Experimental Study On Curing Stabilization Of Typical Lead-Zinc Mine Tailings In Hunan Province

In recent years,heavy metal pollution caused by mining development has attracted more and more attention at home and abroad.The tailings slag developed by the mining industry has a high content of heavy metals,and the open-air piles will rapidly weather,and directly or indirectly pollute the surrounding natural environment through acidification,rainfall leaching,etc.,causing serious heavy metal pollution problems.Water and soil heavy metal pollution is persistent and irreversible.Once the water and soil environment in the mining area is polluted,it is difficult to restore and cure it.Tailings are the most important source of pollution in mines.Based on the principle of source control,tailings treatment is the fundamental strategy to protect the water and soil environment of mines.Hunan is a major mining province,and its lead and zinc mines are very rich.The pollution of tailings from lead and zinc mines is one of the difficulties in the comprehensive ecological management of Hunan mines.Therefore,this study took the typical lead-zinc mine slag in Hunan as the research object,and carried out the repair and mechanism research of cement as the main solidified material and phosphate,carbonate,sulfite and chloride as the main passivation material.To develop solidified and stabilized materials for lead-zinc tailings to provide technical support for comprehensive improvement of mine environment in Hunan and even the whole country.The lead-zinc tailings were taken from a lead-zinc mine in Chenzhou,Hunan Province.The test used sodium sulfite,potassium dihydrogen phosphate,sodium carbonate,and ferric chloride hexahydrate as stabilizers,and cement and fly ash as the main curing agents.Compressive strength and horizontal oscillation leaching toxicity under different ratio conditions are used as indicators to explore the curing/stabilizing treatment effect.The experimental results show that the combination of sodium sulfite and ferric trichloride has the best stabilizing effect on the heavy metals in the waste residue.The concentration of lead ion is 0.02mg/L,the concentration of zinc ion is 0.45mg/L,the concentration of iron ion is 0.21 mg/L,the concentration of manganese ion is 0.02mg/L,the concentration of arsenic ion is 0.0005mg/L,all reach the surface class ? Heavy metal concentration standards for water.When adding cement alone,the compressive strength of the cured product increases with the increase of the cement content,and the leaching concentration of heavy metals decreases;when the cement content is 20%,it meets the requirements of paving the roadbed;part of the cement is replaced with fly ash When solidifying waste residue,the best ratio of fly ash to cement is 1:4,and adding sodium hydroxide with 5%fly ash content can achieve the best compressive strength of 2.79MPa.The stabilizing mechanism of sodium sulfite to heavy metals is mainly formed by the reaction of sulfite ions and heavy metal ions to form sulfite precipitates,and ferric chloride reacts with arsenic to generate arsenate precipitates;the solidification mechanism of cement and fly ash mainly consists of The cementing substances and oxides such as Al and Si adsorb heavy metal ions,thus affecting the mobility of heavy metal ions.In the leaching test,the cured and stabilized material was made into a cube of 3 × 3cm cubes,which was rinsed with water at pH 5.0 and 7.0.The results showed that the stronger the acidity,the more stable the material of heavy metals in are more easily eluted by leaching.Among them,the concentration of eluted lead and manganese is low,which is lower than the detection limit.Zinc,iron,arsenic can be detected and the concentration is low.The leaching concentrations of the three heavy metal elements tend to be in the same range with time.After solidification and stabilization,the exposed heavy metal elements on the surface of the lead-zinc tailings will be washed out,and under acidic conditions,the heavy metals on the shallow surface will also be dissolved into the water a little.In two days,the outflow of heavy metals is very small,iron is about 1.5%,and zinc and arsenic are about 0.5%.The concentration of heavy metals in the leachate in the later stage is maintained at a low concentration,and the effect of solidification and stabilization test is remarkable,which effectively controls the pollution of heavy metals in lead and zinc tailings.