the total water on earth. Whereas, only 3% is fresh water that can be consumed by human and animals [1]. This small percentage of fresh water is being polluted by human activity and there is a pressing need to preserve it. ...
A series of highly mesoporous copper catalysts (5–20 wt.%) supported on silica rice husk were synthesized via sol–gel route at room temperature. The FT-IR and 29 Si MAS NMR spectroscopic studies revealed the successful substitution of copper into the silica matrix. Copper in the +2 oxidation state was evidenced from the DR/UV–vis and XPS analyses. Introduction of copper up to 10 wt.% (RH-10Cu) results in a pro-gressive enhancement in the BET surface area. The activity of the copper catalysts was studied in the liquid-phase oxidation of phenol with H 2 O 2 yielding catechol (CAT) and hydroquinone (HQ). Phenol con-version was influenced by various experimental conditions such as temperature, catalyst dosage, molar ratio of reactants, nature of solvent and percentage metal loading. Excellent activity was achieved when 10 wt.% copper was used and decreased with further increase in the copper loading. RH-10Cu could be regenerated several times without significant loss in the catalytic activity.
... The vigorous analysis of the reaction intermediates is necessary to fully assess the oxidation mechanism of a target contaminant. Evolution and identification of aromatic intermediates of phenol has been widely reported and explained for various oxidation pro- cesses141516. Both, silent and ultrasound-assisted catalytic wet peroxide oxidation of phenol followed the traditional reaction pathway via the formation of catechol and hydroquinone, which were detected after the electrophilic addition of hydroxyl radical to the aromatic ring [2]. Consequently, as briefly mentioned above, phenol degradation can be attributed to the reaction with Å OH radicals rather than to the combined effect of oxidation and pyrolysis. ...
The kinetic study of silent and ultrasound-assisted catalytic wet peroxide oxidation of phenol in water was performed to qualitatively assess the effect of ultrasound on the process kinetics. Various kinetic parameters such as the apparent kinetic rate constants, the surface utilization coefficient and activation energy of phenol oxidation over RuI(3) catalyst were investigated. Comparative analysis revealed that the use of ultrasound irradiation reduced the energy barrier of the reaction but had no impact on the reaction pathway. The activation energy for the oxidation of phenol over RuI(3) catalyst in the presence of ultrasound was found to be 13kJmol(-1), which was four times smaller in comparison to the silent oxidation process (57kJmol(-1)). Finally, 'figures-of-merit' was utilized to assess different experimental strategies such as sonolysis alone, H(2)O(2)-enhanced sonolysis and sono-catalytic oxidation of phenol in order to estimate the electric energy consumption based on the kinetic rate constants of the oxidation process.
Materials based on polymer hydrogels have demonstrated potential as innovative Fenton catalysts for treating water. However, developing these polymer-supported catalysts with robust stability presents a significant challenge. This paper explores the development and application of polymer-supported heterogeneous Fenton catalysts for the environmental remediation of wastewater, emphasizing the enhancement of metal incorporation into catalysts for improved efficiency. The study begins with an introduction to the heterogeneous Fenton process and its relevance to wastewater treatment. It further delves into the specifics of polymer-supported heterogeneous Fenton catalysts, focusing on iron oxide, copper complexes/nanoparticles, and ruthenium as key components. The synthesis methods employed to prepare these catalysts are discussed, highlighting the innovative approaches to achieve substantial metal incorporation. Operational parameters such as catalyst dosage, pollutant concentration, and the effect of pH on the process efficiency are thoroughly examined. The catalytic performance is evaluated, providing insights into the effectiveness of these catalysts in degrading pollutants. Recent developments in the field are reviewed, showcasing advancements in catalyst design and application. The study also addresses the stability and reusability of polymer-supported heterogeneous Fenton catalysts, critical factors for their practical application in environmental remediation. Environmental applications are explored, demonstrating the potential of these catalysts in addressing various pollutants. The Conclusions offers future perspectives, underlining the ongoing challenges and opportunities in the field, and the importance of further research to enhance the efficacy and sustainability of polymer-supported heterogeneous Fenton catalysts for wastewater treatment.
Co3O4 nanomaterials were prepared by different methods. The samples were nominated as Co3O4 (Pr), Co3O4 (Co), and Co3O4 (Hy) due to preparation by precipitation, combustion, and a hydrothermal method, respectively. These nanomaterials were characterized by studying their structural, morphological, and surface properties. The catalytic activity was evaluated by following H2O2 decomposition through fluorometric and gasometric methods. The obtained results showed that the catalytic efficiency of the catalysts was affected by their preparation methods. The order of catalytic activities of the investigated samples using fluorometric method is compatible with that obtained by gasometric method. Co3O4 (Hy) exhibited much higher catalytic activity due to the high surface area, small particle size, different oxidation states, different shapes, and the high production of hydroxyl radical. The antimicrobial activity is studied against standard bacterial and fungal strains, and the studies showed that the hydrothermal method enhanced antimicrobial activity more than other preparation methods.
Vanillin is a high value flavor and fragrance ingredient which is
mostly sourced from synthetic route with a small fraction
obtained from natural vanilla. The catalytic upgrading of
biomass lignin to vanillin is of interest for sustainability and
economic viability of the cellulosic biorefineries. Herein, we
report reduced graphene oxide supported copper oxide (CuOx/
rGO) catalyzed aerobic oxidation of lignin and clove oil derived
isoeugenol to vanillin. We characterized CuOx/rGO by spectroscopic
(powder XRD, FTIR, XPS, Raman) technique to elucidate
active sites of the catalysts. XPS and PXRD characterizations
confirm the presence of nanoparticulate crystalline CuOx in the
form of mixed valence CuO and Cu2O on the rGO surface.
CuOx/rGO with 20% CuOx exhibits superior activity, enabling a
maximum of 53% vanillin yield at mild reaction conditions. The
catalyst retained comparable activity in the 4th cycle. The
reasons for high activity of CuOx/rGO and a plausible
mechanism involving a free-radical pathway are elucidated
In this paper, leaflike copper phosphate films were fabricated by anodization of copper foils in mixed phosphate electrolytes. The optimal leaflike morphology was obtained when copper foil was anodized at 10 V for 60 min. Leaflike copper phosphate films had very good catalytic effect on the dyes degradation through Fenton oxidation. The reaction temperature exerted a significant influence on the decolorization ratio. When the temperature was 75 °C, methyl orange, rhodamine B, alizarin red and neutral red solution could be decolorized completely within 5 min (10 g dye solution/4 cm² film).
Doping of mesoporous ZnO-ZrO2 nanoparticles with transition metal and lanthanides (Cr, Nd, Dy) were used as a catalyst to develop an ultrasensitive fluorometric method for the conversion of non fluorescent coumarin to highly fluorescent 7-hydroxycoumarin using H2O2 or light. It was found that doped- ZnO-ZrO2 mixed oxide can catalyze the decomposition of H2O2 to produce •OH radicals, which in turn convert coumarin to 7-hydroxycoumarin. At contrast, the doping has deleterious effect on conversion of coumarin by light due to high band gap and high concentrations of doping increase the recombination rate of electron and holes. Doped mixed oxides prepared by impregnation method and characterized by studying their structural, surface and optical properties. Chromium doped ZnO-ZrO2 had the highest rate of formation of hydroxyl radical due to decomposition of H2O2 and therefore 7-hydroxycoumarin due to surface area, small crystal size and high redox potential.
