Study on Pure Mercurous Chloride Leaching with Sodium Thiosulfate

Mercurous chloride (Hg2Cl2), also known as Calomel, is a typical mercury-containing mineral found in nature. In this work, the leaching behaviour of pure mercurous chloride dissolved in pure water and in thiosulfate solution was investigated. The mercurous chloride hardly dissolved in sulfuric acid solution at pH of 3 and pure water at pH of 6.4, with the corresponding maximum Hg extraction percentage at 3.1 and 7.5% respectively. However, the Hg extraction percentage increased to 45.8% in sodium hydroxide solution at pH of 11.2. The mercury extraction percentage reached a high of 62.6% in thiosulfate solution, and the leaching kinetics results show that the activation energy is 6.6 kJ/mol. This study indicates that the thiosulfate solution can efficiently extract mercury from mercurous chloride.