基于XRD与SEM研究风淬渣微粉用于重金属污染土壤的修复机理

Study on Repairing Mechanism of Wind Quenching Slag Powder in Heavy Metal Contaminated Soil by XRD and SEM

钢渣是冶金工业中产生的主要固体废弃物,其产量约为每年粗钢产量的15%~20%。由于技术的局限,导致我国钢渣利用率较低,仅为年钢渣产量的10%,同时加之管理制度的不健全,导致钢渣大量露天堆放,对土地资源、地下水源,以及空气质量形成严重影响。面对上述问题,利用钢渣开发一种价格低廉的固化药剂用于重金属污染土壤的修复,既是冶金固体废弃物可持续发展的重要途径之一,也是大幅降低重金属污染土壤修复成本的重要途径之一。该研究创新性是用风淬渣微粉作为固化药剂对含有Cd,Cu,Pb,Ni和Zn的重金属污染土壤进行修复。研究了风淬渣粉磨时间、风淬渣微粉掺量和养护时间对修复重金属污染土壤效果的影响。利用激光粒度分析仪测试风淬渣微粉的粒度分布、比表面积与孔隙度吸附仪测试风淬渣微粉的孔结构、扫描电子显微镜测试风淬渣微粉-重金属污染土壤混合物的微观形貌、X-射线衍射仪测试风淬渣微粉的矿物成分,分析风淬渣微粉修复重金属污染土壤的机理。结果表明,风淬渣的性质安全,对生态环境不存在污染,可以用于修复重金属污染土壤的固化技术。当风淬渣粉磨时间为100 min、风淬渣微粉掺量为20%、养护时间为14 d时,风淬渣微粉对重金属污染土壤中Cu,Cd,Ni,Zn和Pb的固化效果均达到91%以上。随着风淬渣粉磨时间的延长,风淬渣微粉的粒径尺寸减小、粒度分布趋向均匀。风淬渣的多孔结构破坏、比表面积提高,有利于提高风淬渣微粉对重金属污染土壤的修复效果。随着风淬渣微粉掺量的增加,风淬渣微粉形成的水化凝胶(C—S—H)数量增加,有利于提高风淬渣微粉包裹重金属污染土壤的效果,以达到固化重金属污染土壤中Cd,Cu,Pb,Ni和Zn的目的。风淬渣微粉对固化重金属污染土壤中Cu,Cd,Ni,Zn和Pb具有选择性,在不同养护时间下,重金属分别以Cd2SiO4,Cu(OH)2·2H2O,PbCO3,3Ni(OH)2·2H2O,Ni2SiO4,Zn(OH)2和Zn2SiO4形式存在。

Steel slag tailings are the main solid waste in metallurgical industry,with the production of 15%~20% of crude steel.The utilization ratio is quite low and only reaches 10%of steel slag tailings production due to limited technology.Meanwhile,steel slag tailings are disposed of in direct stacking and landfill in general since the management system is not perfect,which pollutes land source,underground water source and air quality.In the face of the above problems,the development of an inexpensive curing agent is used for repairing of heavy metal contaminated soil has become not only one of the main methods to the sustainable development of metallurgical solid waste,but also one of the main methods to achieve the greatly reduce the production cost of heavy metal contaminated soil remediation.Wind quenching slag powder was used as curing agent to repair the heavy metal contaminated soil including Cd,Cu,Pb,Ni and Zn in this paper.This study investigates the wind quenching slag grinding time,wind quenching slag powder content and curing time on the repairing effect of heavy metal contaminated soil.The particle size distribution of wind quenching slag powder was characterized by LPSA,the pore structure of wind quenching slag powder was characterized by BET,the microstructure of mixture of wind quenching slag powder-heavy metal contaminated soil was characterized by SEM,mineral composition of wind quenching slag powder was characterized by XRD in order to the mechanism of wind quenching slag powder repairing heavy metal contaminated soil was analyzed.The results indicate that the properties of wind quenching slag are safe and there is no pollution to the ecological environment,which can be used as a curing technology for remediation of heavy metal contaminated soil.The solidification effect of wind quenching slag powder(the wind quenching slag grinding time,wind quenching slag powder content and curing time are 100 min,20% and 14 d,respectively)on Cd,Cu,Pb,Ni and Zn of heavy metal contaminated soil was more than 91%.With the extension of wind quenching slag grinding time,the particle size of wind quenching slag powder is decreased and its particle size distribution tends to be uniform.The damage of porous structure and the increase of the specific surface area of wind quenching slag are beneficial to improve the effect of wind quenching slag powder on heavy metal contaminated soil restoration.With the increase of wind quenching slag powder content,the amount of hydrated gel(C—S—H)formed by wind quenching slag powder is increased,which is beneficial to improve the effect of wind quenching slag powder covering heavy metal contaminated soil,so as to achieve the purpose of curing Cd,Cu,Pb,Ni and Zn in heavy metal contaminated soil.Wind quenching slag powder can selectively be curing Cu,Cd,Ni,Zn and Pb in heavy metal contaminated soil.Under different curing times,heavy metals exist in the form of Cd2SiO4,Cu(OH)2·2H2O,PbCO3,3Ni(OH)2·2H2O,Ni2SiO4,Zn(OH)2 and Zn2SiO4,respectively.