Adsorption of phenols and endrin from a hazardous waste landfill leachate

Abstract

The removal of phenols and endrin from a hazardous waste landfill leachate with a mixed background of unknown organics and inorganics by adsorption onto activated carbon was investigated. Leachate was passed through a fixed bed of granular activated carbon to study not only adsorption but also the correlation of phenol removal with surrogate chemical indicators. So that observed removal of pollutants would be due solely to adsorption, biodegradation was minimized by acidifying the leachate to a pH of 3 and operating the adsorption tests at a temperature of 4°C. Freundlich isotherms were developed for chemical oxygen demand (COD) in raw leachate and for phenols in raw leachate. The effects of competitive adsorption were evaluated. At low doses with activated carbon, it appeared that adsorption of phenols was inferior to adsorption of possibly higher molecular weight components in the leachate during bottle point development of isotherms. Higher doses with activated carbon allowed phenols to compete well with remaining solutes after higher molecular weight components had occupied their adsorption sites. Breakthrough curves were developed based on effluent concentrations of COD and phenols, and ultraviolet absorbance (at 254 nm) of samples diluted 1:100. Breakthrough data indicated phenols were able to outcompete background COD for adsorption sites within the column. Phenols were not detected in the column effluent until more than 100 bed volumes of leachate had passed through the column. Predicted values for breakthrough curves were calculated using a computer model written in BASIC computer language and based on chromatography theory. Influent was spiked with endrin and the effluent analyzed for breakthrough endrin. High percentage removal of endrin was observed throughout the column run.