Photo-assisted degradation of organic pollutant by CuFeS2 powder in RGB-LED reactors: A comprehensive study of band gap values and the relation between wavelength and electron-hole recombination

Insights into structural and functional regulation of chalcopyrite and enhanced mechanism of reactive oxygen species (ROS) generation in advanced oxidation process (AOP): A review

Chalcopyrite, renowned for its distinctive mixed redox-couple characteristics, exhibits excellent electron transfer properties both on its surface and within its crystal structure. This unique characteristic has attracted significant attention in various fields, including optics, electronics, and magnetism, as well as demonstrated remarkable catalytic efficacy in the environmental field. The rapid and effective electron transfer capability of a catalyst is crucial for advanced oxidation processes (AOPs). However, the performance of CuFeS2 in AOPs is hindered by its low electron transfer efficacy. This review aims to summarize the key steps and mechanisms of chalcopyrite-induced AOPs and provide strategies for enhancing effective electron transfer efficacies by controlling the structure and function of synthetic/natural chalcopyrite. These strategies include enhancing the catalytic performance of chalcopyrite and constructing composites to enhance catalytic activity (e.g., chelating agents, heterojunctions). Additionally, the factors influencing the generation of reactive oxygen species in chalcopyrite-induced AOPs are investigated, such as the types and properties of oxidants (e.g., H2O2, peroxymonocarbonate), the microstructure of catalysts, and reaction conditions in catalytic systems (e.g., pH values, dosage, temperature). Future perspectives on the applications of chalcopyrite are presented at the end of this paper. Overall, this review assists in narrowing the scope of chalcopyrite studies in AOPs and aids researchers in optimizing synthetic/natural catalysts for contaminant treatment.

CuFeS2 supported on dendritic mesoporous silica-titania for persulfate-assisted degradation of sulfamethoxazole under visible light

Sulfamethoxazole (SMX) is a prevalent sulfonamide antibiotic found in the environment, and it has a variety of detrimental effects on environmental sustainability and water safety. Recently, the combination of photocatalysis and sulfate radical-based advanced oxidation processes (SR-AOPs) has attracted a lot of interest as a viable technique for degradation of refractory pollutants. In this study, a visible light active CuFeS2 supported on dendritic mesoporous silica-titania (CuFeS2-DMST) photocatalyst was synthesized to improve the ability of TiO2 to activate persulfate (PS) by introducing CuFeS2 (Fe2+/Fe3+, Cu+/Cu2+ redox cycles). The CuFeS2-DMST/PS/Vis system demonstrated superior SMX degradation efficiency (88.9%, 0.0146 min-1) than TiO2 because of reduced e-/h+ recombination, excellent charge separation and mobility, and a greater surface area than TiO2. Furthermore, after four consecutive photocatalytic cycles, the system demonstrated moderate stability. From chemical quenching tests, O2●-, h+, 1O2, SO4●- and ●OH were found to be the main reactive oxidizing species. The formed intermediates during the degradation process were identified, and degradation mechanisms were proposed. This study proposes a viable technique for activating PS using a low-cost, stable, and high-surface-area TiO2-based photocatalyst, and this concept can be applied to design photocatalysts for water treatment.

Analysis of natural photocatalysts derived from spartina alterniflora with superior removal performance of pollutant

Spartina alterniflora, as an invasive alien species, has been studied in terms of its potential use in immobilization and synergistic photocatalysis against dye contaminants for the first time. Microscopic characterization and Fourier transform infrared (FTIR) spectroscopy results confirmed the presence of abundant 3D wormhole-like pore structures and active functional groups (-OH, -NH2, CO, Si-O-Si). Moreover, the existence of SiO2 was connected the metal oxides with polar groups, which could proceed entire reaction procedure subsequently. Transition metal oxides (such as Fe2O3, TiO2, MnO2 and NiO) contained in photocatalysts might effectively promote the organics decomposition by the visible light excitation. The highest dye removal efficiency of 92.03% could be reached with the addition of 0.02 g photocatalyst. The capture experiment confirmed that the h+ was the dominant active substance during the photocatalytic degradation process. Density functional theory (DFT) calculations verified that the functional groups (-COOH, -OH and -NH2) were exceptional adsorption sites for catalyst, and the calculated adsorption energy were all negative with the order of SRHH-NH2 (-2.712688 eV) < SRHH-OH (-2.075601 eV) < SRHH-COOH (-1.283141 eV), which confirmed that interface interaction effectively bound cationic dyes through the formation of hydrogen bonds at the catalysts-water interface, further accelerating the reaction rate of the entire photocatalytic reduction of dye molecules. Therefore, this work provides a feasible synthesis of natural photocatalysts using solid waste, which suggests excellent adsorption and photocatalysis properties for the treatment of organic industrial pollutant.

