Search Results (403)

Sorption and advanced oxidative processes (AOPs) are potential strategies for the removal of organic compounds, such as caffeine, from aqueous media. Such strategies tend to be more promising when combined with biopolymeric membranes as sorbents and photocatalyst supports. Therefore, the aim of the present study was to investigate sorption and AOP parameters in the performance of chitosan membranes and chitosan/TiO₂ composite membranes in individual and hybrid systems involving the photolysis, photocatalysis, and sorption of caffeine. Caffeine degradation by photolysis was 19.51 ± 1.14, 28.61 ± 0.05, and 30.64 ± 6.32%, whereas caffeine degradation by photocatalysis with catalytic membrane was 18.33 ± 2.20, 20.83 ± 1.49, and 31.41 ± 3.08% at pH 6, 7, and 8, respectively. In contrast, photocatalysis with the dispersed catalyst achieved degradation of 93.56 ± 2.12, 36.42 ± 2.59, and 31.41 ± 1.07% at pH 6, 7, and 8, respectively. These results indicate that ions present in the buffer solutions affect the net electrical charge on the surface of the composite biomaterial with the change in pH variation, occupying active sorption sites in the structure of the biomaterial, which was characterized by Fourier transform infrared spectrometry, thermogravimetric analysis, differential scanning thermogravimetry, and X-ray diffraction. Thus, it is verified that in a combined process of caffeine removal under UV irradiation and use of chitosan/TiO₂ composite membranes in phosphate-buffered medium, the photolysis mechanism is predominant, with little or no contribution from sorption, and that the TiO₂ catalyst promotes a significant reduction in the percentage of pollutant in the medium only when used dispersed and at low pH. Full article

Steel pickling sludge serves as a valuable iron source for synthesizing Fe-based catalysts in heterogeneous advanced oxidation processes (AOPs). Here, MoS₂@CoFe₂O₄ catalyst derived from steel pickling sludge was prepared via a facile solvothermal approach and utilized to activate peroxymonosulfate (PMS) for tetracycline hydrochloride (TCH) degradation. Comprehensive characterization using scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and X-ray diffraction (XRD) confirmed the supported microstructure, composition, and crystalline structure of the catalyst. Key operational parameters—including catalyst dosage, PMS concentration, and initial pH—were systematically optimized, achieving 81% degradation efficiency within 30 min. Quenching tests and EPR analysis revealed ∙SO₄^‒ as the primary oxidative species, while the catalyst maintained high stability and reusability across cycles. TCH degradation primarily occurs through hydroxylation, decarbonylation, ring-opening, and oxidation reactions. This study presents a cost-effective strategy for transforming steel pickling sludge into a high-performance Fe-based catalyst, demonstrating its potential for practical AOP applications. Full article

This study presents the development of a novel Cu–Co–O-codoped graphitic carbon nitride (g-C₃N₄) catalyst for efficient peroxymonosulfate (PMS) activation to degrade sulfamethoxazole (SMX) in aqueous environments. The synthesized Cu–Co–O-g-C₃N₄ catalyst demonstrated exceptional catalytic performance, achieving 90% SMX removal within 10 min—significantly outperforming pristine g-C₃N₄ (14%) and O-doped g-C₃N₄ (22%)—with a reaction rate constant of 0.63 min⁻¹. The superior activity was attributed to the synergistic effects of Cu-Co bimetallic doping and oxygen incorporation, which enhanced the active sites, stabilized metal ions, and minimized leaching. Mechanistic studies revealed a dual-pathway degradation process: (1) a radical pathway dominated by sulfate radicals (SO₄•⁻) and (2) a non-radical pathway driven by singlet oxygen (¹O₂), with the latter identified as the dominant species through quenching experiments. The catalyst exhibited broad pH adaptability and optimal performance at neutral to alkaline conditions. Characterization techniques (XRD, FTIR, XPS) confirmed successful doping and revealed that oxygen incorporation modified the electronic structure of g-C₃N₄, improving charge carrier separation. This work provides a sustainable strategy for antibiotic removal, addressing key challenges in advanced oxidation processes (AOPs), and highlights the potential of multi-heteroatom-doped carbon nitride catalysts for water purification. Full article

