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CuFeS2/activated carbon heterostructure as a microwave-responsive catalyst for reductive and oxidative degradation of ibuprofen, ketoprofen, and diclofenac
Filter is an important component in the air-conditioning system. The airborne microorganisms can be intercepted and further multiply on the filter, which might cause a secondary pollution. The present work proposed a SiC composite filter (SCF), namely combining the filter with the absorbing material SiC. The disinfection efficiency (η) and mechanism of the microwave radiation method (MRM) on E. coli and S. aureus attached to the SCF were experimentally explored. The impacts of the microwave power (P) and disinfection time (t) on η were investigated. The results show that the SCF can be heated well by the microwave, but the normal filter (NF) cannot. The MRM can effectively and rapidly disinfect bacteria on the SCF at a sufficiently high P and an appropriate t. Generally, η increases with P and t. Under a specific P, η can be only increased with t at a certain range and a peak η might be reached. When this peak is achieved, η will not be further increased with t. The disinfection by the MRM is attributed to the thermal and non-thermal effects. Specially, at P = 600 W and t = 10 min, the non-thermal effect contributes about 89.6% to the disinfection of the E. coli and about 43.1% to the S. aureus. A universal relationship between η and temperature is given for E. coli and S. aureus to predict η at various P and t. Finally, the effective temperatures required by the MRM to satisfactorily disinfect bacteria on the SCF are identified, i.e., about 41 °C for E. coli and 71 °C for S. aureus.
In this study nitrogen-doped carbon quantum dots/graphitic carbon nitride nanosheet (CNQD) composites with different contents of nitrogen-doped carbon quantum dots (NCQDs; 2, 4, 6, and 8 wt%) were synthesized. The morphological, physicochemical, and photoelectrochemical properties were investigated using complementary methods such as scanning electron microscopy (SEM), powder X-ray diffraction (pXRD), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), UV/Vis spectroscopy in diffuse reflectance (DRS), photoluminescence (PL), nitrogen physisorption (BET), photocurrent response, and electrochemical impedance spectroscopy (EIS). The photocatalytic activity of the synthesized materials was assessed during diclofenac (DCF) degradation in an aqueous solution under visible light irradiation. As a result, improved photocatalytic efficiency in DCF degradation was observed for all the CNQD composites compared with bulk graphitic carbon nitride (bCN) and nanosheet g-C3N4 (CNS). The fastest DCF degradation was observed for the 6 wt% NCQD on the surface of CNS (CNQD-6), which removed 62% of DCF in 3 h, with an associated k value of 5.41 × 10−3 min−1. The performance test results confirmed the contribution of NCQDs to enhancing photocatalytic activity, leading to an improvement factor of 1.24 over bCN. The morphology of the CNS and the synergistic interaction between NCQDs and CNS were essential elements for enhancing photocatalytic activity. The photoelectrochemical data and photoluminescence analyses showed the efficient migration of photoexcited electrons from NCQDs to the CNS. The reduced charge recombination rates in CNQD photocatalysts might be due to the synergistic interaction between NCQDs and CNS and the unique up-conversion photoluminescence properties of NCQDs. Further investigations revealed that the photogenerated superoxide radicals (•O2−) predominated in the degradation of DCF, and this photocatalyst had good reusability and toxicity reduction abilities. This work provides insight into the effects of NCQDs on the CNS surface to enhance its potential to remove emerging organic pollutants from water and wastewater.
The consumption of açaí fruit (Euterpe oleracea) has largely increased worldwide, resulting in a significant increase in the demand for its pulp. As a result, the small producing communities end up with large amounts of açaí endocarp residues, creating local environmental pollution problems. Therefore, chemical and physical routes were investigated for producing açaí endocarp adsorbents to propose a locally viable solution for this problem. The adsorption properties of the produced biochars were tested for clonazepam (CZM) removal, and the toxicity of the final solutions was evaluated. The results revealed that the chemical route generated biochar with about twice the surface area and pore volume (762 m² g⁻¹ and 0.098 cm³ g⁻¹) than the physical route (498 m² g⁻¹ and 0.048 cm³ g⁻¹). Furthermore, the Sips isotherm better described the CZM adsorption equilibrium for both biochars, with qs values of 26.94 and 61.86 mg g⁻¹ for the physical- and chemical-activated adsorbents. Moreover, recycling studies were performed, and the chemical-activated biochar was stable for up to three cycles, reaching removal rates superior to 80%. Besides, the final toxicity decreased after the adsorptive treatment. Therefore, chemical activation can be used as a simple and effective method for producing stable and compelling adsorbents as an elegant way of adding value to the residues from açaí production, helping solve local environmental problems.
Purpose of Review
In the context of COVID-19 sweeping the world, the development of microbial disinfection methods in gas, liquid, and solid media has received widespread attention from researchers. As a disinfection technology that can adapt to different environmental media, microwave-assisted disinfection has the advantages of strong permeability, no secondary pollution, etc. The purpose of this review is to put forward new development requirements for future microwave disinfection strategies by summarizing current microwave disinfection methods and effects. From the perspective of the interaction mechanism of microwave and microorganisms, this review provides a development direction for more accurate and microscopic disinfection mechanism research.
Recent Findings
Compared to other traditional environmental disinfection techniques, microwave-assisted disinfection means have the advantages of being more destructive, free of secondary contamination, and thorough. Currently, researchers generally agree that the efficiency of microwave disinfection is the result of a combination of thermal and non-thermal effects. However, the performance of microwave disinfection shows the differences in the face of different environmental media as well as different types of microorganisms.
Summary
This review highlights the inactivation mechanism of microwave-assisted disinfection techniques used in different scenarios. Suggestions for promoting the efficiency and overcoming the limitations of low energy utilization, complex reactor design, and inaccurate monitoring methods are proposed.
Pharmaceutical residues have been identified as a priority contaminant due to their toxicity to organisms and the ecosystem as representative refractory organic compounds in water. Therefore, using efficient treatment methods to remove them from wastewater has become a crucial topic of research. Advanced oxidation processes (AOPs) based on the sulfate radical have gained increased attention in recent years due to their superior performance and adaptability in the decomposition of refractory organic contaminants. In this work, scrap printed circuit boards (PCBs) were used to prepare a low-cost and efficient heterogeneous peroxydisulfate (PDS) catalytic activator via thermal treatment with an air combustion non-carbonized catalyst (NCC) and pyrolysis with a nitrogen carbonized catalyst (CC) for the removal of diclofenac (DCF) and ibuprofen (IBF) from water at circumneutral pH. The synthesized catalysts were characterized by several analytical techniques. The effects of various experimental parameters on the removal efficiency were examined. Under optimum conditions, the degradation efficiency reached 76% and 71% with NCC and 63% and 57.5% with CC within 60 min for DCF and IBP, respectively. The mineralization efficiency as measured by TOC removal reached up to 65% after 60 min treatment. The degradation kinetics for both catalysts followed the pseudo-first-order model. Results from quenching tests showed that the reactive oxidizing species (ROS), including 1O2 > SO4˙- > ˙OH, were generated mainly in the NCC/PDS and CC/PDS systems. Overall, the prepared catalysts were found to be effective and reusable for PDS activation for the removal of pharmaceutical pollutants from water. This study provided a promising, robust and efficient heterogeneous catalytic PDS activation based on the strategy of "waste-treats-waste" for the removal of pharmaceutical pollutants from water.