A practical methodology and novel, economical materials were proposed to successfully prepare nanoparticle catalysts for phenol hydroxylation. The preparation was carried out via mechanical alloying (MA) of CuxSn(100−x) powder mixtures (where x = 30, 50, 70, and 100%wt). The mechanical alloyed nanoparticles were characterized using various techniques. X-ray diffraction patterns indicated that η-Cu6Sn5, ε-Cu3Sn, and CuSn phases could be formed in the mechanical alloyed CuxSn(100−x) materials. Transmission electron micrographs and selected area electron diffraction patterns confirmed the presence of η-Cu6Sn5, ε-Cu3Sn, and CuSn phases. Activity of the catalysts, using the optimal conditions of 70 °C reaction temperature for 1 h, 50 mg of Cu0.5Sn0.5, and 1:3 phenol:H2O2 ratio, provided more than 98% conversion with 70% catechol (CAT) and 29% hydroquinone (HQ). Experimental results suggested that the presence of the ε-Cu3Sn phase gave higher activity while Sn reduced benzoquinone (BQ) to HQ. The catalyst maintained its stability with no structural collapse for more than 24 h.
Fe2O3/γ-Al2O3 and Fe2O3/CuO/γ-Al2O3 heterogeneous Fenton catalysts were synthesized for the degradation of phenol solution in the experiment. The morphology and physicochemical properties of the catalysts were characterized by XRD, SEM, TEM, HRTEM, FTIR, and DRS. And the ICP was used to measure the ion leaching of iron and copper. The influence of some important operational parameters were researched on the degradation of phenol, such as pH value, reaction temperature, calcination temperature, catalysts dose, hydrogen peroxide (H2O2) concentration. According to the study, the removal rate could reach 95.4% at 65℃ within 20min under the optimized conditions. In addition, the catalytic ability of the catalysts could meet 88.0% and 75.6% at pH 4.5 and 5.5. The result also showed that the catalysts performed a degradation efficiency of 79% in 3h after the 4th consecutive reuse. Furthermore, the ICP detected that the ion leaching of iron is 0.18mg/L, but the copper ions were not detected in the study.
The copper(II) complexes of poly[(3-(2-pyridyl) acrylic acid)-co-acrylic acid] {P(Pya-co-AA)} were prepared via precipitation polymerization in supercritical carbon dioxide. The complexes were synthesized using a simple and efficient method of using N,N′-methylenebisacrylamide (BIS) as a cross-linker and scCO2 as the reaction solvent. The obtained products were characterized by Fourier transform infrared (FTIR) spectroscopy, UV-Visible spectroscopy, X-ray diffraction and X-ray photoelectron spectra (XPS) analysis. The results indicate that the metal ion was coordinated via the nitrogen and oxygen of Pya. In the method, the properties of the complexes were controlled by operating parameters such as the pressure of scCO2, the ratio of copper, and cross-linker concentration in scCO2. The catalytic activity of the polymer–metal complexes was evaluated for the oxidation of benzyl alcohol using hydrogen peroxide. The results revealed the complexes exhibit high catalytic efficiency and can be reused repeatedly in high yield.
Materials science is totally inserted in current developments in the areas ofcomputing, electronics, engineering, medicine, pharmaceutics, energy, and industrialmanufacture. Nowadays, it is one of the main green alternatives to reverse the environmental damage that these recent advances, unsustainable in their majority, havecaused.In this context, this chapter discusses the advances of materials chemistry in both thecontrol of some industrial water pollutants (heavy metals and synthetic dyes) and the useof ecological and/or milder procedures in industrial oxidation processes.Today, industrial wastewater is one of the most serious environmental problems. Theinorganic and/or organic pollutants present in the wastes are generally originated due tonegligent waste treatments or even no waste treatment at all. Heavy metals, especially Pb2+, Cr6+, Hg2+ and Cd2+, commonly found in industria, pigments, and batteries industries, as well as mining are potential pollutants because oftheir toxic and lethal effects. Moreover, they are non-biodegradable and tend toaccumulate in living organisms, thereby causing severe diseases. In turn, synthetic dyes,represented mainly by the azo-dyes employed in the textile industry, not only causevisual pollution of water bodies, but also diminish the photosynthetic activity of theaquatic biota by restricting the passage of sunlight. In this sense, the utilization ofadsorbents, such as synthetic inorganic polymers (e.g., silica and zeolites), natural clays,and organic-inorganic hybrids (which allow for introduction of organic substances withinteresting functional groups into inorganic supports) has been a noteworthy alternative. Another approach for the removal of azo-dyes from industrial effluents is their oxidativedegradation by heterogeneous catalysts under mild conditions (room temperature andpressure, and use of environmentally friendly oxidants like hydrogen peroxide). On the other hand, environmental problems concerning industrial oxidation reactionsare mainly centered on the employed reagents. This area of fine chemistry is extremelyimportant, because it is responsible for the production of various bulk chemicals, while itis the one field that most needs green innovations. One of the most promising alternativesin this area is the application of efficient/selective heterogeneous catalysts that can beemployed in the presence of green oxidants like hydrogen peroxide.Therefore, we propose to discuss these challenges and present some remarkableliterature results reported by our research groups and others.
Olive mill residues, due to their low biodegradability and high amounts of phytotoxic compounds, are difficult to treat by means of conventional biological processes. In recent years several pretreatments of these by-products have been developed to increase their anaerobic biodegradability and to exploit them for biogas production. However, these processes are often expensive and hard to carry out. In this paper an effective and easy-to-manage pretreatment, based on the use of hydrogen peroxide under alkaline conditions without the addition of catalysts, is proposed. Many experiments were carried out on wet olive mill wastes in order to evaluate the influence of pH and peroxide dosage on process performance. Polyphenols abatements of about 72% were observed. The kinetic analysis of experimental results allowed us to investigate the reaction mechanisms and to optimize the operating procedures. This permitted to reduce the peroxide dosage without the occurrence of a remarkable performance reduction. By means of batch digestion tests, conducted in a pilot scale plant without co-substrates addition, it was verified a negligible biogas production detectable on raw olive mill waste, while a COD reduction about of 77% and a high methane yield of approximately 0.328 LCH4/gCODremoved were obtained on pretreated waste.
Phenol oxidation with hydrogen peroxide using Cu/ZSM5 and Cu/Y5 catalysts
In this work, catalytic activity and stability of Cu/Y5 and Cu/ZSM5 zeolites in phenol oxidation with hydrogen peroxide were examined. The catalyst samples were prepared by the ion exchange method of the protonic form of commercial zeolites. The catalysts were characterized by the powder X-ray diffraction (XRD), AAS, while the adsorption techniques were used to measure the specific surface area.
The thermal programmed desorption of NH3 (NH3-TPD) was used for measuring the total number of acid sites formed on the surface of zeolites.
Catalytic performance of the prepared samples was monitored in terms of phenol, hydrogen peroxide and total organic carbon (TOC) conversion, by-product distribution and a degree of copper leached into the aqueous solution.
It was found that the activity of Cu/Y5 catalyst was generally higher than that of Cu/ZSM5 and that unlike Cu/ZSM5, Cu/Y5 catalyzed phenol oxidation more completely.
Two different porous copper metal-organic frameworks (Cu-MOFs) named as Cu3(BTC)2 and Cu(BDC) were synthesized and applied as heterogeneous catalysts for catalytic wet peroxide oxidation (CWPO) of simulated phenol wastewater (100 mg/L). The characterization including X-ray Powder Diffraction (XRD), Fourier Transform Infra-Red spectroscopy (FT-IR), Scanning Electron Microscopy (SEM), Energy Dispersive X-ray spectroscopy (EDX) were achieved. By comparison, Cu(BDC) exhibited better catalytic degradation performance. Then, Cu(BDC) was selected for further experiments. Several factors including temperature, H2O2 dose, catalyst dose and initial pH of phenol wastewater which could affect the catalytic degradation efficiency by Cu(BDC) were investigated. Under optimum conditions, phenol conversion of 99% and COD (Chemical Oxygen Demand) removal of 93% were achieved. The degradation on different concentration of phenol solution (100 to 1000 mg/L) was also conducted. No matter small or large concentration of phenol solution, satisfactory results with the phenol conversion of 99% and COD removal of over 90% were obtained. After reused twice, the Cu(BDC) could still keep well catalytic performance with phenol conversion of 99% and COD removal of over 85%. Like other copper catalysts, the mechanism of degradation process was also hydroxyl radical mechanism. The leaching of Cu2+ was also monitored by Inductively Coupled Plasma-Atomic Emission Spectrum (ICP-AES) with a negligible release of copper (7 ppm). Overall, Cu-MOFs could be a kind of promising heterogeneous catalyst for catalytic oxidation of phenol with H2O2 as oxidant.
