模拟酸雨淋溶条件下锌冶炼挥发窑渣重金属释放特征

模拟pH值分别为4.0、5.6、7.0酸雨干湿交替淋溶(对应pH4.0、pH5.6、pH7.0处理组)和pH=4.0雨水持续淋溶(CL pH4.0处理组), 开展50 d锌挥发窑渣柱淋溶实验, 研究渣中Cd、Cu、Pb、Zn释放和赋存形态变化特征。结果表明, pH4.0处理组在整个淋溶期间Pb的释放较高, 淋溶第35~50 d促进Cd、Cu和Zn释放。pH4.0和CL pH4.0处理组淋出液Cd、Cu、Zn浓度均在前期第5 d达到峰值, pH5.6和pH7.0处理组于第10 d达到峰值。各处理组淋溶50 d后淋出液中Cd、Cu、Pb和Zn浓度变化范围分别为150~1 438、1.88~234、1.30~5.96和15.2~120 mg/L, 远超GB 25466—2010《铅、锌工业污染物排放标准》限值1 500~14 380、3.76~468、1.30~5.96和7.60~60倍。淋出液Cd浓度较高与其渣中高比例活性态相关, 且酸雨淋溶会促进Cu活化。矿物溶解控制重金属元素溶出释放, 淋溶后PbSO₃衍射峰消失, Cu和Zn赋存矿物衍射峰强度降低。酸雨淋溶下锌挥发窑渣中重金属具有较大环境风险, 需加强降雨淋滤污染防治管控。

Release Characteristics of Heavy Metals in Zinc Smelting Slag from Rotary Kiln Under Eluviation with Simulated Acid Rain

A 50-day column leaching experiment was carried out for zinc smelting slag from rotary kiln, respectively under dry/wet alternation of leaching with simulated acid rain with pH values of 4.0, 5.6, and 7.0 (referred to treatment group with pH4.0, pH5.6 and pH7.0), and continuous leaching with simulated acid rain with pH=4.0 (referred to treatment group with CL pH4.0), for investigating the release and occurrence characteristics of Cd, Cu, Pb and Zn therein. As for the treatment group with pH4.0, an enhanced release of Pb was observed through the whole eluviation time, while enhanced release of Cd, Cu and Zn were found from the 35 d to 50 d of eluviation. The concentration of heavy metals in the leachate from the treatment group with pH4.0 and group with CL pH4.0 all reached a peak value on the 5th day of eluviation, while for the treatment group with pH5.6 and pH7.0, the concentration of heavy metals reached a peak value on the 10th day of eluviation. The concentration of Cd, Cu, Pb and Zn in the leachate was respectively within the range of 150-1 438, 1.88-234, 1.30-5.96 and 15.2-120 mg/L, far exceeding the limited values of 1 500-14 380, 3.76-468, 1.30-5.96 and 7.60-60 times, that are regulated in the Emission Standard of Pollutants for Lead and Zinc Industry (GB 25466—2010). It was found that higher Cd concentration in the leachate was related to the higher percentage of active forms of Cd in the slag, and eluviation with acid rain would promote the activation of Cu in the slag. The dissolution of minerals in the slag controled the dissolution and release of heavy metals. XRD analysis showed that the diffraction peak of PbSO₃ was disappeared after column leaching, and the diffraction peak intensity of Cu- and Zn-containing minerals decreased. It is concluded that heavy metals in the zinc smelting slag under the eluviation with acid rain will pose great environmental risks, and pollution control measures need to be strengthened for it.