Search Results (8)

This study optimized the proportions of synergistic catalysts to efficiently activate potassium peroxymonosulfate (Oxone), generate more reactive oxygen species, and accelerate the chemical oxidation of silicon carbide (4H-SiC) wafers during chemical–mechanical polishing (CMP) for an improved material removal rate (MRR) and surface quality. The Oxone was activated using ultraviolet (UV) catalysis with a photocatalyst (TiO₂) and transition metal (Fe₃O₄) to enhance the oxidation capacity of the polishing slurry through the production of strong oxidizing sulfate radicals (${\mathrm{S}\mathrm{O}}_4^{·-}$). First, the effects of the TiO₂, Fe₃O₄, and Oxone concentrations on the MRR were studied by conducting multiple single-factor experiments. Next, 4H-SiC wafers were polished using different catalyst combinations to verify the synergistic activation of Oxone by multiple catalysts. Finally, the roughnesses, physical features, and elemental compositions of the wafer surfaces were observed before and after polishing. The results showed that CMP with a TiO₂ concentration of 0.15 wt%, Fe₃O₄ concentration of 0.75 wt%, and Oxone concentration of 48 mM decreased the wafer surface roughness from Sa 134 to 8.251 nm and achieved a maximum MRR of 2360 nm/h, which is significantly higher than that associated with traditional CMP methods. The surface of a 4H-SiC wafer polished using CMP with the optimal catalytic system was extremely smooth with no scratches and exhibited many oxides that reduced its hardness. In summary, the proposed UV-TiO₂-Fe₃O₄-Oxone composite catalytic system for 4H-SiC CMP exhibited significant synergistic enhancements and demonstrated excellent surface quality, indicating considerable potential for the polishing of hard materials. Full article

Diethyl phthalate (DEP) is a commonly utilized plasticizer that has gained significant attention due to its widespread occurrence in the environment and its harmful impact on human health. The primary objective of this study was to evaluate and compare several (ultraviolet) UV-(peracetic acid) PAA advanced oxidation processes based on hydroxyl radicals to degrade DEP. The effect of UV-LEDs incorporating PAA at different UV ranges (UV-A, λ = 365 nm; UV-C, λ = 254 nm and VUV, λ = 254 nm) was evaluated. The results demonstrated that DEP was successfully degraded in both the UVC/PAA (removal rate 98.28%) and VUV/PAA (removal rate 97.72%) processes compared to the UVA/PAA process (removal rate of 2.71%). The competitive method evaluated the contribution of R-O•, which were 24.08% and 33.92% in UVC/PAA and VUV/PAA processes, respectively. We also evaluated the effects of peroxymonosulfate (PMS) dosages, UV irradiation, pH and anion coexistence on the removal of DEP. In the UVC/PAA system, DEP degradation was particularly effective (removal rate about 95.52%) over a wider pH range (3–9). As the concentration of HCO₃⁻ ions increased, there may have been some inhibition of DEP removal. The inhibitory effect of HA and Cl⁻ ions on DEP removal were negligible. Analysis of the intermediates revealed that DEP degradation primarily occurred via two pathways: hydrolysis and hydroxylation reactions. This study presents a potential mnethod for the removal of phthalates and offers some guidance for the selection of appropriate disinfection technologies in drinking water treatment. Full article

The tomato brown rugose fruit virus (ToBRFV), a formidable tobamovirus, poses a significant threat to tomato production globally. This comprehensive study is dedicated to establishing an integrated control strategy for ToBRFV, encompassing the entire tomato cultivation process from seed to harvest. Initial investigations revealed a 0.8% seed transmission rate of ToBRFV, with viral presence detected in endosperms but not in seed embryos. Employing a multifaceted approach, infected seeds underwent a meticulous disinfection process. Gradual heating in a rotating thermal machine from 20 °C to 72 °C for 3 days resulted in a remarkable 0.3% contamination rate, rendering the virus non-infectious. Furthermore, ToBRFV-infected seeds underwent UV light treatment at 254 nm for 30 min, resulting in a 50% reduction in contamination rates. Chemical disinfectants, including 1% Tsunami 100 (comprising 30–60% acetic acid, 15.2% peroxyacetic acid, and 11.2% hydrogen peroxide) and 1% Biocon A (a combination of potassium peroxymonosulfate with buffer and organic acid), exhibited notable success. This study not only unravels the intricate dynamics of ToBRFV transmission and inactivation but also underscores the efficacy of integrated control measures. The findings provide valuable insights for the sustainable management of ToBRFV, contributing to the resilience of global tomato cultivation against this viral menace. Full article