The ceramic layers containing Cu(II) were prepared by Micro-arc Oxidation on aluminum under alkaline electrolyte (NaSiO3; Cu(Ac)2; Na2WO4; Na3PO4; Na2B4O7). Using x ray photoelectron spectroscopy, scanning electron microscopy, ultraviolet spectrophotometry and chemical oxygen demand analyzer on the film composition, structure and catalytic properties were characterized. The results showed that when the Cu2p peaks emerged in XPS pattern, the corresponding substances were CuO and Al2CuO4, it told us that there had the catalyst in the ceramic coating composition containing CuO. As can be seen from the SEM image analysis, with the pulse width increased, the ceramic layer surface volcanic hole size also increased and the area density trended to loose. Meanwhile, phenol oxidation test results demonstrated that with the pulse width parameter increasing, the catalytic effect of the micro-arc oxidation ceramic layers trended to increasing. However, at higher pulse width such as 750 microseconds, the conversion rate of phenol was weakened strongly.
Copper hydroxyl sulfate (Cu4(OH)6SO4) and copper hydroxyl sulfate/zinc oxide composite (Cu4(OH)6SO4/ZnO) were successfully synthesized by simple hydrothermal method and applied as heterogeneous catalysts to degrade phenol wastewater in a batch reactor in the presence of hydrogen peroxide (H2O2). The influence of temperature, H2O2 dosage, initial pH and catalyst dosage on phenol and COD removal efficiencies was investigated to get optimum conditions and to understand degradation process more clearly. The Cu2+ concentrations in the solutions after three hours reaction were also measured to prove the catalysts were stable. Excellent results, phenol removal efficiency of 99% and COD removal efficiency of 97%, had been achieved when treating 100 and 500 mg/L phenol wastewater. Even though the catalysts had low specific surface area, mesopores were mainly existed to decrease diffusion control of H2O2 and organics.
A highly convergent and concise synthesis of a triazole analogue of resorcylic acid lactone natural product LL-Z1640-2 has been achieved from easily accessible starting materials in six linear steps in 18 % overall yield. Biological evaluation confirmed the enone system of the natural product is crucial for its activity. The triazole analogue showed good activity (IC50 7.2 μm) against MNK2 kinase, which is an emerging target for cancer chemotherapy.
Hydroxyl functionalized beaded copolymers were synthesized from 2-hydroxy ethyl methacrylate by suspension polymerization using two different crosslinking agents (EDMA, DVB) and diluents (1,1,2,2-tetrachloroethane, 1,2-dichlorobenzene). Microporous beads with high surface area were successfully synthesized and characterized by different techniques. Maximum surface area obtained was 564 m(2)/g bearing uniform, spherical as well as non-aggregation images of beads. Thermal properties such as DTG and DSC reveal that, type of crosslinker (flexible/rigid) is major while its concentration is minor parameter that affect decomposition and softening temperature of copolymer. Swelling ratio of copolymer beads was examined as a function of crosslinker and crosslink density. Swelling behavior is in accordance with copolymer-solvent interaction parameter.
The present work reports the immobilization of horseradish peroxidase (HRP) into microemulsion based organogel-silica composite material. The new matrix containing HRP was applied to oxidize phenol in aqueous solution in the presence of hydrogen peroxide (pH 7.5) using phosphate buffer. Characterization of the composite was carried out using SEM imaging/ mapping and FT-IR, which verified that the silica is well accumulated in the organogel network. The quantification of phenol in aqueous solutions was carried out using HPLC. Parameters influencing oxidation of phenol such as contact time, composite/enzyme amount, H 2 O 2 concentration, stirring time and pH were optimized. The removal reached up to 99% when aqueous solution of phenol (10 mgl -1) was treated with 150 mg organogel-silica composite containing 200 µg of entrapped enzyme and 1.8 ml of 1.0 mM H 2 O 2 at pH 7.5. In addition to oxidation of phenol, it was found that benzoquinone formed in the reaction was removed by organogel-silica composite. The study concludes that HRP can be immobilized into organogel-silica composite with oxidation of phenolic substrate. The new matrix not only oxidizes phenol to muconic acid but also removes benzoquinone, a perilous byproduct in the catalytic oxidation of phenol in aqueous solutions.
Chitosan was cross-linked with hexamethylendiisocyanate and loaded with Pd which was subsequently reduced with NaBH4. The prepared catalyst was characterized by FT-IR and elemental analysis. The metal content was determined by ICP-MS measurements. Several substrates (cyclohex-2-enone, benzalacetophenone, 1,2-diphenylacetylene, and N-benzylidenaniline) were hydrogenated successfully in ethanol at mild conditions (50 °C, p(H2) ∼6 bar) utilizing a microwave reactor. Reaction parameters like temperature, hydrogen pressure, and the solvent were varied. It was shown that the reduction of the catalyst is crucial for catalytic activity. The catalyst was reused ten times for the hydrogenation of cyclohex-2-enone, without showing a dramatic loss in immobilized metal content. Also the polymeric support material did not show any decomposition.
The catalytic behavior of different Cu(Fe)/zeolite catalysts with the MFI morphology in wet peroxide oxidation of formic acid as a model organic substrate was thoroughly examined. The influence of the method for Cu2+ ions introduction into the zeolite matrix, Cu loading and the electron state of Cu on catalytic properties of zeolites, including their stability to leaching of Cu was studied. Cu-substituted ZSM-5 zeolites with the atomic ratio Si/Al = 30 and Cu content of 0.5–1.5, which were prepared by ion exchange, were shown most promising for wet peroxide oxidation. The impact of temperature, initial pH and concentrations of reagents on the catalytic performance of the catalyst with the optimal composition also was studied. The characterization of fresh and spent catalysts using UV–vis DR and ESR spectroscopic techniques led to suppose that the high efficiency of Cu-ZSM-5 to redox reactions in aqueous media is provided by nanostructured square-planar copper oxide clusters localized in the zeolite channels.
The wet air oxidation of phenol over cerium mixed oxides has been carried in autoclave slurry-type reactor and also in a contactor type membrane reactor to assist about the benefits provided by the employment of the mesoporous top layer of a ceramic tubular membrane as catalyst (Ce mixed oxides) support. The effect of mixed oxide composition and use of Pt as dopant onto the phenol removal rate and selectivity towards mineralization have been studied on both types of reactor. For slurry-type reactors, two different autoclave reactors were used: one mechanically stirred highly pressurized, and the other magnetically stirred containing a porous stainless steel membrane as gas diffuser in an attempt to attain higher gas–liquid interfacial area. The performances of these reactors have been compared under similar reaction conditions (i.e. catalyst loading/liquid volume, temperature, phenol concentration) although the way in which reactants are fed to the reaction vessel (different among each other configuration) is clearly affecting the CWO phenol degradation route. From the catalytic systems studied, Pt doped Ce–Zr mixed oxides exhibit the best reaction performance in spite of the achieved phenol conversion levels are below 50%. For autoclave reactors, the gas feeding to the liquid volume by a membrane diffuser has almost no effect on phenol removal for the reaction conditions tested; whereas the catalytic membrane contactor type reactor clearly outperform autoclave reactor provided with membrane diffuser.
