[SnS4]4- clusters modified MgAl-LDH composites for mercury ions removal from acid wastewater.

Abstract

The high acidity of mercury ions (Hg2+) contained wastewater can complicate its safe disposal. MgAl-LDHs supported [SnS4]4- clusters were synthesized for Hg2+ removal from acid wastewater. The active sites of [SnS4]4- clusters were inserted into the interlayers of MgAl-LDHs using an ion-exchange method. The experimental results indicated that [SnS4]4-/MgAl-LDHs composite can obtain higher than 99% Hg2+ removal efficiency under low pH values. The maximum mercury adsorption capacity is 360.6\u202fmg\u202fg-1. It indicated that [SnS4]4- clusters were the primary active sites for mercury uptake, existing as stable Hg2(SnS4) on the surface of the composite. Under low pH values, such a composite seems like a net for HgSO4 molecules, exhibiting great potential for mercury removal from acid solutions. Moreover, the co-exist metal ions such as Zn2+, Na+, Cd2+, Cr3+, Pb2+, Co2+, and Ni2+ have no significant influences on Hg2+ removal. The adsorption isotherms and kinetics were also studied, indicating that the adsorption mechanism follows a monolayer chemical adsorption model. The [SnS4]4-/MgAl-LDHs composite exhibits a great potential for Hg2+ removal from acid wastewater.