Two-dimensional manganese-iron bimetallic MOF-74 for electro-Fenton degradation of sulfamethoxazole.

This study reported a novel application of Mn0.67Fe0.33-MOF-74 with two-dimensional (2D) morphology grown on carbon felt as a cathode for efficiently removing antibiotic sulfamethoxazole in the heterogeneous electro-Fenton system. Characterization demonstrated the successful synthesis of bimetallic MOF-74 by a simple one-step method. Electrochemical detection showed that the second metal addition and morphological change improved the electrochemical activity of the electrode and contributed to pollutant degradation. At pH 3 and 30 mA of current, the degradation efficiency of SMX reached 96% with 12.09 mg L-1 H2O2 and 0.21 mM ·OH detected in the system after 90 min. During the reaction, electron transfer between ≡FeII/III and ≡MnII/III promoted divalent metal ions regeneration, which ensured the continuation of the Fenton reaction. Two-dimensional structures exposed more active sites favoring ·OH production. The pathway of sulfamethoxazole degradation and the reaction mechanisms were proposed based on the intermediates identification by LC-MS and radical capture results. High degradation rates were still observed in tap and river water, revealing the potential of Mn0.67Fe0.33-MOF-74@CF for practical applications. This study provides a simple MOF-based cathode synthesis method, which enhances our understanding of constructing efficient electrocatalytic cathodes based on morphological design and multi-metal strategies.

Effects of foliar applications of Brassinolide and Selenium on the accumulation of Arsenic and Cadmium in rice grains and an assessment of their health risk.

Arsenic and cadmium pose a potential health risk to human beings via rice grain consumption. In the current study, a pot experiment was conducted to evaluate the effect of Br (5 mM and 20 mM) and Se (1 mM) at rice tillering and filling stages on Cd and As accumulation in rice grain and their health risk indices. The results showed that Br or Se applications at different stages of rice improved the photosynthesis, reduce MDA content in flag leaves by 17.41%-38.65%, increased rice biomass and grain yield by 10.50%-29.94% and 10.50%-36.56%, and enhanced grain N and P uptake by 3.25%-34.90%, and 22.98%-72.05%, respectively. Applications of Br and Se effectively decreased Cd and As concentration in rice grain by 31.74%-86.97% and 16.42%-81.13% respectively. Compared to the individual treatment, combined 20 mM Br and 1 mM Se at the filling stage showed the lowest accumulation of As (0.149 mg·kg-1) and Cd (0.105 mg·kg-1) in grain, and its health risk index was below the acceptable limits (HRI < 1). This implies that application of Br and Se at the filling stage is a promising strategy for the safe production of rice in As and Cd co-contaminated regions.

In this study, foliar applications of Br and Se at the grain filling and tillering stage demonstrate their effect on As and Cd accumulation. The findings showed that Br and Se resulted in the Se concentration in grains reaching the Se-enriched level, and the accumulation of As and Cd was the lowest. Furthermore, the application of Br and Se decreased lipid peroxidation, promoted N and P uptake, and increased the rate of photosynthesis in the rice plants, which resulted in increasing rice growth and grain yield. The HRI of heavy metals was below the acceptable limits after application of Br and Se.

Facile synthesis of g-C3N4/Ag2C2O4 heterojunction composite membrane with efficient visible light photocatalytic activity for water disinfection.

Water pollution, deriving from the contamination of pathogenic bacteria, has posed a threat to human's survival and development. Photocatalytic disinfection is being widely studied in decentralized drink water safety, as traditional disinfection technologies are limited by harmful disinfection by-product and excessive energy consumption. Herein, a novel composite membrane (PN/Ag) with plasmonic heterojunction was synthesized for the efficient photocatalytic disinfection through the combination of polyacrylonitrile (PAN), N-doped carbon dots (NCDs)/g-C3N4 and Ag2C2O4 by electrospinning technique and successive ionic layer adsorption and reaction (SILAR) process. The surface plasmon resonance (SPR) effect of Ag nanoparticles and Schottky barrier formation between metal and semiconductor contributed to the efficient separation of electron-hole pairs and the generation of reactive species, resulting in outstanding photocatalytic disinfection of PN/Ag composite membranes (7.48 and 7.70 log inactivation of E. coli and S. aureus respectively in 80 min) and good reusability under visible light illumination. Moreover, the potential Z-scheme photocatalytic mechanisms were proposed for PN/Ag system according to the band structure and reactive species analysis. The as-proposed PN/Ag composite membranes may shed light on the design and application of materials in water purification.

Micro/macrostructure and multicomponent design of catalysts by MOF-derived strategy: Opportunities for the application of nanomaterials-based advanced oxidation processes in wastewater treatment.

Advanced oxidation processes (AOPs) have demonstrated an effective wastewater treatment method. But the application of AOPs using nanomaterials as catalysts is challenged with a series of problems, including limited mass transfer, surface fouling, poor stability, and difficult recycling. Recently, metal-organic frameworks (MOFs) with high tunability and ultrahigh porosity are emerging as excellent precursors for the delicate design of the structure/composition of catalysts and many MOF-derived catalysts with distinct physicochemical characteristics have shown optimized performance in various AOPs. Herein, to elucidate the structure-composition-performance relationship, a review on the performance optimization of MOF-derived catalysts to overcome the existing problems in AOPs by micro/macrostructure and multicomponent design is given. Impressively, MOF-derived strategy for the design of catalyst materials from the aspects of microstructure, macrostructure, and multicomponent (polymetallic, heteroatom doping, M/C hybrids, etc.) is firstly presented. Moreover, important advances of MOF-derived catalysts in the application of various AOPs (Fenton, persulfate-based AOPs, photocatalysis, electrochemical processes, hybrid AOPs) are summarized. The relationship between the unique micro/macrostructure and/or multicomponent features and performance optimization in mass transfer, catalytic efficiency, stability, and recyclability is clarified. Furthermore, the challenges and future work directions for the practical application of MOF-derived catalysts in AOPs for wastewater treatment are provided.