Research On Leaching Of Mercury Tailings With Hypochlorite

Mercury tailings are low-value waste from mercury ore-pressing,which is difficult recycling because of its low mercury content.Now,due to environment concerns,original mercury mining has been halted,but mercury tailings are still in storage.The threat to the environment pollution of mercury tailings cannot be overlooked.In this paper,experiment raw material is mercury tailings.TCCA(Trichloroisocyanuric acid)-HCl leaching,NaClO-NaOH and Na₂S₂O₃ two steps leaching were carried out respectively,with their result analyzed.Higher mercury leaching rate is aspired for reducing mercury content in mercury tailings,in other word,reducing the mercury tailings pollution.Test result show that,the optimal conditions of TCCA-HCl leaching process were:leaching temperature 30?,TCCA concentration 1.0g/L,HCl concentration 0.1mol/L,stirring speed 300rpm,and liquid-solid ratio 10.Under the optimal conditions,the leaching rate of mercury reached the highest,which is 96.29%.The optimal conditions of NaClO-NaOH and Na₂S₂O₃ two steps leaching process were as follows.Step one:NaCIO concentration 0.2mol/L,leaching temperature 25?,leaching time 1 hour and liquid-solid ratio 10.Step two:Na₂S₂O₃ concentration 0.2mol/L,leaching time 4 hours,leaching temperature 25? and liquid-solid ratio 10.Under the optimal conditions,the leaching rate of mercury was 86.29%.The above two processes are both pollution-free to environment.In TCCA-HCl leaching process,a high leaching rate can be obtained in a short time.Mercury content in mercury tailings can be reduced from 580g/t to 21.52g/t.In NaClO-NaOH and Na₂S₂O₃ two steps leaching process,a good leaching rate can be obtained with a mild leaching reaction and cheap medicine.Mercury content in mercury tailings can be reduced from 580g/t to 79.52g/t.