Mo3S132− Intercalated Layered Double Hydroxide: Highly Selective Removal of Heavy Metals and Simultaneous Reduction of Ag+ Ions to Metallic Ag0 Ribbons

We demonstrate a new material by intercalating Mo3 S132- into Mg/Al layered double hydroxide (abbr. Mo3 S13 -LDH), exhibiting excellent capture capability for toxic Hg2+ and noble metal silver (Ag). The as-prepared Mo3 S13 -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 (≈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+ (≈1 ppm), achieving a large separation factor (SFAg/Cu ) of ≈8000 at the large Cu/Ag ratio of 520. The overwhelming adsorption capacities for Ag+ (qmAg =1073 mg g-1 ) and Hg2+ (qmHg =594 mg g-1 ) place the Mo3 S13 -LDH at the top of performing sorbent materials. Most importantly, Mo3 S13 -LDH captures Ag+ via two paths: a) formation of Ag2 S due to Ag-S complexation and precipitation, and b) reduction of Ag+ to metallic silver (Ag0 ). The Mo3 S13 -LDH is a promising material to extract low-grade silver from copper-rich minerals and trap highly toxic Hg2+ from polluted water.