改性黄土材料对Pb(Ⅱ)的吸附阻滞特性实验和内在机理探究

EXPERIMENTAL STUDY ON Pb(Ⅱ)ADSORPTION RETARDATION AND INTERNAL MECHANISM OF MODIFIED LOESS

垃圾填埋场垫层是防止渗滤液向下方土体运移进而污染地下水的重要屏障。为了研究改性黄土材料对重金属Pb^(2+)的吸附阻滞特性,以天然黄土为主要材料,生物炭、膨润土、纳米零价铁为添加剂,Pb(NO_(3))_(2)作为污染溶液,通过7 d的渗透试验研究改性黄土对Pb^(2+)的吸附阻滞效果。并结合FTIR试验探究改性黄土材料吸附Pb^(2+)前后表面基团变化。结果表明:从试件渗出液Ca^(2+)离子浓度可知天然黄土吸附Pb^(2+)主要是方解石矿物的界面沉淀作用;膨润土改性黄土试件对Pb^(2+)的去除效率略有提高;FTIR试验检测到生物炭、纳米零价铁改性黄土中丰富的含氧官能团,证实了官能团通过络合作用吸附大量Pb^(2+)。生物炭、纳米零价铁改性黄土增强了对Pb^(2+)的吸附性,其在渗透试验后期对Pb^(2+)的去除效率达到80%以上,很大程度上延长了改性黄土对Pb^(2+)的阻滞时长。所得为改性黄土垫层的长期重金属吸附阻滞性能提供重要参考。

Landfill lining is an important barrier to prevent leachate from moving to the soil and contaminate groundwater.In order to study the adsorption and blocking characteristics of improved loess on heavy metal Pb^(2+),this study took natural loess as the main material,Biochar,Bentonite,Nanoscale zero-valent iron(nZVI)were used as additives.Pb(NO_(3))_(2)was used as the contamination solution to study the adsorption blocking effect of modified loess on Pb^(2+)through a seven-day seepage test.Combined with FTIR test,the changes of surface groups before and after Pb^(2+)adsorption on modified loess were investigated.The results show that the adsorption of Pb^(2+)by natural loess is mainly due to the interfacial precipitation of calcite minerals,according to the concentration of Ca^(2+)in the exudate of samples.The removal efficiency of Pb^(2+)by bentonite improved loess sample was slightly increased.FTIR test detected abundant oxygen-containing functional groups in biochar and nZVI modified loess,which confirmed that functional groups adsorbed a large amount of Pb^(2+)through complexation.The improved loess with biochar and nZVI enhanced the adsorbability of Pb^(2+),and the removal efficiency of Pb^(2+)reached more than 80%in the late stage of the permeability test,which greatly prolonged the block time of Pb^(2+)in the improved loess.The findings of this study provide an important reference for improving the long-term heavy metal adsorption retardation of loess linings.