Search Results (144)

In this study, the degradation of Nile Blue dye was investigated using homogeneous and heterogeneous photocatalytic methods based on the photo-Fenton reaction. More specifically, for homogeneous photocatalysis, the classical photo-Fenton (UV/Fe²⁺/H₂O₂) and modified photo-Fenton-like (UV/Fe²⁺/S₂O₈²⁻) systems were studied, while for heterogeneous photocatalysis, a commercial MOF catalyst, Basolite F300, and a natural ferrous mineral, geothite, were employed. Various parameters—including the concentrations of the oxidant and catalyst, UV radiation, and pH—were investigated to determine their influence on the reaction rate. In homogeneous systems, an increase in iron concentration led to an enhanced degradation rate of the target compound. Similarly, increasing the oxidant concentration accelerated the reaction rate up to an optimal level, beyond which radical scavenging effects were observed, reducing the overall efficiency. In contrast, heterogeneous systems exhibited negligible degradation in the absence of an oxidant; however, the addition of oxidants significantly improved the process efficiency. Among the tested processes, homogeneous techniques demonstrated a superior efficiency, with the conventional photo-Fenton process achieving complete mineralization within three hours. Kinetic analysis revealed pseudo-first-order behavior, with rate constants ranging from 0.012 to 0.688 min⁻¹ and correlation coefficients (R²) consistently above 0.90, confirming the reliability of the applied model under various experimental conditions. Nevertheless, heterogeneous techniques, despite their lower degradation rates, also achieved high removal efficiencies while offering the advantage of operating at a neutral pH without the need for acidification. Full article

The extensive use of herbicide 2-methyl-4-chlorophenoxyacetic acid (MCPA), coupled with its limited biodegradability, has led to its ubiquitous presence in aquatic environments. This work investigates the removal of MCPA (100 mg/L) in the aqueous phase via solar photo-Fenton. The process was carried out in a 700 mL reactor using a Xe lamp that simulates solar radiation (λ: 250–700 nm). A parametric study was conducted to assess the influence of dissolved O₂ on the reaction medium, Fe²⁺ dosage, H₂O₂ concentration and pH₀. The results indicate that dissolved O₂ boosts pollutant mineralization, even working at sub-stoichiometric H₂O₂ concentrations. Under optimal reaction conditions ([Fe²⁺]: 7.5 mg/L, [H₂O₂]₀: 322 mg/L (stoichiometric dose), pH₀: 3.5), the MCPA reached almost complete mineralization (X_TOC: 98.40%) in 180 min. Phytotoxicity and ecotoxicity assessments of treated effluents revealed that even working at sub-stoichiometric H₂O₂ dosages, toxicity decreases with the solar photo-Fenton treatment. Finally, the solar photo-Fenton process was evaluated in relevant matrices (river water and WWTP secondary effluent) and a realistic pollutant concentration (100 µg/L). In all cases, the pollutant degradation was ≥70% in 60 min, demonstrating the potential of this technology as a tertiary treatment. Full article

This article provides an overview of the use of electrochemical advanced oxidation processes (EAOPs) applied to the treatment of water contaminated by pesticides. Given the global increase in the use of pesticides and the ineffectiveness of conventional treatment methods, EAOPs emerge as promising alternatives. They stand out for their efficiency in the degradation of organic compounds, minimal reliance on additional chemical reagents, and minimal generation of waste. The main methods addressed include anodic oxidation, photoelectro-oxidation, electro-Fenton and photoelectro-Fenton, which use hydroxyl radicals, a potent non-selective oxidant, to mineralize pollutants. A total of 165 studies were reviewed, with emphasis on the contributions of countries such as China, Spain, Brazil, and India. Factors such as electrode type, presence of catalysts, pH, and current density influence the effectiveness of treatments. Combined processes, especially those integrating UV light and renewable sources, have proven to be more efficient. Despite challenges related to electrode cost and durability, recent advances highlight the sustainability and scalability of EAOPs for the treatment of agricultural and industrial effluents contaminated with pesticides. Full article

Controlled iron extraction from iron-based sludge (Fe-Sludge) drainage and its use as a Fenton’s reagent is investigated in the current study for eliminating organics from launderette discharge stream. The influences of the iron dosage, hydrogen peroxide concentration, and pH are assessed as treatment factors for their direct impact on the oxidation of organic compounds. Additionally, optimal oxidation conditions are determined using the response surface methodology (RSM) technique, and the ranges of treatment variables are analyzed. The optimum values of a pH of 2.0, Fe sludge concentration of 99 mg/L, and H₂O₂ content of 402 mg/L resulted in optimal organics removal of up to 98%, expressed as Chemical Oxygen Demand (COD) removal. The oxidation efficacy attained from the design is confirmed and the model validation is assessed, and the suggestive model is accepted since it possesses a correlation coefficient of 97.7%. The thermodynamic and kinetic models are also investigated, and the reaction showed that the temperature increases resulted in the oxidation efficiency being reduced. The oxidation efficiency expressed as COD reduction is clearly characterized by first-order reaction kinetics. The thermodynamic characteristics indicated that the oxidation reaction was exothermic and not spontaneous. Full article

