Search Results (65)

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

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

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

The reliance on acidic working environments presents a significant bottleneck in the development and widespread application of peroxymonosulfate (PMS)-activated high-valent iron-oxo systems and iron-based catalysts. In this study, we present a system of non-homogeneous activation of peroxymonosulfate that is capable of overcoming the acidic environment in heterogeneous to generate continuous non-radicals for the selective degradation of organic pollutants such as sulfamethoxazole. The system takes advantage of amphiprotic hydroxides to create a homogeneous neutral pH microenvironment at the heterogeneous interface of the catalyst. The generation of the neutral pH microenvironment is capable of inducing the formation of high-valent iron-oxo species and a more stable cycling of iron ions in the iron-based material., promoting sustained catalytic activity A series of design quenching experiments, electron paramagnetic resonance (EPR) experiments, and three-dimensional excitation-emission matrix fluorescence spectroscopy (3D-EEM) which were conducted to assess the selectivity of FeCo-LDH/PMS under high salt or natural organic conditions, as well as its effectiveness in treating real wastewater. These findings offer a novel approach to overcoming pH limitations and enhancing the selectivity of target pollutants in advanced oxidation processes (AOPs). Full article

The increasing presence of persistent pollutants in industrial wastewater underscores the shortcomings of conventional treatment methods, prompting the adoption of advanced oxidation processes (AOPs) for sustainable water remediation. This review examines the development of AOPs, focusing on their ability to produce hydroxyl radicals and reactive oxygen species (ROS) to mineralize complex pollutants. Homogeneous systems such as Fenton’s reagent show high degradation efficiency. However, challenges like pH sensitivity, catalyst recovery issues, sludge generation, and energy-intensive operations limit their scalability. Heterogeneous catalysts, such as TiO₂-based photocatalysts and Fe₃O₄ composites, offer improved pH adaptability, visible-light activation, and recyclability. Emerging innovations like ultraviolet light emitting diode (UV-LED)-driven systems, plasma-assisted oxidation, and artificial intelligence (AI)-enhanced hybrid reactors demonstrate progress in energy efficiency and process optimization. Nevertheless, key challenges remain, including secondary byproduct formation, mass transfer constraints, and economic feasibility for large-scale applications. Integrating AOPs with membrane filtration or biological treatments enhances treatment synergy, while advances in materials science and computational modeling refine catalyst design and reaction mechanisms. Addressing barriers in energy use, catalyst durability, and practical adaptability requires multidisciplinary collaboration. This review highlights AOPs as pivotal solutions for water security amid growing environmental pollution, urging targeted research to bridge gaps between laboratory success and real-world implementation. Full article

As the most promising techniques for refractory antibiotic degradation in wastewater management, sulfate radical-based advanced oxidation processes (SR-AOPs) have attracted considerable attention. However, systematic studies on potassium peroxymonosulfate (PMS) activation by MOF-derived metal oxides coated with LDH materials are still lacking. In this work, a series of catalysts consisting of CoCu-MOFs coated with CuAl/LDH were synthesized for PMS activation in the removal of sulfamethoxazole (SMX). As expected, CoCu-MOFs coated with CuAl/LDH catalyst showed high SMX removal and stability in PMS activation. In the CoCu/LDH/PMS reaction, the SMX removal was nearly 100% after 60 min, and the mineralization reached 53.7%. The catalyst showed excellent catalytic stability and low metal leaching concentrations (Co: 0.013 mg/L, Cu: 0.313 mg/L), as detected by ICP. Sulfate radicals and hydroxyl radicals were identified as the dominant reactive species in the CoCu/LDH/PMS system. Moreover, the presence of ¹O₂ in the process revealed the coupling of non-radical and radical processes. The XPS results showed that the layered structure of CoCu/LDH promoted the recycling of metal ions (high and low valence), which facilitated heterogeneous PMS activation. The effects of different reaction conditions and reuse cycles were also determined. The SMX oxidation pathways were proposed based on the intermediates identified by LC/MS. The high activity and stability of CoCu/LDH provide a new mechanistic understanding of PMS activation catalysts and their potential utilization in practical wastewater treatment. Full article