With water scarcity becoming worse, and demand increasing, the urgency for the water industry to hit net-zero carbon is accelerating. Even as a multitude of utilities have pledged to reach net-zero by 2050, advancing beyond the energy–water nexus remains a heavy lift. This paper, using a systematic literature review that complies with Preferred Reporting Items for Systematic Review and Meta-Analysis (PRISMA), aims to propose sustainable water resource management (SWRM) strategies that may assist water utilities in decarbonizing their value chains and achieving net-zero carbon. In total, 31 articles were included from SCOPUS, ResearchGate, ScienceDirect, and Springer. The findings show that water utilities are responsible for 3% of global greenhouse gas emissions and could reduce these emissions by more than 45% by employing a few strategies, including the electrification of transport fleets, the use of renewables, advanced oxidation processes (AOPs) and energy-efficient technologies. A broad-based case study from Scottish Water shows a 254,000-ton CO₂ reduction in the period since 2007, indicative of the potential of these measures. The review concludes that net-zero carbon is feasible through a mix of decarbonization, wastewater reuse, smart systems and policy-led innovation, especially if customized to both large and small utilities. To facilitate a wider and a more scalable transition, research needs to focus on development of low-cost and flexible strategies for underserved utilities. Full article

Through the use of heterogeneous catalysts, catalytic ozone oxidation technology, an effective and eco-friendly advanced oxidation process (AOP), facilitates the breakdown of ozone into reactive oxygen species (like ·OH) and greatly increases the mineralization efficiency of pollutants. This study examines the development of heterogeneous ozone catalysts through a critical evaluation of the five primary preparation techniques: ion exchange, sol–gel, coprecipitation, impregnation, and hydrothermal synthesis. Each preparation method’s inherent qualities, benefits, drawbacks, and performance variations are methodically investigated, with an emphasis on how they affect the breakdown of different resistant organic compounds. Even though heterogeneous catalysts are more stable and reusable than homogeneous catalysts, they continue to face issues like active component leaching, restricted mass transfer, and ambiguous mechanisms. In order to determine the key paths for catalyst selection in catalytic ozone treatment going forward, the main goal of this review is to provide an overview of the accomplishments in the field of the heterogeneous ozone catalyst treatment of wastewater that is difficult to degrade. Full article

This study investigates the formation and toxicity of disinfection by-products (DBPs) arising from the reactions between individual reactive chlorine species (RCS) and dissolved organic matter (DOM) during water treatment. Individual chlorine radicals (Cl^•) and dichloride radicals (Cl₂^•−) were selectively generated with a laser flash photolysis technique, and their interactions with Suwannee River natural organic matter (SRNOM) were analyzed. Results demonstrated a biphasic pattern of DBP formation, where initial increases in RCS exposure enhanced DBP concentrations and toxicities, followed by subsequent decreases at higher RCS exposure. Variations among DBP classes, including trichloromethanes, chloroacetic acids, and chloroacetaldehydes, highlighted the complexity of RCS-DOM interactions. Toxicity assessments further indicated chloroacetonitriles and chloroacetic acids as major toxicity contributors at varying RCS exposures. This study highlights the impact of RCS exposure levels to DBP formation and toxicities, providing mechanistic insights for optimizing parameters in RCS-mediated advanced oxidation processes (AOPs) for safer water treatment. Full article

As human living standards have improved, the demand for industrial products—such as food, dyes, cosmetics, pharmaceuticals, and others—has significantly increased. This surge in production has, in turn, led to a rise in industrial wastewater (IW) generation, which is often marked by low biodegradability and a high concentration of toxic or refractory compounds. This review highlights the use of coagulation–flocculation–decantation (CFD) and advanced oxidation processes (AOPs) for treating such wastewater. A comprehensive analysis of CFD is provided, covering the underlying mechanisms, types of coagulants (including metal-based, animal-derived, mineral, and plant-based), and the optimal operational conditions required to maximize treatment efficiency. This review discusses the properties and performance of these coagulants in detail. In addition, this paper explores the methods used in AOPs to reduce organic carbon, focusing particularly on the roles of hydroxyl and sulfate radicals. Emphasis is placed on the enhancement of these processes using radiation, chelating agents, and heterogeneous catalysts, along with their effectiveness in IW treatment. Finally, the integration of CFD as a pre-treatment step to improve the efficiency of subsequent AOPs is provided. Full article

In recent years, extensive attention has been paid to advanced oxidation processes (AOPs) with peracetic acid (PAA), a widely used disinfectant, using transition metal ions for the degradation of organic contaminants within water environments. Mn(II) has been widely used as an effective homogeneous transition metal catalyst for oxidant activation, but it has shown poor performances with PAA. Since the stability of manganese species can be enhanced through the addition of ligands, this study systematically investigated a novel AOP for the oxidation of carbamazepine (CBZ) using an Mn(II)/PAA system with several different ligands added. The reactive species were explored through UV-vis spectrometry, scavengers, and probe compounds. The results suggest that Mn(III)–ligand complexes and other high-valent Mn species (Mn(V)) were generated and contributed obviously toward efficient CBZ oxidation, while radicals like CH₃CO₂^• and CH₃CO₃^• were minor contributors. The oxidation efficiency of Mn(II)/PAA/ligands depended highly on ligand species, as ethylene diamine tetraacetic acid (EDTA) and oxalate (SO) could promote the oxidation of CBZ, while pyrophosphate (PPP) showed modest enhancement. The results obtained here might contribute to the removal of residue pharmaceuticals under manganese-rich waters and also shed light on PAA-based AOPs that could help broaden our present knowledge of manganese chemistry for decontamination in water treatment. Full article

