Microwave-assisted modification of magnetic Mg/Al/Fe-LDH hydrotalcite for efficient arsenic removal from water

Abstract

In recent years, arsenic contamination in aquatic environments has become increasingly severe. Hydrotalcites are widely used for arsenic removal, but challenges remain regarding their removal efficiency and recyclability. To enhance the adsorption performance of Hydrotalcite-like(LDH) for arsenic and facilitate solid–liquid separation, in this study, magnetic Fe₃O₄ was combined with LDH and thermally modified using microwave treatment to obtain microwave-assisted modification of magnetic LDH(WFe₃O₄@MAF-LDH), which was used for arsenic removal. The results showed that WFe₃O₄@MAF-LDH effectively removed arsenic over a wide pH range. The adsorption of As(III) and As(V) by the material was well described by pseudo-first and pseudo-second-order kinetic models. Thermodynamic analysis confirmed that the adsorption process was spontaneous, and the maximum adsorption capacity of WFe₃O₄@MAF-LDH for As(III) was 217.62 mg/g. The inhibitory effect of coexisting anions on As(III) adsorption followed the order of SO₄²⁻ > NO₃⁻ > Cl⁻. In addition, the material demonstrated strong and stable pollutant adsorption properties. Mechanically, arsenic removal by WFe₃O₄@MAF-LDH involved electrostatic interactions, ion exchange, coordination reactions, and oxidation–reduction reactions, as evidenced by material characterization means. Density Functional Theory(DFT) calculations revealed hydrogen bonding between H₃AsO₃/HAsO₄²⁻ and WFe₃O₄@MAF-LDH, with MAF-LDH playing an important role in arsenic removal. In summary, WFe₃O₄@MAF-LDH demonstrated excellent arsenic removal, structural stability, and environmental friendliness, providing a valuable reference for the development of efficient adsorption treatment materials for arsenic-containing wastewater.