硫化砷渣的环境稳定性与金属释放风险研究

Long-term environmental stability and heavy metals release mechanism of arsenic sulfide sludge

以湖南某铜冶炼企业硫化砷渣为研究对象,基于对其物理、化学及工艺矿物学基本特性进行分析,研究模拟堆存、静态侵蚀及半动态侵蚀环境下硫化砷渣的长期稳定性及潜在环境风险。研究结果表明:模拟堆存前后硫化砷渣中As浸出质量浓度由1 712 mg/L上升至9 956 mg/L,Cd质量浓度由12.38 mg/L上升至56.90 mg/L,而Cu,Pb和Zn浸出质量浓度始终低于标准限值;模拟堆存前后硫化砷渣的潜在生态风险等级均为严重风险,且各金属元素中对于潜在生态风险贡献最大的金属为As;在静态侵蚀环境中,硫化砷渣中各元素呈现两段式浸出特征,前期释放速率较快,之后释放速率逐渐减缓并最终趋于平缓;静态侵蚀过程金属释放主要是通过表面吸附物质的解吸、溶解实现;As在中性地下水环境、模拟强酸雨环境中的浸出行为符合双常数模型,在模拟弱酸雨、填埋场环境中符合Elovich方程,说明硫化砷渣在环境中发生了较复杂的表面反应;半动态侵蚀过程中As2O3逐渐溶解,且硫化砷中硫被氧化产生了单质硫;渣表面的絮状团聚减少,但仍附有大量细颗粒,表明有新产物生成;硫化砷渣中As浸出在中性地下水环境中受扩散及界面化学反应过程的混合控制,在模拟酸雨及填埋场环境中主要受内扩散控制。研究结果可为铜冶炼硫化砷渣的环境污染防治及环境风险防控提供参考。

Based on the the basic characteristics of physics, chemistry and process mineralogy, the long-term stability and potential environmental risk of arsenic sulfide sludge sampled from a copper smelter of Hunan Province in simulated stockpiling, static erosion and semi dynamic erosion environments were studied. The results show that after simulated stacking, the leaching mass fraction of As in arsenic sulfide sludge increases from 1 712 mg/L to 9 956 mg/L, and the leaching mass fraction of Cd increases from 12.38 mg/L to 56.90 mg/L, while the leaching mass fraction of Cu, Pb and Zn are always lower than the relevant standard limited values. The potential ecological risk levels of arsenic sulfide sludge before and after simulated stockpiling are a serious risk,and As contributes the most. During the static erosion, the metals in arsenic sulfide sludge mostly show the characteristics of two-stage leaching. The release rate is larger in the early stage, and then gradually slows down and finally tends to be stable. The release of metals in the static leaching process is mainly achieved by the desorption and dissolution of substances adsorbed on the surface. The leaching behavior conforms to the two constant equation in the neutral groundwater environment and the simulated strong acid rain environment, and conforms to the elovich equation in the simulated weak acid rain environment and the simulated landfill environment, indicating that a relatively complex surface reaction occurs. During the semi dynamic erosion, As2O3gradually dissolves, and the sulfur in arsenic sulfide oxidizes to elemental sulfur. The flocculent agglomeration on the surface reduces, but a large amount of fine particles still attaches, indicating the formation of new products.The leaching process of As in arsenic sulfide sludge is controlled by the mixing of diffusion and interfacial chemical reaction in neutral groundwater environment, and is mainly controlled by internal diffusion in simulated acid rain environment and simulated landfill environment. This study can provide reference for the prevention and control of environmental pollution and environmental risk of arsenic sulfide sludge from copper smelting.