ABSTRACT

Lead–zinc tailings are generated during the mining process which is considered as hazardous solid waste due to its high heavy metal content and leachability in the natural state. At present, the most effective technology for disposing heavy metals in solid wastes is the solidification/stabilization (S/S) technique. In terms of S/S technology, chemical stabilization is one of the most potential and practical method. This paper aims to investigate the S/S property of four typical chemical agents (Na₂S, NaH₂PO₄, TMT and Na₂EDTA) on the heavy metals in lead–zinc tailings. The results reveal that the heavy metals lead and zinc in tailings are stabilized more effectively by using chelating agents TMT than by using inorganic chemical agents Na₂S and NaH₂PO₄. When the dosage of TMT reaches 4%, the leaching concentration of lead and zinc is 0.18 and 14.60 mg/L according to toxicity characteristic leaching procedure (TCLP), and the stabilization efficiency of lead and zinc is 99.31% and 80.92%, respectively, while the leaching concentration of lead and zinc just drops to 0.41 and 16.00 mg/L with addition of 10% NaH₂PO₄. Furthermore, the leaching concentration of heavy metal lead in tailings treated by 4% Na₂EDTA increases to 53.44 mg/L which far exceeds the standard of pollution control. Therefore, considering stabilization efficiency and dosage, TMT is the preferred agent for solidifying heavy metals in lead–zinc tailings.

摘要

铅锌尾矿是在采矿过程中产生的，由于其高重金属含量和自然状态下的可浸出性，被认为是危险的固体废物。目前，处理固体废物中重金属最有效的技术是固化/稳定化（S/S）技术。就S/S技术而言，化学稳定是最具潜力和实用性的方法之一。本文旨在研究四种典型化学试剂（Na ₂ S、NaH ₂ PO ₄、TMT 和 Na ₂EDTA）关于铅锌尾矿中的重金属。_{结果表明，使用螯合剂TMT比使用无机化学剂Na 2} S和NaH ₂ PO ₄更有效地稳定尾矿中的重金属铅和锌。TMT投加量达到4%时，按照毒性特征浸出程序（TCLP），铅、锌的浸出浓度分别为0.18和14.60 mg/L，铅和锌的稳定化效率分别为99.31%和80.92% , 而添加10% NaH ₂ PO ₄ , 铅和锌的浸出浓度仅下降到0.41和16.00 mg/L 。_{此外，4% Na 2}处理尾矿中重金属铅的浸出浓度EDTA增加到53.44 mg/L，远超污染控制标准。因此，考虑到稳定化效率和用量，TMT是铅锌尾矿中重金属固化剂的首选。