This review provides a descriptive analysis of metformin, highlighting its environmental presence and classification as an emerging contaminant. It examines the risks associated with metformin and evaluates advanced oxidation processes (AOPs) for its degradation, including photolysis, photocatalysis, electrolysis, and ozonation. Metformin, a widely used biguanide for type 2 diabetes, is increasingly detected in aquatic environments due to its incomplete metabolism in humans, raising ecological concerns. While certain AOPs, such as ultraviolet (UV) photocatalysis and ozonation, achieve high degradation rates of 99.9% and 100%, respectively, they produce toxic by-products harmful to aquatic systems. Solar photocatalysis, despite a lower degradation rate (74.22%), stands out for operating without artificial energy and generating fewer hazardous by-products. The review identifies gaps in current degradation strategies and underscores the need for clean, sustainable methods. Future research directions include advancing biological and photocatalytic technologies to improve AOPs’ efficiency while minimizing environmental risks. Full article

The increasing presence of emerging contaminants in aquatic environments, particularly endocrine disruptors (EDs), has raised significant environmental and public health concerns due to their toxicity, persistence, and ability to interfere with the endocrine systems of both aquatic organisms and humans. Among these compounds, the steroid hormones 17β-estradiol (E2) and 17α-ethinylestradiol (EE2) stand out, as they are frequently detected in wastewater, even after conventional treatment processes, which often exhibit limited removal efficiency. In this context, advanced oxidation processes (AOPs), especially those based on the generation of sulfate radicals (SO₄•⁻), have emerged as promising alternatives due to their high redox potential, extended half-life, and broad effectiveness across various pH levels. This work reviews recent advances in AOPs for the degradation of E2 and EE2, focusing on sulfate radical-based processes. The main degradation mechanisms, operational parameters, removal efficiency, challenges for large-scale application, and gaps in the current literature are discussed. The analysis indicates that despite their high effectiveness, sulfate radical-based processes still require further investigation in real wastewater matrices, the assessment of the toxicity of by-products, and the optimization of operational variables to be established as viable and sustainable technologies for wastewater treatment. Full article

Persistent organohalogen pollutants—including halogenated nitrophenols (HNCs), trichloroethylene (TCE), and per- and polyfluoroalkyl substances (PFAS)—pose serious environmental and health risks due to their stability, toxicity, and bioaccumulation potential. This review critically assesses current remediation technologies including advanced oxidation processes (AOPs), adsorption, membrane filtration, and thermal treatments. While these methods can be effective, they are often limited by high costs, energy demands, toxic byproduct formation, and sustainability concerns. Emerging biological approaches offer promising alternatives. Among these, fungal-based degradation methods (mycodegradation) remain significantly underrepresented in the literature, despite fungi demonstrating a high tolerance to contaminants and the ability to degrade structurally complex compounds. Key findings reveal that white-rot fungi such as Phanerochaete chrysosporium and Trametes versicolor possess enzymatic systems capable of breaking down persistent organohalogens under conditions that inhibit bacterial activity. This review also identifies critical research gaps, including the need for direct comparative studies between fungal and bacterial systems. The findings suggest that integrating mycodegradation into broader treatment frameworks could enhance the environmental performance and reduce the long-term remediation costs. Overall, this review highlights the importance of diversifying remediation strategies to include scalable, low-impact biological methods for addressing the global challenge of organohalogen contamination. Full article

Organic soil pollution poses a persistent threat to environmental sustainability by disrupting nutrient cycling and ecosystem functioning. The biochar-activated persulfate (PS)-based advanced oxidation process (AOP) has emerged as a promising strategy for the sustainable remediation of organic-contaminated soils. This review provides a comprehensive overview of the recent progress in the PS-based degradation of organic pollutants, with a particular focus on the role of biochar as an efficient and environmental activator. This review further summarizes advancements in the design of modified biochars, including metal (Fe, Cu, Co, Mn, Zn, and La), non-metal (N, S, B, P), and functional group modifications, aimed at enhancing the PS activation efficiency while minimizing secondary environmental risks. Importantly, the overlooked contributions of soil microorganisms in PS/biochar systems are discussed, highlighting their potential to complement chemical oxidation and contribute to eco-compatible remediation pathways. This review emphasizes the sustainability-oriented evolution of PS/biochar technology, highlighting the importance of a cost-efficient implementation, ecological compatibility, and the rational engineering of smart, regenerable catalysts. These insights support the advancement of PS/biochar-based AOPs toward scalable, intelligent, and environmentally sustainable soil remediation. Full article