A polymer–metal complex containing poly(4-vinylpyridine) (4-VP) and copper(II) ions was investigated along with the catalytic properties of its products. The water-insoluble polymer–copper(II) complex was synthesized in supercritical carbon dioxide by using methanol as a cosolvent and N,N′-methylenebisacrylamide as a cross-linker. Fourier transform infrared spectroscopy and X-ray diffraction results reveal that the metal ion is coordinated via the nitrogen of 4-VP. The morphology and size of the products were characterized by scanning electron microscopy and ZetaSizer nano analysis. The results show that the spheres were about 200 nm in diameter when the pressure was 18 MPa. The maximum surface area (49.38 m2/g) was obtained via standard nitrogen adsorption analysis by using 3 mL of methanol. The polymer–copper(II) complex catalyst was used for the catalytic oxidation of phenol at room temperature and at atmospheric pressure by using H2O2 as an oxidant. As a result, an efficient catalytic performance was achieved, wherein the maximum phenol conversion was 78.3%. The current work presents a novel and simple method to prepare polymer–metal complexes.
The Mediterranean region is the largest olive oil producer in the world, consequently in this area olive oil mill wastewaters have a high seasonal pollution potential. Due to the presence of phytotoxic compounds, such as poly-phenols, the olive oil mill wastewater is not easily biodegradable, and, therefore, the direct biological treatment is not recommended. Many techniques have been proposed for the their treatment, such as catalytic wet oxidation, ozonization, photo-catalysis, etc., among which, the catalytic oxidation seems to give good results. The present paper reports the results of an experimental investigation carried out with the aim to define a new catalytic oxidation process with hydrogen peroxide using copper-based catalyst, able to reduce the phytotoxicity of olive oil mill wastewaters and to recover the catalyst after oxidation treatment. The experimental results have showed that, operating in a slurry type reactor at mild operating conditions, it is possible to reduce the organic chemical oxygen demand down to 10% and the polyphenols amount of wastewater down to 1%. Therefore, the process is able to increase the rapidly biodegradable substrate content up to 80%, to remove color and total suspend solid amount and to minimize the metal loss of the catalyst after oxidation process, with a recover of about 80% with respect to its initial amount, permitting to reuse it for a long life cycle.
This review is designed to highlight the recent advances in the field of organometallic and coordination macromolecules. It is organized by the particular properties that the macromolecules possess. The aim of this article is to provide a comprehensive review of the synthesis and properties of organometallic and coordination photo- and electro-active macromolecules. It will also describe the utilization of theses classes of polymers as magnetic or liquid crystalline materials, as well as sensors and catalysts.
Two new tetraazamacrocycle complexes, namely, 7,16-dinicotinoyl[Ni{Me4(4-MeBzo)2[14]tetraeneN4}] and 7,16-diisonicotinoyl[Ni{Me4(4-MeBzo)2[14]tetraeneN4}] (where [Ni{Me4(4-MeBzo)2[14]tetraeneN4}]=5,7,12,14-tetramethyldi-4-methylbenzo[b,i][1,4,8,11]tetraazacyclo-tetradecahexaenatonickel(II)) were synthesized by acylation of [Ni{Me4(4-MeBzo)2[14]tetraeneN4}] and characterized using spectral and microanalytical data. All tetraazamacrocycle complexes were found to catalyze chemical oxidation of phenol by H2O2 to catechol and hydroquinone and it is found that 7,16-diisonicotinoyl[Ni{Me4(4-MeBzo)2[14]tetraeneN4}] showed the best performance. Catechol as the major product and hydroquinone as the minor were characterized respectively under optimal values of some parameters such as amount of catalyst, reaction temperature, oxidant and substrate concentration, effect of reaction media and reaction time. Electrocatalytic oxidation of phenol on glassy carbon electrode modified by the synthesized macrocycle complexes has also been studied.
The thermal degradation of chitosan and chitosan–cupric ion compounds in air was studied using thermogravimetric and differential thermal analyses in the temperature range 30–600 °C. The impact of cupric ion on the thermo‐oxidative degradation of chitosan was investigated. Fourier transform infrared and X‐ray diffraction analyses were utilized to determine the microstructure of the chitosan–cupric ion compounds. Kinetic parameters such as activation energy, pre‐exponential factor, Gibbs energy, and enthalpy and entropy of activation were determined using the Coats–Redfern equation. The results show that the thermo‐oxidative degradation of chitosan and chitosan–cupric ion compounds is a two‐stage reaction. The impact of cupric ion on the thermo‐oxidative degradation of chitosan is significant, and all thermodynamic parameters indicate that the thermo‐oxidative degradation of chitosan and chitosan–cupric ion compounds is a non‐spontaneous process and proceeds via a mechanism involving nucleation and growth, with an Avrami–Erofeev function (A4) with the integral form [−ln(1 − α)]4. Copyright © 2010 Society of Chemical Industry
Compared with conventional precipitation polymerization method, cross-linked poly(4-vinylpyridine) (P4VP) and its microgels copolymerized with α-methacrylic acid (MAA) were synthesized through a new route of stabilizer-free polymerization in supercritical fluids. The yellow, dry, fine powders were directly obtained from precipitation polymerization of 4-vinylpyridine in supercritical carbon dioxide (scCO2) at pressures ranging from 70.0 to 230bar, using N,N′-methylenebisacrylamide as cross-linker. The effects of the reaction pressure, cross-linker ratio, initiator concentration, and reaction time were investigated. The capacity of this microgel for adsorption of copper(II) was also studied. At higher cross-linker concentrations, a high yield of the cross-linked P4VP microgel was generated in scCO2, and its particle size was less than 300nm. Polymerization of cross-linked P4VP in scCO2 was extremely sensitive to the density of the continuous phase. The adsorption followed the Langmuir isotherm. The adsorption capacities of cross-linked P(4VP-co-MAA) and cross-linked P4VP were 47.2 and 26.9mgg−1, respectively.
a b s t r a c t The catecholase activity of a copper(II) complex coordinated by a tripodal pyrazole-based ligand was investigated in continuous flow catalysis. The covalent immobilization of the complex on the surface was achieved by a two steps method. First, the porous graphite felt support is functionalized by electro-chemical reduction of 4-carboxymethyl-benzenediazonium salts. Second, the complex is covalently immobilized by esterification reaction between the COOH-containing linker and a primary alcohol group present on the C6 chain of the ligand. The two steps of the immobilization process were optimized by using nitro-containing molecules and cyclic voltammetry analyses. The copper complex exhibits higher catecholase activity in continuous flow catalysis than in solution with a 50 times lower amount of cata-lyst, underlining the advantages of the flow procedure. The presence of H 2 O 2 is detected after catalysis, showing that the four-electron reduction of dioxygen to water does not occur unlike the natural enzyme.
The performance of a commercial CuO/alumina catalyst used in the catalytic wet peroxide oxidation (CWPO) of 1 g/l phenol solutions is investigated in a batch reactor. The effect of temperature, catalyst load, hydrogen peroxide concentration and dosage strategies on phenol mineralization, hydrogen peroxide consumption efficiencies and catalyst stability was studied. Experiments were performed at 298, 323 and 343 K, using catalyst loads of 1 g/l or 25 g/l and concentrations of hydrogen peroxide 1.3, 2.6 and 3.9 times the stoichiometric requirement added at once or in distributed doses. The critical goal of the CWPO in terms of Process Intensification is to achieve total phenol mineralization working at optimal hydrogen peroxide consumption efficiencies while retaining catalyst stability. The present work highlights the complexity of this objective and shows viable working alternatives.
Results indicate that high temperatures and concentrations of catalyst and hydrogen peroxide (added at once) can be employed when fast mineralization and high pH values are required in order to prevent catalyst leaching, although oxidant consumption efficiencies are then low. However, simultaneous high mineralization and hydrogen peroxide consumption efficiencies are obtained with a proper oxidant dosage strategy at high temperature, using high catalyst load. Then, hydrogen peroxide degradation into non-oxidising (parasitic) species is minimized with final TOC conversions close to 90%. The drawback of this strategy is that the rate of reaction is lower because of the limited amount of oxidant available.
