Search Results (18)

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

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

Escalating herbicide pollution in natural water bodies necessitates further exploration of effective remediation strategies. This study investigated the electro-degradation of Terbutryn (TBT) at concentrations comparable to those encountered in agricultural practices. Anodic oxidation (AO), electro-Fenton (EF), and photoelectron-Fenton (PEF) were employed for TBT abatement. AO achieved moderate removal (68%), EF significantly improved efficiency (99%), and PEF surpassed both, reaching near complete removal (99.4%) by combining EF with UV light-induced •OH generation. Statistical analysis confirmed that optimizing treatment conditions was crucial. All three factors (current density, Fe²⁺ concentration, and initial TBT concentration) independently affected the PEF process ability to remove TBT pollutants. However, the interplay between these factors was even more important. Sufficient Fe²⁺ was critical for high TBT concentrations, and a balance between current density, Fe²⁺, and initial TBT concentration was necessary. Excessive levels of any could hinder COD removal. High-performance liquid chromatography (HPLC) was employed to monitor the degradation profile of by-products, including desthiomethyl Terbutryn, 2-hydroxy Terbutryn, and cyanuric acid. The analysis of these degradation products facilitated the proposal of a degradation pathway for Terbutryn. PEF stands out as a viable approach for TBT removal, especially in high-TBT wastewater. Full article

Dairy wastewater (DW) contains a high concentration of organic and inorganic pollutants. In recent years, extensive research has been conducted to develop more efficient techniques for the treatment of DW. Electrochemical advanced oxidation processes (EAOPs) have gained significant attention among the various treatment approaches. EAOPs rely on electrochemical generation of hydroxyl radicals (•OH) which are considered highly potent oxidizing compounds for the degradation of pollutants in DW. In this paper, we provide an overview of the treatment of DW using various EAOPs, including anodic oxidation (AO), electro-Fenton (EF), photo electro-Fenton (PEF), and solar photo electro-Fenton (SPEF) processes, both individually and in combination with other techniques. Additionally, we discuss the reactor design and operating parameters employed in EAOPs. The variation in degradation efficiency is due to different oxidizing agents produced in specific approaches and their pollutant degradation abilities. In AO process, •OH radicals generated on electrode surfaces are influenced by electrode material and current density, while EF procedures use Fe²⁺ to create oxidizing agents both on electrodes and in the DW solution, with degradation mechanisms being affected by Fe²⁺, pH, and current density; additionally, PEF and SPEF approaches enhance oxidizing component production and pollutant degradation using ultraviolet (UV) light. Integration of EAOPs with other biological processes can enhance the pollutant removal efficiency of the treatment system. There is a scope of further research to exhibit the effectiveness of EAOPs for DW treatment in large scale implementation. Full article

Pesticides ensure greater productivity in less time; however, they spread beyond the perimeters to which they are applied to reach non-target organisms, thereby affecting plant, animal, and human health. Thiamethoxam (TMX) is considered to be one of the main agents responsible for poisoning bees and potentially contaminating surface and groundwater. Conventional water-treatment protocols are unable to degrade thiamethoxam; therefore, electrochemically advanced oxidative processes (EAOPs) have become promising alternatives owing to their ease of operation and cost-effectiveness. Herein, we examined the use of EAOPs to oxidize thiamethoxam in commercial Actara^® and analyzed treatment efficiencies through phytotoxicity studies using cucumber and maize seeds as bioindicators. In addition, the cost of each process was analyzed based on the resulting current efficiency. The treated solutions were used to germinate seeds that were analyzed for total protein, hydrogen peroxide, lipid peroxidation (MDA), superoxide dismutase (SOD), and catalase (CAT) activities. EAOPs were found to effectively oxidize TMX, with more than 50% degraded and 80% COD removed under all treatment conditions, even when the commercial product was used. The photoelectro-Fenton process using 10 mg L⁻¹ FeSO4 and 100 mg L⁻¹ H₂O₂ exhibited the best results, with 79% of the TMX degraded and 83% of the COD removed, additionally exhibiting the lowest estimated operating cost (USD 1.01 dm⁻³). Higher enzymatic SOD and CAT activities, total protein content, and H₂O₂ concentration were observed; however, no significant changes in MDA were recorded. This treatment protocol effectively oxidizes TMX and reduces its phytotoxicity in maize and cucumber seedlings. Full article

