H2xMnxSn3‐xS6 (x = 0.11–0.25): A Novel Reusable Sorbent for Highly Specific Mercury Capture Under Extreme pH Conditions

Abstract The H 2x Mn x Sn 3‐x S 6 (x = 0.11–0.25) is a new solid acid with a layered hydrogen metal sulfide (LHMS). It derives from K 2x Mn x Sn 3–x S 6 (x = 0.5–0.95) (KMS‐1) upon treating it with highly acidic solutions. We demonstrate that LHMS‐1 has enormous affinity for the very soft metal ions such as Hg 2+ and Ag + which occurs via a rapid ion exchange process. The tremendous affinity of LHMS‐1 for Hg 2+ is reflected in very high distribution coefficient K d Hg values (>10 6 mL g −1 ). The large affinity and selectivity of LHMS‐1 for Hg 2+ persists in a very wide pH range (from less than zero to nine) and even in the presence of highly concentrated HCl and HNO 3 acids. LHMS‐1 is significantly more selective for Hg 2+ and Ag + than for the less soft cations Pb 2+ and Cd 2+ . The Hg 2+ ions are immobilized in octahedral sites between the sulfide layers of the materials via Hg–S bonds as suggested by pair distribution function (PDF) analysis. LHMS‐1 could decrease trace concentrations of Hg 2+ (e.g. <100 ppb) to well below the acceptable limits for the drinking water in less than two min. Hg‐laden LHMS‐1 shows a remarkable hydrothermal stability and resistance in 6 M HCl solutions. LHMS‐1 could be regenerated by treating Hg‐loaded samples with 12 M HCl and re‐used without loss of its initial exchange capacity.