Study On Chemical Compatibility Of Soil-polymer Amended Bentonite Vertical Barriers Exposed Subjected To Phenol Solutions

In recent years,China’s industrial structure adjustment and urban development transformation have led to ecological environment problems such as organic matter and heavy metal pollution existing in industrial enterprises’ relocation sites,which seriously restrict the safe reuse of land.In order to effectively control the transport of pollutants in underground water and soil,it is urgent to study the vertical isolation barrier technology with excellent anti-seepage and intercepting performance and develop the modified bentonite with high performance for industrial pollution,the development of remediation technology of solid waste landfill site and the construction of beautiful China.This research through the test,the molecular dynamics simulation and theoretical analysis of sodium carboxymethyl cellulose（CMC）of modified bentonite and hexadecyl trimethyl ammonium bromide（CTMAB）organic bentonite is the basic engineering characteristics of the vertical isolation barrier material,impervious performance and made a systematic study of adsorption properties,obtain the following main research results:（1）In this study,five kinds of commercial CMC with different molecular weight and degree of substitution were used to prepare modified bentonite.The influence of CMC molecular weight and degree of substitution on the expansion and impermeability of modified bentonite under the action of phenol pollution was studied,and an optimized preparation scheme of CMC modified bentonite was proposed.（2）The chemical compatibility of CMC modified bentonite and CMC+CTMAB modified bentonite under phenol pollution was compared.CMC+CTMAB modified bentonite has better chemical compatibility than CMC modified bentonite.Under the same concentration of phenol,the modification of CTMAB inhibited the expansion properties of CMCⅢ-CB to a certain extent,but effectively enhanced the chemical compatibility of the expansion properties.In addition,when CTMAB dosage parameter f value is 0.1 and 0.3,the anti-seepage performance of CMCⅢ modified organic bentonite has no significant change.（3）Engineering properties of CMC and CMC+CTMAB modified backfill materials were studied,including workability,compression consolidation and permeability.The influence of CMC modification and CMC+CTMAB modification on the water content of backfill materials to meet the slump requirement was clarified.The permeability coefficient of each backfill material generally decreases with the increase of consolidation stress.When the consolidation stress is greater than 100 k Pa,the permeability coefficient decreases more significantly.In the permeability test,CMC modification enhanced the anti-seepage performance of backfill material in tap water,while CTMAB modification did not affect the permeability coefficient of backfill material.Under the influence of high concentration of phenol,CMC modification can effectively reduce the permeability coefficient of backfill materials.When vertical barrier engineering is carried out for high-risk blocks,the dosage of CMC modified swelling is recommended to use 9.6%.（4）The interaction between modified bentonite and phenol was studied by molecular dynamics simulation.The interaction between the modified materials and phenol molecules was analyzed through the interaction configuration,the relative content distribution of each component perpendicular to the（001）surface of montmorillonite and the diffusion of phenol molecules were clarified,and the microscopic mechanism of the modification of CMC,CTMAB and CMC+CTMAB to improve the adsorption performance of bentonite was analyzed.（5）The modification mechanism and microstructure of CMC and CMC+CTMAB modified bentonite before and after phenol pollution were studied by microscopic test.The polymer CMC molecular chain successfully entered the bentonite montmorillonite clay lamellar,and the carboxylic acid on CMC adsorbed water molecules to form hydrogel to effectively fill the large pores between bentonite particles,thus reducing the permeability coefficient of backfilling materials.CTMAB intercalated into the montmorillonite lamellar,on the one hand,the hydration of CMCⅢ modified bentonite has little influence,on the other hand,the montmorillonite lamellar spacing increases,promote the adsorption of phenol from water phase to organic phase,thus enhancing the expansion and anti-seepage performance of bentonite chemical compatibility and adsorption performance.The combined action of CMC and CTMAB significantly improved the chemical compatibility of bentonite under the action of phenol pollution.