This paper evaluates the treatment of textile wastewater using new composites as adsorbents and/or heterogeneous catalysts for Fenton oxidation. The efficiency of the process was explored as a function of the experimental parameters: pH, hydrogen peroxide concentration and iron oxides content. The composites with high iron oxides content were effective to adsorb contaminants in textile wastewater, and the adsorptive capacity increased with the superficial iron concentration. These solids were also used as heterogeneous Fenton catalysts and had the advantage of being effective at pH 3.0 with a consumption of hydrogen peroxide lower than required by the homogeneous Fenton process.
The effects of chloride concentration on the rates of decomposition of H2O2 by ferric ion and on the rate of oxidation of an organic solute in homogeneous aqueous solution have been investigated. Experiments were carried out in a batch reactor, in the dark, at pH ≤ 3, 25.0 ± 0.5 °C and at controlled ionic strength (≤1 M). The concentrations of chloride ranged from 0 to 1 M ([Fe(III)]0 = 0.2 or 1 mM, [H2O2]0 = 1, 10 or 50 mM). The spectrophotometric study shows that chloride ions compete with hydrogen peroxide for the complexation of Fe(III) and that H2O2 does not form complexes with iron(III)-chlorocomplexes. The kinetic study showed that the rates of decomposition of H2O2 decreased in the presence of chloride. The measured rates were accurately predicted by a kinetic model which incorporates the formation of iron(II) and iron(III)-chlorocomplexes and reactions involving Cl2− radicals. At a fixed pH, the pseudo-first-order rate constants were found to decrease linearly with the molar fraction of Fe(III) complexed with chloride. The kinetic model was also able to predict the rate of oxidation of a probe compound (atrazine) by Fe(III)/H2O2 in the presence of chloride. Computer simulations indicate that Cl2− which represents the predominant radical contributes to the oxidation of atrazine.
In this work, the degradation and mineralization of Orange II solutions (0.1 mM) using catalysts based on pillared saponite impregnated with several iron salts is reported. Oxidation is carried out in a batch reactor, in presence of various hydrogen peroxide concentrations, and in a wide range of temperature and pH values. Twelve samples are prepared, with three iron loads (7.5, 13.0 and 17.0 wt.%) and four iron salts as precursors, namely Fe(II) acetate, Fe(II) oxalate, Fe(II) acetylacetonate and Fe(III) acetylacetonate. The samples are characterized using X-ray diffraction, thermal analysis, infrared spectroscopy, energy dispersive spectroscopy and adsorption of nitrogen at 77 K. The catalytic results show that these solids present good properties for the degradation and mineralization of Orange II solutions, allowing to reach, in the best conditions and after 4 h of oxidation, 99% of dye degradation with 91% of total organic carbon (TOC) reduction (at 70 °C), using only ca. 90 mg of clay catalyst per litre of solution. Nevertheless, 96% of dye removal with 82% of mineralization are also reached at 30 °C. Besides, the amount of iron released into the final solution is lower than 1 ppm, in the worst of the cases, and 0.09 ppm in the best case.
A practical, inexpensive, green chemical process for degrading environmental pollutants is greatly needed, especially for persistent chlorinated pollutants. Here we describe the activation of hydrogen peroxide by tetraamidomacrocylic ligand (TAML) iron catalysts, to destroy the priority pollutants pentachlorophenol (PCP) and 2,4,6-trichlorophenol (TCP). In water, in minutes, under ambient conditions of temperature and pressure, PCP and TCP are completely destroyed at catalyst:substrate ratios of 1:715 and 1:2000, respectively. The fate of about 90% of the carbon and about 99% of the chlorine has been determined in each case. Neither dioxins nor any other toxic compounds are detectable products, and the catalysts themselves show low toxicity.
Two macroacyclic ligands represented as L1 and L2 with 3N2O and 5N donor atoms, respectively, have been synthesized by Schiff base condensation. They were subsequently grafted on a silica surface via covalent bonds. The organic ligands L1 and L2 as well as the heterogenized ligands L1·SiO2 and L2·SiO2 reacted with copper(II) leading to the formation of dinuclear copper(II) complexes. Catalytic oxidation of 3,5-di-t-butylcatechol (DTBC) by dioxygen was studied using as catalysts the homogeneous Cu2(L1) and Cu2(L2) and the heterogenized Cu2(L1)·SiO2 and Cu2(L2)·SiO2 complexes. These complexes were found to be very effective catalysts for DTBC oxidation producing mainly 3,5-di-t-butylquinone (DTBQ). During the catalytic process the formation of an o-semiquinone radical has also been confirmed. The immobilized on modified silica surface copper(II) complexes gave significantly higher DTBC conversion than the homogeneous copper(II) complexes.
The ability of chitosan, prepared from waste prawn shell, to sorb copper (II) ions from aqueous solutions has been studied. Equilibrium studies show that chitosan has a maximum sorption capacity for copper ions of about 40mg/g chitosan. The mass transport characteristics have been investigated by monitoring the kinetics in an agitated batch adsorber. An external mass transfer coefficient and an intraparticle diffusion rate parameter have been determined for a number of system variables including agitation, initial copper ion concentration, chitosan mass, chitosan particle size and solution temperature.
Homogeneous (Cu2+ ions) and heterogeneous (Cu2+-pillared clay) Fenton-like catalysts have been compared in the conversion of p-coumaric acid. The performances of the two classes of catalysts are similar for an analogous amount of copper, but there are
some relevant differences in terms of (i) the presence of an induction time, (ii) the turnover frequency, (iii) the efficiency
in the use of H2O2, (iv) the initial attack of p-coumaric acid (hydroxylation on the aromatic ring or oxidative attack on the double bond of the lateral chain), and (v) the
effect of dissolved oxygen on the removal of total organic carbon (TOC). These differences were interpreted in terms of reaction
network of generation of radical oxygen species and of organics conversion. The possible formation of a surface peroxo adduct
coordinated to a copper binulcear site was also evidenced for the solid heterogeneous catalyst.
Poly(2-vinyl pyridine) [P2VP] and poly(4-vinyl pyridine) [P4VP]/copper iodide binary mixtures were studied by differential scanning calorimetry (DSC) in order to investigate the phase behavior of the blends at microscopic level. The glass transition temperature (Tg) of the P2VP/copper iodide binary mixtures as compared with pure polymer increased by 80°C when the amount of Cu(I) in the blend was increased up to 40/60 wt/wt monomer/inorganic salt composition for P2VP. For P4VP, the Tg increased by 40°C in an 80/20 wt/wt decreasing by 10°C at 60/40 wt/wt. Fourier transform infrared (FTIR) and Raman spectroscopy provided molecular-level data, suggesting that copper coordinates with pyridine rings via nitrogen ion pairs in a metal-ligand bonding. Conductivity measurements were carried out at different temperatures and compositions, and upon increasing the amount of copper iodine in the blends, the conductivity increased drastically. © 2000 John Wiley & Sons, Inc. Adv Polym Techn 19: 113–119, 2000
Reaction between N,N′-bis(salicyledene)diethylenetriamine (H2saldien) covalently bonded to chloromethylated polystyrene cross linked with 5% divinylbenzene (abbreviated as PS-H2saldien, I) and aqueous potassium vanadate at ca. pH 6.5 results in the formation of polymer-anchored complex PS-[VO(saldien)] (1). Cupric acetate on reaction with I in methanol gives PS-[Cu(saldien)] (2). Formations of these complexes were confirmed by IR and electronic spectroscopic techniques, elemental and thermo gravimetric analyses and scanning electron micrographs. Catalytic potential of these complexes have been tested for the oxidation of phenol and hydroquinone using 30% H2O2 as an oxidant. Various reaction parameters such as substrate to oxidant ratio, concentration of catalysts and solvent of the reaction medium have been optimised to get maximum oxidation of phenol to p-benzoquinone selectively. Under optimised conditions, i.e. phenol (1.88g, 20mmol), H2O2 (4.56g, 40mmol), PS-[Cu(saldien)] (30mg), temperature (70°C) and water (10ml), the phenol conversion was found to be 22.2% and percentage yield of the main products p-benzoquinone and catechol are 14.4% and 7.8%, respectively. PS-[VO(saldien)] exhibits only 3% conversion in water with 100% selectivity towards benzoquinone. Both the catalysts become more selective towards catechol formation along with higher conversion in acetonitrile. The selectivity of p-benzoquinone was also found to be dependent on volume and nature of solvent, and temperature. Hydroquinone oxidation was also found to be pH dependent; carbonate buffer gives quantitative conversion within 30min at 1:6 substrate to oxidant ratio.