The widespread contamination of aquatic environments by tetracycline antibiotics (TCs) poses a substantial threat to public health and ecosystem stability. Although photo-Fenton processes have demonstrated remarkable efficacy in degrading TCs, their practical application is limited by challenges associated with catalyst recyclability. This study reports the development of a novel magnetic recoverable SrFe₁₂O₁₉/g-C₃N₄ heterostructure photocatalyst synthesized via a facile one-step co-calcination method using industrial-grade precursors. Comprehensive characterization revealed that nitrogen defects and the formation of heterojunction structures significantly suppress electron (e⁻)–hole (h⁺) pair recombination, thereby markedly enhancing catalytic activity. The optimized 7-SFO/CN composite removes over 90% of oxytetracycline (OTC) within 60 min, achieving degradation rate constants of 0.0393 min⁻¹, which are 9.1 times higher than those of SrFe₁₂O₁₉ (0.0043 min⁻¹) and 4.2 times higher than those of g-C₃N₄ (0.0094 min⁻¹). The effectively separated e⁻ play three critical roles: (i) directly activating H₂O₂ to generate ·OH radicals, (ii) promoting the redox cycling of Fe²⁺/Fe³⁺ ions, and (iii) reducing dissolved oxygen to form ·O₂⁻ species. Concurrently, h⁺ directly oxidize OTC molecules through surface-mediated reactions. Furthermore, the 7-SFO/CN composite exhibits exceptional operational stability and applicability, offering a transformative approach for scalable photocatalytic water treatment systems. This work provides an effective strategy for designing efficient and recoverable photocatalysts for environmental remediation. Full article

This study presents a comprehensive kinetic analysis of sulfamethoxazole (SMX) degradation by the photo-Fenton process, highlighting its potential for removing emerging micropollutants in water treatment. The degradation of SMX followed pseudo-first-order kinetics, with increasing Fe(II) concentrations significantly accelerating the oxidation rate. A kinetic model was developed to describe SMX removal, aromaticity loss, and color changes during treatment. Although SMX was rapidly eliminated, intermediate aromatic and chromophoric compounds persisted, requiring extended reaction times for complete mineralization. The kinetic modeling of aromaticity and color revealed distinct degradation pathways and rate constants, showing a strong dependence on iron dosage. The formation of nitrate and sulfate was used to monitor nitrogen and sulfur mineralization, respectively. Optimal nitrate formation was achieved at 22 mol SMX: 1 mol Fe(II), beyond which excessive iron promoted radical scavenging and the formation of stable Fe–aminophenol complexes, inhibiting complete nitrogen oxidation and aromatic degradation. Moreover, excessive Fe(II) led to increased water coloration due to complexation with partially oxidized aromatic byproducts. These findings emphasize the need for optimized catalyst dosing to balance degradation efficiency and minimize secondary effects. The proposed kinetic models offer a predictive tool for improving photo-Fenton-based treatments and integrating them with biological processes to enhance micropollutant bioremediation. Full article

Organic pollutants released into water bodies have posed a serious threat to aquatic ecosystems. The elimination of organic pollutants from water through the photo-Fenton process has attracted extensive attention. Among various photo-Fenton catalysts, iron oxides have been intensively studied due to their environmentally benign characteristics and abundance. However, the rapid recombination of photogenerated charge carriers (e⁻–h⁺) and slow Fe(III)/Fe(II) cycling of iron oxides restrict their catalytic performance. Thus, this state-of-the-art review focuses on the recent research development regarding iron oxide-based heterojunctions with enhanced catalytic performance to eliminate organic pollutants. This review provides a fundamental understanding of the iron-based heterogeneous photo-Fenton reaction. In addition, various heterojunctions for photocatalytic applications are comprehensively summarized. A thorough discussion is held on the material design for iron oxide-based heterojunctions with improved photo-Fenton catalytic performance. Ultimately, the challenges and prospects of iron oxide-based heterojunction catalysts for photo-Fenton water decontamination are outlined. Full article

