Efficient removal of Hg2+ from aqueous solution by a novel composite of nano humboldtine decorated almandine (NHDA): Ion exchange, reducing-oxidation and adsorption.

Efficient removal of Hg2+ from aqueous solution is key for environmental protection and human health. Herein, a novel composite of nano humboldtine decorated almandine was synthesized from almandine for the removal of Hg2+. Results showed that the Hg2+ removal process followed pseudo-second-order kinetic model and Langmuir equation, and the maximum adsorption capacity was 575.17 mg/g. Furthermore, Hg2+ removal by the composite was pH-dependent and low pH value facilitated the removal of Hg2+. SEM and HADDF-STEM results suggested a new rod morphology was generated and the adsorbed mercury was mainly enriched into this structure after reaction with Hg2+ solution. The removal mechanisms of Hg2+ by the composite was pH dependent, and included ion exchange, surface complexation, reduction and oxidation. Our results demonstrated that the composite was an ideal material for Hg2+ removal and the transformation ways of mercury related species could be a significant but currently underestimated pathway in natural and engineered systems. ga1 • A novel composite of NHDA could efficiently remove Hg2+ from solution. • The maximum Hg2+ adsorption capacity was 575.17 mg/g. • The removal mechanisms were ion exchange, surface complexation, reducing-oxidation. • Hg2+ removal processes and mechanisms were different for different pH values. [ABSTRACT FROM AUTHOR]