Effect of Anions and Related Organic Compounds on the Kinetics of Thiocyanate Oxidation in a Solar-induced Oxidative System

The presence of emerging organic micropollutants (MPs), such as antibiotics, pesticides and pharmaceutical products is widespread due to their extensive use in medicine, industry, agriculture, and daily human consumption. Despite their typically low concentrations and shorter half-lives compared to persistent organic pollutants, MPs pose significant risks by contaminating aquatic ecosystems and potentially leaching into drinking water sources due to their emissions, biological toxicity, and propensity for bioaccumulation. Their classification as potential carcinogens and endocrine disruptor underscores the urgent need for efficient wastewater treatment solutions. The integration of advanced oxidation processes (AOPs) with catalytic ceramic membranes (CCMs) offers a promising approach to enhance organic matter removal in water treatment while reducing membrane fouling. The use of CCM in the hybrid process intensifies the organic pollutants degradation and mineralization, but its practical application faces challenges such as limited catalytic activity, the formation of toxic by-products and sensitivity to water matrices. This thesis work aims to address these limitations and improve the removal efficiency in the hybrid process by developing CCMs with enhanced catalytic activity, versatility in various oxidant activation and reduced interference from background species.
\nThe use of bimetallic oxides (e.g., Co-Mn) enhances the activation of oxidants, generating stronger reactive oxygen species (ROS) that efficiently degrade MPs and facilitate the mineralization of their by-products, significantly reducing post-treatment toxicity. The incorporation of Fe₃O₄ enables the CCM to activate different oxidants, including peroxymonosulfate (PMS), peroxydisulfate (PDS), and the Fenton process (H₂O₂). This broadens the range of oxidants to be activated and MPs that can be degraded. Furthermore, the catalytic active layer on the CCM surface minimizes interference from water matrices by selectively rejecting background components, allowing only micropollutants to permeate and undergo degradation within the CCM substrate, thus ensuring efficient ROS utilization.
\nThis research involved the development and evaluation of various CCMs, including a Co-Mn bimetallic oxide impregnated CCM (CoMn₂O₄-CCM) fabricated via a citrate-acid wet impregnation method, which demonstrated superior sulfamethoxazole (SMX) removal in continuous flow experiments due to enhanced redox cycling (Chapter 3). The CCM was effective in removing 99% SMX within hydraulic retention time (HRT) of 13.7 s, achieving a low specific oxidant consumption of 1.2 M PMS M-1 TOC. The investigation highlighted the critical role of process parameters in optimizing the CCM/PMS system's performance. The ratio between catalyst loading in CCM, oxidant concentration and pollutant concentration influenced the availability of active sites on the catalyst to activate oxidants in the process and the possibility of self-scavenging of the generated reactive oxidizing species (ROS). Fe₃O₄-impregnated CCM, developed using a facile ethylene-glycol gel method, showed effective atrazine (ATZ) removal across different AOPs and water matrices, such as settled water and RO retentate (Chapter 4). The resulting Fe3O4-CCM efficiently activated peroxymonosulfate (PMS) to generate reactive oxygen species (ROS), achieving a 99% removal of atrazine (ATZ) within a short hydraulic retention time (HRT) of 5.7 s. The versatile Fe3O4-CCM could also effectively activate H2O2 and peroxydisulfate (PDS). It demonstrated robustness in real wastewater matrices (settled water and RO-reject) collected from local water reclamation and treatment plants and in presence of humic acid. Moreover, a CCM with a Co₃O₄ impregnated layer and a TiO₂-coated surface demonstrated enhanced acetaminophen (ACT) degradation with minimized interference from organic matter in real water samples (Chapter 5). The CCMs effectively activated peroxymonosulfate (PMS), achieving ACT degradation of 85% and 93% in real water matrices (reverse osmosis retentate and settled water, respectively) and 99% in MQ water. The CCMs demonstrated consistent performance across multiple operational cycles, even in the presence of humic acid (HA) (96% ACT reduction). The study identified by-products formed during the degradation process and analyzed their toxicity, revealing a significant reduction in post-treatment toxicity. It also explored degradation pathways involving both radical and non-radical mechanisms, identifying radical pathway reactive oxygen species (ROS) such as SO₄•⁻, •OH, O₂•⁻, as well as non-radical pathways like ¹O₂, electron transfer mechanisms. The mechanistic study provided insights into the optimal conditions for each pathway. The CCMs also demonstrated effective degradation of micropollutants in the presence of background species such as anions and humic acid and exhibited good performance when tested with real water samples. Furthermore, the CCMs showed good reusability and long-term performance, confirming their potential for practical and sustainable operation in real-world water treatment scenarios. Furthermore, the reusability and long-term performance of the CCMs were evaluated, demonstrating their potential for practical and sustainable operation in real water treatment scenarios. 
\nOverall, this research provides a novel and effective solution for tackling the challenge of emerging micropollutants in water treatment. The advanced CCM-AOP hybrid systems developed here can be applied to diverse water matrices, offering a scalable and adaptable approach for municipal and industrial wastewater treatment facilities. These findings contribute to safer water management practices by enhancing the degradation of harmful contaminants, minimizing toxic by-products, and offering a pathway toward cleaner, safer drinking water and a more sustainable water purification process.