Iron oxides and hydroxides (Fe-OH) extracted from natural sources have garnered significant attention for their diverse catalytic applications. This article provides a comprehensive overview of the catalytic potential of naturally occurring Fe-OH, focusing on the influence of natural sources and preparation methods on their morphological characteristics and application in heterogeneous catalysis. The unique physicochemical properties of these catalysts, including their high surface area, redox activity, and tunable surface chemistry, make them promising candidates for various catalytic processes. The review discusses key catalytic reactions facilitated by natural Fe-OH, such as advanced oxidation processes (AOPs), electrochemical applications, catalytic cracking, and biodiesel production. Furthermore, it highlights recent advancements and challenges in utilizing these materials as heterogeneous catalysts. By presenting an analysis of the catalytic potential of natural iron oxides, this review aims to stimulate further research about the use of these materials, which are widely distributed in the Earth’s crust. Full article

This study presents the development and application of a batch-type photoelectrochemical reactor employing advanced oxidation processes (AOPs) with in situ generated TiO₂ particles for the efficient degradation of azo dyes. The reactor uses titanium sheets as electrodes, facilitating the electrochemical generation of TiO₂, which acts as a photocatalyst under UV light. This study specifically targets azo dyes frequently encountered in industrial wastewater, focusing on Brilliant Blue, Erythrosine, and Tartrazine, which together form the Navy Blue dye composition. The experimental methodology replicates real-world conditions, ensuring the results are representative of practical scenarios. Key findings demonstrate that the in situ production of TiO₂ enables effective heterogeneous photocatalysis, achieving significant dye degradation rates. This research highlights the novelty of combining in situ TiO₂ generation with a batch-type reactor, offering advantages in cost-effectiveness, scalability, and environmental impact. Comparative analysis with existing methods underscores the reactor’s potential for industrial applications, particularly in wastewater treatment. Furthermore, this study outlines the mechanistic insights into dye degradation and provides a foundation for optimizing photocatalytic processes to address environmental challenges. Full article

Sulfonamides, including sulfadoxine (SDX), are widely used antibiotics, particularly for malaria treatment. However, their extensive use has led to environmental pollution, microbial resistance, and public health risks. Advanced Oxidation Processes (AOPs) offer promising methods to degrade such pollutants in water, though they may generate more toxic by-products. This study evaluates three AOPs with different hydroxyl radical generation principles: the Fenton reagent (H₂O₂/Fe²⁺), hydrogen peroxide photolysis (UV-C/H₂O₂), and heterogeneous photocatalysis (UV-A/TiO₂). Heterogeneous photocatalysis showed superior performance, achieving 100% degradation and 77% mineralization under optimized conditions. Further analysis explored the effects of UV dose, catalyst concentration, and pH on process efficiency. The influence of water matrices, including Ultrapure Water (UW), Tap Water (TW), and Surface Water (SW) from the Aliakmonas River, was also examined. High-Resolution Mass Spectrometry identified 11 SDX transformation products formed during photocatalysis, with their formation mechanisms reported for the first time. An ecotoxicity assessment using ECOSAR software revealed insights into the potential environmental impact of these by-products. Full article

