Heavy Metal Release Law And Ecological Risk Assessment Of Antimony Ore Waste Under Leaching

Antimony ore waste is a waste ore that does not contain industrial value after mining and beneficiation in the antimony ore area under natural environmental conditions.The accumulation of these waste rocks occupies most of the land area,and releases a large number of heavy metals through rain and weathering,causing serious harm to the surrounding environment and threatening people’s health.In this study,the South Xikuangshan mining area in Lengshuijiang City,Hunan Province is taken as the research area,and the antimony waste rock in the mining area is taken as the research object.Through a large number of literature reading and field survey in the early stage,the on-site waste rock samples are collected and brought back to the laboratory for XRF element composition analysis and XRD phase composition characterization analysis,the static and dynamic leaching experiments of waste rocks are carried out under different conditions,and the occurrence forms of heavy metals in waste rocks are studied.According to the research results,the potential ecological risks caused by the leaching waste rocks and leaching liquid under different conditions are analyzed and discussed,which provides a theoretical basis and scientific basis for the evaluation and prevention of heavy metal pollution in the leaching stream of waste rock yard in antimony mining area,which is of great significance.The experimental results are as follows:(1)The mineral composition and the contents of Sb,Mn,Zn and Cr in antimony waste rock was tested and analyzed.The composition of elements in the original antimony waste rock was analyzed and tested by XRF fluorescent spectrum analyzer.The contents of the four heavy metals Sb,Mn,Zn and Cr discussed in this study were 10940 mg/kg,1150 mg/kg,860mg/kg and 150 mg/kg respectively,which exceeded the soil environmental background value of Hunan Province by 3671.1,2.6,9.1 and 2.1 times respectively,in which the content of Sb seriously exceeded the standard.XRD analysis shows that the mineral composition of antimony ore waste rock is mainly quartz and calcite,accompanied by a small amount of stibnite,pyrite and other minerals.(2)The release law of heavy metals in antimony waste rock under different leaching conditions was revealed.The effects of different particle size,solid-liquid ratio,rainfall pH value,the rainfall intensity and other conditions on the leaching and release of heavy metals in antimony waste rock were explored through simulated rainwater static leaching experiment and dry wet alternating dynamic leaching experiment on the collected antimony waste rock samples.The experimental results show that the precipitation rate of Sb,Mn,Zn and Cr in small particle size waste rock is faster and the released concentration is greater.The precipitation amount of Sb,Mn,Zn and Cr are increases with the increase of solid-liquid ratio.When the pH value of simulated rainwater is 7.6,the leaching release rate and precipitation amount of heavy metals Sb and Mn is greater,while when the pH value is 3.6,the leaching release rate and precipitation amount of Zn and Cr are greater.When the rainfall intensity is smaller,the precipitation amount of Sb,Mn,Zn and Cr heavy metals are larger.The cumulative release amount of heavy metals in antimony ore waste rock under different rainfall intensity is 60 mm/h > 120 mm/h > 180 mm/h.(3)The occurrence forms of Sb,Mn,Zn and Cr before and after leaching of antimony waste rock were studied.The occurrence forms of Sb,Mn,Zn and Cr heavy metals represent the migration degree of heavy metals and are affected by various leaching conditions.The results show that the elements sb,Mn,Zn and Cr in the original waste rock are mainly in the form of residue,and the bioavailability is low.After rainfall leaching,the residual state of Sb,Mn and Cr decreased in varying degrees.The higher the pH value,the greater the transformation of Sb to exchangeable state and the greater the transformation of Mn to carbonate bound state.The lower the pH,the greater the degree of Cr transformation to exchangeable state and iron manganese oxidation state.The smaller the rainfall intensity,the greater the transition degree of Sb to exchangeable state;The greater the degree of transformation of Mn to organic bound state and carbonate bound state;The degree of morphological transformation of Cr to exchangeable state and iron manganese oxidation state is greater.The morphological changes of Zn were not obvious under different leaching conditions.(4)Through RAC risk assessment index method and hankanson potential ecological risk assessment method,the risk assessment of waste rock and leachate pollution after leaching is carried out respectively.The results show that the RAC ecological risk assessment index method shows that the heavy metals with high potential pollution after leaching include Sb and Cr.After leaching under the condition of pH = 7.6,the active states of heavy metals Sb and Zn generally account for a larger proportion;Mn and Cr have higher activity under the condition of pH=3.6.When the degree of pollution is 60 mm/h,it is higher.The hankanson potential ecological risk assessment method shows that when the rainfall intensity is 60 mm/h,the comprehensive potential ecological risk degree of heavy metals in the leaching solution is medium ecological risk,when the rainfall intensity is 120 mm/h and 180 mm/h,the comprehensive potential ecological risk degree of heavy metals in the leaching solution is light ecological risk,and the order of comprehensive potential ecological risk index is 60mm/h > 120 mm/h > 180 mm/h.Under the condition of pH=7.6,the comprehensive potential ecological risk degree of heavy metals in leaching solution is high ecological risk,and the other two pH values are moderate ecological risk.The order of comprehensive potential ecological risk index is: pH=7.6 > pH=5.6 > pH=3.6.