Chalcopyrite as an oxidants activator for organic pollutant remediation: A review of mechanisms, parameters, and future perspectives

Advanced oxidation processes (AOPs) based on oxidants have attracted attention for the degradation of organic pollutants. The combination of chalcopyrite with oxidants such as persulfate, peroxide, percarbonate, and others shows promise as a system due to its ability to activate through various pathways, leading to the formation of numerous radical and non-radical species. In this review, the generation of sulfate radical (SR) and hydroxyl radical (HR) in AOPs were summarized. The significance of chalcopyrite in various approaches including Fenton, photo-Fenton, and photo/Fenton-like methods, as well as its involvement in electrochemical Fenton-based processes was discussed. The stability and reusability, toxicity, catalyst mechanism, and effects of operational parameters (pH, catalyst dosage, and oxidant concentration) are evaluated in detail. The review also discusses the role of Fe2+/3+, Cu1+/2+, S2- and Sn2- present in CuFeS2 in the generation of free radicals. Finally, guidelines for future research are presented in terms of future perspectives.

Enhanced UV-light driven photocatalytic performance of magnetic CoFe2O4/TiO2 nanohybrid for environmental applications

In this work, CoFe₂O₄/TiO₂ nanostructure was prepared through a facile and effective solvothermal route for efficient use in the degradation of the Erionyl Red A-3G model pollutant under ultraviolet irradiation. Characterization analysis indicated the successful heterojunction among the precursors. The composite presented band gap value of 2.75 eV, being smaller than that of the pristine TiO₂, as well as mesoporous structure. The catalytic activity of nanostructure was investigated by employing a 2² factorial experimental design with 3 central points. The optimized reaction conditions were set as pH = 2 and catalyst dosage = 1.0 g L^-1 for an initial pollutant concentration of 20 mg L^-1. The prepared nanohybrid presented remarkable catalytic activity, reaching color removal efficiency of 95.39% after 15 min, as well as total organic carbon (TOC) removal of 69.4% after 120 min. The kinetic studies of TOC removal followed the pseudo-first order model, with a rate constant of 0.10 min^-1. Moreover, the nanostructure presented magnetic behavior, being easily separated from the aqueous medium through the use of a simple external magnetic field.

Progress and prospective of heterogeneous catalysts for H2O2 production via anthraquinone process

This paper reviews the improvement in the field of catalytic hydrogenation of 2-ethylanthraquinone to 2-ethylanthrahydroquinone for the successful production of hydrogen peroxide. Hydrogen peroxide is being used in almost all industrial areas, particularly in the chemical industry and in environmental protection, as the most promising oxidant for cleaner and environmentally safer processes. A variety of hydrogenation catalysts have been introduced for hydrogenation of 2-ethylanthraquinone in the production of hydrogen peroxide via anthraquinone (AQ) process. The aim of the present study is to describe the catalysts used in the hydrogenation of 2-ethylanthraquinone and the reaction mechanism involved with different catalytic systems. The hydrogenation of 2-ethylanthraquinone using metals, alloy, bimetallic composite, and supported metal catalyst with the structural modifications has been incorporated for the production of hydrogen peroxide. The comprehensive comparison reveals that the supported metal catalysts required lesser catalyst amount, produced lower AQ decay, and provided higher catalyst activity and selectivity. Furthermore, the replacement of conventional catalysts by metal and metal alloy-supported catalyst rises as a hydrogenation trend, enhancing by several times the catalytic performance.