Study On Pollution Characteristics,Combined Purification And Biological Effects Of Mercury-Thallium Mine Waste Leachate

The mercury-thallium mine in Southwest,Guizhou Province,is a representative polymetallic mining area in southwest China.A large amount of mercury-thallium mine wastes containing highly toxic heavy metals（such as Hg,AS,Sb and Tl）are produced in the mining process.Under the leaching or leaching action of long-term rain,the wastes accumulated in the open air continue to produce special acid mine wastewater with polymetallic composite pollution.This caused serious environmental pollution of surrounding farmland water bodies,and threatened the health of local residents through the food chain.Therefore,it is particularly urgent to clarify the pollution characteristics of mercury and thallium mine waste leach solution,and to control and evaluate its pollution effect.However,systematic studies on the pollution characteristics,combined purification and biological effects of mercury-thallium mine waste leach solution are rarely reported.This paper takes the waste of mercury-thallium mine in southwest Guizhou Mill as the research object,and analyzes the effects of static soaking,horizontal oscillation and dynamic leaching on the pollution characteristics of mercury-thallium mine waste leach solution.The effects of different oxidation environments created by O₂and Fe（III）on the release of heavy metals in mercury-thallium mine wastes were revealed.On this basis,the effects of common litters of large wetland plants（Canna indica L.）,biological organic matter（cow dung）with high nitrogen and phosphorus rich and active microbial characteristics,combined with the most common natural mineral（carbonate rock）with calcium rich and continuous alkali production characteristics in karst area on the change of heavy metal content in the leaching solution of mercury-thallium mine waste（complex purification）were studied.Finally,clover seeds and kale seeds were used as representative plants for ecological restoration and land reclamation,and bioluminescent bacteria were used as test organisms.In terms of the difference of biological effects on plant seed germination and bioluminescent bacteria before and after purification of mercury-thallium mine waste leaching solution,To evaluate the practical effect and feasibility of combining the above biomass（cow dung and litter）with natural minerals（carbonate rocks）in the treatment of mercury-thallium mine waste leach solution,the relevant results can provide theoretical reference and technical support for pollution control and ecological purification of mercury-thallium mine waste leach solution.The main research results are as follows:（1）Dynamic leaching and strong oxidation environment can obviously promote the release of sulfate and heavy metals in mercury-thallium mine wastes.Dynamic leaching can obviously promote the release of sulfate and highly toxic heavy metals（Hg,As,Sb and Tl）in mercury-thallium mine wastes,and the content of heavy metals in the initial leaching is the highest.With the increase of leaching times,the leaching concentrations of sulfate and heavy metals gradually decrease,while the concentration of heavy metals in horizontal oscillation and static soaking is relatively low,but the process lasts long.Finally,the leaching equilibrium is reached.Fe³⁺solution and oxygen-rich deionized water（O₂）can effectively promote the release of SO₄^2-,Hg,As and Fe,indicating that SO₄^2-,Hg,As and Fe are more likely to migrate in a strong oxidizing environment,and the stronger the oxidizing ability of the environment,the greater the degree of heavy metal release.The specific performance is 1000 mg/L Fe³⁺>500 mg/L Fe³⁺>O₂.Fe³⁺solution inhibited the release of Tl and Sb significantly,but Fe³⁺did not inhibit the release of Tl and Sb under dynamic leaching conditions.（2）Biomass-mineral materials can effectively remove heavy metals from the mercury-thallium mine waste leaching solution,increase the p H and reduce Eh of the solution.Biomass-mineral materials reached equilibrium after reaction for 4～8 h,and the purification effect of mineral materials was the best,while that of biomass was poor.The removal rates of As from carbonate rocks,cow dung and litter were 95.64%,78.6%and 87.15%,respectively.The removal rates of Tl were 82%,56.88%and59.88%,respectively.The removal rates of Fe were 99%,88%and 58.82%.Within 10min after the biomass-mineral material was added,the p H rose rapidly and showed different changes according to the different substances added.Finally,the p H of litter stabilized at about 4.5,and the p H of other experimental groups stabilized at about 7.（3）The removal mechanism of heavy metals from mercury-thallium mine wastes by biomass materials and mineral materials is different.The removal of heavy metals by the three experimental materials is not a reaction mechanism dominated by physical adsorption.Biomass（cow dung and litter）has rich functional groups.By comparing the Fourier infrared spectroscopy of biomass before and after the reaction with the leachate of mercury-thallium mine waste,it is found that a large number of functional groups,such as hydroxyl and carboxyl groups,are deflecated.These functional groups and heavy metal ions undergo ion exchange,chemical adsorption,coordination,electrostatic and other reactions to remove heavy metals.While natural minerals（carbonate rocks）mainly neutralize and precipitate metal ions,and then remove heavy metal ions from water through adsorption.（4）The unpurified leached solution of mercury-thallium mine waste severely inhibited seed germination and the relative luminescence intensity of luminescent bacteria.The germination rate of the representative plant（clover）for ecological restoration and the representative plant（cabbage）for land reclamation were 17.25%and 0%,respectively.When interacting with luminescent bacteria,the relative luminescence intensity of luminescent bacteria was 22.02%,indicating that the unpurified mercury thallium mine waste leaching solution had strong toxic effects on clover seeds,cabbage seeds and luminescent bacteria,and the toxic degree of cabbage seeds was significantly greater than that of white clover seeds,which might be because white clover belongs to the local dominant plant.The ability to stress and degrade pollutants is relatively good.（5）The relative luminescence intensity of seed germination and luminescent bacteria was significantly different from that of mercury-thallium waste leachate treated with biomass-mineral materials.The treatment solution can inhibit plant seeds to varying degrees,and the diluted treatment solution can effectively promote the germination and growth of plant seeds.Single treatment solution（carbonate rock,cow dung and litter）had a greater inhibition degree on the relative luminescence intensity of luminous bacteria,while composite treatment solution（carbonate rock plus litter,carbonate rock plus cow dung,cow dung plus litter and carbonate rock plus cow dung plus litter）had a smaller inhibition rate on the relative luminescence intensity of luminous bacteria.And dilute to 25%concentration condition to promote the relative luminous intensity of luminous bacteria.