This study examines the degradation of sulfamethoxazole (SMX) in water using the photo-Fenton process, focusing on dissolved oxygen (DO) dynamics, organic matter mineralization, and water quality improvement. The results show that SMX degradation follows a rapid kinetic pattern, achieving complete removal within 30 min. However, total organic carbon reduction occurs more gradually, indicating the persistence of organic intermediates before full mineralization into CO₂ and H₂O. DO evolution follows a biphasic trend: an initial decline due to oxidative consumption, followed by an increase due to H₂O₂ decomposition into O₂. Initially, at [H₂O₂]₀ ≥ 3.0 mM, DO sharply increases, while at [Fe(II)]₀ = 5.0 mg/L, DO reaches a minimum of 0.3 mg/L due to higher reactive oxygen species (ROS) production. Water quality parameters such as color, turbidity, and aromaticity were also monitored. Aromaticity significantly decreases within 30 min, confirming SMX ring cleavage. Color and turbidity initially intensify and increase due to intermediate formation but later decrease as mineralization progresses. Optimal conditions (1 mol SMX: 10 mol H₂O₂: 0.05 mol Fe(II)) ensure efficient degradation with minimal oxygen depletion without excessive scavenging effects. These findings confirm that the photo-Fenton process effectively removes SMX while improving water quality, making it a sustainable alternative for pharmaceutical wastewater treatment. Full article

The discharge of wastewater containing persistent organic pollutants presents significant ecological and health challenges due to their toxicity and resilience. Recent advances in advanced oxidation processes (AOPs) and other remediation mechanisms, notably utilizing natural mineral materials (NMMs), offer promising solutions to these challenges. NMMs, with their cost-effectiveness, accessibility, eco-friendly nature, non-toxicity, and unique structural properties, have shown significant promise in environmental remediation and could effectively replace conventional catalysts in related applications. These minerals enable the activation of oxidants, generating reactive oxygen species crucial for the degradation of pollutants. This article reviews the mechanisms of NMMs in various AOPs, including photocatalysis, Fenton-like reactions, and persulfate-activation-based processes, and discusses the potential of these materials in enhancing pollutant degradation efficiency, with a focus on the activation of persulfates and the photo-induced redox processes. The synergy between photocatalytic properties and catalytic activation provided by NMMs offers a robust approach to managing water pollution without the drawbacks of secondary waste production, thus supporting sustainable remediation efforts. Full article

This study investigates the synthesis and evaluation of ZnO/g-C₃N₄ composites as efficient green catalysts for advanced oxidation processes (AOPs) targeting the treatment of contaminated water. The composites were synthesized using a ternary deep eutectic solvent and physically–chemically characterized in detail, confirming their structural integrity and successful synthesis. Photocatalytic, photo-Fenton- and electro-Fenton-like experiments were conducted using Rhodamine B as a model contaminant to evaluate the catalytic performance, reuse and stability of the synthesized material. The synthesized ZnO/g-C₃N₄ composites demonstrated excellent photocatalytic activity under LED light (395 nm), achieving a pollutant removal of around 59% in 90 min. The combined effect of the designed catalyst and Fenton-like process, a photo-Fenton-like process, significantly improved this performance, achieving removal of close to 95% in 60 min due to the synergistic effects of the irradiation and H₂O₂ activation. Finally, the catalytic action of synthesized ZnO/g-C₃N₄ composites in the electro-Fenton-like process exhibited superior efficiency, achieving 90% removal within 45 min and kinetic constants four times higher than those of anodic oxidation alone. In addition, reuse studies confirmed the stability and catalytic activity of the composites for several cycles with high removal efficiencies, demonstrating their viability for long-term and scalable water treatment applications. These findings highlight the potential of ZnO/g-C₃N₄ composites synthesized through DES as a sustainable and cost-effective alternative for water remediation technologies. Full article

Water pollution by dyes is a major environmental problem, particularly in the textile, food, and pharmaceutical industries. These dyes are often complex chemical compounds that are difficult to remediate due to their chemical stability, their solubility in water, and their resistance to conventional treatment processes such as filtration, coagulation, or decantation. Thus, to date, there is still a need to make water treatment processes more performant and cost-efficient. The main aim of this research is to prepare photocatalytically active MFI-type zeolites from natural clays and support iron oxide nanoparticles. These catalysts were characterized and evaluated for the capture and the photo-Fenton degradation of methylene blue (MB) in aqueous solution. After 10 min under photo-Fenton conditions, Fe/MTK-MFI presented almost complete removal of MB for up to four consecutive cycles. Full article

