The presence of organic micro-pollutants (OMPs) in wastewater treatment effluents is becoming a major threat to the water safety for aquatic and human health. Photo-electrocatalytic based advanced oxidation process (AOP) is one of the emerging and effective techniques to degrade OMPs through oxidative mechanism. This study investigated the application of heterojunction based BiVO4/BiOI photoanode for acetaminophen (40 μg L−1) removal in demineralized water. Photoanodes were fabricated by electrodeposition of BiVO4 and BiOI photocatalytic layers. Optical (UV–vis diffusive reflectance spectroscopy), structural (XRD, SEM, EDX) and opto-electronic (IPCE) characterization confirmed the successful formation of heterojunction for enhanced charge separation efficiency. The heterojunction photoanode showed incident photon to current conversion efficiency of 16% (λmax = 390 nm) at an external voltage of 1 V under AM 1.5 standard illumination. The application of the BiVO4/BiOI photoanode in the removal of acetaminophen at 1 V (external bias) vs Ag/AgCl under simulated sunlight showed 87% removal efficiency within the first 120 min compared to 66% removal efficiency of the BiVO4 photoanode. Similarly, combining BiVO4 and BiOI exhibited 57% increase in first order removal rate coefficient compared to BiVO4. The photoanodes also showed moderate stability and reusability by showing 26% decrease in overall degradation efficiency after three cycles of each 5 h experiment. The results obtained in this study can be considered as a stepping stone towards the effective removal of acetaminophen as an OMP present in wastewater.@en

AdOx is een combinatie van een adsorptieproces en een oxidatietechniek. Een veelbelovende technologie om medicijnresten uit afvalwater te halen. En winnaar van de Waterinnovatieprijs 2021, categorie Gezond Water en Gezonde Bodem.@en

Removal of bromate (BrO₃⁻) has gained increasing attention in drinking water treatment process. Photocatalysis technology is an effective strategy for bromate removal. During the photocatalytic reduction of bromate process, the photo-generated electrons are reductive species toward bromate reduction and photo-generated holes responsible for water oxidation. In this study, the monoclinic bismuth vanadate (BiVO₄) single crystal was developed as a visible photocatalyst for the effective removal of bromate. The as-synthesized BiVO₄ photocatalyst with optimized {010} and {110} facets ratio could achieve almost 100% removal efficiency of BrO₃⁻ driven by visible light with a first-order kinetic constant of 0.0368 min⁻¹. As demonstrated by the electron scavenger experiment and density functional theory (DFT) calculations, the exposed facets of BiVO₄ should account for the high photocatalytic reduction efficiency. Under visible light illumination, the photo-generated electron and holes were spatially transferred to {010} facets and {110} facets, respectively. The BiVO₄ single crystal photocatalyst may serve as an attractive photocatalyst by virtue of its response to the visible light, spatially charge transfer and separation as well as high photocatalytic activity, which will make the removal of BrO₃⁻ in water much easier, more economical and more sustainable.

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Electrochemical oxidation of water to produce highly reactive hydroxyl radicals (OH) is the dominant factor that accounts for the organic compounds removal efficiency in water treatment. As an emerging carbon-based material, the investigation of electrocatalytic of water to produce OH on Graphdiyne (GDY) anode is firstly evaluated by using first-principles calculations. The theoretical calculation results demonstrated that the GDY anode owns a large oxygen evolution reaction (OER) overpotential (ηOER = 1.95 V) and a weak sorptive ability towards oxygen evolution intermediates (HO*, not OH). The high Gibbs energy change of HO* (3.18 eV) on GDY anode makes the selective production of OH (ΔG = 2.4 eV) thermodynamically favorable. The investigation comprises the understanding of the relationship between OER to electrochemical advanced oxidation process (EAOP), and give a proof-of-concept of finding the novel and robust environmental EAOP anode at quantum chemistry level.@en