The ability of ultrasound/peracetic acid (US/PAA) to degrade the azo dye Sunset Yellow FCF (SSY) was evaluated considering the impacts of power, pH, inorganic carbon, common salts, radical scavengers, and real water matrices. Pseudo-first-order rate constants revealed synergy indices of 2.90, 3.28, 2.22, and 2.03 at electrical powers of 40, 60, 80, and 100 W, respectively. Selective scavenger assays revealed a mixed radical regime. •OH radical involvement was confirmed by inhibition with alcohols (tert-butanol, 2-propanol), benzoic acid, nitrobenzene, sodium azide, and phenol, while suppression by TEMPO highlighted the key role of PAA-derived acyl and peroxyl radicals. Nitrobenzene caused pronounced inhibition at elevated doses, while nitrite acted as a decisive quencher by converting •OH and other oxidants into less reactive species. Carbonate alkalinity exerted dual effects: at acidic pH (3.7–4.4) it diverted •OH radicals to carbonate radicals and reduced cavitation through dissolved CO2, whereas at near-neutral pH it buffered conditions toward the optimum (pH 9) and enhanced degradation. Common anions (chloride, sulfate, nitrate) at ≤10 mM produced minor effects. Tests in environmental waters revealed the following reactivity order: seawater > ultrapure water > tap water ≈ Zamzam water > tertiary effluent. Enhanced performance in seawater was attributed to halide-mediated formation of reactive chlorine and bromine species, while inhibition in effluent was linked to organic matter scavenging. Overall, US/PAA emerges as a robust and adaptable advanced oxidation process for azo dye abatement across diverse water matrices.

Superiority of UV222 radiation by in situ aquatic electrode KrCl excimer in disinfecting waterborne pathogens: Mechanism and efficacy

Insights into the application of the anodic oxidation process for the removal of per- and polyfluoroalkyl substances (PFAS) in water matrices

Retrieving the spent photocatalysts from the reaction system is always a challenging task. Therefore, the present work is focused on immobilizing sulfur-doped-Bi2O3/MnO2 (S-BOMO) heterojunction photocatalysts over different support matrices and evaluating their performance for the removal of sulfamethoxazole (SMX) in water under visible light. Our findings revealed S-BOMO coated clay beads (S-BOMO CCB) achieving more than 86% (240 min) SMX degradation ∼3, ∼1.3, and ∼2 times higher compared to S-BOMO coated on the different substrates, including glass beads, floating stones, and polymer material substrates, respectively. Mott-Schottky measurements confirmed the construction of the Z-scheme heterojunction involving MnO2 and 2S-Bi2O3. This Z-scheme mechanism, along with its narrow band gap of 1.58 eV, resulted in a rapid spatial transfer of the photogenerated charge carriers between the semiconductors and is believed to enhance the overall photocatalytic activity of the nanocomposite. Radical trapping and electron paramagnetic resonance results clearly established the active role of hydroxyl radicals and hydrogen peroxide in the degradation of SMX. Further, the 2S-BOMO CCB demonstrated excellent stability and photocatalytic activity over multiple runs. According to the sensitivity analysis and the results of anion effect experiments, phosphate and sulfate ions exhibit a significant impact on sulfamethoxazole degradation. Toxicity analysis revealed that 2S-BOMO CCB and sulfamethoxazole degradation byproducts were apparently innocuous. Additionally, the practical applicability of 2S-BOMO CCB was examined in various real water matrices, with the degradation efficiency followed the order: tap water < groundwater < surface water < hospital wastewater < municipal wastewater < pharmaceutical industry wastewater. The economic assessment revealed the reduction in the overall cost of the immobilized 2S-BOMO following the recovery process. Overall, the findings of this work provided critical insights into the synthesis and performance of incredibly effective and stable immobilized photocatalysts for the degradation of pharmaceutical pollutants.

Ozone activation over core-shell nanoreactors for enhanced organic pollutants degradation: Surface-bound superoxide radicals induced by confinement effect.