Advanced oxidation processes (AOPs) show significant promise to degrade recalcitrant water contaminants, such as 1,4-dioxane, but slow degradation kinetics limit the energy efficiency of this technology. We realized substantial enhancements in the degradation of 1,4-dioxane (a suspected carcinogen) using gold-coated titanium dioxide (Au/TiO₂) Janus nanoparticles (JNPs) irradiated with above-bandgap ultraviolet (UV) light (peak wavelength, 254 nm). To explain this result, we combined experimental measurements quantifying 1,4-dioxane degradation at varying UV wavelengths with finite-element simulations that provided explanatory insight into the light–matter interactions at play. The enhanced photocatalytic activity at the optimal condition (254 nm light, high intensity, Au/TiO₂) resulted from a larger quantity of photogenerated holes in the TiO₂ capable of reacting with water to form hydroxyl radicals that degrade 1,4-dioxane. This increased production of holes resulted from two sources: (1) more viable electron–hole pairs were created under 254 nm light owing to increased light absorption by the TiO₂ that was localized near the surface; (2) the metal sequestered photogenerated electrons from the TiO₂, which prevented electron–hole pairs from recombining, leaving more holes available to react with water. Our results motivate the exploration of different metal coatings (especially non-precious metals) and suggest a path toward broader implementation of TiO₂-based photocatalytic AOPs, which can effectively remove many water pollutants that survive conventional treatment techniques. Full article

N-Nitrosodimethylamine (NDMA) is a widely recognized disinfection by-product that poses significant carcinogenic risks in drinking water. Conventional methods for NDMA removal, such as nanofiltration and reverse osmosis membranes, have limited efficacy due to NDMA’s small molecular weight and polar properties. Advanced oxidation processes (AOPs) have shown promise, but traditional Fenton processes often fall short due to the chemical structure of nitrosamines in NDMA. This study proposes a novel, cost-effective approach using a one-step carbonization method to synthesize a catalyst from ferric ammonium citrate (FAC). The resulting FAC-600 integrates zero-valent iron and iron carbide with carbon-based functional groups, enhancing catalytic and electron transport activities. Our experiments demonstrated that the FAC-600/persulfate (PS) AOP system achieves over 90% NDMA removal across a wide concentration range (50 μg L⁻¹ to 1000 μg L ⁻¹) with a limited dosage of 0.5 g L⁻¹. Mechanistic insights revealed that superoxide and hydroxyl radicals dominate NDMA degradation, facilitated by the presence of dissolved oxygen and PS. This study underscores the potential of the FAC-600/PS AOP system as a robust and efficient solution for NDMA removal, promising safer drinking water through practical application. Full article

Industrial organic wastewater, with its complex composition, high biological toxicity, and recalcitrance, has become a major challenge in water pollution control. This is especially true for antibiotic-containing wastewater, such as ofloxacin wastewater, for which there is an urgent need to develop effective treatment technologies. Conventional treatment processes are insufficiently efficient, while individual advanced oxidation processes (AOPs) have drawbacks such as poor oxidation selectivity and catalyst deactivation. To address these issues, researchers have explored the coupling of different AOPs and found that such combinations can enhance the oxidation performance, achieve complementary advantages, reduce the equipment costs, and offer great development potential. An experiment was conducted to evaluate the performance of an Ozone-Electro-Fenton coupled process in treating ofloxacin industrial wastewater. The results demonstrated that under the same conditions, after four hours of treatment, the coupled process achieved a 70% reduction in the UV absorption peak of the wastewater, compared to less than 20% for individual processes, indicating a significant synergistic effect. Further optimization of the ozone aeration structure revealed that with a hole size of 0.5 mm, single-layer aeration holes, and six holes, the COD removal rate reached 96% after six hours, the ozone utilization improved to 85%, and the gas holdup stabilized at 4.6%. Under these conditions, the mixture of ozone and air bubbles formed mixed bubbles. Influenced by the electric field and electrode plate wall effects, the bubble residence time was prolonged. The bubble size was approximately 2.8 mm, the gas flow horizontal velocity was about 18.5 m/s, and after a horizontal displacement of 0.17 mm in the wastewater, the lateral velocity became zero. The ratio of the distance between the bubble center and the wall to the equivalent bubble diameter was approximately 3.45. The bubbles were subject to a strong wall effect, which extended their residence time. This not only facilitated the removal of small bubbles from the electrode plates but also enhanced the ion diffusion near the plates, thereby boosting pollutant degradation. This study shows that the Ozone-Electro-Fenton coupled process is highly effective in degrading ofloxacin industrial wastewater, offering an innovative solution for treating other antibiotic-containing wastewater. Future research will focus on further optimizing the process, improving its adaptability to complex matrix wastewater, and validating it at the pilot scale to promote its engineering application. Full article