Experimental Study On Improvement Of Bentonite Liner Based On Cr(Ⅵ) Adsorption And Its Hydraulic Conductivity

Landfill leachate contains a variety of anions,cations and heavy metals pollutants,in which hexavalent chromium Cr(Ⅵ)with high toxicity exists in the form of anionic compounds and has very strong mobility,which will pass through the composite liner with the process of water seepage and pollute groundwater and soil.Na-bentonite is often used in engineering as a basic impermeable lining material by virtue of its extremely low hydraulic conductivity and self-healing ability.If the targeted barrier ability of hexavalent chromium Cr(Ⅵ)of bentonite lining can be improved and enhanced while maintaining the low hydraulic conductivity,it is of great significance to enhance the barrier prevention technology of heavy metal pollution such as Cr(Ⅵ).On The basis of reading and analyzing the current situation of heavy metal pollution control,this paper chooses adsorption materials such as ion exchange resin and activated carbon as additives to improve bentonite,and uses batch adsorption test and flexible wall permeability test as research methods.The research and development technology of adsorptive impermeable liner was explored from the adsorption characteristics of Cr(Ⅵ)and the evolution mechanism of hydraulic permeability characteristics of bentonite modified liner,which provided research reference and scientific and technological support for future heavy metal pollution barrier prevention technology.The main contents of this paper are as follows:(1)The chemical composition data of landfill leachate and industrial wastewater from different regions in China were summarized and summarized,and the chemical composition characteristics of landfill leachate in China were quantified by indicators such as ion type,concentration range,p H,ionic strength(I)and ion relative abundance(RMD),and the typical preparation scheme of landfill composite leachate was proposed.(2)Batch adsorption experiments of Cr(Ⅵ)in aqueous solution and composite leachate were carried out with Na-bentonite,modified bentonite mixed with ion exchange resin and activated carbon as adsorbates.The adsorption characteristics and removal ability of Cr(Ⅵ)on Na-bentonite and modified bentonite were analyzed,and the adsorption law of Cr(Ⅵ)on modified bentonite with different additives and mixing ratio was obtained.(3)The hydraulic permeability of modified adsorptive bentonite was studied when tap water and composite leachate were used as infiltration media,and the quantitative variation of hydraulic conductivity of modified adsorptive bentonite with infiltration time,confining pressure and mixing ratio was analyzed.Based on the two indexes of adsorption ability and anti-seepage ability of modified bentonite to Cr(Ⅵ),a preliminary technical scheme of modified bentonite liner with targeted barrier of Cr(Ⅵ)was proposed.