A novel sol-gel method was employed in this study to efficiently synthesize SnO2 nanoparticles to catalyze the ozonation of acetaminophen (ACT) from aqueous solutions. The influence of various parameters including Sn source, type of capping and alkaline agents, and calcination temperature on the catalytic activity of the SnO2 preparations was investigated. The SnO2 nanoparticles prepared by tin tetrachloride as Sn source, NaOH as gelatin agent, CTAB as capping agent and at calcination temperature of 550 °C (SnNaC-550) exhibited the maximum performance in the catalysis of ACT. The optimized catalyst (SnNaC-550) had spherical-homogeneous and cubic-shaped nanocrystalline particles with 5.5 nm mean particle size and a BET surface area of 81 m2/g, which resulted in 98% degradation and 84% mineralization of 50 mg/L ACT at 20 and 30 min reaction time, respectively when combined with ozonation (COP). Based on the radical scavenger experiments, •OH was the major oxidizing agent involved in the removal of ACT. LC/MS analysis showed that short-chain carboxylic acids were the main intermediates. Furthermore, the SnNaC-550 catalytic activity was preserved after four successive cycles. Collectively, the new method has the potential to efficiently synthesize stable and reusable SnO2 nanoparticles to catalyze the ozonation of ACT from aquatic environments.@en

Continuous development of industry and civilization has led to changes in composition, texture and toxicity of waste water due to the wide range of pollutants being present. Considering that the conventional wastewater treatment methods are insufficient for removing micropollutants and nutrients to a high level, other, alternative, treatment methods should be used to polish wastewater treatment plant effluents. In this study we developed an alternative, polishing concept for removal of ammonium and micropollutants that could potentially be incorporated in existing wastewater treatment plants. We demonstrated a method to use high silica MOR zeolite granules as an adsorbent for simultaneous removal of the micropollutant sulfamethoxazole (SMX) and ammonium (NH4+) ions from aqueous solutions. At an initial NH4+ concentration of 10 mg/L the high silica zeolite mordenite (MOR) granules removed 0.42 mg/g of NH4+, similar to the removal obtained by commonly used natural zeolite Zeolita (0.44 mg/g). However, at higher NH4+ concentrations the Zeolita performed better. In addition, the Langmuir isotherm model showed a higher maximum adsorption capacity of Zeolita (qmax, 4.08 mg/g), which was about two times higher than that of MOR (2.11). The adsorption capacity of MOR towards SMX, at both low (2 µg/L) and high (50 mg/L) initial concentrations, was high and even increased in the presence of NH4+ ions. The used adsorbent could be regenerated with ozone and reused in consecutive adsorption–regeneration cycles with marginal decrease in the total adsorption capacity.@en

Currently available (photo-)electrochemical technologies for water treatment establish a trade-off between low-pollutant concentration and costs. This paper aims at decoupling these two variables by designing a photo-oxidation device using earth abundant materials and an electronic-free approach. The proposed device combines a graphite/graphite electrochemical system with a silicon-based solar cell that provides the necessary electrical power. First, the optimum operational voltage for the graphite/graphite electrochemical system was found to be around 1.6 V. That corresponded closely to the voltage produced by an a-Si:H/a-Si:H tandem solar cell of approximately 1.35 V. This configuration was shown to provide the best pollutant degradation in relation to the device area, removing 70% of the initial concentration of phenol and 90% of the methylene blue after 4 h of treatment. The chemical oxygen demand (COD) removal of these two contaminants after 4 h of treatment was also promising, 55 and 30%, respectively. Moreover, connecting several solar cells in series led to higher pollutant degradation but lower COD removal, suggesting that the degradation of the intermediate components is a limiting factor. This is expected to be due to the higher currents achieved by the series-connected configuration, which would favor other reactions such as polymerization over the degradation of intermediate species.

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The removal of organics by photoelectrocatalytic oxidation offers a viable option to remove the contaminants at low concentrations. In this paper, we propose a BiVO4 thin films synthesized via spray pyrolysis for photoelectrocatalyic oxidation of phenol with solar light. We compare the properties of BiVO4 with those of the commonly used photocatalyst TiO2. In addition, BiVO4 films with W gradient doping were fabricated and tested for improving the photocatalytic performance of BiVO4. X-ray diffraction, atomic force microscopy, incident photon to current efficiency and spectrophotometry have been conducted for BiVO4 films of different thicknesses, as well as for TiO2. The electrochemical impedance spectroscopy and dark conductivity measurements were conducted. Phenol removal has been measured for both the TiO2 and BiVO4 samples. The best performance was found to be for a 300 nm undoped BiVO4 film, being able to reduce the phenol concentration up to 30.0% of the initial concentration in four hours.

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