Homogeneous (Cu2+ ions) and heterogeneous (Cu2+-pillared clay) Fenton-like catalysts were compared in the conversion of p-coumaric acid. The performances of the 2 classes of catalysts are similar for an analogous amt. of Cu, but there are some relevant differences in terms of (i) the presence of an induction time, (ii) the turnover frequency, (iii) the efficiency in the use of H2O2, (iv) the initial attack of p-coumaric acid (hydroxylation on the arom. ring or oxidative attack on the double bond of the lateral chain), and (v) the effect of dissolved oxygen on the removal of total org. carbon. These differences were interpreted in terms of reaction network of generation of radical O species and of orgs. conversion. The possible formation of a surface peroxo adduct coordinated to a Cu binuclear site was also evidenced for the solid heterogeneous catalyst. [on SciFinder(R)]
The chemical process industries (CPI) must treat wastewaters containing a wide variety of contaminants, ranging from toxic organics like phenol, benzene, other aromatics, formaldehyde, and amines, to inorganics such as sulfite, sulfide, mercaptans, and cyanide, to heavy metals such as hexavalent chrome. These wastewaters also have a wide range of concentrations and combinations of contaminants. The streams must be treated as inexpensively as possible and in a safe manner, preferably by processes that are easy to operate on-site and that require a minimum of labor and technical know-how. And, of course, the ultimate goal of this treatment is that the treated water meet all federal, state, and local discharge regulations. One available wastewater treatment technology that few engineers seem to be familiar with is the Fenton reactor. In this advanced oxidation process, toxic wastewater is reacted with inexpensive ferrous sulfate catalyst and hydrogen peroxide in a simple, nonpressurized (typically batch) reactor to yield (if reacted to completion) carbon dioxide and water. This article offers guidance on the use of this process by first explaining the mechanisms of Fenton`s chemistry and then outlining how to apply it to industrial wastewater treatment.
Continuous catalytic wet air oxidation (CWAO) was investigated as a suitable precursor for the biological treatment of industrial wastewater that contained phenols (phenol, o-cresol, 2-chlorophenol and p-nitrophenol), aniline, sulfolane, nitrobenzene or sodium dodecylbenzene sulfonate (DBS). Seventy-two-hour tests were carried out in a fixed bed reactor in trickle flow regime, using a commercial activated carbon (AC) as catalyst. The temperature and total pressure were 140 °C and 13.1 bar, respectively. The influence of hydroxyl-, methyl-, chloride-, nitro-, sulfo- and sulfonic-substituents on the oxidation mechanism of aromatic compounds, the occurrence of oxidative coupling reactions over the AC, and the catalytic activity (in terms of substrate elimination) were established. The results show that the AC without any supported active metal behaves bifunctionally as adsorbent and catalyst, and is active enough to oxidate phenol, o-cresol, 2-chlorophenol and DBS, giving conversions between 30 and 55% at the conditions tested. The selectivity to the production of carbon dioxide was considerable with total organic carbon (TOC) abatement between 15 and 50%. The chemical oxygen demand (COD) reduction was between 12 and 45%. In turn, aniline, sulfolane, p-nitrophenol and nitrobenzene conversions were below 5% and there was almost no TOC abatement or COD reduction, which shows the refractory nature of these compounds.
Metal, metal oxide, and plastic surfaces were modified with poly(vinylpyridine) using adsorption, spin-coating, and dip-coating techniques and various metal, semiconductor, and dielectric nanoparticles were subsequently attached. Prior to the modification, the substrates were treated with glow discharge plasma for cleaning purposes and to introduce surface functional groups that are capable of interaction with the polymer. UV−vis absorption spectroscopy, atomic force, and electron scanning microscopies were used to characterize polymer layers and layers of immobilized nanoparticles. The surface modification with poly(vinylpyridine) via adsorption technique is suggested as a simple, effective, and highly versatile method for the preparation of single, mixed, and multilayered assemblies of various nanoparticles on different substrates.
Chitosan is a well-known biopolymer, whose high nitrogen content confers remarkable ability for the sorption of metal ions from dilute effluents. However, its sorption performance in both equilibrium and kinetic terms is controlled by diffusion processes. Gel bead formation allows an expansion of the polymer network, which improves access to the internal sorption sites and enhances diffusion mechanisms. Molybdate and vanadate recovery using glutaraldehyde cross-linked chitosan beads reaches uptake capacities as high as 7−8 mmol g-1, depending on the pH. The optimum pH (3−3.5) corresponded to the predominance range of hydrolyzed polynuclear metal forms and optimum electrostatic attraction. While for beads, particle size does not influence equilibrium, for flakes, increasing sorbent radius significantly decreases uptake capacities to 1.5 mmol g-1. Sorption kinetics are mainly controlled by intraparticle diffusion for beads, while for flakes the controlling mechanisms are both external and intraparticle diffusions. The gel conditioning increases the intraparticle diffusivity by 3 orders of magnitude: intraparticle diffusivities range between 10-13 and 10-10 m2 min-1, depending on the sorbent size and the conditioning.
The oxidation of aqueous phenol by oxygen has been studied at elevated temperature and pressure by use of the stopped flow technique. High performance liquid chromatography has been used to identify the oxidation products and estimate their concentrations. A detailed reaction mechanism is proposed.
The catalysts with copper(II) ions stabilized onto different polymeric matrixes are prepared on either bulk (Cu/chitosan, Cu/polyethyleneimine-polyacrylic acid (PPA), and Cu-diiminate-impregnated polystyrene, polyarylate, or polymethylmethacrylate) or composite supports (egg-shell type Cu/chitosan/SiO2 and Cu/PPA/SiO2). The morphology of the samples and peculiarities of Cu(II) cationic sites are studied by SEM and ESR methods, and the catalyst activities are compared in oxidation of o- and p-dihydroxybenzenes by air in water. The catalytic activity of Cu(II) centers is governed by the coordination of isolated copper ions: for the most active catalysts, i.e., Cu/chitosan and Cu/PPA, the symmetry of isolated Cu2+-sites approximates a coordinatively unsaturated square-planar structure. At the same time, accessibility of active sites to water differs for different polymers, so the contribution of hydrophilicity to the reaction pattern cannot be excluded. Redox transformations of the active sites in the course of catalytic tests do not cause copper leaching from the polymer matrix. The binary composite systems with a film of low-loaded hydrofilic Cu-polymer supported on macroporous SiO2 demonstrate substantially higher activity in oxidation of hydroquinone and 3,4-dihydroxyphenylalanine, as compared with the bulk Cu/polymer samples. In turn, the specific activity of Cu/chitosan/SiO2 exceeds significantly that of Cu/PPA/SiO2 due to stabilization of a thinner and more uniform film of chitosan at the surface of silica.
