Passivation Of Heavy Metals By Attapulgite And Applied To Tailings And Farmland

With the rapid development of mining activities in recent years,the soil surrounding mining areasand farmland have been heavily polluted by heavy metals,mainly Cd,Pb,Zn,As,and Cu.These heavy metals are highly toxic,have strong migratory ability,and are easily spread through the food chain.Further,it accumulates in the human body and has great harm to the human body and the environment.Mineral remediation as a rapid,efficient method of heavy metal pollution repair has attracted widespread at tention.This article first screened the clay mineral materials,and then carried out heavy metal passivation repair experiments on the mineral deposits of the Hengyang metal mine and the farmland of the Ganxian county of Jiangxi through the methods of mineral restoration.The main results were as follows:(1)The attapulgite has more comprehensive passivation ability,and under the ext reme conditions of higher acidity,the passivation effect of the attapulgite is obviously better than the other two types of passivation agents,taking into account the economical nature of the material addition,Low-ration attapulgite was used to passivatite the heavy metal of tailings dams and farmland.(2)The contents of Cr,Zn,Cd,Pb,As,Cu,and Hg in the tailings of Hengyang Shuikoushan mining area are extremely high,and the heavy metal content increases with the increase of the sample depth,indicating that heavy metals in tailings have obvious migration and infiltration.The passivation of heavy metals with the low ratio attap ulgite to the Hengyang tailings has a significant effect of heavy metals passivation.The average leaching concentrations of Cr,Zn,Cd,Pb,and Cu in the tailings are reduced by 30.5% and 87.8%,respectively.82.9%,47.4%,and 43.1%.Attapulgite has a larg e capacity for passivating heavy metals in tailings ponds.The addition of attapulgite at low ratios is sufficient to effectively passivate heavy metals in the soil within the rad iation range(diameter 60 cm)of spin-column spray.(3)The Cd in the farmland of Ganxian County,Jiangxi Province,exceeded the standard.Heavy metal passivation tests were conducted in cropland.The results showed that adding about 600 kg of attapulgite peracre of paddy field to passivatethe heavy metals in farmland soil,and the passivation effect of Cd was good.In the experimenta l field with attapulgite,the leaching content of Cd in most soil samples was significant ly lower.The average leaching concentration of Cd was 0.80 mg/L,which was lower t han the Cd leaching identification standard of 1.0 mg/L,compared to the control with out attapulgite.In the experimental group,the average leaching concentration of Cd in the test soil decreased by 60.7%.The average content of Cd in control field rice is 0.87mg/kg,which exceeds the national standard value of Cd food safety 0.2mg/kg;in experimental field rice with addition attapulgite,the average content of Cd is 0.19mg/kg,lower than Cd National food safety standards,compared with the control field,attapulgite significantly reduced the Cd content in experimental rice,a drop of 78.2%.The results show that attapulgite has significant effect on the passivation of heavy metals in tailings dam and farmland.Mineral remediation,as a simple and highly eff icient method for remediating heavy metals,has broad application prospects in the future.