含铜镍尾矿重金属溶出特性试验研究

Study on the dissolution characteristics of heavy metals in Nickle-Copper tailings

本研究以位于我国东北典型铜镍矿区为研究对象,对其进行尾矿重金属溶出特性分析,通过静态浸出实验研究尾矿粒径和固液比对尾矿中镍(Ni)释放浓度及溶液pH的影响;并研究模拟酸雨条件下尾矿中Ni和铜(Cu)的溶解释放规律;此外,也分析了微生物对尾矿中重金属的溶出特性的影响.结果表明:在初始pH=7. 0的浸出液中,尾矿中的Ni在第1天就释放得较为完全,其质量浓度达到0. 85～1. 73 mg/L。减小尾矿粒径会增加Ni释放量,固液比过高会减小Ni的浸出;模拟酸雨(pH=4. 0和6. 0)条件下,淋溶液pH值相对较稳定,说明尾矿的缓冲能力较强,低pH条件利于Ni和Cu的溶出.静态浸出和动态淋溶实验初期,Ni的质量浓度基本高于《污水综合排放标准》(GB8978-1996)中的Ni排放限值(1. 0 mg/L),说明铜镍尾矿具有污染水环境的风险.微生物溶出试验结果表明:35 d后Ni和Cu浸出率达到了38. 4%和32. 7%,较酸浸条件下分别提高了74. 5%和28. 7%,说明微生物作用会加剧重金属Ni和Cu的释放,从而增加其环境风险.

In this study,a typical Ni- Cu mine located in northeastern China was investigated.The leaching characteristics of heavy metals from the tailings were analyzed.Effects of particle size and solid-to-liquid ratio on the leaching characteristics of Ni in the tailings were studied through static leaching experiments.The dissolution and release of Ni and Cu in the tailings under the simulated acid rain conditions were also studied.In addition,effects of bioleaching on the release of heavy metals from the tailings were analyzed.The results of static leaching experiments by using a leaching solution with an initial pH value of 7.0 showed that Ni release from the tailings mainly happened on the first day and the Ni concentration was 0.85~1.73 mg/L.Smaller size of tailings can increase Ni release,while too big a solid-liquid ratio will reduce the leaching of Ni.In the dynamic leaching process under the simulated acid rain (pH=4.0 and 6.0) condition,the pH values of the leaching solutions were relatively stable,indicating that the tailings have a strong buffering capacity.The leaching concentrations of Ni and Cu under a lower pH condition were higher.In the initial stages of static leaching and dynamic leaching experiments,concentrations of Ni were higher than the discharge limit of Ni (1.0 mg/L) according to the Comprehensive Wastewater Discharge Standard (GB8978-1996),indicating that the Ni-Cu tailings have a risk of water pollution.The results of bioleaching test showed that the leaching ratio of Ni and Cu reaches 38.4% and 32.7% after 35 days,which increases by 74.5% and 28.7% than those in acid leaching,respectively.This suggests that microbe can increase the release of Ni and Cu,thus it can increase the environmental risk.