Sorption of pentachlorophenol on peat-bentonite mixtures

Batch kinetic and isotherm studies were carried out to determine the adsorp tive characteristics of peat and bentonite mixtures for pentachlorophenol, and to examine the hydraulic conductivity of peat - bentonite mixtures to d etermine if they are applicable for use as cutoff barriers. Batch kinetic s tudies showed that over 90% of PCP was removed from water spiked with appro ximately 1 mg/l of PCP using a peat-bentonite (5%) mixture. The equilibrium time was 8 hours. The optimum pH range for adsorption of PCP by the peat-b entonite mixture was found to be 3-3.5. Batch isotherm studies showed that the adsorption of PCP by the peat-bentonite mixture from aqueous solution w as best described by the Freundlich isotherm equation. Batch adsorption stu dies using various ratios of bentonite in the mixture showed that the adsor ption of PCP decreased linearly with increased amount of bentonite in the m ixture, indicating that adsorption of PCP by the peat moss portion of the m ixture was the dominant process. The inverse of the hydraulic conductivity was found to increase exponentially with an increase in the bentonite conte nt of the mixture over the range studied. The minimum hydraulic conductivit y observed was 3.3 x 10(-7) cm/s for a 50% peat - 50% bentonite mixture. Pe at-bentonite mixtures can be used to successfully remove PCP from aqueous m edia and can be used effectively as a barrier to attenuate the migration of PCP through soil and groundwater systems.