Hollow LaFeO3 (LFO) spheres was prepared for the first time by surfactant-assisted hydrothermal method. The sample was characterized in detail, suggesting the successful synthesis of LFO which was consisting of hollow core and porous shell. The large specific surface area, accessible pores, and low band gap energy suggests its high photocatalytic performance towards adsorption and photo-Fenton degradation of Ibuprofen under visible light irradiation. Ibuprofen (IBP), which has been widely used as one of anti-inflammatory drugs for treatment of several diseases was selected as a pharmaceutical model. It was found that the hollow LFO spheres induced a significant improvement in the visible-light-Fenton catalytic performance, as compared with pure LFO. The degradation rate using hollow LFO under optimal conditions (temperature = 25 °C, IBP concentration = 10 mg L−1, catalyst dosage = 1.0 g L−1, initial H2O2 concentration = 0.2 g L−1 and initial solution pH = 5) was 96.2% after 90-min exposure to the visible light. This was 27.6% greater than that of pure LFO. Particularly, the pseudo-first-order reaction rate constant for hollow LFO was 0.0419 min−1, which was approximately 3 times higher than that for pure LFO (0.0159 min−1). The newly developed photocatalyst, hollow LFO, exhibited a good stability for recycle and reuse, which is crucial for its potential use in industrial application.
Atrazine and diuron are two pesticide compounds with very low surface interaction capacity, whose adsorption efficiency remains a challenge in environmental remediation applications. In this work, statistical physics (sta-phy) modelling and density functional theory (DFT) calculations have explored several still unveiled mechanisms involved. A model activated carbon (AC) sample was produced with Hovenia dulcis fruit residues, a local invasive tree species. The adsorption process was spontaneous and endothermic, and the adsorption capacities (Qm) increased as the temperature increased. The number of adsorbate molecules per site (n) decreased as the density of the receptor site (Nm) increased, revealing that the temperature influences the geometry of the molecules during the surface interaction. According to the electrostatic mapping provided by the DFT calculations, it was possible to infer that the obtained Qm values for atrazine, between 42.54 to 73.20 mg g⁻¹, can be a response caused by its own self-repulsion. For diuron, due to its increased neutrality, the potential balance of the electrostatic charges between adsorbate-adsorbent tends to be more effective, resulting in higher Qm values, ranging from 97.91 to 119.7 mg g⁻¹. Therefore, the combination of sta-phy modelling with quantum mechanics calculations is a powerful tool for mechanism interpretation, capable of providing complementary insights into the adsorption process from both adsorbent and adsorbate perspectives.
In this study, graphitic carbon nitride was used as a support for CuO/TiO2 nanocomposite and was used for the photodegradation of ketoprofen (KP) in various water qualities. The formation of the CuO/TiO2@GCN nanocomposites was proven using different characterization methods. PXRD and Raman analyses of TiO2 and CuO/TiO2 showed that the composite peaks shifted relative to those of TiO2, showing interactions between the two materials. The morphology of CuO/TiO2@GCN consisted of CuO/TiO2 nanoparticles on the surface of the mat‐like GCN. CuO/TiO2@GCN had a narrower band gap and its photoluminescence emission peak was lower than of TiO2. CuO/TiO2@GCN was found to be the best performing photocatalyst that could be used over 3 cycles without major loss in activity. Also, the material was shown to be able to photocatalyze KP in groundwater. The by‐products of the photodegradation were identified by LC–MS. The electrical energy consumed for this process was 2.66E5 kWh/m³. The superior photocatalytic efficiency of CuO/TiO2@GCN relative to TiO2 was attributed to the increased charged separation and that light of higher wavelength was harvested.
Pharmaceuticals are an important class of micropollutants within the freshwater environment. There is sufficient evidence of their impacts on exposed biota to warrant further research to better assess their risk. We reviewed ecotoxicological freshwater studies conducted from 2010-2020 on carbamazepine, diclofenac, and ibuprofen, three high-use pharmaceuticals frequently detected globally in surface waters. One hundred and thirteen studies encompassing short-term (mean exposure duration 6.4 days) and long-term exposures (mean 37.8 days) were reviewed. Study designs were examined and critiqued using a qualitative analysis, and a quantitative analysis compared toxicities (lowest observed effect concentration, LOEC) between the three pharmaceuticals in both short- and long-term tests. Short-term tests were predominant (60% of studies), as reported in past related reviews. Examination of experimental designs highlighted important limitations. Most studies had low replication (n=3 per treatment) and provided no effect sizes for their findings, and 55% of studies did not supply measurements of actual exposure concentrations. Thirty-five percent of studies detected clear effects (mostly negative) at environmentally relevant concentrations. In short-term studies, biomarkers were the most sensitive endpoints; the same applied to community-level endpoints in long-term studies. The LOECs of all three pharmaceuticals (0.05-10 μg L⁻¹) were similar in both short- and long-term studies. Future research should prioritise long-term, environmentally relevant exposures, using a combination of biomarker and community-level endpoints. Due to the acute toxicity of pharmaceuticals, future studies should investigate how these contaminants may modify communities and ecosystems, rather than single-species approaches. Finally, a comprehensive meta-analysis would be pertinent when enough long-term, environmentally relevant studies with rigorous designs and effect size information have accumulated.
Ag–Ag2O nanoparticles were synthesized using Osmium sanctum plant extract. The nanoparticles were sensitized with polythiophene (PTh) and were characterized via scanning electron microscopy with energy dispersive X-ray and elemental mapping, transmission electron microscopy, X-ray diffraction (XRD), Fourier-transform infrared, and UV–vis spectroscopy analyses. The elemental mapping results revealed that the samples were composed of C, S, Ag, and O elements which were uniformly distributed in the nanohybrid. XRD analysis confirmed the crystalline nature of Ag–Ag2O nanoparticles, and the average particle size was found to be ranging between 36 and 40 nm. The optical band gap of Ag–Ag2O, PTh, and Ag–Ag2O/PTh was found to be 2.49, 1.1, 1.5, and 0.68 eV. The catalytic activity of Ag–Ag2O, PTh, and Ag–Ag2O/PTh was investigated by degrading paracetamol drug under microwave irradiation. Around 80% of degradation was achieved during 20 min irradiation. All degradation kinetics were fitted to the pseudo-first-order model. A probable degradation pathway for paracetamol degradation was proposed based on liquid chromatography mass spectrometry analysis of degraded fragments.
