Effect of substitution reaction with tin chloride in thermal treatment of mercury contaminated tailings

Sites contaminated by mercury (Hg) from artisanal small-scale gold mine tailings have been found near agricultural land. For the active implementation of the Minamata Convention on Mercury, development of technology for the remediation of Hg contaminated sites is required. This study examined the conditions for the thermal treatment of Hg contaminated tailings at reduced temperature by introducing SnCl2 as an additive. Thermogravimetric analysis (TGA) was used to identify the possibility of converting typical Hg compounds (HgO, HgS) in the environment to HgCl2. The operation conditions for thermal treatment such as temperature, retention time, and ratio of [Cl2]/[Hg] were derived from lab scale experiments using commercial Hg compounds (HgO, HgS), additive (SnCl2), and tailings. The tailings with Hg content of 26.39 mg-Hg/kg were reduced to 3.87 mg-Hg/kg and 4.57 μg-g/L of leaching concentration through the application of the Korea standard leaching test. Both concentrations were below the standard limit of soil pollution and hazardous waste classification criteria. The sequential extraction procedure was applied to evaluate the Hg stability of residual tailings. The results show that this method will be effective for remediation of small scale Hg contaminated areas. [Display omitted] •SnCl2 accelerated the evaporation of mercury species in the thermal treatment.•Mercury substitution reaction by SnCl2 additives was suggested by TGA analysis.•The stability of mercury species and the leaching properties were evaluated. Main findings of this study: Addition of tin chloride was effective to reduce temperature of thermal treatment of Hg contaminated tailings. Substitution reaction of mercury by tin was suggested on the basis of TGA analysis.