Layered double hydroxides, which can be synthesized from metal ions and their analogs, have abundant interlayer ions, surface functional groups, and adsorption characteristics that have been extensively studied. But the adsorption-desorption process may cause secondary pollution of the environment. In this study, the layered double hydroxides that adsorbed Congo red were converted into mixed metal oxide/carbon composites by a calcining carbonization method, and its adsorption performance for heavy metal ions Pb(Ⅱ) in aqueous solution was studied in detail. The results show that the prepared mixed metal oxide/carbon composites have a faster adsorption rate and higher adsorption capacity for Pb(Ⅱ). The adsorption capacity reached more than 150 mg·g-1 in 30 min, and increased with the content of Mg2+ introduced into the layered double metal hydroxide, reaching a maximum of 368 mg·g-1. The removal mechanism of Pb(Ⅱ) by mixed metal oxide/carbon composites was caused by the formation of insoluble Pb3(CO3) 2(OH) 2 on the surface. This research lays the foundation for the application of mixed metal oxide/carbon composites in the remediation of lead-containing soils.
Keywords: Pb(Ⅱ); adsorption; adsorption mechanism; composite material; mixed metal oxide.