In this contribution to the special software-centered issue, the ORCA program package is described. We start with a short historical perspective of how the project began and go on to discuss its current feature set. ORCA has grown into a rather comprehensive general-purpose package for theoretical research in all areas of chemistry and many neighboring disciplines such as materials sciences and biochemistry. ORCA features density functional theory, a range of wavefunction based correlation methods, semi-empirical methods, and even force-field methods. A range of solvation and embedding models is featured as well as a complete intrinsic to ORCA quantum mechanics/molecular mechanics engine. A specialty of ORCA always has been a focus on transition metals and spectroscopy as well as a focus on applicability of the implemented methods to “real-life” chemical applications involving systems with a few hundred atoms. In addition to being efficient, user friendly, and, to the largest extent possible, platform independent, ORCA features a number of methods that are either unique to ORCA or have been first implemented in the course of the ORCA development. Next to a range of spectroscopic and magnetic properties, the linear- or low-order single- and multi-reference local correlation methods based on pair natural orbitals (domain based local pair natural orbital methods) should be mentioned here. Consequently, ORCA is a widely used program in various areas of chemistry and spectroscopy with a current user base of over 22 000 registered users in academic research and in industry.
The adsorptive properties of the pesticides 2,4-D, mecoprop, and dicamba on a pinus-based biochar were scrutinized from conventional and statistical physics approaches.
Firstly, the pinus-based biochar was prepared from Pinus elliottii and extensively
characterized. Then, the conventional adsorption studies were made using kinetic
equilibrium and thermodynamics. Subsequently, the statistical physics model of Hill
was used to interpret the data. Finally, the pinus-biochar was used to uptake the
pesticides from a real river water sample. The results revealed that the pinus-biochar is a rich-carbon material (carbon content higher than 99%) with high thermal stability,
interesting textural features, and proper characteristics to effectively uptake small and
polar organic molecules. At a pH of 7.0 and using 1.0 g L-1, the biochar reduced the
concentration of pesticide solutions from 50 μg L-1 to less than 4.0 μg L-1 in 2 h of
operation. The conventional evaluation revealed that the General order model properly
represented the kinetic profile of the pesticides adsorption, while the Langmuir model
better represented the isotherms. The maximum uptakes of 2,4-D, mecoprop, and
dicamba at 298 K were 100.9 μg g-1, 122.5 μg g-1, and 95.9 μg g-1. The statistical
physics model of Hill could explain the adsorption of all pesticides, and new insights
were proposed for the adsorption mechanism. The pinus-based biochar was also
efficient in decontaminating river waters containing the pesticides, using 5.0 g L-1.
Finally, it can be concluded that pinus-based biochar is a rich-carbon material able to
efficiently uptake the pesticides 2,4-D, mecoprop, and dicamba from synthetic and
natural waters. The efficiency, even in a concentration range of μg L-1, was attributed
to the intrinsic features of the new material
Non-steroidal anti-inflammatory drugs (NSAIDs) are among the most frequently used pharmaceuticals for human therapy, pet therapeutics, and veterinary feeds, enabling them to enter into water sources such as wastewater, soil and sediment, and seawater. The control of NSAIDs has led to the advent of the novel materials for treatment techniques. Herein, we review the occurrence, impact and toxicity of NSAIDs against aquatic microorganisms, plants and humans. Typical NSAIDs, e.g., ibuprofen, ketoprofen, diclofenac, naproxen and aspirin were detected at high concentrations in wastewater up to 2,747,000 ng L-1. NSAIDs in water could cause genotoxicity, endocrine disruption, locomotive disorders, body deformations, organs damage, and photosynthetic corruption. Considering treatment methods, among adsorbents for removal of NSAIDs from water, metal-organic frameworks (10.7-638 mg g-1) and advanced porous carbons (7.4-400 mg g-1) were the most robust. Therefore, these carbon-based adsorbents showed promise in efficiency for the treatment of NSAIDs.
Ibuprofen and acetaminophen as two anti-fever agents have been widely used in human. Due to lack of full understanding, this work firstly summarized their occurrence and fate in municipal wastewater treatment plants (WWTPs) across 30 countries. The respective influent concentrations of ibuprofen and acetaminophen were not detected (ND)-39,830,000 and ND-66440000 ng/L, while their corresponding respective effluent concentrations were ND-58710 and ND-90500 ng/L. The removal efficiencies of ibuprofen and acetaminophen in municipal WWTPs were 6.5-100 % and 14.3-100 % with respective average removal efficiencies of 87.6 % and 94.7 %. There have been many batch studies on ibuprofen biodegradation with kbio values available, while such investigation for acetaminophen was very limited. The theoretically calculated removal efficiency of ibuprofen with kbio agreed well with that of the observed average removal efficiency of on-site investigations on full-scale WWTP, which was quite different from natural estrogens and some other emerging contaminants. One possible reason is that conjugated ibuprofen could be easily cleaved and the cleavage step gives little effect on the biodegradation of ibuprofen. Due to extremely high concentrations of ibuprofen and acetaminophen in influent of municipal WWTP, their concentration levels in effluent likely high enough to pose adverse effects on some aquatic organisms. To protect water environment, advanced treatment is necessary to further remove residue ibuprofen and acetaminophen in the effluent. To the best of our knowledge, this is the systematical summarization on the occurrence and fate of ibuprofen and acetaminophen in municipal WWTP as well as their potential effect on aquatic organisms, which addressed known knowledge and unknowns to be further investigated.
The Co2SnO4/Co3O4/SnO2 material was successfully prepared via co-precipitation method and used as a catalyst to activate peroxymonosulfate (PMS) for the degradation of diclofenac (DCF). Several parameters such as catalyst amount, PMS concentration, DCF initial concentration and the effect of inorganic anions were evaluated. The results of the efficiency of Co2SnO4/Co3O4/SnO2-PMS system for DCF elimination, the degradation pathways and the identification of by-products were presented. About 98% of DCF (30 mg/L) was decomposed by PMS (0.25 mM) in the presence of Co2SnO4/Co3O4/SnO2 (150 mg/L) within 2 min of reaction. The radical scavenging experimental results revealed that singlet oxygen 1O2 was the only reactive specie responsible for the catalytic degradation of DCF. The removal rate after three runs was unchanged, indicating that Co2SnO4/Co3O4/SnO2 catalyst exhibited high catalytic performance and excellent stability.