The use of hydrogen peroxide (produced in situ or ex situ) as the main agent in oxidative processes of environmental pollutant removal is widely studied. The degradation of water pollutants, such as dyes, pharmaceuticals, cosmetics, petroleum derivatives, and even pathogens, has been successfully obtained by different techniques. This review gives an overview of the more recent methods developed to apply oxidative processes mediated by H₂O₂ and other reactive oxygen species (ROS) in environmental catalysis, with particular attention to the strategies (Fenton-like and Bio-Fenton, photo- and electro-catalysis) and the materials employed. A wide discussion about the characteristics of the materials specifically studied for hydrogen peroxide activation, as well as about their chemical composition and morphology, was carried out. Moreover, recent interesting methods for the generation and use of hydrogen peroxide by enzymes were also presented and their efficiency and applicability compared with the Fenton and electro-Fenton methods discussed above. The use of Bio-Fenton and bi-enzymatic methods for the in situ generation of ROS seems to be attractive and scalable, although not yet applied in full-scale plants. A critical discussion about the feasibility, criticalities, and perspectives of all the methods considered completes this review. Full article

Advancements in biological wastewater treatment with sustainable and circularity approaches have a wide scope of application. Biological wastewater treatment is widely used to remove/recover organic pollutants and nutrients from a diverse wastewater spectrum. However, conventional biological processes face challenges, such as low efficiency, high energy consumption, and the generation of excess sludge. To overcome these limitations, integrated strategies that combine biological treatment with other physical, chemical, or biological methods have been developed and applied in recent years. This review emphasizes the recent advances in integrated strategies for biological wastewater treatment, focusing on their mechanisms, benefits, challenges, and prospects. The review also discusses the potential applications of integrated strategies for diverse wastewater treatment towards green energy and resource recovery, along with low-carbon fuel production. Biological treatment methods, viz., bioremediation, electro-coagulation, electro-flocculation, electro-Fenton, advanced oxidation, electro-oxidation, bioelectrochemical systems, and photo-remediation, are summarized with respect to non-genetically modified metabolic reactions. Different conducting materials (CMs) play a significant role in mass/charge transfer metabolic processes and aid in enhancing fermentation rates. Carbon, metal, and nano-based CMs hybridization in different processes provide favorable conditions to the fermentative biocatalyst and trigger their activity towards overcoming the limitations of the conventional process. The emerging field of nanotechnology provides novel additional opportunities to surmount the constraints of conventional process for enhanced waste remediation and resource valorization. Holistically, integrated strategies are promising alternatives for improving the efficiency and effectiveness of biological wastewater treatment while also contributing to the circular economy and environmental protection. Full article

The aim of the paper is to present information from the literature concerning the course of electrochemical wastewater treatment processes in regard to organic micro-pollutant removal. Most often, in order to remove xenobiotics that are difficult to degrade biochemically, advanced oxidation processes and photochemical processes with or without catalysts are used. The efficiency of these processes can be supported by the flow of electric current through the solution being purified in a special system. This paper presents the theoretical foundations of processes such as electrocoagulation, electroflotation, and advanced chemical and photochemical oxidation supported by electric power. Among the processes where the Fenton’s reagent is the oxidant, the electro-Fenton and photo-electro-Fenton processes are also described. This information is supplemented with examples of the use of these processes for removal/degradation of selected organic compounds such as pesticides, dyes, pharmaceuticals, cosmetic ingredients, and other organic xenobiotics from wastewater. Full article

Constructing heterostructure within electrocatalysts proves to be an attractive approach to adjust the interfacial charge redistribution to promote the adsorption of reactive species and accelerate the charge transfer. Herein, we present the one-pot solvothermal synthesis of Ti₃C₂ supported hollow CoS₂/CoS microsphere heterostructure with uneven charge distribution as the cathodic catalyst, which displays a superior quasi-first-order degradation rate (0.031 min⁻¹) for sulfamethazine (SMT) in photo-assisted electric–Fenton (EF) process. CoS₂/CoS/Ti₃C₂ is proven to favor the 2e⁻ oxygen reduction reaction (ORR), with H₂O₂ selectivity up to 76%. The built-in potential present in the heterojunction helps to accelerate electron transfer, thus promoting the production of H₂O₂. Subsequently, H₂O₂ is rapidly activated to produce ∙OH due to the synergistic effect of Co and S. Notably, CoS₂/CoS/Ti₃C₂ exhibits enhanced photo-assisted EF (PEF) performance under light. The excellent photocatalysis properties of CoS₂/CoS/Ti₃C₂ are attributed to that the unique hollow microsphere structure of catalyst improves the light absorption, and the uneven charge distribution of CoS₂/CoS heterojunctions promotes the separation of photo-generated holes and electrons. Given the above advantages, CoS₂/CoS/Ti₃C₂ cathode delivers a high degradation rate of 98.5%, 91.8%, and 94.5% for SMT, bisphenol A, and sulfadiazine, respectively, with TOC removal efficiency of 76% for SMT with 120 min. This work provides a novel light of the design and construction of efficient PEF cathodes for the treatment of antibiotic wastewater. Full article

