Organically-modified magnesium silicate nanocomposites for high-performance heavy metal removal

A disulfide-grafted polyethyleneimine (PES)@Mg2SiO4 composite was synthesized, characterized, and used successfully to remove heavy metals from wastewater. It was grafted with a huge number of dithiocarbamate moieties as sites for specific adsorption. By comparative studies, it was found that the morphology, structure and properties were influenced by the trapped organic components in the composites. PES@Mg2SiO4 exhibits a larger specific surface area and better adsorption activity compared with Mg2SiO4, polyethyleneimine (PEI)@Mg2SiO4 and PEI@Mg2SiO4–CS2. The adsorption behaviors of the obtained composites were investigated for the recovery of Hg2+, Pb2+ and Cd2+. PES@Mg2SiO4 shows the highest adsorption capacities of 714 mg g−1 for Hg2+, 400 mg g−1 for Pb2+ and 323 mg g−1 for Cd2+, which fits the Langmuir isotherm model. Besides this, it also exhibits excellent adsorption capacity for Cu2+, Bi3+ and metal complexes. Its application in petrochemical wastewater demonstrates its enormous potential for heavy metal wastewater treatment.