The presence of pharmaceuticals in aquatic ecosystems is an issue of increasing concern. Regardless of the low concentration of pharmaceuticals in water, they can have a toxic effect on both humans and aquatic organisms. Advanced oxidation processes (AOPs) have been described as a promising technique for eliminating pharmaceuticals due to their high efficiency. However, the cost associated with the application of these processes and their high reagents and energy requirements have affected the implementation of AOPs at large scales. Biochar has been suggested to be used as a catalyst in AOPs to overcome these limitations. Biochar is considered as an alternative heterogeneous catalyst thanks to its physicochemical characteristics like its specific surface area, porous structure, oxygen-containing functional groups, electrical conductivity, persistent free radicals (PFRs), modifiable properties, and structure defects. This carbonaceous material presents the capacity to activate oxidizing agents leading to the formation of radical species, which are needed to degrade pharmaceuticals. Additionally, AOP/biochar systems can destroy pharmaceutical molecules following a non-radical pathway. To enhance biochar catalytic performance, modifications have been suggested such as iron (Fe) impregnation, heteroatom doping, and supporting semiconductors on the biochar surface. Although biochar has been efficiently used in combination with several AOPs for the mineralization of pharmaceuticals from water, further research must be conducted to evaluate different regeneration techniques to increase biochar’s sustainable applicability and reduce the operational cost of the combined process. Moreover, operational conditions influencing the combined system are required to be evaluated to discern their effect and find conditions that maximize the degradation of pharmaceuticals by AOP/biochar systems. Full article

In this work, NiCo₂O₄ was synthesized from bimetallic oxalate and utilized as a heterogeneous catalyst to active peroxymonosulfate (PMS) for the degradation of tetracycline (TC). The degradation efficiency of TC (30 mg/L) in the NiCo₂O₄ + PMS system reached 92.4%, with NiCo₂O₄ exhibiting satisfactory reusability, stability, and applicability. Radical trapping test and electron paramagnetic resonance (EPR) results indicated that SO₄^•−, •OH, O₂^•−, and ¹O₂ were the dominating reactive oxygen species (ROS) for TC degradation in the NiCo₂O₄ + PMS system. Seven intermediates were identified, and their degradation pathways were proposed. Toxicity assessment using T.E.S.T software (its version is 5.1.1.0) revealed that the identified intermediates had lower toxicity compared to intact TC. A rice seed germination test further confirmed that the NiCo₂O₄ + PMS system effectively degraded TC into low-toxicity or non-toxic products. In conclusion, NiCo₂O₄ shows promise as a safe and efficient catalyst in advanced oxidation processes (AOPs) for the degradation of organic pollutants. Full article

Heterogeneous Advanced Oxidation Processes (H-AOPs) are considered a new process for removing emerging pollutants. In this case, the high reactivity of hydroxyl radicals is used to degrade persistent organic pollutants. This review explores the state-of-the-art catalyst for hydroxyl radical generation in AOPs. As a parasite reaction, chloride ions appear in alkaline conditions and compete with the active sites. The theoretical foundation of catalyst performance is explored, focusing on the fundamental principles that govern the efficiency and mechanism of hydroxyl or chloride radical production. The synthesis and electronic modification sections explore the modifications of catalysts. It discusses key methodologies for catalyst preparation, with a particular emphasis on electronic modification that enhances both activity and stability. Finally, laboratory and pilot applications highlight the effectiveness of novel or modified catalysts in different scenarios. These last findings provide insights into the future directions for research and application, aiming to draw attention to the gap between laboratory studies and real-world implementations. Full article

Ketoprofen is a non-biodegradable drug and is not removed by conventional treatments. The need to remove pharmaceutical compounds from water and wastewater has aroused considerable interest in advanced oxidation processes (AOP), whose effectiveness depends on the generation of reactive free radicals capable of oxidizing and decomposing numerous compounds. Heterogeneous photocatalysis is an efficient method if an active semiconductor is used. In this work, the photodegradation reaction of ketoprofen promoted by TiO₂ was studied, analyzing the kinetics obtained by changing variables such as temperature, initial concentration, and quantity of photocatalyst. It was determined that the mechanism is of the Langmuir–Hinshelwood type and that the system is operating in the kinetic regime, while tests at different temperatures have shown that the adsorption of ketoprofen and byproducts are both exothermic. Experimental data were interpreted with reliable models that allow to retrieve quantitatively the kinetic and thermodynamic parameters. Full article

