Studies on the effect of solid waste leachate on the cation exchange capacity of bentonite



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The purpose of this research was to determine the effectiveness of using a Wyoming bentonite clay as a solid waste landfill liner to prevent seepage of leachate into groundwater supplies. A search of the literature was made to determine representative cation concentrations and pH's of a solid waste landfill leachate for use in laboratory investigation. Laboratory studies were conducted on the permeability and cation-exchange capacity of bentonite subjected to different concentrations and pH's of calcium chloride solutions. Each calcium chloride solution used represented a solid waste leachate occurring in a landfill at a particular time. The solutions were used as pore fluids for permeability measurements and also were mixed directly with bentonite to determine the effect on cation-exchange properties and Atterberg Limits. Results indicated a slight increase in permeability with increasing calcium ion concentration, and an increase in cation-exchange capacity with increasing pH. The plastic and liquid limits were found to increase with decreasing calcium ion concentration and increasing pH. The increase in permeability is small enough not to impair the effectiveness of a clay bentonite liner for use as a landfill liner.