Efficient Removal Of Typical Heavy Metals In Mercury-thallium Mine Waste And Purification Of Removal Solution

The mercury-thallium mine waste in Xingren City,Qianxinan,Guizhou Province,is a complex multi-phase,multi-heavy metal complex system consisting of a large amount of tailings,perimeter rocks and smelting slags abandoned during the mercury thallium mining and metallurgy process.These large amounts of mercury and thallium mine wastes stored in open piles under long-term weathering and leaching,continuously release high concentrations of typical heavy metals with high biological toxicity to the surrounding environment,such as arsenic（As）,antimony（Sb）,mercury（Hg）,thallium（Tl）,etc.,posing a great threat to the local ecological environment and the health of residents.The traditional way to control the pollution of mercury and thallium mine waste dumps is to mulch the surface of the dumps and re-green them with grass to prevent the release and diffusion of heavy metals,but it does not effectively remove or sequester the typical heavy metals in mercury and thallium mine waste.Under the long-term leaching of rainwater,the leachate（such as As,Sb,Hg,Tl,etc.）containing high concentrations of typical heavy metals with high biological toxicity seeps into surface water,groundwater and surrounding agricultural soil without purification,causing serious environmental pollution.Therefore,how to efficiently remove typical heavy metals（As,Sb,Hg,Tl）with high concentration and high biotoxicity from mercury thallium mine waste and deep purification of heavy metals in the removal solution is an important direction for ecological management and remediation of poor mine habitat.In this paper,based on the research on the content and morphology of typical heavy metals（As,Sb,Hg,Tl）in mercury-thallium mine waste,the process of"alkalization-oxidation-acidification"combined removal of typical heavy metals from mercury-thallium mine waste is used to efficiently remove As,Sb,Hg,Tl from the waste in sequence,and The combined precipitation method was used to purify the dissolved As,Sb,Hg and Tl in the removal solution,so as to realize the harmless treatment of typical heavy metals in mercury-thallium mine waste and achieve the purpose of pollution source reduction.The results of the study can provide theoretical reference and technical support for the efficient reduction of heavy metals in mercury thallium mine waste and subsequent ecological restoration.The results of the study are as follows:（1）Combined alkalization-oxidation-acidification can achieve the harmless treatment of As and Sb in mercury-thallium mine waste.The optimum conditions for the removal of As and Sb were as follows:sample size<74μm,concentration of alkaline removal agent（Na OH）0.2 mol/L,solid-liquid ratio 1:10,removal temperature 60℃,removal time 6 h,stirring rate 12 r/s.Under the optimum conditions,the removal rate of As and Sb from mercury-thallium mine waste was73.41%and 39.86%,respectively.After four cycles of As and Sb removal,the removal rate of As and Sb from mercury-thallium mine waste was 92.03%and 60.21%,which basically realized the harmless treatment of As and Sb in waste.（2）Combined alkalization-oxidation-acidification can realize the harmless treatment of Hg in mercury-thallium mine waste.The optimum process conditions for Hg removal were:oxidizing destructant（Na Cl O）8%,solid-liquid ratio 1:7,removal temperature 40℃,removal time 4h,stirring rate 12r/s.Under the optimum process conditions,the Hg removal rate reached 64.47%.After four cycles of removal,the removal rate of Hg from mercury-thallium mine waste was 84.79%,which basically realized the harmless treatment of Hg in waste.（3）Combined alkalization-oxidation-acidification can realize the harmless treatment of Tl in mercury-thallium mine waste.The optimum process conditions for Tl removal were:concentration of acidifying agent（H₂SO₄）0.3 mol/L,removal time4h,removal temperature 50℃,solid-liquid ratio 1:10,stirring rate 10r/s.Under the optimum process conditions,the removal rate of Tl could reach 75.40%.After four cycles of removal,the removal rate of Tl from mercury-thallium mine waste was87.75%,which basically realized the harmless treatment of Tl in waste.（4）The combined precipitation method can effectively remove dissolved As and Sb from the removal solution.dissolved As and Sb in the alkaline removal solution were removed by Na₂S-9H₂O,Ca（OH）?and Fe SO₄-7H₂O at p H=13.31（original removal solution）,10%precipitant dosage and 2h precipitation time,respectively,and99.93%,100%and 100%of As;Na₂S-9H₂O and Fe SO₄-7H₂O removed 100%and96.97%of Sb in the removal solution,respectively,and achieved the purification of dissolved As and Sb in the removal solution.（5）The combined precipitation method can effectively remove the dissolved Hg from the removal solution.97.75%and 98.41%of the dissolved Hg in the removal solution were removed by 10%dosage of Na₂S-9H₂O and K₂Fe O₄ at p H=7 and 10 min precipitation time,respectively,to achieve the purification of the dissolved Hg in the removal solution.（6）Combined precipitation method can effectively remove dissolved Tl from the removal solution.100%and 99.20%of Tl were removed by 0.5%dosage of Na₂S-9H₂O and K₂Fe O₄,respectively,and 100%of Tl was removed by 20%dosage of Fe SO₄-7H₂O under the conditions of p H=11 and 10 min precipitation time,which achieved the purification of dissolved Tl from the removal solution.The removal of dissolved Tl in the removal solution was achieved.In summary,the combined alkalization-oxidation-acidification process can sequentially and efficiently remove As,Sb,Hg and Tl from mercury-thallium mine waste,thus realizing the harmless treatment of heavy metals in the waste.By using the combined precipitation method,we can remove dissolved As,Sb,Hg and Tl from the removal solution and achieve the purpose of eliminating the pollution source.