Multifunctional Sites for Enhanced Adsorption of Arsenic Using Sulfydryl-Modified Biochar/MgFe-Layered Double Hydroxides

Arsenic contamination in water poses a significant threat to the environment and human health due to the high toxicity of arsenic. Therefore, the development of functionalized materials with an enhanced adsorption capacity for arsenic remains a key research focus in water purification. In this study, straw powder was hydrothermally pretreated and subsequently pyrolyzed with zinc chloride at 700 °C to produce hydrothermal biochar with tailored pores. The hydrothermal biochar was then modified with sulfhydryl groups, and Sulfhydryl-Modified Biochar/MgFe-Layered Double Hydroxides (SH@HB/MgFe-LDH) composites were synthesized using the coprecipitation method. By utilizing HB with a high surface area, a composite material with a high specific surface area of 479.3677 m²/g was prepared. The experimental results indicated that the SH@HB/MgFe-LDH composites exhibited excellent arsenic adsorption performance across a wide pH range, achieving an arsenic adsorption capacity as high as 388.01 mg/g. The adsorption process and mechanism of the SH@HB/MgFe-LDH composites were investigated through adsorption kinetics, adsorption isotherms, thermodynamic analysis, and X-ray photoelectron spectroscopy. Additionally, recycling studies demonstrated that the composites maintained stable performance over three reuse cycles, showing good potential for practical applications. Overall, the SH@HB/MgFe-LDH composites offer an effective solution for arsenic pollution control in water while promoting the high-value utilization of agricultural and forestry waste.