Removal and magnetic recovery of heavy metals and pesticides from soil by layered double hydroxides modified biotite

Novel biotite (Bt) supported different amounts of Mg-Al layered double hydroxide (LDH@Bt) with a threedimensional hierarchical structure was fabricated via in-situ growth method. The structural and morphology characterization indicate that LDHs stably and uniformly dispersed on Bt surface, but excessive LDHs still lead to obvious aggregation of LDHs. The removal performance of LDH@Bt for heavy metal of Cu2+/Pb2+ and pesticides of glyphosate (GLY)/2-methyl-4-chlorophenoxyacetic acid (MCP) in soil was investigated, and the removal rates of LDH@Bt composite for four contaminants were higher than those of LDHs and Bt. Intraparticle diffusion and pseudo-second-order model well described the kinetics of heavy metals and pesticides removal. Adsorption isotherm data of Cu(2+)and Pb2+ yielded better accordance of Freundlich model, while data of GLY and MCP were fitted Langmuir model well. In addition, different adsorption mechanisms for removal of Cu2+/Pb2+ by precipitation and removal of GLY/MCP by surface adsorption were proposed. The application performance and recovery ability of LDH@Bt composite in soil were evaluated by column leaching experiments and magnetic collectability tests. The excellent removal performance and magnetic collectability provided a promising strategy for remediation and elimination of heavy metals and pesticides contaminations from soil.