Reduced graphene oxide supported on Gd2MoO6-ZnO nanorod photocatalysts used for the effective reduction of hexavalent chromium

Graphene-based strontium niobate-zinc oxide heterojunction photocatalyst for effective reduction of hexavalent chromium

A hydrothermal technique was employed to synthesize a Sr₂Nb₂O₇-rGO-ZnO (SNRZ) ternary nanocatalyst, in which ZnO and Sr₂Nb₂O₇ were deposited on reduced graphene oxide (rGO) sheets. The surface morphologies, optical properties, and chemical states, of the photocatalysts were characterized to understand their properties. The SNRZ ternary photocatalyst was superior over the reduction of Cr (VI) to harmless Cr (III) compared to the efficiencies obtained using bare, binary, and composite catalysts. The effects of various parameters, including the solution pH and weight ratio, on the photocatalytic reduction of Cr (VI) were investigated. The highest photocatalytic reduction performance (97.6%) was achieved at pH 4 and a reaction time of 70 min. Photoluminescence emission measurements were used to confirm efficient charge migration and separation across the SNRZ, which improved the reduction of Cr (VI). A feasible reduction mechanism for the SNRZ photocatalyst is proposed. This study presents an effective, inexpensive, non-toxic, and stable catalyst, for the reduction of Cr (VI) to Cr (III) using SNRZ ternary nanocatalysts.

A simple nanocomposite photocatalyst HT-rGO/TiO2 for deoxynivalenol degradation in liquid food

A simple nanocomposite photocatalyst HT-rGO/TiO₂ for deoxynivalenol (DON) degradation was synthesized by hydrothermal method to maintain the quality of cereal grains and byproducts. The characterization of HT-rGO/TiO₂ was analyzed by XRD, FTIR, Raman spectroscopy, and XPS. Moreover, according to UV-vis DRS analysis, HT-rGO/TiO₂ had a smaller band gap, indicating a wider response range to light and a higher utilized rate of quantum photons. Additionally, the results of LC-MS showed that the hydroxyl group at the C3 position, and the unsaturated bond between C9 and C10, and the epoxy group at C12 and C13 positions of DON molecule were destroyed step by step by photocatalytic degradation. These groups have active effects on the DON toxicity, which means it is successful to degrade DON in liquid-food by HT-rGO/TiO₂ photocatalyst.

High-ratio {100} plane-exposed ZnO nanosheets with dual-active centers for simultaneous photocatalytic Cr(VI) reduction and Cr(III) adsorption from water

The development of an efficient catalyst for the simultaneous removal of Cr(VI) and Cr(III) from water is required to eliminate the risk of Cr(III) reconversion in the photocatalytic Cr(VI) reduction process. ZnO with large regions of high-energy {001} and {101} surfaces is often used to degrade various pollutants due to its high activity. However, the more readily available low-energy facets have relatively limited its applications. Here, we report a new strategy that employs a high proportion of {100} plane-exposed ZnO nanosheets for simultaneous photocatalytic Cr(VI) reduction and Cr(III) adsorption. The mechanism of Zn-O co-exposed on the {100} plane as the dual-active centers to jointly promote Cr(VI) reduction and Cr(III) adsorption was clarified at the atomic level. ZnO nanosheets with a high exposure ratio of the {100} plane achieve a total Cr removal rate of over 90% within 120 min under simulated sunlight irradiation, neutral conditions, and a negligible difference in the band structure.

Ce2(MoO4)3 synthesized with oleylamine and oleic acid as additives for photocatalysis: effect of preparation method

Ce₂(MoO₄)₃ was prepared using dielectric barrier discharge (DBD) plasma method, co-precipitation method and hydrothermal method, respectively, with water/ethanol (W/O) as solvent, oleylamine (OAm) and oleic acid (OAc) as additives. Preparation method showed significant influence on the morphological and structural properties, as well as photocatalytic performance. Ce₂(MoO₄)₃ synthesized with DBD plasma (MO-P) was mainly flowerlike nanosheets, which were beneficial to promoting electron transfer and providing more space for catalytic activity. Also, MO-P samples exhibited more oxygen vacancies, which were conducive to the photocatalytic performance. What's more, MO-P showed lower PL intensity and narrow energy gap, which implied a slow photoelectron-hole pair recombination rate and an increased electron transfer rate. The degradation rate of methyl orange (50 mg/L) could achieve 98% within 12 min with 0.5 g/L MO-P. Hydroxyl radicals (·OH) and superoxide radicals (·O₂^-) played a major effect. Plasma synthesis method exhibited potential application prospect in photocatalysts preparation.

Photocatalytic Removal of Cr(VI) by Thiourea Modified Sodium Alginate/Biochar Composite Gel

Heavy metal pollution is an important problem in current water treatments. Traditional methods for treating chromium-containing wastewater have limitations such as having complicated processes and causing secondary pollution. Therefore, seeking efficient and fast processing methods is an important research topic at present. Photocatalysis is an efficient method to remove Cr(VI) from aqueous solutions; however, conventional photocatalysts suffer from a low metal absorption capacity, high investment cost, and slow desorption of trivalent chromium from the catalyst surface. In this study, a novel composite gel was synthesized by chemically modifying thiourea onto sodium alginate, which was then mixed with biochar. The composite gel (T-BSA) can effectively remove 99.98% of Cr(VI) in aqueous solution through synergistic adsorption and photocatalytic reduction under UV light irradiation. The removal mechanism of Cr(VI) was analyzed by FT-IR, FESEM, UV-DRS and XPS. The results show that under acidic conditions, the amino group introduced by chemical modification can be protonated to adsorb Cr(VI) through electrostatic interaction. In addition, the biochar as a functional material has a large specific surface area and pore structure, which can provide active sites for the adsorption of Cr(VI), while the photo-reduced Cr(III) is released into the solution through electrostatic repulsion, regenerating the adsorption sites, thereby improving the removal performance of Cr(VI). Biochar significantly intensifies the Cr(VI) removal performance by providing a porous structure and transferring electrons during photoreduction. This study demonstrates that polysaccharide-derived materials can serve as efficient photocatalysts for wastewater treatment.