Microwave (MW)-assisted catalytic degradation of organic pollutants draws increasing attention owing to its high efficiency in wastewater treatment. This work developed Cu-loaded biochar (CuBC) catalysts for time-efficient mineralization of refractory and high-concentration oxytetracycline (OTC). With only 1 min at 80 °C, Na2S2O8 achieved 100% total organic carbon (TOC) removal over the Cu5BC, while NaClO mineralized 73.3% TOC over the metal-free BC, in contrast to a relatively low mineralization efficiency (< 35%) achieved by H2O2. The high efficiency in MW-assisted oxidation systems could be ascribed to reactive oxidizing species (•SO4- or •ClO), which otherwise were barely detectable in a conventional heating system. The interactions between CuBC and MW were revealed by correlating the physiochemical characteristics to the MW absorption ability. The proposed catalytic systems can contribute to the development of a high-throughput and low-carbon wastewater treatment technology.
Non-steroidal anti-inflammatory drugs (NSAIDs) are the most widely used analgesics to treat inflammatory pain. Despite their efficacy, recent studies show that NSAID use in early acute pain can prolong pain and inflammation and delay their resolution. We suggest using analgesics without inflammation-related properties in early acute pain instead of NSAIDs.
This study explores a simple and efficient, physically modified ball-milled activated carbon (ACBM) preparation from granular activated carbon (GAC), which can be demonstrated for groundwater application. The colloidal stability of the ACBM plays a vital role in the activation of peroxymonosulfate (PMS) and the degradation of pollutants. Adsorption kinetics and isotherm studies explain that the ACBM has more active sites and maximum adsorption capacity (qmax = 509 mg g-1) on the surface of the materials than GAC. The 92% of ibuprofen degradation was achieved at 240 min along with 0.1 g L-1 of ACBM, 5 mM of PMS, and 6.3 of initial solution pH. A chemical scavenger and electron spin resonance spectra also confirmed the formation of reactive oxygen species such as radicals (O2•-, HO•, SO4•-) and non-radical (1O2) in the ACBM/PMS system. Three major degradation pathways, hydroxylation, demethylation, and decarboxylation involved in ibuprofen degradation. Nearly 13 degradation by-products were detected during the ACBM/PMS oxidation of ibuprofen. The toxicity analysis of oxidation by-products of ibuprofen was also discussed by computational simulation employing the ecological structure-activity relationships software. The ACBM/PMS system was successfully applied to the natural groundwater system for ibuprofen degradation. Hence, the ACBM/PMS system is an excellent catalyst for real groundwater applications.
Ibuprofen (IBP) is a carcinogenic non-steroidal anti-inflammatory drug (NSAID). It is of certain hazard to aquatic animals and may cause potential harm to human health. As traditional methods cannot effectively remove such a pollutant, many advanced oxidation processes (AOPs) have been developed for its degradation. The electro-Fenton process has the advantages of strong oxidative ability, a synergistic effect of various degradation processes, and a wide application range. This study developed a high-performance gas diffusion electrode (GDE) for electrochemical hydrogen peroxide (H2O2) production. The optimum system performance was found at the current density of 10 mA cm⁻², pH of 7.0, and air flow rate at 0.6 L min⁻¹, where the accumulation of H2O2 could reach as high as 769.82 mg L⁻¹. The computational fluid dynamics (CFD) simulation results revealed a fast mass-transfer property in this electro-Fenton system with U-tube GDEs, which resulted in a deep-level degradation (∼100%) of the pollutant (IBP) and a low-concentration degradation of 10 mg L⁻¹ within a 120-min reaction period. The high-performance liquid chromatography-mass spectrometry (LC-MS) studies demonstrated that the hydroxyl radicals were the primary active species in the electro-Fenton system and that the degradation intermediates of IBP were mainly 1-(4-isobutylphenyl) ethanol and 2-hydroxy-2-(4-isobutyl phenyl) propanoic acid through four probable electro-Fenton degradation pathways. This report provides a facile and efficient way to construct a high-performance electro-Fenton reactor, which could be effectively used in advanced oxidation processes (AOPs) to remove emerging contaminants in wastewater and natural water.
Inexpensive iron-based catalysts are the most promising catalysts for microwave pyrolysis of waste plastics, especially a large number of disposable medical masks (DMMs) with biological hazards produced by spread of COVID-19. However, most synthesized iron-based catalysts have very low microwave heating efficiency due to the enrichment state of iron. Here, we prepared FeAlOx catalysts using the microwave heating method and found that the microwave heating efficiency of amorphous iron and hematite is very low, indeed, these materials can hardly initiate pyrolysis at room temperature, which limits the application of iron-based catalysts in microwave pyrolysis. By contrast, a mixture of DMMs and low-valent iron oxides produced by hydrogen reduction at 500 °C can be heated by microwaves to temperatures above 900 °C under the same conditions. When the hydrogen reduction temperature was incerased to 800 °C, the content of metallic iron in the catalyst gradually increased from 0.34 to 21.43%, which enhanced the microwave response ability of the catalyst, and decreased the gas content in the pyrolysis product from 78.91 to 70.93 wt%; corresponding hydrogen yield also decreased from 29.03 to 25.02 mmolH2·g⁻¹DMMs. Moreover, the morphology of the deposited solid carbon gradually changed from multi-walled CNTs to bamboo-like CNTs. This study clarifies the pyrolysis mechanism of microwave-assisted iron catalysts and lays a theoretical foundation for their application in microwave pyrolysis.
Catalytic performances and leaching behavior of 9 natural iron minerals as heterogeneous electro-Fenton catalysts for the treatment of imidacloprid wastewater were studied. The results showed that magnesioferrite exhibited the best catalytic ability among these minerals with UV absorbance at 270 nm (UV270) removal of 49.11% and COD removal of 83.59% within 4 h using graphite cathode and Ti/(RuO2)0.88-(IrO2)0.12 anode at initial pH 3 with a catalyst dose of 5 g/L, a current density of 40 mA/cm² and an electrode spacing of 2 cm. The instantaneous current efficiency (ICE) at 4 h and energy consumption (EC) reached 2.30% and 2.20 kWh/gCOD respectively. It was found that the components contained in natural iron minerals, such as Al, alkali metal (K) and alkaline earth metals (Mg, Ca, Ba), would dissolve into the electrolyte solution, raising the final pH to 6.5-8.5 and ultimately reducing the reaction efficiency. Except magnetite and magnesioferrite, other minerals, such as ilmenite and V-Ti magnetite, were likely to cause secondary pollution. The subsequent adjustment to alkaline state for chemical precipitation of leached Mn was needed. Pyrite showed relatively high leachability in hazardous elements (especially Pb), which should be carefully evaluated before its actual application in electro-Fenton process.
