Advanced oxidation (e.g., fenton-like reagent oxidation and ozone oxidation) is a highly important technology that uses strong oxidizing free radicals to degrade organic pollutants and mineralize them. The fenton-like reactions have the characteristics of low cost, simple operation, thorough reaction and no secondary pollution. Fenton-like reagents refer to a strong oxidation system composed of transition metal ions (e.g., Fe³⁺, Mn²⁺ and Ag⁺) and oxidants (hydrogen peroxide, potassium persulfate, sodium persulfate, etc). Graphene and carbon nanotube possess a distinctive mechanical strength, flexibility, electrical and thermal conductivity and a very large specific surface area, which can work as an excellent carrier to disperse the catalyst and prevent its agglomeration. Fullerene can synergize with iron-based materials to promote the reaction of hydroxyl groups with organic pollutants and enhance the catalytic effect. Fenton-like catalysts influence the catalytic behavior by inducing electron transfer under strong interactions with the support. Due to the short lifespan of free radicals, the treatment effect is usually enhanced with the assistance of external conditions (ultraviolet and electric fields) to expand the application of fenton-like catalysts in water treatment. There are mainly light-fenton, electro-fenton and photoelectric-fenton methods. Fenton-like catalysts can be prepared by hydrothermal method, impregnation and coordination-precipitation approaches. The structures and properties of the catalysts are characterized by a variety of techniques, such as high-resolution transmission electron microscopy, high-angle annular dark-field scanning transmission electron microscopy and X-ray absorption near-edge structure spectroscopy. In this paper, we review the mechanisms, preparation methods, characterizations and applications status of fenton-like reagents in industrial wastewater treatment, and summarize the recycling of these catalysts and describe prospects for their future research directions.

Extensive use of fossil fuels can lead to energy depletion and serious environmental pollution. Therefore, it is necessary to solve these problems by developing clean energy. Graphene materials own the advantages of high electrocatalytic activity, high conductivity, excellent mechanical strength, strong flexibility, large specific surface area and light weight, thus giving the potential to store electric charge, ions or hydrogen. Graphene-based nanocomposites have become new research hotspots in the field of energy storage and conversion, such as in fuel cells, lithium-ion batteries, solar cells and thermoelectric conversion. Graphene as a catalyst carrier of hydrogen fuel cells has been further modified to obtain higher and more uniform metal dispersion, hence improving the electrocatalyst activity. Moreover, it can complement the network of electroactive materials to buffer the change of electrode volume and prevent the breakage and aggregation of electrode materials, and graphene oxide is also used as a cheap and sustainable proton exchange membrane. In lithium-ion batteries, substituting heteroatoms for carbon atoms in graphene composite electrodes can produce defects on the graphitized surface which have a good reversible specific capacity and increased energy and power densities. In solar cells, the performance of the interface and junction is enhanced by using a few layers of graphene-based composites and more electron-hole pairs are collected; therefore, the conversion efficiency is increased. Graphene has a high Seebeck coefficient, and therefore, it is a potential thermoelectric material. In this paper, we review the latest progress in the synthesis, characterization, evaluation and properties of graphene-based composites and their practical applications in fuel cells, lithium-ion batteries, solar cells and thermoelectric conversion.

Mesoporous Mn-doped Fe nanoparticle-modified reduced graphene oxide (Mn-doped Fe/rGO) was prepared through a one-step co-precipitation method, which was then used to eliminate ethyl violet (EV) in wastewater. The prepared Mn-doped Fe/rGO was characterized by X-ray diffraction, X-ray photoelectron spectroscopy, Raman spectroscopy, high-resolution transmission electron microscopy, scanning electron microscopy, energy dispersive spectroscopy, N₂-sorption, small angle X-ray diffraction and superconducting quantum interference device. The Brunauer–Emmett–Teller specific surface area of Mn-doped Fe/rGO composites was 104.088 m²/g. The EV elimination by Mn-doped Fe/rGO was modeled and optimized by artificial intelligence (AI) models (i.e., radial basis function network, random forest, artificial neural network genetic algorithm (ANN-GA) and particle swarm optimization). Among these AI models, ANN-GA is considered as the best model for predicting the removal efficiency of EV by Mn-doped Fe/rGO. The evaluation of variables shows that dosage gives the maximum importance to Mn-doped Fe/rGO removal of EV. The experimental data were fitted to kinetics and adsorption isotherm models. The results indicated that the process of EV removal by Mn-doped Fe/rGO obeyed the pseudo-second-order kinetics model and Langmuir isotherm, and the maximum adsorption capacity was 1000.00 mg/g. This study provides a possibility for synthesis of Mn-doped Fe/rGO by co-precipitation as an excellent material for EV removal from the aqueous phase.

Reduced graphene oxide loaded with an iron-copper nanocomposite was prepared in this study, using graphene oxide as a carrier and ferrous sulfate, copper chloride and sodium borohydride as raw materials. The obtained material was prepared for eliminating hazardous dye carmine and the binary dye mixture of carmine and Congo red. The process of carmine dye removal by the nanocomposite was modeled and optimized through response surface methodology and artificial intelligence (artificial neural network–particle swarm optimization and artificial neural network–genetic algorithm) based on single-factor experiments. The results demonstrated that the surface area of the nanocomposite was 41.255 m²/g, the pore size distribution was centered at 2.125 nm, and the saturation magnetization was up to 108.33 emu/g. A comparison of the material before and after the reaction showed that the material could theoretically be reused three times. The absolute error between the predicted and experimental values derived by using artificial neural network–particle swarm optimization was the smallest, indicating that this model was suitable to remove carmine from simulated wastewater. The dose factor was the key factor in the adsorption process. This process could be described with the pseudo-second-order kinetic model, and the maximum adsorption capacity was 1848.96 mg/g. The removal rate of the mixed dyes reached 96.85% under the optimal conditions (the dosage of rGO/Fe/Cu was 20 mg, the pH was equal to 4, the initial concentration of the mixed dyes was 500 mg/L, and the reaction time was 14 min), reflecting the excellent adsorption capability of the material.