龙葵对典型酸性矿山废水重金属的处理效果研究

Study on the treatment of heavy metals in typical acidic mine drainage by Solanum nigrum L.

  • 摘要: 酸性矿山废水(AMD)的pH低、重金属浓度高,是矿区生态环境的一大威胁。开展高效、可持续、环保、低成本的AMD处理技术研究十分必要。以硫铁矿(PR)和银铅矿(SL)2种典型强酸性AMD(PR-AMD、SL-AMD)为研究对象,设计龙葵(Solanum nigrum L.)吸收模拟试验对AMD进行处理。通过投加氢氧化钠调节2种AMD的pH为5和7后(PR-pH5、PR-pH7和SL-pH5、SL-pH7),进一步利用龙葵水培试验对重金属进行净化处理。结果表明:PR-AMD中铁和硫酸根浓度较高,但重金属污染程度较低,而SL-AMD中存在以Cd、Zn和Cu为主的多金属复合污染。2种AMD的pH调整为5后更有利于龙葵的生长,但龙葵对重金属的吸收能力受到AMD组分的显著影响。龙葵对SL-AMD中的Cd具有较高的富集和地上转移能力,但对PR-AMD中的Cd吸收后主要富集在根部。除了SL-pH5处理组水中的Cd和Zn外,其他处理组中重金属的浓度均显著低于GB 8978—1996《污水综合排放标准》中标准限值。PR-AMD中Cd的去除主要是通过龙葵吸收作用,其他重金属(Pb、Zn、Cu和As)主要通过中和沉淀作用从水中去除;而SL-AMD中重金属去除原因主要为中和沉淀作用。上述结果表明碱性中和复合龙葵深度净化方法对AMD的修复具有一定应用前景。

     

    Abstract: Acid mine drainage (AMD) poses a significant environmental threat to mining areas due to its elevated heavy metal content and low pH. It is imperative to conduct research on efficient, sustainable, cost-effective, and environmentally friendly AMD treatment technologies. This study focused on two types of strong acidic AMD, namely the pyrite deposit type (PR) and Ag-Pb deposit type (SL), as experimental subjects. An absorption simulation experiment was devised with Solanum nigrum L. for the treatment of AMD. The pH of AMD was adjusted to 5 or 7 (PR-pH5, PR-pH7, SL-pH5, SL-pH7) using sodium hydroxide, followed by hydroponic experiments to assess heavy metal removal. The results revealed that PR-AMD had high concentrations of Fe and sulfate but the degree of heavy metals contamination was low, while SL-AMD exhibited combined contamination of Cd, Zn, and Cu. Adjusting the pH to 5 favored Solanum nigrum L. growth, yet the AMD composition significantly influenced its ability to absorb heavy metals. Solanum nigrum L. demonstrated a remarkable capacity to accumulate and transfer Cd in SL-AMD, whereas Cd in PR-AMD was predominantly concentrated in the roots. Except for Cd in SL-pH5 treatment, heavy metal concentrations in all treatments were significantly below the limits specified in the Integrated Wastewater Discharge Standard (GB 8978-1996). Cd reduction in PR-AMD was primarily attributed to Solanum nigrum L. uptake, while neutralization and precipitation processes were the main mechanisms for removing Pb, Zn, Cu, and As from water in SL-AMD. In summary, the study suggested that the combination of alkaline neutralization and Solanum nigrum L. phytoremediation hold promise for AMD treatment, showcasing potential applications in addressing this environmental challenge.

     

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