Heterogeneous Fenton-like systems were exploited for the degradation of Reactive Red X–3B (RR X–3B) using iron-carbon composite, sponge iron, chalcopyrite and pyrite as catalysts. The effect of operational variables on the catalytic activity and metal leaching behavior of catalysts was evaluated and the catalytic mechanism was discussed. The experimental results showed that under the optimum conditions, chemical oxygen demand (COD) removals by Fenton-like systems could reach 89.91%, 86.84%, 80.11% and 60.02% with iron-carbon composite, sponge iron, chalcopyrite and pyrite, respectively. Micro-electrolysis of iron-carbon composite and sponge iron resulted in higher COD removal at acid pH range. Electron Paramagnetic Resonance (EPR) analysis and quenching tests showed that •OH was the main reactive oxygen species responsible for the degradation of RR X–3B. A large amount of Fe²⁺ leached from iron-carbon composite and sponge iron, which served as a homogeneous Fenton catalyst during the degradation of RR X–3B. In contrast, much lower amount of Fe²⁺ was leached from chalcopyrite and pyrite, and surface catalysis of the minerals played more important role in the generation of •OH. Surface characterization and density functional theory (DFT) calculation results illustrated that ≡Fe(II) was the primary surface catalytic site during the reaction. The reduction of ≡Fe(III) and ≡Cu(II) can be facilitated by sulfides on the mineral surface. The Fenton-like systems catalyzed by iron-based materials exhibited higher H2O2 utilization and COD removal than classical Fenton system. With the lower metal leaching concentration and stable surface property, chalcopyrite and pyrite may be more practical applicable from a long-term catalytic activity point of view.
In this study, a novel heterostructure i.e., ZnFe2O4 nanosphere-decorated α-NiMoO4 nanorods on coffee biochar (BC), was fabricated via a hydrothermal method. The magnetically separable α-NiMoO4/ZnFe2O4/BC composite demonstrated 98.65% degradation of ketoprofen (KP) in 180 min under visible light irradiation. Analysis of cyclic tests, total organic carbon, and fluorescence excitation-emission matrices revealed the excellent stability and mineralization abilities of photocatalysts, respectively. The effects of influencing factors (pH, anions, and different concentrations of KP/photocatalysts) on degradation of KP by the photocatalysts were suggested as promising prospects in water/wastewater treatment. BC acts as a conductor and an electron mediator in heterostructure. The enhanced photocatalytic performance of the heterostructure was ascribed to increased visible light absorption and efficient photoinduced charge carrier separation. Furthermore, photoluminescence spectral and electrochemical investigations indicated the efficient separation of photoinduced charge carriers. Electron spin resonance spectroscopy and scavenger experiments demonstrated that •OH played a major role in KP degradation. According to the liquid chromatography-tandem mass spectroscopy analysis, KP was degraded via three degradation pathways by 24 degraded intermediates. This study provides a new perspective on fabrication of efficient heterojunction photocatalysts exhibiting good recovery and insight on mechanisms and pathways underlying KP degradation.
Irresponsible discharge of hexavalent chromium (Cr(VI)) containing industrial wastewater is a serious environmental issue, and a great risk to human health. In this work, a novel class of microwave (MW) responsive core/shell-structured ZnFe2O4@ZnIn2S4 ([email protected]) catalysts were prepared for aqueous Cr(VI) reduction. These catalysts exhibited “unexpectedly” high MW catalytic activity. The one with the ZFO:ZIS molar ratio = 1:3 led to 100% Cr(VI) reduction within 15 min in a solution with the Cr(VI) concentration as high as 100 mg/L, which is superior to in the cases of using other photocatalysts previously reported. More significantly, the [email protected] catalysts exhibited an excellent Cr(VI) reduction ability even at a pH value as high as 6, close to that of industrial wastewater, demonstrating additionally their great feasibility. The excellent MW catalytic activity of the composite catalysts can be attributed to the MW induced “hot spots” effect. The MW responsive [email protected] core/shell-structured catalysts developed in this work can be a promising candidate for high efficiency catalytic reduction of Cr(VI) in wastewater.
UV/chlorine is an effective process for pollutant degradation in water treatment. It was reported that the concentrations of hydroxyl radical (HO•) and chlorine radical (Cl•) could rise significantly by adding TiO2 in UV/chlorine. In this study, the degradation of ibuprofen (IBP), a frequently detected pollutant in aquatic environments, was investigated in the UV/chlorine/TiO2 process. The pseudo-first-order kinetics rate constant for IBP degradation by UV/chlorine/TiO2 was nearly 3-fold higher than the sum of the rate constant by UV/chlorine and UV/TiO2. HO• and Cl• were the primary radicals and chlorine oxide radical (ClO•) also participated in the degradation of IBP in UV/chlorine/TiO2. The kinetic model was used to assess the effect of different influencing factors (chlorine, chloride, and bicarbonate dosage, and pH) on degradation kinetics and radical roles. Meanwhile, the probe experiment with nitrobenzene was performed to evaluate the reliability of the modeling results. The electrical energy per order (EE/O) was determined under varied chlorine and TiO2 dosage, and the lowest EE/O of UV/chlorine/TiO2 was obtained to be about 40% and 50% of that of UV/chlorine and UV/TiO2, respectively. Toxic products could be generated during IBP degradation in all three processes, while less reaction time was needed for the removal of solution toxicity by UV/chlorine/TiO2. When achieving IBP degradation by one order of magnitude, less disinfection byproducts were generated in UV/chlorine/TiO2 compared with UV/chlorine both with and without 24 h post-chlorination. Furthermore, a chlorine-substituted product of IBP was detected, and both HO• and Cl• participate in the formation of this product based on density functional theory (DFT) study.
A novel catalyst was synthesized employing coal and volcanic rock waste (VRW) residues enriched with iron nanoparticles, and its efficiency was investigated upon the degradation of (2,4-dichlorophenoxy) acetic acid (2,4-D) and atrazine (ATZ) pesticides. The composite was synthesized by a facile and effective chemical precipitation technique and extensively characterized by XRD, FTIR, XRF, ICP-OES, ICP-MS, and SEM-EDS. The effects of pH, catalyst dosage, and initial pollutant concentration were investigated in single and binary systems irradiated with microwave (MW) under atmospheric pressure. The optimal reaction conditions were obtained at pH 3 and 5 for 2,4-D and ATZ in single systems and pH 3 in binary systems, respectively, with 20 mg L À1 of initial pollutant concentration and 0.1 g L À1 of CVRWMag (coal, VRW, and nano-Fe 3 O 4) catalyst. The kinetic data fitted better to the pseudo-first-order model (R 2 > 0.965). In addition, the phytotoxicity was investigated with Lactuca sativa seeds, and the root elongation and the seed germination rate were enhanced as the MW irradiation time increased. The complete degradation of both compounds was reached within 30 min, with outstanding mineralization efficiency. The degradation efficiency was attributed to hydroxyl radical (Å OH) formation and electrostatic surface interaction, enhanced by hot spot formation. Therefore, the CVRWMag is a promising MW absorbing catalyst for the removal and degradation of pesticides without the need for H 2 O 2 or any radical enhancing agent addition.