In this work, the heterojunctions of CuInS₂ embedded in the g-C₃N₄ materials (xCuInS₂/g-C₃N₄, abbreviated as xCIS/GCN) was successfully prepared for peroxymonosulfate (PMS) activation under visible light. The catalysts are characterized by different techniques, such as XRD, FTIR, SEM, TEM, and UV-vis. The unique heterojunction composites can suppress the recombination of photogenerated pairs. The catalytic results showed that the 3CIS/GCN exhibited excellent catalytic levofloxacin (LVF) degradation efficiency, while more than 98.9% of LVF was removed in 60 min over a wide pH range. SO₄^•−, O₂^•−, OH^•, and ¹O₂ were verified as the main reactive species for LVF degradation via the quenching experiments and electron paramagnetic resonance technology (EPR). The synergetic effect of xCIS/GCN, PMS, and visible light irradiation was discussed. The possible LVF degradation pathway was proposed through byproducts analysis (LC-MS). Moreover, the 3CIS/GCN/vis-PMS system has very low metal leaching. Owing to xCIS/GCN having good properties for PMS activation, it has potential applications for LVF or other hazardous pollutants degradation. Full article

Diclofenac sodium was extensively used for treating arthritis, osteoarthritis and skeletal muscular injuries, which ultimately caused troubles for aquatic organisms as well as human beings. In this study, homogeneous catalytic advanced oxidation processes, including Fe²⁺/persulfate, Fe²⁺/peroxymonosulfate and Fe²⁺/H₂O₂, were used for the degradation of diclofenac sodium in water, without using UV-C light. About 89, 82 and 54% DCF sodium was decomposed by Fe²⁺/persulfate, Fe²⁺/peroxymonosulfate and Fe²⁺/H₂O₂, respectively, in 60 min. The degradation of diclofenac sodium followed the pseudo first-order kinetics, in all cases. The degradation efficiency of diclofenac sodium was significantly affected in the presence of various anions, such as NO₃⁻, HCO₃⁻ and SO₄²⁻. The mineralization studies revealed 62, 45 and 32% total carbon removal by Fe²⁺/persulfate, Fe²⁺/peroxymonosulfate and Fe²⁺/H₂O₂, respectively, in 60 min. In addition, the degradation byproducts of diclofenac sodium were determined by FTIR analysis. The results revealed that the Fe²⁺/oxidant system, particularly Fe²⁺/persulfate, was a promising technology for the elimination of toxic pharmaceuticals, such as diclofenac sodium, from the water environment. Full article

The large production of wine and almonds leads to the generation of sub-products, such as winery wastewater (WW) and almond skin. WW is characterized by its high content of recalcitrant organic matter (biodegradability index < 0.30). Therefore, the aim of this work was to (1) apply the coagulation–flocculation–decantation (CFD) process with an organic coagulant based on almond skin extract (ASE), (2) treat the organic recalcitrant matter through sulfate radical advanced oxidation processes (SR-AOPs) and (3) evaluate the efficiency of combined CFD with UV-A, UV-C and ultrasound (US) reactors. The CFD process was applied with variation in the ASE concentration vs. pH, with results showing a chemical oxygen demand (COD) removal of 61.2% (0.5 g/L ASE, pH = 3.0). After CFD, the germination index (GI) of cucumber and corn seeds was ≥80%; thus, the sludge can be recycled as fertilizer. The SR-AOP initial conditions were achieved by the application of a Box–Behnken response surface methodology, which described the relationship between three independent variables (peroxymonosulfate (PMS) concentration, cobalt (Co²⁺) concentration and UV-A radiation intensity). Afterwards, the SR-AOPs were optimized by varying the pH, temperature, catalyst type and reagent addition manner. With the application of CFD as a pre-treatment followed by SR-AOP under optimal conditions (pH = 6.0, [PMS] = 5.88 mM, [Co²⁺] = 5 mM, T = 343 K, reaction time 240 min), the COD removal increased to 85.9, 82.6 and 80.2%, respectively, for UV-A, UV-C and US reactors. All treated wastewater met the Portuguese legislation for discharge in a municipal sewage network (COD ≤ 1000 mg O₂/L). As a final remark, the combination of CFD with SR-AOPs is a sustainable, safe and clean strategy for WW treatment and subproduct valorization. Full article

