SPB和SPC固化稳定化镍锌污染土的强度及环境特性研究

以某汽配厂搬迁遗留电镀车间的镍(Ni)、锌(Zn)复合污染土为研究对象,研究2种新型固化剂SPB和SPC固化稳定化污染土的强度及环境安全特性。通过室内试验研究2种固化剂修复污染土的无侧限抗压强度(qu)、干密度(rd)、酸碱度(pH)、酸缓冲能力(ANC)及重金属浸出毒性、重金属形态分布等参数随固化剂掺量和养护龄期的变化规律。室内试验结果表明,污染土经固化剂SPB和SPC处理后q_u和rd显著提高,相同固化剂掺量、反应稳定(28 d)后,SPC固化土qu略高于SPB固化土,2种固化土rd基本相同;固化剂SPB和SPC使活性形态重金属转化为较稳定形态,重金属浸出浓度显著降低,但2种固化剂对重金属的固化稳定化效果存在差异,固化剂SPC固化稳定化Ni的效果优于固化剂SPB,而固化剂SPB固化稳定化Zn的效果更优;固化土pH显著提高,其中固化剂掺量10%、反应稳定后,SPB和SPC固化土pH分别为9.51和9.07;SPB和SPC固化土ANC均显著提高。另外,小试试验结果表明,SPC固化土pH低于PC固化土;固化剂SPC在短期养护(7 d)的固化效果优于PC。研究结果可以为固化剂SPB和SPC在实际工程的现场应用提供参考和建议。

Experimental study on the strength and environmental properties of Ni and Zn contaminated soil stabilized by SPB and SPC binders

The systematic investigation on the strength and environmental safety properties of the SPB and SPC stabilized soil is presented in this paper. The field soil which has been industrial contaminated with nickel(Ni) and zinc(Zn) is studied. The SPB binder is composed of superphosphate and cement-activated steel slag and the SPC binder is composed of superphosphate and quicklime. The stabilized soils were tested for the unconfined compression strength，dry density，soil pH，acid neutralization capacity，toxic leaching characteristics and contaminant speciation varying with dosages and curing periods. The results demonstrate that the addition of two binders increases the unconfined compressive strength and soil pH，but reduces the toxicity leaching concentration of Ni and Zn. These results are interpreted based on the variations in chemical speciation of Ni and Zn and the capacity index of acid buffer of the stabilized soils. It was also found that the SPC stabilized soil had a lower pH value than that of PC under curing of 28 days. The SPC shows higher immobilization efficiency than PC at early curing. Overall，this study demonstrates that the SPB and SPC binders have positive effects on the immobilization of the heavy metal and the strength of the stabilized soils.