Tetracycline (TC) is a group of antibiotics that includes chlorotetracycline (CTC), doxycycline (DC), and oxytetracycline (OTC). TC is the secondary most used antibiotic worldwide to treat diseases caused by bacteria. It is noteworthy that in the human and animal metabolic processes, about 60% and 17-80% of the TC dosage administered are not adsorbed and are excreted in urine and feces. Its widespread use in human and veterinary treatments is leading to the situation of environmental contamination, both in soil, surface, and underground waters. The first two sections of this review paper present an overview of the problem of water and soil contamination, and the situation on the worldwide use of TC. The third section focuses on analytical methods for detecting TC in the most diverse types of samples. Furthermore, in the following chapters it is discussed TC toxicity and the application of chemical, physical, and biological processes in removing TC in wastewater. At last, hybrid and emerging technologies for TC degradation as an environmental contaminant are presented, and some future challenges that must be faced by this research field are summarized. A critical analysis from the authors' perspective is presented at the end of each session.
This work investigated the relation between direct band-gap conversion and excitation wavelength towards catalysis efficiency in red, green, and blue (RGB) light-emitting diode (LED) reactors. An integrating sphere and spectroradiometer system obtained the emission wavelengths of the operating modes spectra of the RGB-LED reactors. The effects of pH, catalyst, and H2O2 dosage were investigated, and the optimal photocatalysis conditions were found to be at pH 3, catalyst loading of 0.25 g L⁻¹, 0.25 mmol L⁻¹ of H2O2(aq) (30% v/v) for an initial model pollutant concentration of 75 mg L⁻¹ and reaction time of 60 min. Under the higher intensity red mode (R1), the highest color removal rate was reached (88.1%), while in the conventional white light mode (WL), the decolorization efficiency remained 64.3%. Furthermore, the R1 mode showed a superior TOC removal than the WL mode, reaching the final removal efficiencies of 91.86% and 61.06%, respectively. Contrary to what has been reported, as the dominant wavelength of the irradiation source decreased, the efficiency also tended to decrease. The electron-hole recombination increased as the irradiation mode decreased, and a work function (φ) representing this phenomenon was obtained by the deduction of the relation between energy (E) and frequency (f) of the photons involved. Therefore, the insights presented in this work are valuable tools in increasing LED photocatalysis efficiency.
In recent years, Non-Steroidal Anti-Inflammatory Drugs (NSAIDs) have surfaced as a novel class of pollutants due to their incomplete degradation in wastewater treatment plants and their inherent ability to promote physiological predicaments in humans even at low doses. The occurrence of the most common NSAIDs (diclofenac, ibuprofen, naproxen, and ketoprofen) in river water, groundwater, finished water samples, WWTPs, and hospital wastewater effluents along with their toxicity effects were reviewed. The typical concentrations of NSAIDs in natural waters were mostly below 1 μg/L, the rivers receiving untreated wastewater discharge have often showed higher concentrations, highlighting the importance of effective wastewater treatment. The critical analysis of potential, pathways and mechanisms of microbial degradation of NSAIDs were also done. Although studies on algal and fungal strains were limited, several bacterial strains were known to degrade NSAIDs. This microbial ability is attributed to hydroxylation by cytochrome P450 because of the decrease in drug concentrations in fungal cultures of Phanerochaete sordida YK-624 on incubation with 1-aminobenzotriazole. Moreover, processes like decarboxylation, dehydrogenation, dechlorination, subsequent oxidation, demethylation, etc. also constitute the degradation pathways. A wide array of enzymes like dehydrogenase, oxidoreductase, dioxygenase, monooxygenase, decarboxylase, and many more are upregulated during the degradation process, which indicates the possibility of their involvement in microbial degradation. Specific hindrances in upscaling the process along with analytical research needs were also identified, and novel investigative approaches for future monitoring studies are proposed.
A novel green composite catalyst was prepared by doping CuFe2O4 nanoparticles in the malt bagasse biochar. Composites with different ratios of malt biochar and CuFe2O4 were produced and characterized by XRD, FE-SEM, EDS, HR-TEM, UV-Vis, and Zeta potential. The results revealed that CuFe2O4 was successfully supported on the malt biochar surface. The prepared composites showed the band gap energies were narrower than of CuFe2O4, increasing the photocatalytic activity. At 60 minutes of heterogeneous photo-Fenton, tests under visible light indicated CuFe2O4 removed 39% of the rhodamine B color, while composites CFO1B3, CFO1B1, and CFO3B1 removed 88%, 81%, and 44% of the dye, respectively. The recycling of the CFO1B3 composite indicated that it can be used in eight cycles without major losses in efficiency. In sunlight, the CFO1B3 composite achieved efficiencies of 100% for 10 mg L⁻¹ and 50 mg L⁻¹ of rhodamine B at 10 and 20 minutes of reaction, respectively. In the proposed mechanism, it was verified that the radical •OH, O2•− and h⁺ were the predominant reactive species involved in the degradation to intermediates of low m/z. Results showed that the novel composite formed is a promising photocatalyst for removing organic pollutants in water.
In this study, the Z-scheme heterojunction photocatalysts Ag/NH2-MIL-125(Ti)/CdS (AMC-5, AMC-10 and AMC-20) were first successfully obtained by stepwise deposition of Ag and CdS. The morphology, crystallinity and photochemical properties of the materials were investigated. The N2 adsorption-desorption isotherm showed that AMC-10 had a large specific surface area (363.41 m²/g). Cyclic tests proved that the heterojunction exhibited good stability. In comparison, AMC-10 exhibited a significantly higher photocatalytic activity. Results suggested that 94.2% ketoprofen (10 mg/L) can be photocatalytically degraded to intermediates and small molecules after 180 min of simulated sunlight illumination. AMC-10 had a large degradation rate constant 0.0168 min⁻¹, which is 3.15 and 2.50 times higher than that of CdS and NH2-MIL-125(Ti), respectively. The total organic carbon removal percentage of ketoprofen was 57.5%. Free radical trapping experiments indicated that ·O2⁻ and h⁺ were the main active species, which can also be verified by the detection of electron paramagnetic resonance. Possible degradation pathways and reaction mechanisms were proposed by band potential calculations and liquid chromatography-mass spectrometry. The results of Vibrio qinghaiensis sp.-Q67 culture demonstrated that the biotoxicity of ketoprofen increased first and then decreased with time. It can be concluded that the Z-scheme heterojunction of Ag/NH2-MIL-125(Ti)/CdS was beneficial for the separation of photo-generated electrons and holes and the noble metal Ag nanoparticles play the important role in the photocatalytic degradation with the surface plasmonic resonance effect and Schottky junction.
