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The continuous release of antibiotics to the environment via wastewater is becoming a priority. Since conventional depuration systems are unable to remove these substances, aquatic organisms in natural water bodies receiving effluents are facing a continuous risk of harmful effects. Advanced oxidation processes, such as heterogeneous photocatalysis...
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... A comparison of this study with several ciprofloxacin degradation methods is shown in Table 2. It can be seen that the effect of this method tends to have a better degradation efficiency than photocatalytic [12,56] and Fenton oxidation [57], ozonation microbubble [11] and lower than the ozonation system [58]. However, if we look in more detail at ozonation by Wajahat et al. [58], the initial concentration is too small, namely, 7.9 mg/L, while in this study it was able to effectively achieve ciprofloxacin degradation at high ciprofloxacin concentrations, namely 30 mg/L. ...
... In addition, degradation with ferrates can be carried out at room temperature, making it easier to observe. Photocatalytic Bi2WO6/Ag/AgBr pH = 7, initial concentration = 50 µg/L 57% [56] Fenton oxidation Fe 2+ /H2O2 pH = 3.5, initial concentration = 15 mg/L 74.40 [57] Ozonation Ozone pH = 9, initial concentration = 7.91 mg/L 98.7 [58] Ozonation microbubbles Ozone pH = 7, concentration = 10.94 mg/L 83.5 [11] Determination of the mechanism of the degradation reaction Chromatogram results from LC-MS analysis of ciprofloxacin degradation products with ferrate (VI) have several peaks with different retention times as shown in Figure 10 and Table 3. N and O atoms in ciprofloxacin are able to donate their lone pair to Fe (VI) to form complex compounds. In general, ciprofloxacin complexes with metals are formed in the carbonyl group on the piperazine ring [59]. ...
Ciprofloxacin (CIP) antibiotic liquid waste is the most common waste found in hospital discharge waters. The accumulation of CIP can increase mutation, microbial resistance, and toxicity in the environment due to its low biodegradability and longevity in waters. Thus, methods for eliminating CIP are important. The Advanced Oxidation Process (AOP) method with ferrate (VI) has good redox potential in water disinfection, and degradation of organic and inorganic pollutants. Therefore, this study aims to degrade CIP waste with ferrate (VI). The ferrate (VI) used was synthesized from the electrolysis of transformer scrap metal plates under extremely alkaline conditions. The success of the synthesis was proven by the presence of FeO(OH) groups characterized using FTIR, XRF, and XRD. Then, the effect of time, pH, and CIP degradation was studied. The results showed that the maximum performance was obtained at pH 7 and 120 min with the addition of 1.1 mg ferrate at initial CIP concentration of 30 mg/L. The concentration of CIP decreased with increasing treatment time which was confirmed by UV-Vis Spectrophotometer. This condition is able to degrade 86.7 % of CIP. In addition, the LC-MS results show that degradation occurs due to a reaction between HFeO4-/H2FeO4 and the active site of piperazine ring antibiotics. This shows that Ferrate has a promising potential to reduce ciprofloxacin antibiotic pollution from hospital wastewater for a better environment.
... In the Cu-Ti-NT sample, an increment in defects at the interface extends the lifetime of the charge carriers. This lifetime enhancement of the exciton is also produced in the Ni-Ti-NT material through a different mechanism; the less negative value of E indicates that the incorporation of Ni generates additional energy states, which act as an electron trap [59,60]. ...
A combined theoretical and experimental work was performed to assess the carbon dioxide (CO2) evolution reaction into short chain hydrocarbons. The theoretical calculations were performed by using Density Functional Theory (DFT) at the DFT + U level. The reaction mechanisms were elucidated with the string method by comparing the photocatalytic behavior of the pristine Ti-NT surface, previously synthesized in our group, and the M -doped Ti-NT (M -Ti-NT, where M = Cu, Ni) systems. For the pristine material, the results showed lower adsorption energies of the CO2 molecule (−0.27 eV), as compared to that obtained with the M -doped Ti- NT systems. Ni-Ti-NT showed an enhancement in photocatalytic performance with respect to the other surfaces, by yielding small activation energies throughout the reaction path. On the experimental side, Ti-NT and M-Ti-NT (M = Cu, Ni) materials were characterized through several techniques to assess their structural, morphological, textural, and optoelectronic properties. The photocatalytic CO2 reduction was evaluated under wavelength illumination between 440–540 nm. The liquid solar fuel identified products were HCOOH, CH2O, and CH3OH, showing a different distribution among photocatalysts which correlates with the position of the conduction band of the photocatalysts. Doping with Cu and Ni of the Ti-NT structure enhances the carriers’ density which improves the photoactivity mainly in the case of Ni-Ti-NT. The photocatalytic experimental results agree with the theoretical calculations.
