基于钼尾矿和金尾矿的多孔建材制品重金属浸出行为及环境影响

Leaching behavior and environmental effect of heavy metals from porous building materials prepared by molybdenum tailing and gold tailing

针对金属尾矿及其制备的建材制品,分析了6种重金属(As、Cd、Cr、Mn、Pb、Zn)的总量.参照水槽浸出试验方法研究了重金属的累积释放行为,并利用双常数速率方程、Elovich方程和二级动力学方程对建材制品中重金属的长期释放量进行预测.采用改进的欧洲共同体标准物质局(BCR)逐级提取法研究了重金属赋存形态,并利用风险评估编码法(RAC)对建材制品重金属的环境风险进行评价.结果表明,金属尾矿中大部分重金属总量高于中国土壤元素背景值.建材制品中的重金属累积浸出量随浸出时间呈现早期快速增加,后期趋于平衡的规律.动力学方程拟合结果发现重金属在不同建材制品中最优动力学方程拟合结果不同,预测30年的重金属浸出量,大部分重金属浓度低于中国土壤元素背景值,且浸出率低于10%.尾矿及其建材制品的重金属赋存形态可以看出尾矿制备建材制品对部分重金属有一定的固化作用,残渣态含量增加. RAC结果表明,建材制品中的重金属生态风险处于中风险及以下水平.

The content of heavy metals(As,Cd,Cr,Mn,Pb,Zn)in tailings and their building materials was analyzed.The cumulative release behavior of heavy metals in building materials was studied according to the tank test.The long-term release of heavy metals in building materials was predicted by using the double constant rate equation,Elovich equation and second order kinetic equation.The chemical speciation of heavy metals was analyzed by modified European Community Bureau of Standards(BCR)step-by-step extraction method,and the environmental risk of heavy metals in building materials was evaluated by the risk assessment code(RAC).The results show that the content of many heavy metals in metal tailings is higher than the background value of soil elements in China.The cumulative leaching amount of heavy metals from building materials increased rapidly in the early stage and tended to be balanced in the later stage.The results of kinetic equation fitting show that the optimal kinetic equation fitting results of heavy metals in different building materials are different.The prediction of cumulative release amount of most heavy metals of 30 years is lower than the background value of soil elements in China,and the leaching rate is less than 10%.The chemical speciation shows that some heavy metals can be solidified by preparing the building materials from tailings,and the content of residual fraction increases.RAC results show that the ecological risk of heavy metals in building materials is below the medium risk level.