Real hospital wastewater was effectively treated by a promising technology based on degradation reaction catalyzed by Fe⁰ under microwave irradiation in this work. Fe⁰ powders were synthesized and characterized by different techniques, resulting in a single-phase sample with spherical particles. Optimum experimental conditions were determined by a central composite rotatable design combined with a response surface methodology, resulting in 96.8% of chemical oxygen demand reduction and 100% organic carbon removal, after applying MW power of 780 W and Fe⁰ dosage of 0.36 g L⁻¹ for 60 min. Amongst the several organic compounds identified in the wastewater sample, diclofenac and ibuprofen were present in higher concentrations; therefore, they were set as target pollutants. Both compounds were completely degraded in 35 min of reaction time. Their plausible degradation pathways were investigated and proposed. Overall, the method developed in this work effectively removed high concentrations of pharmaceuticals in hospital wastewater.
The present work describes the electrochemical energy storage performance of CuFeS2 (Chalcopyrite), which is well known for its high electrical conductivity, natural abundance, and low cost. The laboratory synthesis method for CuFeS2 nanoflakes by facile one step solvothermal method is successfully accomplished. The as-synthesized CuFeS2 nanoflakes are subjected to both Physical and chemical characterization, as well as electrochemical characterization. CuFeS2 sample has been coated over carbon cloth substrate for the fabrication of flexible electrode for supercapacitor. The Cu¹⁺ and Fe³⁺ ions offer a synergistic contribution in the redox mechanism and substantiate an eminent electrochemical performance for supercapacitor. Galvanometric Charge Discharge (GCD) profile of CuFeS2 electrode in three electrode system manifests a high specific capacitance of 219 F g⁻¹ at 1 A g⁻¹ in an aqueous medium of 2 M KOH electrolyte with the potential range of -0.5 to 0.5 V. Further in two electrode system, the symmetric supercapacitor based on CuFeS2 electrode exhibits a high specific capacitance of 120 F g⁻¹ at a current density of 1 A g⁻¹ in aqueous 2 M KOH electrolyte. The symmetric supercapacitor based on CuFeS2 electrode delivers a maximum specific energy of 16 Wh Kg⁻¹ at a specific power of 1146 W kg⁻¹with a capacitive retention of 94% over 6000 cycles. These factors inclusively promote CuFeS2 as a promising electrode material for supercapacitor application.
The presence of pharmaceuticals in the aquatic environment, both in marine and freshwater reservoirs, is a major concern of global environmental protection. Among the drugs that are most commonly used, NSAIDs tend to dominate. Currently, being aware of the problem caused by drug contamination, it is extremely important to evaluate the scale and the full spectrum of its consequences, from short-term to long-term effects. The influence on non-target aquatic animals can take place at many levels, and the effects can be seen both in behaviour and physiology, but also in genetic alterations or reproduction disorders, affecting the development of entire populations. This review summarises all the advances made to estimate the impact of NSAIDs on aquatic animals. Multicellular animals from all trophic levels, inhabiting both inland waters, seas and oceans, have been considered. Particular attention has been paid to chronic studies, conducted at low, environmentally-relevant concentrations, to estimate the real effects of the present pollution. The number of such studies has indeed increased in recent years, allowing for a better insight into the possible consequences of pharmaceutical pollution. It should be stressed, however, that our knowledge is still limited to a few model species, while there are many groups of organisms completely unexplored regarding the effects of drugs. Therefore, the main aim of this paper was to summarise the current state of knowledge on the toxicity of NSAIDs in aquatic animals, also identifying important gaps and major issues requiring further analysis.
The preparation of covalently linked manganese(III) meso-tetrakis(2,6-dichlorophenyl)porphyrin acetate to aminopropyl functionalized silica gel and its full characterization by standard spectroscopic methods including Fourier transform infrared spectroscopy (FTIR), thermogravimetry (TG) and scanning electronic microscopy (SEM) is described. The supported metalloporphyrin was evaluated as catalyst in the degradation of trimethoprim (TMP), using hydrogen peroxide as green oxidant. Catalyst was reused for five consecutive cycles without significant loss of activity or catalyst degradation/leaching. Degradation products were identified by UHPLC-MS, allowing to propose a plausible degradation pathway. Furthermore, ecotoxicity (EC50 and EC20) of TMP-based solutions (before and after degradation) were evaluated towards the bacterium V. fischeri, the microalgae R. subcapitata and the invertebrate B. calyciflorus.
A magnetic photocatalyst Fe3O4@MIL-53(Fe) was successfully obtained from the calcination treatment of pristine MIL-53(Fe) to degrade ibuprofen (IBP) under visible light. The results suggested that Fe3O4 and MIL-53(Fe) co-existed after the calcination of MIL-53(Fe) at 400 ℃ (CM53-400) and pearl-like Fe3O4 nanoparticle intimately combined with MIL-53(Fe) in CM53-400. Fe3O4@MIL-53(Fe) composites exhibited superior photocatalytic performance due to the unique structure and electron transfer between Fe3O4 and MIL-53(Fe). CM53-400 processed the best catalytic ability for IBP degradation, achieving 99% removal of IBP in the presence of H2O2 within 60 min. The improved photocatalytic activity of CM53-400 may originate from the enhanced photoexcited electron-hole pairs separation. The active species, h⁺, •OH, e- and •O2⁻, played important roles in the photo-degradation processes. In addition, due to the stable activity of CM53-400 toward IBP decomposition and the strong magnetism of CM53-400 composite, CM53-400 photocatalysts bring new insights into the practical application for removing the organic contaminants from water.
The disposal of wastewater containing large amounts of dyes is a public health and environmental problem, due to its toxicity into the aquatic biota, the reduction in sunlight penetration, which consequently interference in photosynthetic activity. In the present study a new composite, based on the heterojunction of reduced graphene oxide (rGO) and chalcopyrite (CuFeS2), was developed to treat a real textile wastewater (RW). The efficiency of the composite assisted by microwave irradiation was evaluated to catalyze the decolorization and degradation of RW containing a high concentration of the azo Direct Black 22 (DB22). A small amount (0.5 w/w%) of rGO on CuFeS2 was enough to uplift the efficiency of decolorization to 74 % of DB22 and 97 % TOC in the RW, only in the first min of treatment, and 97 % and 99 %, respectively, at 6 min. The improvement in catalytic activity can be attributed to the dipolar polarization effect, hot spots and the generation of hydroxyl radicals. Additionally, a synergistic effect between the composite and microwave irradiation, assisted by hydrogen peroxide, reduced the RW phytotoxicity, improving the radicle length of Lactuca sativa three times (from 0.87 cm to 2.65 cm with the application of a single minute of treatment). The reduction in phytotoxicity led to an increase in the germination percentage from 36 % to 53 %. Finally, the use of MW irradiation coupled to a novel rGO-CuFeS2 composite, in presence of H2O2 under acid medium, provides a feasible and highly rapid method to treat RW, reducing its phytotoxicity.
