Mo3S132- Intercalated Layered Double Hydroxide: Highly Selective Removal of Heavy Metals and Simultaneous Reduction of Ag+ Ions to Metallic Ag-0 Ribbons

We demonstrate a new material by intercalating Mo3S132- into Mg/Al layered double hydroxide (abbr. Mo3S13-LDH), exhibiting excellent capture capability for toxic Hg2+ and noble metal silver (Ag). The as-prepared Mo3S13-LDH displays ultra-high selectivity of Ag+, Hg2+ and Cu2+ in the presence of various competitive ions, with the order of Ag+ > Hg2+ > Cu2+ > Pb2+ >= Co2+, Ni2+, Zn2+, Cd2+. For Ag+ and Hg2+, extremely fast adsorption rates (approximate to 90% within 10 min, > 99% in 1 h) are observed. Much high selectivity is present for Ag+ and Cu2+, especially for trace amounts of Ag+ (approximate to 1 ppm), achieving a large separation factor (SFAg/Cu) of approximate to 8000 at the large Cu/Ag ratio of 520. The overwhelming adsorption capacities for Ag+ (q(m)(Ag) = 1073 mgg(-1)) and Hg2+ (q(m)(Hg) = 594 mgg(-1)) place the Mo3S13-LDH at the top of performing sorbent materials. Most importantly, Mo3S13-LDH captures Ag+ via two paths: a) formation of Ag2S due to Ag-S complexation and precipitation, and b) reduction of Ag+ to metallic silver (Ag-0). The Mo3S13-LDH is a promising material to extract low-grade silver from copper-rich minerals and trap highly toxic Hg2+ from polluted water.