天然及改性凹凸棒对稀土尾矿土壤中重金属铅的钝化效果研究

赣南离子型稀土矿的大肆开采，以及尾矿废渣不合理处置，造成矿区周边环境中重金属铅含量超标，破环矿区生态环境。本文利用不同剂量（质量分数分别为5%、10%和15%）的天然及改性凹凸棒作为钝化剂，利用扫描电镜和傅里叶红外光谱对两种钝化剂的表面特征和官能团进行分析，采用BCR重金属连续提取法对钝化能力和效果进行评价，并以此研究土壤中铅的形态变化，借鉴国外的重金属TCLP提取法评估重金属污染土壤的环境质量。结果表明：经过50d的培养，土壤pH值从4.76显著升高至接近7.0。改性后凹凸棒使铅的酸提取态含量从25.69mg/kg降低至7.42mg/kg，并促进其向残渣态转化，残渣态含量比对照组增加了1.38倍，TCLP提取态含量比对照组降低了65.70%，从而显著降低了铅的生物可利用度和生态风险。与天然凹凸棒相比，改性后凹凸棒对稀土尾矿土壤修复具有较为良好的效果。

Study on the Passivation Effect of Natural and Modified Attapulgite on Heavy Metal Lead in Soils of the Rare Earth Tailings

BACKGROUND: The large-scale mining of ion-type rare earth mines in southern Jiangxi and the unreasonable disposal of tailings and slag caused heavy metal lead content to be deposited in the surrounding environment of the mining area, exceeding the standard level, and destroying the ecological environment of the mining area.
OBJECTIVES: To passivate the lead in the soil of the mining area to reduce its bioavailability and ecological risks.
METHODS: Natural and modified attapulgite with different dosages (mass fractions of 5%, 10%, and 15%) were used as passivating agents. Scanning electron microscopy and Fourier infrared were used to analyze the surface characteristics and functional groups of the two passivating agents. Passivation ability and effect were evaluated by BCR continuous extraction method of heavy metals, and form changes of lead in the soil were also studied by this method. Environmental quality of heavy metal contaminated soil was also evaluated using foreign heavy metal TCLP extraction methods.
RESULTS: After 50 days of cultivation, the modified attapulgite reduced the acid-extracted content of lead from 25.69 to 7.42mg/kg, the residual content increased by 1.38 times and the TCLP extracted content decreased by 65.70% compared to the control group, significantly reducing the bioavailability and ecological risk from lead.
CONCLUSIONS: Compared with the natural attapulgite, the modified attapulgite has a better effect on the soil remediation of rare earth tailings.