镍钴采选行业废石和尾矿中重金属淋溶释放规律研究

镍钴采选废石和尾矿中重金属的溶出释放规律对矿区的重金属污染防治具有重要意义。但目前，国内还没有对镍钴行业采选产生的尾矿和废石中重金属的溶出规律开展研究。本文以镍钴采选企业的尾矿和废石作为样本，开展了毒性浸出实验。研究了不同pH值、离子强度、温度等实验条件对重金属溶出的影响，探讨了镍钴采选过程中所产生的尾矿和废石中重金属的溶出特性和释放规律。实验结果表明，尾矿样品中Ni的浸出浓度为42.28 mg·L^-1，是最大允许排放浓度的8.86倍，为具有浸出毒性特征的危险废物；废石样品中重金属Ni和Cu的溶出浓度分别为4.72 mg·L^-1和26.2 mg·L^-1，超过最大允许排放浓度，属于第Ⅱ类一般工业固体废物。pH对样品中Ni、Cr、Pb、Co和As的溶出量影响较大，其中尾矿中Ni和Cu在pH较低的条件下，可达到44.28 mg·L^-1和53 mg·L^-1，远高于最大允许排放浓度，而Hg、Cd和Cu的溶出量随pH值的变化不大。除As以外，样品中大多数重金属的溶出质量浓度在酸性条件下比在中性条件下高，这表明在酸性环境条件下，这些重金属对周围生态环境的潜在风险更大。离子强度的变化对Cd和Co的溶出量的变化并不明显，而当离子强度变化时，Ni、Cr、Pb、Hg、Cu和As的溶出量可能达到最大，使周围环境的潜在生态风险增大。当温度达到35~40℃时，部分重金属如Co、Pb、Cd 等，溶出量将达到最大；当温度低于25℃时，除 Ni 以外，大部分重金属溶出量很低。而温度变化对重金属Cu、As、Cr和Hg的溶出量的影响不明显，波动范围较小，对周围生态环境产生的潜在生态风险较小。

Leaching characteristics and release law of heavy metals from the mining mullock and tailings in nonferrous metal mining industry

Leaching characteristics and release law of heavy metals from the mining mullock and tailings in nonferrous metal mining industry are significant to the heavy metal pollution control in nonferrous metal mining-area. However, there are few researches about these aspects in nickel and cobalt mining industry. In this study, heavy metal leaching and toxicity experiments were carried out with the mining mullock and tailings from some nickel and cobalt mining areas. The effects of pH, ionic strength, temperature on the leaching amounts of heavy metal were studied. Their leaching characteristics and release laws were investigated. According to the experimental results, the leaching concentration of Ni from the mining mullock is 42.28 mg·L^-1, which is 8.86 times of the maximum allowable emission concentration. So the mining mullock are hazardous waste solid based on its leaching toxicity characteristics. The leaching concentrations of Ni and Cu from the tailing are 4.72 mg·L^-1 and 26.2 mg·L^-1, respectively, which are both larger than the maximum allowable emission concentration. So the tailings are classified to the Class II of general industrial solid waste. pH has significant influence on the leaching amounts of Ni, Cr, Pb, Co and As. Under the condition of low pH, the leaching concentrations of Ni and Cu from the tailings can reach the level of 44.28 mg·L^-1 and 53 mg·L^-1, which are much larger than the maximum allowable emission concentration. On the other hand, pH has little impact on the leaching concentrations of Hg, Cd, and Cu. Except for As, the leaching concentration of most heavy metals in samples under acid condition are higher than those under neutral condition, which indicates that that these heavy metals have higher potential risk ecological environment under the condition of acidic environment. The change of the ionic strength has little influence on the leaching concentrations of Cd, and Co from the samples. However, when the ionic strength changed, the leaching concentration of Ni, Cr, Pb, Hg, Cu and As may reach the maximum value, which may results the high potential ecological risk of the surrounding environment. On the one hand, when the temperature come to 35-40℃, the leaching concentrations of some heavy metals such as Co, Pb, Cd approach the maximum value. On the other hand, when the temperature is lower than 25℃, the leaching concentrations of most heavy metals are very low except for Ni. However, the effect of temperature on the leaching concentration of Cu, As, Cr and Hg is not obvious. The fluctuation range of the leaching concentration is also relatively small, which results in the low potential ecological risk on the surrounding environment.