Bismuth vanadate (BiVO₄, BV) is a widely explored photocatalyst for photo(electro)chemical applications, but its full photocatalytic potential is hindered by the fast recombination and low mobility of photogenerated charge carriers. Herein, we propose the photodeposition of different amounts of Prussian blue (PB) cocatalysts on the surface of monoclinic BV to obtain BV-PB composite photocatalysts with increased photoactivity. The as-prepared BV and BV-PB composites were characterized by an array of analytic techniques such scanning eletron microscopy (SEM), transmission eletron microscopy (TEM), X-day diffraction (XRD), and spectroscopic techniques including Fourier-transform infrared spectroscopy (FTIR), diffuse reflectance spectroscopy (DRS), electrochemical impedance spectroscopy (EIS), photoluminescence (PL), and Raman spectroscopy. The addition of PB not only increases the absorption of visible light, as indicated by DRS, but also improves the charge carriers’ transfer across the photocatalysts/solution interface and hence reduces electron-hole (e⁻-h⁺) recombination, as confirmed by EIS and PL measurements. Resultantly, the BV-PB composite photocatalysts with optimum PB loading exhibited enhanced Cr(VI) photoreduction efficiency as compared to pristine BV under visible light illumination from low-power blue light-emitting diodes (LEDs), thanks to the cocatalyst role of PB which mediates the transfer of photoexcited conduction band (CB) electrons from BV to Cr(VI) species in solution. Moreover, as compared to pristine BV and BV + H₂O₂, a drastic increase in the methylene blue (MB) photo-oxidation efficiency was observed for BV-PB in the presence of a minute quantity of H₂O₂ due to a synergic effect between the photocatalytic and Fenton-like processes. While pure BV photodegraded around 70% of MB dye within 120 min, the BV-PB/H₂O₂ and BV/H₂O₂ system could degrade almost 100% of the dye within 20 min (k_obs. = 0.375 min⁻¹) and 40 min (k_obs. = 0.055 min⁻¹), respectively. The practical approach employed in this work may pioneer new prospects for synthesizing new BV-based photocatalytic systems with low production costs and high photoredox efficiencies. Full article

Heterogeneous photo-electro-Fenton process is an attractive technology for the removal of recalcitrant pollutants. To better exploit the presence of an irradiation source, a bifunctional catalyst with TiO₂ nanoparticles embedded into an iron–chitosan matrix was developed. The catalytic activity of the catalyst was improved by the optimization of the loaded TiO₂ content. The prepared composite catalysts based on TiO₂, Fe₃O₄ and chitosan were called TiO₂/Fe₃O₄-CS beads. The best catalyst with an optimal ratio TiO₂/Fe = 2 exhibited a high efficiency in the degradation and mineralization of chlordimeform (CDM) insecticide. Under the optimum conditions (concentration of catalyst equal to 1 g L⁻¹ and applied current intensity equal to 70 mA), a real effluent doped with 30 mg L⁻¹ of CDM was efficiently treated, leading to 80.8 ± 1.9% TOC reduction after 6 h of treatment, with total removal of CDM after only 1 h.The generated carboxylic acids and minerals were identified and quantified. Furthermore, the stability and reusability of the developed catalyst was examined, and an insignificant reduction in catalytic activity was noticed for four consecutive cycles of the photo-electro-Fenton process. Analyses using SEM, XRD and VSM showed a good stability of the physicochemical properties of the catalyst after use. Full article

