The effect of cobalt doping on the efficiency of semiconductor oxides in the photocatalytic water remediation

Abstract The effect of cobalt doping on semiconductors materials synthesized via solution and hydrothermal methods was investigated by testing its photocatalytic efficiency on pollutants abatement. X Ray Diffraction technique was used to evaluate samples crystallographic phases allowing to identify different species due to the introduction of the dopants. Diffuse Reflectance UV–vis Spectroscopy was employed to determine the bandgap as well as the absorption corresponding to d-d transitions for cobalt doped systems. Finally, Electron Paramagnetic Resonance Spectroscopy was adopted to perform a pre-screening of the photoactivity of the prepared samples. The Co-doped TiO2 and ZnO materials photoactivity was assessed on phenol degradation, selected as pollutant probe, under UVA irradiation. Doping TiO2 with cobalt in low amounts (0.25% and 0.5%) prepared by hydrothermal method leads to an enhancement on phenol degradation. Also, the presence of Co-doped ZnO obtained by hydrothermal process if prepared with defined cobalt amount (0.5 or 1%) promote an increasing on phenol abatement. Ketoprofen was used to evaluate the doping effect, being the Co-doped ZnO material more efficient on ketoprofen mineralization comparing with bare material. The ketoprofen and its transformation products were easily abated and, in wastewater, they were completely eliminated within 1 h, endorsing that inserting cobalt can improve the ZnO photocatalysis efficiency for water remediation

Photo-Activation of Persulfate and Hydrogen Peroxide by Humic Acid Coated Magnetic Particles for Bisphenol A Degradation

Abstract Magnetic particles (MPs) coated with humic acid (HA) prepared under anoxic atmosphere were tested as heterogeneous photo-Fenton catalyst for the activation of hydrogen peroxide (H2O2) and persulfate (S2O82-) using Bisphenol A (BPA) as a model pollutant. The role of HA coating, pH value and H2O2/S2O82- concentration were investigated. A positive contribution of HA coating on H2O2 and S2O82- activation was found. The highest BPA degradation rates were achieved at acidic conditions (pH 3) with both H2O2 and S2O82-, however persulfate showed a significant efficiency even at pH 6, interesting feature in the light of decreasing the wastewater treatment costs. By the addition of selective quenching agents, •OH and SO4•– were identified as the main reactive species involved in the BPA abatement. An important contribution of the S2O82- photolysis on the overall BPA transformation was highlighted. The reuse of the catalyst was investigated and similar efficiency using H2O2 and S2O82- activation was observed until the third catalytic cycle. Experiments carried out using real wastewater samples, showed a good, even if less efficient compared to pure water, BPA removal

Attenuation of toxicity and occurrence of degradation products of the fungicide tebuconazole after combined vacuum UV and UVC treatment of drinking water

Antifungal azoles are the most frequently used fungicides worldwide and occur as active ingredients in many antifungal pharmaceuticals, biocides, and pesticides. Azole fungicides are frequent environmental contaminants and can affect the quality of surface waters, groundwater, and drinking water. This study examined the potential of combined vacuum UV (185 nm) and UVC (254 nm) irradiation (VUV/UVC) of the azole fungicide tebuconazole and the transformation product 1,2,4-trizole on degradation and changes in ecotoxicity. In vivo ecotoxicity was examined before and after UV treatment using bioassays with test organisms from different trophic levels to integrate changes in biological effect of the parent compound and the degradation products. The test battery included the luminescent bacterium Aliivibrio fischeri, the Gram-positive bacterium Bacillus subtilis, the fungus Fusarium graminearum, the green microalga Raphidocelis subcapitata, and the crustacean Daphnia magna. The combined VUV/UVC treatment of tebuconazole in drinking water efficiently degraded the parent compound at the µg/L-mg/L level and resulted in transformation products with lower toxicity than the parent compound. A direct positive correlation was observed between the applied UV dose (fluence, J/cm(2)), the disappearance of tebuconazole, and the decrease in ecotoxicity. The combined VUV/UVC process does not require addition of supplementary oxidants or catalysts and our study suggests that VUV/UVC-mediated photolysis of azole fungicides in water can decrease the overall toxicity and represent a potentially environmentally friendly treatment method. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s11356-022-19691-0