The application of chitosan–cellulose hydrogel beads as an adsorbent for Cu adsorption from aqueous solutions was examined. Chitosan was blended with cellulose to make chitosan–cellulose hydrogel beads and the hydrogel beads were crosslinked with ethylene glycol diglycidyl ether (EGDE). It was found that the addition of cellulose to chitosan made the hydrogel beads materially denser and the crosslinking reaction improved the chemical stability of the chitosan–cellulose beads in solutions with pH values down to 1. Batch adsorption experiments indicated that both the chitosan–cellulose and the crosslinked chitosan–cellulose hydrogel beads had high adsorption capacities for Cu removal, with the optimum pH in the range around neutral, although the crosslinked chitosan–cellulose beads always exhibited slightly lower adsorption capacities than the non-crosslinked beads. The adsorption isotherm of the chitosan–cellulose beads can be well-fitted to the Langmuir model, but that of the crosslinked chitosan–cellulose can only be well described by the Freundlich model. Copper adsorption kinetics on both types of the beads clearly followed an initial transport-controlled adsorption phenomenon. Fourier Transform Infrared (FTIR) Spectroscopy and X-ray photoelectron spectroscopy (XPS) revealed that Cu adsorption on the beads mainly involved the nitrogen atoms in chitosan to form surface complexes.
Progress towards environmentally responsible processing is marked by the elimination of waste and by-product generation and reduced dependence on hazardous chemicals. The key to both is often provided by catalytic as alternatives to stoichiometric processes.Heterogeneous catalysis, long established in bulk-chemicals processing, is beginning to make inroads into the fine-chemicals industry also. This tendency is helped by the availability of novel catalytic materials and modern techniques of creating and investigating specific active sites on catalyst surfaces. In this overview, examples from the areas of acid/base and redox catalysis are chosen to illustrate the trend from non-catalytic to catalytic processes.
Metal cations can be adsorbed by chelation on amine groups of chitosan in near neutral solutions. In the case of metal anions, the sorption proceeds by electrostatic attraction on protonated amine groups in acidic solutions. However, the presence of ligands and the pH strongly control sorption performance (sorption isotherm) and the uptake mechanism (changing the speciation of the metal may result in turning the chelation mechanism into the electrostatic attraction mechanism). Several examples are discussed with precious metals (Pd, Pt), oxo-anions (Mo, V) and heavy metals (Cu, Ag). Sorption performance (equilibrium uptake but also kinetics) is also strictly controlled by other structural parameters of the polymer (degree of deacetylation, crystallinity for example) that control swelling and diffusion properties of chitosan. The identification of the limiting steps of the sorption process helps in designing new derivatives of chitosan. Diffusion properties may be improved by physical modification of chitosan (manufacturing gel beads, decreasing crystallinity). Selectivity can be enhanced by chemical modification (grafting, for example, sulfur compounds). Several examples are discussed to demonstrate the versatility of the material. This versatility allows the polymer to be used under different forms (from water soluble form, to solid form, gels, fibers, hollow fibers …) for polymer-enhanced ultrafiltration and sorption processes. These interactions of metal ions with chitosan can be used for the decontamination of effluents, for the recovery of valuable metals but also for the development of new materials or new processes involving metal-loaded chitosan. Several examples are cited in the design of new sorbing materials, the development of chitosan-supported catalysts, the manufacturing of new materials for opto-electronic applications or agriculture (plant disease treatment …).
Chitosan is an optically active biopolymer that is characterized by a strong affinity for transition metals. The polymer can be used as a support for the preparation of heterogeneous catalysts in the form of colloids, flakes, gel beads, fibers (including hollow fibers), or immobilized on inorganic supports (alumina, silica, or other metal oxides). The conformation of the polymer (together with its flexibility) is an important advantage for this kind of application. The ease with which it can be modified physically and chemically opens up avenues for manufacturing a wide range of catalysts for applications in the fields of hydrogenation, oxidation, and fine chemical synthesis reactions. This review summarizes the main advances published over the last 15 years, outlining the procedures for preparing these materials, describing how they are tested in a series of reactions and discussing the main controlling parameters that should be taken into account in order to optimize their catalytic activity.
The adsorption of Cu(II) ions onto chitosan and cross-linked chitosan beads has been investigated. Chitosan beads were cross-linked with glutaraldehyde (GLA), epichlorohydrin (ECH) and ethylene glycol diglycidyl ether (EGDE) in order to obtain sorbents that are insoluble in aqueous acidic and basic solution. Batch adsorption experiments were carried out as a function of pH, agitation period, agitation rate and concentration of Cu(II) ions. A pH of 6.0 was found to be a optimum for Cu(II) adsorption on chitosan and cross-linked chitosan beads. Isotherm studies indicate Cu(II) can be effectively removed by chitosan and cross-linked chitosan beads. Adsorption isothermal data could be well interpreted by the Langmuir equation. Langmuir constants have been determined for chitosan and cross-linked chitosan beads. The experimental data of the adsorption equilibrium from Cu(II) solution correlated well with the Langmuir isotherm equation. The uptakes of Cu(II) ions on chitosan beads were 80.71 mg Cu(II)/g chitosan, on chitosan-GLA beads were 59.67 mg Cu(II)/g chitosan-GLA, on chitosan-ECH beads were 62.47 mg Cu(II)/g chitosan-ECH and on chitosan-EGDE beads were 45.94 mg Cu(II)/g chitosan-EGDE. The Cu(II) ions can be removed from the chitosan and cross-linked chitosan beads rapidly by treatment with an aqueous EDTA solution and at the same time the chitosan and cross-linked chitosan beads can be regenerated and also can be used again to adsorb heavy metal ions.
Catalytic liquid-phase hydrogenation of aqueous nitrate solutions is presented as a potential, advanced treatment technology for the removal of excessive quantities of nitrate ions from polluted drinking water streams. Catalysts are briefly reviewed first, followed by mechanistic speculations and kinetics that have been proposed for the liquid-phase nitrate reduction. Subsequently, a novel process scheme consisting of integrated ion-exchange and catalytic denitrification steps is discussed.This paper reviews also the developments in the field of catalytic wet-air oxidation (CWAO). Particular attention was given to the heterogeneously catalyzed wet-air oxidation of real industrial wastewaters (such as Kraft bleach plant effluents) in batch and continuous-flow oxidation reactors. Finally, considerable potential of the CWAO process to ultimately destroy organic pollutants in industrial effluents and detoxify them by using novel titania-supported Ru catalysts is reported.
Degradation experiments using 5 mmol/l ethylenediaminetetraacetic acid (EDTA) solutions at pH 3 were performed in the presence of H2O2 and metals such as Fe2+, Fe3+, Cu2+ and mixtures of Fe2+/Cu2+ and Fe3+/Cu2+ under UV-A irradiation (366 nm)—photo-Fenton and photo-Fenton-like reactions—at different metal/EDTA concentration ratios in order to determine the best conditions for EDTA photochemical removal. Analogous dark reactions were performed for comparison. The reaction course was monitored by both EDTA and TOC determinations. Hydrogen peroxide demand was also evaluated in all cases. In terms of TOC removal, photo-Fenton-like reactions were remarkably more efficient than the analogous Fenton-like reactions. When EDTA was monitored, Fenton-like reactions showed variable performances, being more efficient with EDTA:Fe2+ and EDTA:Fe3+ ratios of 1:1. However, in these both cases, reaction rates were lower than the ones obtained under irradiation. Total mineralization ranged from 31% (Cu2+ system) to 92% (Fe2+, Fe3+, Fe3++Cu2+ and Fe2++Cu2+ systems) after 4 h of irradiation. Percentage of TOC removal was higher in the presence of iron because some photoactive intermediates were probably formed during EDTA degradation.
Chitin is the most abundant natural amino polysaccharide and is estimated to be produced annually almost as much as cellulose. It has become of great interest not only as an underutilized resource, but also as a new functional material of high potential in various fields, and recent progress in chitin chemistry is quite noteworthy. The purpose of this review is to take a closer look at chitin and chitosan applications. Based on current research and existing products, some new and futuristic approaches in this fascinating area are thoroughly discussed.