The increase in world population and human activities are leading to an increase in water stress in many regions of the planet, coupled with a decrease in the quality of water bodies. Advanced oxidation processes have demonstrated great potential for the reduction of almost any organic pollutant; however, it is necessary to intensify this type of treatment in order to reduce contact times and to reach a greater number of pollutants. The generation of sulfate radicals by activation of peroxymonosulfate (PMS) by divalent iron (Fe²⁺) and/or titanium dioxide (TiO₂) were statistically studied to understand the role of these compounds as activators, using methylene blue as target pollutant because of its ease of handling and analysis. A factorial experimental design was used to study the influence of different variables (PMS, Fe²⁺, and TiO₂) in the presence of UV-A or UV-C. There were relevant differences in the discoloration of methylene blue when analyzing the size of the effects and significance of the experiments, when UV-A or UV-C was used, being faster with UV-C. For instance, total discoloration of methylene blue was reached after 60 min with the system PMS/UV-C, while after 90 min only the 59% of methylene blue disappeared in presence of PMS/UV-A. Both Fe²⁺ and TiO₂ in combination with PMS and UV increased the discoloration effect. So, in the presence of Fe²⁺, total discoloration of methylene blue was observed after 30 min in presence of UV-A, while this yield was reached in 7.5 min under UV-C. In the case of PMS/TiO₂, it required 60 min under UV-A radiation to totally remove methylene blue, and around 15 min with UV-C. Statistically, the three variables were observed to have the main effect in combination with UV. Furthermore, the PMS/Fe²⁺ system has a significant interaction with UV-A and UV-C radiation, while the interaction of PMS/TiO₂ was significant under UV-A, but with a negative effect under UV-C, or in other words the high elimination rates observed are achieved by the oxidation potential of UV-C, and the effect of PMS and TiO₂ by itself. Full article

This study explores the capability of Sulfate Radical-based Advanced Oxidation Processes (SR-AOPs) for the simultaneous disinfection and decontamination of urban wastewater. Sulfate and hydroxyl radicals in solution were generated activating peroxymonosulfate (PMS) under UV-C irradiation at pilot plant scale. The efficiency of the process was assessed toward the removal of three CECs (Trimethoprim (TMP), Sulfamethoxazole (SMX), and Diclofenac (DCF)) and three bacteria (Escherichia coli, Enterococcus spp., and Pseudomonas spp.) in actual urban wastewater (UWW), obtaining the optimal value of PMS at 0.5 mmol/L. Under such experimental conditions, bacterial concentration ≤ 10 CFU/100 mL was reached after 15 min of UV-C treatment (0.03 kJ/L of accumulative UV-C radiation) for natural occurring bacteria, no bacterial regrowth was observed after 24 and 48 h, and 80% removal of total CECs was achieved after 12 min (0.03 kJ/L), with a release of sulfate ions far from the limit established in wastewater discharge. Moreover, the inactivation of Ampicillin (AMP), Ciprofloxacin (CPX), and Trimethoprim (TMP) antibiotic-resistant bacteria (ARB) and reduction of target genes (ARGs) were successfully achieved. Finally, a harmful effect toward the receiving aquatic environment was not observed according to Aliivibrio fischeri toxicity tests, while a slightly toxic effect toward plant growth (phytotoxicity tests) was detected. As a conclusion, a cost analysis demonstrated that the process could be feasible and a promising alternative to successfully address wastewater reuse challenges. Full article