Photoelectro-Fenton (PEF) process can continuously promote the occurrence of Fenton reaction and the generation of active species, which is an advanced oxidation technology for pollutant degradation. However, the lack of bifunctional catalysts restricts the development of PEF technology. In this study, the electronic rearrangement MOF-525 modified by metalloporphyrin (named MOF-525-Fe/Zr) was prepared, to load on the carbon felt as a novel cathode catalyst, which is used in PEF process. A series of characterization and photoelectric chemical properties tests combined with DFT calculation showed that the modification of MOF-525 could not only have the large specific surface area and multistage pore structure but also co-stimulate the metal-to-ligand charge transfer (MLCT) and ligand-to-cluster charge transfer (LCCT) by photoelectric synergy. These charge transitions provide periodic electron donor-acceptor conduction paths in MOF-525-Fe/Zr, which can improve the active species formation and transfer efficiency. Owing to their favorable pore and electronic structure as well as stability, MOF-525-Fe/Zr shows great promise for the application in the catalytic process of PEF. Sulfamethoxazole (SMX) degradation was enhanced by MOF-525-Fe/Zr with the TOC removal rate above 75% both in river water and tap water. Finally, the reasonable pathway of PEF catalytic degradation of SMX was proposed by HPLC-MS analysis. In conclusion, this study provides a new idea for reconstructing the electronic structure of MOFs catalyst and broadening the practical application of PEF technology. Full article

Water covers about 70% of the Earth’s surface, but the amount of freshwater available for human use is only 2.5% and, although it is continuously replenished via the water cycle, freshwater is a finite and limited resource. The Earth’s water is affected by pollution and while water quality is an issue of global concern, the specific regulations on contaminants of emerging concern (CECs) are limited. In order to achieve the goals set by EU regulations, the treatment of wastewater is a scientifically and technologically challenging issue. Metal–organic frameworks (MOFs) are promising materials used for the removal of priority and emerging contaminants from wastewater, since they can mitigate those contaminants via both adsorption as well as catalysis processes. MOFs can offer selective adsorption of CECs by various adsorption mechanisms. The catalytic removal of priority and emerging organic contaminants from wastewater using MOFs implies Fenton, electro-Fenton, and photo-Fenton processes. Overall, MOFs can be considered as promising materials for the elimination of priority and emerging organic contaminants from various wastewater types, but the involved processes must be studied in detail for a larger number of compounds. Full article

Nowadays, water pollution is one of the most dangerous environmental problems in the world. The presence of the so-called emerging pollutants in the different water bodies, impossible to eliminate through conventional biological and physical treatments used in wastewater treatment plants due to their persistent and recalcitrant nature, means that pollution continues growing throughout the world. The presence of these emerging pollutants involves serious risks to human and animal health for aquatic and terrestrial organisms. Therefore, in recent years, advanced oxidation processes (AOPs) have been postulated as a viable, innovative and efficient technology for the elimination of these types of compounds from water bodies. The oxidation/reduction reactions triggered in most of these processes require a suitable catalyst. The most recent research focuses on the use and development of different types of heterogeneous catalysts, which are capable of overcoming some of the operational limitations of homogeneous processes such as the generation of metallic sludge, difficult separation of treated water and narrow working pH. This review details the current advances in the field of heterogeneous AOPs, Fenton processes and photocatalysts for the removal of different types of emerging pollutants. Full article

This study focused on the reduction of the treatment cost of mature landfill leachate (LL) by enhancing the coagulation pre-treatment before a UVA-LED photo-Fenton process. A more efficient advanced coagulation pretreatment was designed by combining conventional coagulation (CC) and electro-coagulation (EC). Regardless of the order in which the two coagulations were applied, the combination achieved more than 73% color removal, 80% COD removal, and 27% SUVA removal. However, the coagulation order had a great influence on both final pH and total dissolved iron, which were key parameters for the UVA-LED photo-Fenton post-treatment. CC (pH = 5; 2 g L⁻¹ of FeCl₃6H₂O) followed by EC (pH = 5; 10 mA cm⁻²) resulted in a pH of 6.4 and 100 mg L⁻¹ of dissolved iron, whereas EC (pH = 4; 10 mA cm⁻²) followed by CC (pH = 6; 1 g L⁻¹ FeCl₃6H₂O) led to a final pH of 3.4 and 210 mg L⁻¹ dissolved iron. This last combination was therefore considered better for the posterior photo-Fenton treatment. Results at the best cost-efficient [H₂O₂]:COD ratio of 1.063 showed a high treatment efficiency, namely the removal of 99% of the color, 89% of the COD, and 60% of the SUVA. Conductivity was reduced by 17%, and biodegradability increased to BOD₅:COD = 0.40. With this proposed treatment, a final COD of only 453 mg O₂ L⁻¹ was obtained at a treatment cost of EUR 3.42 kg COD⁻¹. Full article