... Additionally, from the kinetics study, it was obvious that the rate of the degradation process using the composite material was approximately faster five times faster than using unmodified Bi 2 WO 6 photocatalyst. In a similar study on the degradation of ciprofloxacin, 57 % removal efficiency was achieved when 120 mg of Bi 2 WO 6 /Ag/AgBr photocatalyst was added to 250 mL solution of 30 mg/L ciprofloxacin after 5 h of irradiation under visible light (Durán-Álvarez et al., 2019). ...
The pollution of water bodies by residual pharmaceuticals is a major problem globally. Bismuth tungstate mediated photocatalysis has been effective in the removal of these organics from water. Bismuth tungstate (Bi2WO6) has proven to be an excellent visible light active photocatalyst because of its non-toxicity, low band gap energy and ease of preparation. It has been widely applied for the removal of a wide array of organic pollutants, particularly dyes, from wastewater. However, recently, much attention has been channelled to its application for the degradation of pharmaceuticals. In this present review, the recent trends in the applications of Bi2WO6 based photocatalysts for the removal of pharmaceuticals in wastewater are comprehensively discussed. The fabrication of Bi2WO6 based photocatalysts with enhanced photocatalytic performances through morphology control, doping and formation of heterojunctions are highlighted. Much discussion centres on the mechanisms and possible degradation pathways of antibiotic pharmaceuticals in wastewater. Finally, areas needing more attention and investigation on the use of Bi2WO6 based photocatalysts for removal of pharmaceuticals from wastewater especially towards real-life applications are presented for future research directions.
... The produced heterostructure showed an improvement in photocatalytic activity compared to the unmodified Bi 2 WO 6 . This is mainly due to the presence of Ag as well as the heterojunction formed by the two semiconducting materials AgBr and Bi 2 WO 6 [95]. While the addition of Ag nanoparticles enhanced the photocatalytic activity significantly, it is not cost-effective; other lower-cost materials are suggested for utilization, such as doping with S or B. To overcome the drawbacks, such as material agglomeration, that can happen in some of the modified materials, Zheng et.al. ...
Antibiotics are chemical compounds that are used to kill or prevent bacterial growth. They are used in different fields, such as the medical field, agriculture, and veterinary. Antibiotics end up in wastewater, which causes the threat of developing antibacterial resistance; therefore, antibiotics must be eliminated from wastewater. Different conventional elimination methods are limited due to their high cost and effort, or incomplete elimination. Semiconductor-assisted photocatalysis arises as an effective elimination method for different organic wastes including antibiotics. A variety of semiconducting materials were tested to eliminate antibiotics from wastewater; nevertheless, research is still ongoing due to some limitations. This review summarizes the recent studies regarding semiconducting material modifications for antibiotic degradation using visible light irradiation.
... Electrochemical testing was carried out by an electrochemical workstation (Zahner PP211, Germany). The test conditions were Ag/ AgCl as the reference electrode and Pt wire as the counter electrode [31][32][33]. To prepare a working electrode, NiO/Bi 2 WO 6 powder was deposited on conductive glass with a frequency of 0.1 * 10 6 Hz and a 150 W cold light source. ...
In this paper, a hydrangea-like Bi2WO6 material was first synthesized by a hydrothermal method. Then, as a carrier, a NiO-Bi2WO6 composite photocatalyst was successfully synthesized by the hydrothermal method and high-temperature calcination and applied to studying the removal of benzothiophene (BT) from fluid catalytic cracking (FCC) gasoline. The morphology, crystal structure and elemental composition of the catalyst were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS); ultraviolet-visible diffuse reflectance spectroscopy (UV–Vis-DRS) and electronic impedance spectroscopy (EIS) were used to characterize the light absorption and charge transfer ability of the catalyst. The characterization confirmed that the NiO-Bi2WO6 composite photocatalyst was successfully prepared. Moreover, the effects of catalyst dosage, NiO loading and different substrates on the desulfurization rate were investigated by photocatalytic oxidation desulfurization experiments. The experimental results showed that under the conditions of a catalyst dosage of 1.2 g/L and NiO loading of 30%, the highest desulfurization rate of BT was 95.37%. The active species in the reaction process were studied through active radical capture experiments and qualitative analysis of the substances before and after the reaction was carried out via gas chromatography (GC), and the reaction mechanism of the catalyst was explored in depth. The results indicated that the catalyst mainly oxidized BT to benzothiophene sulfone (BTO2) under the oxidation of superoxide radicals to achieve deep desulfurization. Cycling experiments demonstrated that the catalyst still had high stability and catalytic activity after six cycles.
