Effective utilization of calcined MgAl-layered double hydroxides for adsorption of gold (I) thiosulfate complexes

Abstract Layered double hydroxides (LDHs) have been widely used to remove anions from water owing to their ability to exchange interlayer anions. In this study, LDHs synthesized by coprecipitation method were used as raw materials to produce calcined layered double hydroxides (CLDH), in order to investigate the adsorption of gold (I) complexes from a thiosulfate solution. The effects of solution pH, adsorption temperature, initial gold concentration, and thiosulfate concentration on the adsorption of Au(S2O3)23- by the CLDH were systematically studied. The results showed that the adsorption of Au(S2O3)23- by the CLDH is a very fast endothermic process, and that the adsorption equilibrium can be reached in 2 h. More than 85% of Au(S2O3)23- could be recovered over a wide gold concentration range. Increasing the initial gold concentration resulted in faster and more efficient CLDH adsorption of Au(S2O3)23-, the cumulative adsorption capacity of activated carbon for gold was 11.8 mg/g. The adsorption followed pseudo-second-order kinetics and was well described by the Freundlich model. The adsorption mechanism involves the CLDH adsorbing Au(S2O3)23- species in an anionic solution based on the memory effect, which restores its original layered structure. The Au(S2O3)23- loaded CLDH (CLDH-Au) could be recycled by elution with CO32-. The present results reveal that the recovery of gold ions from a thiosulfate leaching solution using CLDH has good application prospects in gold hydrometallurgy.