Method And Application Of Polymer Modified Bentonite Based On Membrane Performance

Bentonite has been considered as the most ideal material for hydraulic barrier with impermeability and cheapness.Geosynthetic clay liner(GCL)made from bentonite has been widely used in bottom liners and cover systems at refuse landfill and mining facilities around the world.However,further studies have shown that the permeability of sodium bentonite is increased in magnitude with aggressive leachates having acid and cations due to the reaction of cation exchange.Yet,the landfill leachate is composed of complex components(more than 100 kinds of pollutants),and the concentration of pollutants is often high,and changes with landfill time,biodegradability is low.Under the action of high concentration of leachate,the impervious performance and long-term pollution resistance of natural sodium bentonite can not meet the needs of engineering,and the general sodium modiified bentonite is more difficult to achieve the standard of Engineering practice.Therefore,it is of great practical significance to explore new soil modification methods and increase the impervious capacity of the liner.This paper point at the situation of general bentonite can not meet the long-term anti-seepage application in strong acid and high salt contaminated liquid,the calcium bentonite,widely used in the commercial geosynthetic clay liner(GCL)were used in the experiments.The Organic bentonite was modified by sodium acrylate wet polymerization process.Experimental studied the effect on swelling index of modified bentonite for the raw materials that sodium carbonate(Na2CO3),acrylic acid(CH2=CHCOOH),potassium persulfate(K2S2O8)and N-N'methylenebisacrylamide.The synthesis process was optimized with reaction temperature,solid-liquid ratio.According to the micro analysis technology of FTIR,SEM,STEM,found the microstructure change of composition and structure of the modified bentonite,analyzed the implementation mechanism of sodium polyacrylate modified bentonite.The permeability behavior in acidic environment and heavy metal salt solution(Pb(NO3)2)and adsorption for organic pollutants phenol of the modified bentonite were tested,the main results are as follows:1.Recommend the use of sodium polyacrylate as the modifier obtain a chemical resistance bentonite ratio is:bentonite 625%wt;sodium carbonate 64.6%wt(fully reaction with acrylic acid);N-N' methylenebisacrylamide 2.5%wt;potassium persulfate 1.25%wt;solid-liquid ratio 1:2;reaction temperature is 75 ?;%wt is the percentage of the raw material relative to acrylic acid.2.The addition of sodium polyacrylate with hydrophilic organic groups is a main reason for modified bentonite with high water absorption,high expansion and the structure changed from the original layered stack to three-dimensional cavity structure.3.Both in acidic environment and heavy metal salt(Pb(NO3)2)solution,the modified bentonite has higher swelling index and lower permeability coefficient than the raw bentonite,and much stronger in the chemical resistance stability.4.Sodium polyacrylate modified bentonite enhanced mechanism of chemical resistance:sodium polyacrylate and Nanometer Bentonite Composite makes the bentonite particles are wrapped with a layer of negatively charged sodium polyacrylate three-dimensional network,the network has to resist the invasion of metal cations,but the resistance of the cation concentration a certain limit,when the concentration exceeds the limit of low permeability of bentonite will gradually fail.5.Super hydrophilic water absorbent resin is better than bentonite in hydrophilism,and can not form the same as alkyl organic phase extraction space when the adsorption of hydrophobic organic pollutants.Therefore,the adsorption capacity of organic is limited,it is not suitable to be used as an organic modifier to improve the organic adsorption capacity of bentonite.The above synthetic organic modified bentonite method and mechanism have important value for guiding the production of chemical resistant bentonite impermeable material and solving the pollution liquid seepage problem in special environment.