... As part of the ODS methods, photocatalytic desulphurization (PDS) has appeared as a green and encouraging technique, mainly due to its low energy consumption, high performance, safety, low cost, and able to convert harmful sulphur compounds into safer products [6][7][8]. Nevertheless, the main struggle encountered by PDS is to discover a potential catalyst that has less propensity to aggregate in the reaction solution, a hindered recombination of electron-hole, a narrow band gap energy and a wide spectrum consumption [9,10]. ...
Novel fibrous silica zinc (FSZnIS) catalyst was synthesized by in-situ hydrothermal-microwave method and the catalyst was analyzed by X-ray Diffraction (XRD), N2 physisorption, Field emission scanning electron microscopy (FESEM), Fourier transform infrared (FTIR), UV–Vis diffuse reflectance spectroscopy (UV–Vis DRS) and photoluminescence (PL). The catalyst was employed in photocatalytic desulphurization of dibenzothiophene (DBT) in model fuel. The performance of FSZnIS was compared with bare fibrous silica (KCC-1), commercial ZnO and fibrous silica zinc prepared by impregnation method (FSZnIP). The photoactivity towards catalytic desulphurization of DBT is in the following order: FSZnIS (88.9%) > FSZnIP (62.4%) > KCC-1 (53.9%) > ZnO (44.4%). The best performance was achieved using 0.375 gL⁻¹ of FSZnIS catalyst over 100 mgL⁻¹ DBT in model fuel. This is predominantly due to the well distribution of ZnO on KCC-1, high surface area (411.2 m² g⁻¹), high number of Si–O–Zn bonds, appropriate band gap energy (2.95 eV), and proficient charge separation. These criteria mutually encouraged effective harvesting of visible light (420 nm) and good mobility of charge carriers for enhanced visible light driven performance. A kinetics study determined by Langmuir–Hinshelwood model demonstrated that the photodesulphurization obeyed the pseudo-first-order and adsorption was the rate-limiting step.
Graphic Abstract
... Several bismuth-based semiconductors cannot produce • OH radicals via the oxidation of water molecules in virtue of the low oxidation potential of the photoholes in the valence band [46][47][48]. The generation of •OH radicals by the photocatalysts was indirectly assessed through the fluorescence produced by the hydroxyl form of terephthalic acid, measured at 365 nm [49]. ...
... The OTC molecule is comprised by four aromatic rings, substituted by hydroxyl, amine and amide moieties (Table S1), which is a strong nucleophile. Previous studies have demonstrated that the photohole driven reaction can degrade this molecule using bismuth-based semiconductors as photocatalysts [46,47]. Therefore, it is expected that the undoped material which displays the highest specific surface area, and the lowest E g value can produce the maximum degradation yield, but upon doping with Ni 2+ , other factors appear, such as the generation of •OH radicals, which increases the degradation rate. ...
BiYO3 powders were synthesized by the Pechini method under low-temperature conditions. When the heat treatment was performed at T < 600 °C, a mixture of tetragonal and cubic phases was obtained, while for T ≥ 600 °C, only the fluorite-like cubic phase was observed. Based on the Rietveld refinement, approximately 2% and 1% of the tetragonal phase remained in samples calcined at 400 °C and 500 °C for 1 h, respectively. The crystal size calculated for these samples was 4.4–48.1 nm, depending on the calcination temperature. The specific surface area of the samples diminished with heat treatment and reached a minimum at 800 °C. The band gap of samples with mixed phases was close to 2.16 eV and was ∼2 eV for samples with a cubic phase. Photocatalytic tests demonstrate that BiY0.995Ni0.005O3 calcined at 800 °C had the best performance: it degraded more than 80% of the antibiotic oxytetracycline when irradiated with visible light. The Ni-doped BiYO3 material could degrade the antibiotic in tap water at an environmentally relevant concentration (μg L⁻¹ levels) and showed steady activity throughout four reaction cycles.
