改性磷矿渣稳定铅污染土的赋存形态及浸出特性试验研究

Experimental study of mechanical and microstructure properties of modified waste phosphorus slag treated lead-contaminated soils

采用改性磷矿渣(MPS)对铅(Pb)污染土进行稳定化处理.基于浸出试验、形态提取试验和矿物分析试验,研究了改性磷矿渣(MPS)添加量对稳定土中Pb的浸出特性、赋存形态和矿物成分的影响规律,并与相同添加量的普通硅酸盐水泥(OPC)作对比.结果表明:MPS和OPC均可降低污染土中Pb的浸出特性,但MPS对Pb稳定效果明显优于OPC.与OPC稳定土相比,MPS稳定土具有更好的环境安全特性和较低的溶出风险.形态提取试验表明:OPC可促进Pb从弱酸提取态向可还原态转化,而MPS可促进Pb从弱酸提取态向可氧化态转化,污染土中Pb赋存形态的改变是MPS和OPC稳定土Pb变化的主要原因.矿物分析试验表明:OPC对Pb的稳定机制为包裹、吸附和沉淀作用,而MPS稳定对Pb的稳定机制为生成难溶的氟磷氯铅矿沉淀.铅污染土中矿物成分的变化是Pb赋存形态和浸出特性变化的根本原因.

Modified phosphorus slag(MPS)and portland cement(OPC)were used to stabilize lead-contaminated soils.Leaching test,sequential extractions test and XRD test were conducted to investigate the variation of stabilize properties of MPS treated lead-contaminated soils along with MPS and OPC dosage.Results showed that the OPC and MPS could reduced Pb leaching concentration of stabilized soil,while the environmental security characteristics of MPS stabilize soil is better than OPC stabilize soil.Sequential extraction procedures revealed that the majority of acid soluble fraction of Pb were converted to reducible fraction with OPC stabilized.While the majority of acid soluble fraction of Pb was converted to oxidizable fraction with MPS stabilized.XRD test revealed that the stabilized mechanism of Pb in OPC stabilized soil was encapsulated,adsorption and precipitation.While the estabilized mechanism of Pb in MPS stabilized soil was Pb5[PO4]3 Cl precipitation.The difference of lead concentration of OPC and MPS stabilized soil was attributed to the difference of species distribution and stabilized mechanism of Pb.