The widespread environmental contamination resulting from the misuse of tetracycline antibiotics (TCs) has garnered significant attention and study by scholars. Photocatalytic technology is one of the environmentally friendly advanced oxidation processes (AOPs) that can effectively solve the problem of residue of TCs in the water environment. This study involved the synthesis of the heterogeneous magnetic photocatalytic material of CoFe₂O₄/NaBiO₃ via the solvothermal method, and it was characterized using different characterization techniques. Then, the photocatalytic system under visible light (Vis) was coupled with peroxymonosulfate (PMS) to explore the performance and mechanism of degradation of tetracycline hydrochloride (TCH) in the wastewater. The characterization results revealed that CoFe₂O₄/NaBiO₃ effectively alleviated the agglomeration phenomenon of CoFe₂O₄ particles, increased the specific surface area, effectively narrowed the band gap, expanded the visible light absorption spectrum, and inhibited recombination of photogenerated electron–hole pairs. In the Vis+CoFe₂O₄/NaBiO₃+PMS system, CoFe₂O₄/NaBiO₃ effectively activated PMS to produce hydroxyl radicals (·OH) and sulfate radicals (SO₄⁻). Under the conditions of a TCH concentration of 10 mg/L⁻¹, a catalyst concentration of 1 g/L⁻¹ and a PMS concentration of 100 mg/L⁻¹, the degradation efficiency of TCH reached 94% after 100 min illumination. The degradation of TCH was enhanced with the increase in the CoFe₂O₄/NaBiO₃ and PMS dosage. The solution pH and organic matter had a significant impact on TCH degradation. Notably, the TCH degradation efficiency decreased inversely with increasing values of these parameters. The quenching experiments indicated that the free radicals contributing to the Vis+CoFe₂O₄/NaBiO₃+PMS system were ·OH followed by SO₄⁻, hole (h⁺), and the superoxide radical (O₂⁻). The main mechanism of PMS was based on the cycle of Co³⁺ and Co²⁺, as well as Fe³⁺ and Fe²⁺. The cyclic tests and characterization by XRD and FT-IR revealed that CoFe₂O₄/NaBiO₃ had good degradation stability. The experimental findings can serve as a reference for the complete removal of antibiotics from wastewater. Full article

Recalcitrant compounds resulting from anthropogenic activity are a significant environmental challenge, necessitating the development of advanced oxidation processes (AOPs) for effective remediation. This study explores the synthesis of cuprous oxide nanoparticles on cellulose-based paper (Cu₂O@CBP) using Eucalyptus globulus leaf extracts, leveraging green synthesis techniques. The scanning electron microscopy (SEM) analysis found the average particle size 64.90 ± 16.76 nm, X-ray diffraction (XRD) and Raman spectroscopy confirm the Cu₂O structure in nanoparticles; Fourier-transform infrared spectroscopy (FTIR) suggests the reducing role of phenolic compounds; and ultraviolet–visible diffuse reflectance spectroscopy (UV-Vis DRS) allowed us to determine the band gap (2.73 eV), the energies of the valence band (2.19 eV), and the conduction band (−0.54 eV) of Cu₂O@CBP. The synthesized Cu₂O catalysts demonstrated efficient degradation of methylene blue (MB) used as a model as recalcitrant compounds under LED-driven visible light photocatalysis and heterogeneous Fenton-like reactions with hydrogen peroxide (H₂O₂) using the degradation percentage and the first-order apparent degradation rate constant (k_app). The degradation efficiency of MB was pH-dependent, with neutral pH favoring photocatalysis (k_app = 0.00718 min⁻¹) due to enhanced hydroxyl (·OH) and superoxide radical (O₂·⁻) production, while acidic pH conditions improved Fenton-like reaction efficiency (k_app = 0.00812 min⁻¹) via ·OH. The reusability of the photocatalysts was also evaluated, showing a decline in performance for Fenton-like reactions at acidic pH about 22.76% after five cycles, while for photocatalysis at neutral pH decline about 11.44% after five cycles. This research provides valuable insights into the catalytic mechanisms and supports the potential of eco-friendly Cu₂O nanoparticles for sustainable wastewater treatment applications. Full article