Capsule: A novel rGO-CuFeS2 catalyst was developed and applied together with microwave irradiation for an ultra-fast degradation treatment (6 min) in real textile wastewater.
In this paper, two dimensional/two dimensional (2D/2D) Ti3C2/g-C3N4 (T/CN) heterostructure of was constructed and used to activate peroxymonosulfate (PMS) for the degradation of diclofenac (DCF) in water in the presence of light illumination. Compared with single photocatalytic process by T/CN (0.040/min) and with pure g-C3N4 nanosheets in PMS system (0.071/min), 5.0 and 3.0 times enhanced activities were achieved in the T/CN-PMS system at optimum Ti3C2 (1.0 wt%) loading under light illumination (0.21/min). Moreover, the decomposing processes of DCF in T/CN-PMS system were applicable in a wide initial pH range (3–14), therefore, overcoming the limitation of pH dependent in traditional PMS system. Based on the synergistic effect of photocatalysis and PMS oxidation processes, the ¹O2 was generated as primary reactive species for the removal of DCF in T/CN-PMS system. The DCF degradation mechanism was further proposed through the liquid chromatography-mass spectrometry (LC-MS) results and density functional theory (DFT) calculations.
Non-Steroidal Anti-Inflammatory Drugs (NSAIDs) represent one of the main therapeutic class of molecules contaminating aquatic ecosystems worldwide. NSAIDs are commonly and extensively used for their analgesic, antipyretic and anti-inflammatory properties to cure pain and inflammation in human and veterinary therapy. After use, NSAIDs are excreted in their native form or as metabolites, entering the aquatic ecosystems. A number of monitoring surveys has detected the presence of different NSAIDs in freshwater ecosystems in the ng/L - μg/L concentration range. Although the concentrations of NSAIDs in surface waters are low, the high biological activity of these molecules may confer them a potential toxicity towards non-target aquatic organisms. The present review aims at summarizing toxicity, in terms of both acute and chronic toxicity, induced by the main NSAIDs detected in surface waters worldwide, namely acetylsalicylic acid (ASA), paracetamol (PCM), diclofenac (DCF), ibuprofen (IBU) and naproxen (NPX), both singularly and in mixture, towards freshwater invertebrates. Invertebrates play a crucial role in ecosystem functioning so that NSAIDs-induced effects may result in hazardous consequences to the whole freshwater trophic chain. Acute toxicity of NSAIDs occurs only at high, unrealistic concentrations, while sub-lethal effects arise also at low, environmentally relevant concentrations of all these drugs. Thus, further studies represent a priority in order to improve the knowledge on NSAID toxicity and mechanism(s) of action in freshwater organisms and to shed light on their real ecological hazard towards freshwater communities.
A magnetic TiO2/Fe3O4/activated carbon composite was used as a photocatalyst for the removal of contaminants of emerging concern (CECs) and effluent organic matter (EfOM) of real and simulated effluents from municipal wastewater treatment plants (MWWTPs). While the catalyst showed limited activity under simulated solar irradiation in the absence of ozone, the CECs were completely eliminated and dissolved organic carbon (DOC) removal efficiencies reached up to more than 75% by simulated solar photocatalytic ozonation. The effects of EfOM (0-30 mg·L⁻¹ DOC), carbonate/bicarbonate (0-60 mg·L⁻¹ IC) and PO4-P (0-3.5 mg·L⁻¹) concentrations of the secondary effluent on the photocatalytic activity was studied. Both EfOM and carbonate/bicarbonate concentration accelerated the DOC removal in single ozonation experiments (i.e., absence of catalyst and radiation) due to the presence of initiators of the hydroxyl radical chain, the formation of secondary oxidants (i.e., hydrogen peroxide and carbonate radical) and the buffering capacity of the effluent. However, the interaction of EfOM and carbonate/bicarbonate with the catalyst brought about a decrease of its photocatalytic activity. Phosphates, in the concentration range studied, did not influence appreciably the catalytic activity. The reusability of the catalyst was evaluated through eight consecutive simulated solar phototacalytic ozonation runs. Samples of fresh and reused catalysts were examined by bulk composition analysis, N2 adsorption-desorption isotherms, XRD, XPS, SQUID magnetometry and the pHPZC. Despite some changes in the porous structure and the fixation of some oxygen groups on the carbon surface as a result of ozonation, the catalyst showed good stability and the oxidation efficiency was maintained through runs.
In this work, CuFeS2 chalcogenide powders were easily produced by conventional and microwave methods, and for the first time, the influence of synthesis route on their properties and consequent catalytic activity in the photo–Fenton reaction was investigated. X–ray diffraction, N2 adsorption–desorption isotherms, Fourier–transform infrared spectroscopy, transmission and scanning electron microscopy, energy dispersive X–ray spectroscopy and X–ray photoelectron spectroscopy were employed to characterize and point out the main properties and differences among samples. The CuFeS2 particles were used as catalysts for tartrazine dye degradation by the photo–Fenton reaction under visible irradiation. The results showed that the CuFeS2 prepared by microwave–assisted method (CuFeS2–MW) present higher crystallinity, higher concentration of Fe²⁺ on its surface and remarkable catalytic activity, reaching 99.1% of tartrazine decolorization and 87.3% of mineralization, at a rate twice as fast as CuFeS2 prepared by the conventional method. The catalyst showed high catalytic efficiency and stability during the reaction after five recycles. The hydroxyl radical was revealed to be the reactive species responsible for tartrazine degradation. A mechanism was proposed to elucidate how these free radicals are generated from the catalytic decomposition of H2O2 by CuFeS2–MW.
This work deals with the degradation of three emerging contaminants (acetaminophen, ibuprofen and antipyrine) in water under simulated solar light using different catalysts of TiO2/activated carbon heterostructures. The heterostructures, based on anatase phase, were successfully synthesized following three different methods (solvothermal, microwave-assisted and sol-gel), using lignin as carbon precursor. The sol-gel photocatalyst only yielded 50% conversion of acetaminophen and a low mineralization (15%), probably due to the higher crystal and particle sizes and lower surface area of this heterostructure, as a consequence of the higher temperature reached during the heat-treatment included in this synthesis route to achieve anatase crystallization. In contrast, the heterostructure prepared by the microwave-assisted procedure achieved complete conversion after 6 h of reaction. Regarding the contaminants, ibuprofen was the most easily removed, requiring 3 h for complete disappearance, while antipyrine showed the highest resistance to photodegradation, not being completely removed after 6 h. The photocatalytic performance was also evaluated for a mixture of these three pharmaceuticals at different initial pH. The fastest and highest mineralization (ca. 50 %) occurred around neutral pH. The study proposes the oxidation degradation pathways of the three pharmaceuticals under solar-simulated irradiation from the analysis of the reaction intermediates.