TESTING THE ABILITY OF BENTONITE-AMENDED NATURAL ZEOLITE (CLINOPTINOLITE) TO REMOVE HEAVY-METALS FROM LIQUID WASTE

The design of environmentally sound liquid waste containment structure s has become a crucial task in engineering applications due to ever in creasing groundwater contamination from such sites. Construction of su ch structures usually requires a bottom liner of low hydraulic conduct ivity as part of the design. In order to reduce the hazards associated with liquid wastes including landfill leachate, bentonite-amended nat ural zeolite is proposed as an alternative to conventional earthen lin ers. Among many contaminants associated with liquid wastes, heavy meta ls are the most dangerous ones. This paper deals with determining the ability of natural zeolite to remove heavy metals from aqueous waste. For this purpose, crushed natural zeolite (clinoptinolite) is amended with commercial powdered bentonite to yield a soil mixture low in perm eability and high in ion-exchange capacity. Leachate from a convention al landfill is used as the percolation fluid. Concentrations of certai n heavy metals in the effluent fluid percolated through the bentonite- zeolite mixture are compared with that of initial leachate. The conclu sion is reached that certain metals are efficiently removed from the i nfluent solution by the soil matrix whereas some ions do not show sign ificant reduction in concentration. This is attributed to high hydraul ic conductivity of the bentonite-zeolite mixture.