Morphology control enables [SnS4]4− clusters and MgFe-LDHs dual active sites for the adsorption of mercury and arsenic ions

Abstract

• Two spherical compounds were firstly reported and used for heavy metals removal. • Hg and As are removed selectively using different sorbents with the same active site. • The dual active sites retained the adsorption for both Hg and As in acid wastewater. The effluent associated with mercury and arsenic has attracted a wide concern due to their high hazardous risk to human beings and the environment. In this study, the layered double hydroxides (LDHs) loaded/coated [SnS 4 ] 4− ([SnS 4 ] 4− @MgFe-LDHs and [SnS 4 ] 4− /MgFe-LDHs) materials were prepared for Hg(II) and As(III) selective adsorption under various conditions. The results shown that morphology controlling method could adjust the selective adsorption of Hg and As. For Hg(II) removal, the [SnS 4 ] 4− @MgFe-LDH was 50.5% and the [SnS 4 ] 4− /MgFe-LDH-1, −2, and −3 was up to 92.9%, 97.1% and 71.4%, respectively. And the adsorption behavior of Hg(II) transformed from the physical adsorption ([SnS 4 ] 4− @MgFe-LDH) to the chemical adsorption ([SnS 4 ] 4− /MgFe-LDHs), which profited from the regulation of surface enhancing the exposed S active sites. However, for As(III) removal, the [SnS 4 ] 4− @MgFe-LDH was 47.6%, while the three different [SnS 4 ] 4− /MgFe-LDHs were down to both approximately 20%. The adsorption kinetics study confirmed that the As(III) adsorption was complex and contained both chemical and physical adsorption. Furthermore, for the [SnS 4 ] 4− @MgFe-LDH, [SnS 4 ] 4− /MgFe-LDH-1 and −3, the physical adsorption was the dominated process, while the [SnS 4 ] 4− /MgFe-LDH-2 enhanced the chemical adsorption process due to the urchin-like morphology with rough surface that exposing more active sites. Therefore, different morphology control methods realized high efficient removal of As and Hg ions.