Catalytic wet oxidation has proved to be effective at eliminating hazardous organic compounds, such as phenol, from waste waters. However, the lack of active long-life oxidation catalysts which can perform in aqueous phase is its main drawback. This study explores the ability of bimetallic supported catalysts to oxidize aqueous phenol solutions using air as oxidant. Combinations of 2% of CoO, Fe2O3, MnO or ZnO with 10% CuO were supported on gamma-alumina by pore filling, calcined and later tested. The oxidation was carried out in a packed bed reactor operating in trickle flow regime at 140 degrees C and 900 kPa of oxygen partial pressure. Lifetime tests were conducted for 8 days. The pH of the feed solution was also varied. The results show that all the catalysts tested undergo severe deactivation during the first 2 days of operation. Later, the catalysts present steady activity until the end of the test. The highest residual phenol conversion was obtained for the ZnO-CuO, which was significantly higher than that obtained with the 10% CuO catalyst used as reference. The catalyst deactivation is related to the dissolution of the metal oxides from the catalyst surface due to the acidic reaction conditions. Generally, the performance of the catalysts was better when the pH of the feed solution was increased.
A new process is described for the preparation of chitosan gel beads using molybdate as the gelling agent. This new gelation technique leads to a structure different from that produced during alkaline coagulation of a chitosan solution. Instead of a morphology characterized by large open pores, gel beads produced in a molybdate solution, under optimum conditions (pH 6; molybdate concentration, 7 g x L(-1)), have a double layer structure corresponding to a very compact 100-microm thick external layer and an internal structure of small pores. Experimental conditions, especially pH and molybdate concentration, were selected to optimize molybdate content and the stability of the bead shape.
The metal removal capability of prawn shell is evaluated in this study using copper as a model sorbate. A mild deacetylation method was used to convert chitin on the periphery of the shell to chitosan. The equilibrium and kinetic characteristics of copper adsorption on partially deacetylated prawn shell are studied in batch stirred-tank experiments. The extent of copper removal increases with an increase in pH. Both the Langmuir model with pH-dependent parameters and the extended Langmuir-Freundlich model with pH-independent parameters account very well for the measured equilibrium data. Modeling studies using two different second order surface reaction models demonstrate that transient profiles obtained experimentally for a range of initial metal concentrations (C0) and adsorbent dosage are in good agreement with calculated curves of both models. The two rate models can be used for an accurate description of measured kinetic data so long as their rate constants are properly correlated with the two system variables. In contrast, deviation exists between experimental data and theoretical curves calculated from a diffusion-based model.
This work reports on the evolution of the toxicity of phenol-containing simulated wastewater upon catalytic wet oxidation with a commercial copper-based catalyst (Engelhard Cu-0203T). The results of the study show that this catalyst enhances detoxification, in addition to its effect on the oxidation rate. The EC50 values of the intermediates identified throughout the oxidation route of phenol have been determined and used to predict the evolution of toxicity upon oxidation. The predicted values have been compared with the ones measured directly from the aqueous solution during the oxidation process. To learn about the evolution of toxicity through out the routes of phenol oxidation, experiments have been performed with simulated wastewaters containing separately phenol, catechol, and hydroquinone as original pollutants. The significant increase of toxicity observed during the early stages of phenol oxidation is not directly related to the development of the brown color that derives mainly from catechol oxidation. This increase of toxicity is caused by the formation of hydroquinone and p-benzoquinone as intermediates, the former showing the highest toxicity. Furthermore, synergistic effects, giving rise to a significant increase of toxicity, have been observed. These effects derive from the interactions among copper leached from the catalyst and catechol, hydroquinone, and p-benzoquinone and demand that close attention be paid to this potential problem in catalytic wet oxidation.
The adsorption of phenol onto chitin, a naturally occurring material was studied as a function of initial pH, temperature and initial phenol concentration. The highest phenol adsorption capacity was determined as 21.5 mgg(-1) for 300 mgdm(-3) initial phenol concentration at pH 1.0 and 40 degrees C. Adsorption data were well described by the Freundlich Model, although they could be modeled by the Langmuir equation. The pseudo-first-order and pseudo-second-order kinetic models were applied to test the experimental data. The pseudo-second-order kinetic model provided the best correlation of the experimental data compared to the pseudo-first-order model. The thermodynamic constants of the adsorption process; DeltaG degrees , DeltaH degrees and DeltaS degrees were evaluated as -19.4 kJmol(-1) (at 40 degrees C), 10.2 kJmol(-1) and 0.093 kJmol(-1)K(-1), respectively. These showed that adsorption of phenol on chitin was endothermic and spontaneous.
Several phenol derivatives were evaluated regarding their capacities for Fe(3+) and Cu(2+) reduction. Selected compounds were assayed in Fenton-like reactions to degrade Azure B. 3,4-Dihydroxyphenylacetic, 2,5-dihydroxyterephtalic, gallic, chromotropic and 3-hydroxyanthranilic acids were the most efficient reducers of both metallic ions. The reaction system composed of 3-hydroxyanthranilic acid/Fe(3+)/H(2)O(2) was able to degrade Azure B at higher levels than the conventional Fenton reaction (87% and 75% of decolorization after 20min reaction, respectively). Gallic and syringic acids, catechol and vanillin induced Azure B degradations at lower levels as compared with conventional Fenton reaction. Azure B was not degraded in the presence of 10% (v/v) methanol or ethanol, which are OH radical scavengers, confirming the participation of this radical in the degradation reactions. Iron-containing reactions consumed substantially more H(2)O(2) than reactions containing copper. In iron-containing reactions, even the systems that caused a limited degradation of the dye consumed high concentrations of H(2)O(2). On the other hand, the reactions containing Fe(3+), H(2)O(2) and 3-hydroxyanthranilic acid or 3,4-dihydroxyphenylacetic acid were the most efficient on degradation of Azure B and also presented the highest H(2)O(2) consumption. These results indicate that H(2)O(2) consumption occurs even when the dye is not extensively degraded, suggesting that part of the generated OH radicals reacts with the own phenol derivative instead of Azure B.
With the goal of predicting the photocatalytic behaviour of different phenolic compounds (catechol, resorcinol, phenol, m-cresol and o-cresol), their adsorption and interaction types with the TiO(2) Degussa P-25 surface were studied. Langmuir and Freundlich isotherms were applied in the adsorption studies. The obtained results indicated that catechol adsorption is much higher than those of the other phenolics and its interaction occurs preferentially through the formation of a catecholate monodentate. Resorcinol and the cresols interact by means of hydrogen bonds through the hydroxyl group, and their adsorption is much lower than that of catechol. Finally, phenol showed an intermediate behaviour, with a Langmuir adsorption constant, K(L), much lower than that of catechol, but a similar interaction. The interaction of the selected molecules with the catalyst surface was evaluated by means of FTIR experiments, which allowed us to determine the probability of OH radical attack to the aromatic ring.
Cop-per catalyst by immobilizing Cu(II) ions on Chitosan and PVP
- U I Castro
- I Sanchez
- J Font
- A Fortuny
- F Stüber
- A Fabregat
- C Bengoa
U.I. Castro, I. Sanchez, J. Font, A. Fortuny, F. Stüber, A. Fabregat, C. Bengoa, Cop-per catalyst by immobilizing Cu(II) ions on Chitosan and PVP, 17th International Congress of Chemical and Process Engineering (CHISA 06), CD-ROM of Full Texts, 2006, pp. 1–15, ISBN: 8086059456.
Heterogeneous catalysis on Chitosan-based materials: a review
E. Guibal, Heterogeneous catalysis on Chitosan-based materials: a review, Prog.
Polym. Sci. 30 (2005) 71–109.
Thermal behaviour and electrical conductivity of poly(vinylpyridine)/copper complexes
- Rodrigues