Heterogeneous photocatalysis/persulfate oxidation process has been considered as a promising technology for dye contaminants removal. The magnetic ZnFe2O4/active carbon (AC) composites were hydrothermally synthesized and firstly used to activate peroxydisulfate (PDS) for rhodamine B (RhB) degradation under visible LED light irradiation. The optimized Vis-ZnFe2O4/AC(4/1)-PDS system can enhance the RhB degradation efficiency by 32.01% and 13.87% compared with Vis-ZnFe2O4-PDS and Vis-AC-PDS systems, respectively. The influence of operational parameters such as catalyst dosage (0.2 - 0.4g L-1), PDS concentration (1.0 - 2.0g L-1), temperature (25 - 45°C), solution pH (2.7 - 10.9), and coexisting inorganic ions (Cl-, NO3-, HCO3-, PO43-, Cu2+, Fe3+, and Ca2+) on RhB degradation was studied, and 100% of RhB (20mg L-1) was degraded after 80min at operational condition: 0.30g L-1 of ZnFe2O4/AC(4/1) and 1.5g L-1 of PDS, solution pH of 2.74, reaction temperature of 25°C. The quenching experiments, EPR test, and XPS analysis were employed to reveal the proposed mechanism, which demonstrated that 1O2 played a more important role than other reactive species (SO4•-, •OH, O2•-, and h+) in RhB degradation. The generation of 1O2 via the two routes was as follows: (i) the in situ formed active oxygen (O*) reacted with HSO5- to produce 1O2; (ii) O2•- was oxidized by h+ to form 1O2. After five consecutive cycles, the photodegradation efficiency of RhB by ZnFe2O4/AC(4/1) catalyst slightly decreased from 88.52 to 83.92%, indicating the excellent reusability of ZnFe2O4/AC(4/1) photocatalyst. As designed, Vis-ZnFe2O4/AC-PDS oxidation system can effectively remove RhB from the different real water matrices, and the degradation efficiency of RhB in tap water, river water, and secondary effluent was 78.24%, 79.55%, and 74.53% after 80min of reaction, respectively.

Polystyrene microplastics have emerged as a global environmental concern due to their widespread distribution and potential risks to ecosystems and human health. Accurate quantification of microplastics in water matrices remains challenging due to the limitations of conventional detection methods. This study adapted an incremental modification staining-spectrophotometry method for the quantitative detection of microplastic concentration in water, based on the adsorption of hydrophobic dyes onto the surface of microplastics, combined with UV-vis spectrophotometry. Under optimal conditions (pH = 7, room temperature, 1 µm polystyrene microplastics, deionized water, no interferents), there was a good linear relationship between absorbance and polystyrene microplastic concentration in the range of 5-100 mg L-1, with a correlation coefficient (R2) of 0.9933, a limit of detection of 0.76 mg L-1, and a spike recovery rate of 108.65%. Furthermore, the method exhibited strong anti-interference capability, retaining good linearity (R2 > 0.99) and recovery rates (>95%) under various environmental conditions, including temperatures of 25 °C and 45 °C, pH values of 3, 7, 11, and 13, and the presence of common coexisting ions (Ca2+, Na+, K+, SO42-, CO32-, and Cl-). Satisfactory linearity was also achieved in real water matrices such as tap water and lake water. Characterization using optical microscopy, scanning electron microscopy, and Fourier-transform infrared spectroscopy confirmed that the staining process involves physical adsorption without altering the chemical structure or morphology of the polystyrene microplastics. Compared with conventional methods, this approach offers advantages including operational simplicity, high sensitivity, good linearity, and strong environmental adaptability, making it a promising tool for rapid quantitative detection of small-sized polystyrene microplastics in water.

Sustainable degradation of bisphenol A using a pH-responsive TiO2/g-C3N4/rGO photocatalyst with easy recovery.

Activation of ozone by peroxymonosulfate for selective degradation of 1,4-dioxane: Limited water matrices effects

Evaluating synergy of dual-wavelength deep-UV radiation (222 + 282 nm) for synchronous water decontamination and disinfection

Facile synthesis of 2D/0D Bi2O3/MnO2 Z-scheme heterojunction for enhanced visible light-assisted photocatalytic degradation of acetaminophen

Insights of emerging contaminants removal in real water matrices by CWPO using a magnetic catalyst

BACKGROUNDIn this study, graphitic carbon nitride (g‐C3N4) photocatalyst was successfully synthesized via calcination of urea under argon flow and tested for methyl paraben (MeP) degradation in aqueous media under simulated solar light for the first time. Its structural, morphological, and optical properties were investigated with the use of X‐Ray diffraction (XRD), diffuse reflectance spectroscopy (DRS), and Brunauer‐Emmett‐Teller (BET) surface area analysis method.RESULTSThe as‐synthesized g‐C3N4 exhibited high photocatalytic performance towards the degradation of MeP in ultra‐pure water (UPW), yielding a near‐complete elimination after 90 min of irradiation. Experimental results revealed that the photocatalytic reaction followed pseudo‐first‐order kinetics. Furthermore, the photocatalytic degradation of MeP was found to be strongly pH‐dependent. Experiments in real water matrices (bottled water (BW) and wastewater (WW)), as well as in UPW, spiked with inorganic and organic additives (bicarbonate ions, humic acid) affected the target compound degradation. For instance, the apparent rate constant of MeP in UPW was approximately 4 and 8 times greater than that of BW and WW, respectively. The addition of persulfate ions in the reaction mixture enhanced the performance of the present photocatalytic system. Trapping experiments revealed that photogenerated holes play a leading role in the photocatalytic degradation of MeP.CONCLUSIONOur findings demonstrate that g‐C3N4 photocatalysis can be used as an efficient technology for the removal of hazardous organic micropollutants, such as parabens. © 2020 Society of Chemical Industry (SCI)

Degradation pathways and organic matter transformation of acesulfame potassium electro-oxidation in real water matrices