Humic acid coated magnetic particles as highly efficient heterogeneous photo-Fenton materials for wastewater treatments

Abstract Heterogeneous photo-Fenton reaction with iron-based magnetic materials has been proposed as an alternative to the homogeneous Fenton process to remove contaminants of emerging concern (CECs) because of the low cost, facile recovery and reuse. The iron-based material is not only a reservoir to maintain an effective concentration of iron in solution, but it also activates H2O2 at the surface. Magnetic particles (MPs) coated with different amount of humic acid (HA), prepared by co-precipitation method under anoxic and oxygenated conditions were synthesized. Their features were characterized by different techniques (XPS, XRD, TGA, SEM and FTIR). The ability of those materials to promote Fenton and photo-Fenton-like processes was investigated using 4-chlorophenol as standard substrate. The HA coating increased the catalyst efficiency, both in the dark and under irradiation, showing the best performance at pH below 4 under simulated sunlight. The iron speciation at the MPs surface had a paramount role in the H2O2 (photo)activation, although the processes promoted by the released iron in solution were not negligible on the overall degradation process. It was demonstrated a role of the surface defectivity to promote faster degradations as a consequence of not only a faster photodissolution, but also a higher heterogeneous reactivity promoted by defective sites. The best performing MPs/HA showed high efficiency for the abatement of CECs, namely Carbamazepine, Ibuprofen, Bisphenol A and 5-Tolylbenzotriazole also in real wastewater. The obtained results demonstrated the potential application of the heterogeneous (photo)-Fenton process activated by these inexpensive and environmental friendly materials in advanced wastewater treatments

Photo-activation of persulfate and hydrogen peroxide by humic acid coated magnetic particles for Bisphenol A degradation

International audienceMagnetic particles (MPs) coated with humic acid (HA) prepared under anoxic atmosphere were tested as heterogeneous photo-Fenton catalyst for the activation of hydrogen peroxide (H 2 O 2) and persulfate (S 2 O 8 2−) using Bisphenol A (BPA) as a model pollutant. The role of HA coating, pH value and H 2 O 2 /S 2 O 8 2− concentration were investigated. A positive contribution of HA coating on H 2 O 2 and S 2 O 8 2− activation was found. The highest BPA degradation rates were achieved at acidic conditions (pH 3) with both H 2 O 2 and S 2 O 8 2− , however persulfate showed a significant efficiency even at pH 6, interesting feature in the light of decreasing the wastewater treatment costs. By the addition of selective quenching agents, % OH and SO 4 %-were identified as the main reactive species involved in the BPA abatement. An important contribution of the S 2 O 8 2− photolysis on the overall BPA transformation was highlighted. The reuse of the catalyst was investigated and similar efficiency using H 2 O 2 and S 2 O 8 2− activation was observed until the third catalytic cycle. Experiments carried out using real wastewater samples, showed a good, even if less efficient compared to pure water, BPA removal

Elucidation of the photoinduced transformations of Aliskiren in river water using liquid chromatography high-resolution mass spectrometry

International audienceAliskiren was selected as a compound of potential concern among a suspect screening list of more than 40,000 substances on a basis of high occurrence, potential risk and the absence of information about its environmental fate. This study investigated the photoinduced degradation of aliskiren in river water samples spiked at trace levels exposed to simulated sunlight. A half-life time of 24 h was observed with both direct and indirect photolysis playing a role on pollutant degradation. Its photo-induced transformation involved the formation of six transformation products (TPs), elucidated by LC-HRMS - resulted from the drug hydroxylation, oxidation and moieties loss with subsequent cyclization structurally. The retrospective suspected analysis performed on a total of 754 environmental matrices evidenced the environmental occurrence of aliskiren and two TPs in surface waters (river and seawater), fresh water, sediments and biota. In silico bioassays suggested that aliskiren degradation undergoes thought the formation of TPs with distinct toxicity comparing with the parent compound