In recent years, efforts have been made in developing new and more efficient water purification methods and the synthesis of catalysts with greater catalytic activity that are more stable and can be used in wide pH ranges. Pillared clays represent a viable alternative for removing organic contaminants. The clays, usually smectites, are modified by inserting inorganic pillars (Al, Zr, Cr, Fe, Ti, Ga, and Mn) between the layers of the clay, increasing its surface area, porosity, catalytic activity, and thermal stability. This review describes the importance of using pillared clays with different polyoxycations in Fenton, photo-Fenton, ozonation, wet catalytic oxidation of hydrogen peroxide, and photocatalysis processes. Pillared iron clays (Fe-PILCs) are promising catalysts capable of generating hydroxyl radicals that can oxidize organic contaminants, thus facilitating their removal. The current challenges of the PILC application at industrial scale are also discussed. Full article

The development of efficient and sustainable photocatalysts for wastewater treatment remains a critical challenge in environmental remediation. In this study, a ternary photocatalyst, Cu-Cu₂O/g-C₃N₄, was synthesized by embedding copper-copper oxide heterostructural nanocrystals onto g-C₃N₄ nanosheets via a simple deposition method. Structural and optical characterization confirmed the successful formation of the heterostructure, which combines the narrow bandgap of Cu₂O, the high stability of g-C₃N₄, and the surface plasmon resonance (SPR) effect of Cu nanoparticles. The photocatalytic performance was evaluated through the degradation of Rhodamine B (RhB) in a photo-Fenton-like reaction system under visible light irradiation. Among the catalysts tested, the 30 wt% Cu-Cu₂O/g-C₃N₄ composite exhibited the highest catalytic efficiency, achieving a reaction rate constant approximately 3 times and 1.5 times higher than those of Cu-Cu₂O and g-C₃N₄, respectively. Mechanistic studies suggest that the heterostructure facilitates efficient charge separation and promotes the reduction of Cu²⁺ to Cu⁺, thereby enhancing ∙OH radical generation. The catalyst also demonstrated excellent stability and reusability across a wide pH range. These findings provide a new strategy for designing highly efficient photocatalysts for organic pollutant degradation, contributing to the advancement of advanced oxidation processes for environmental applications. Full article

Sulfamethoxazole (SMX) is an antibiotic that is extensively used in veterinary medicine, and its occurrence in wastewater and surface water can reach up to 20 μg/L. SMX is categorized as a pollutant of emerging concern by the US EPA due to its persistence and effects on humans and the environment. In this study, photo-Fenton technology is proposed for the removal of SMX. Aqueous solutions of SMX (50.0 mg/L) are treated in a 150 W UV photoreactor, using [Fe²⁺]₀ = 0.5 mg/L and varying [H₂O₂]₀ = 0–3.0 mM. During the reaction, colour (AU) was assessed along with SMX (mg/L), turbidity (NTU), and TC (mg/L). SMX degrades to aromatic intermediates with chromophoric groups, exhibiting colour (yellow to brown) and turbidity. As these intermediates are mineralized into CO₂ and H₂O, the colour and turbidity of the water lose intensity. Using a molar ratio of 1 mol SMX:10 mol H₂O₂, the maximum degradation of aromatic species takes place (71% elimination), and colourless water with turbidity < 1 NTU is obtained. A kinetic modelling for aromaticity loss and colour formation as a function of the oxidant concentration has been proposed. The application of this model allows the estimation of oxidant amounts for an efficient removal of SMX under environmentally friendly conditions. Full article

The challenge of microcontaminants (MCs) in wastewater effluent has been addressed by using different technologies, including advanced oxidation processes (AOPs) and adsorption. This work evaluates the benefits and synergies of combining these two processes. The AOPs were photo-Fenton and UV/H₂O₂ operated under natural pH but with different reagents dosages, lamps, and chelating agents. Chelating agents were used at analytical (ethylenediamine-N,N-disuccinic acid and citric acid) and technical grade (citric acid) to simulate scaling-up conditions. The adsorption process was studied via granular activated carbon (GAC) filtration using fresh and regenerated GAC. Four AOP scenarios were selected and coupled with GAC filtration, showing benefits for both processes. AOP treatment time decreased from 10–15 min to 5 min, resulting in a reduction in energy consumption of between 50 and 66%. In the photo-Fenton process, it was possible to work with low reagent dosages (1.5 mg L⁻¹ iron and 20 mg L⁻¹ of H₂O₂). However, the use of UV/H₂O₂ showed close removal, highlighting it as a real alternative. An extension of the GAC lifetime by up to 11 times was obtained in all the scenarios, being higher for regenerated than for fresh GAC. Furthermore, the toxicity and phytotoxicity of the treated wastewater were evaluated, and no acute toxicity or slight variation in the phytotoxicity was observed in the combination of these processes. Full article