Adsorption Isotherm and Kinetic Modeling of Chlordecone on Activated Carbon Derived from Date Stones

Abstract

International audienceEnvironment contamination by pesticides is a major issue threatening human health. Adsorption is one of the most effective processes for removing pesticides, such as the organochlorine compounds chlordecone. The objective of this study was to determine the rate of chlordecone adsorption from drinking water by date stones-based activated carbon (C.A.). This laboratory scaleexperimental study was performed during March 2016 to September 2016 in the Laboratory of Water and Environmental Sciences, Lebanese University-Faculty of Public Health. The used activated carbon was derived from date stones and activated chemically by phosphoric acid.In order to determine the adsorption efficacity of chlordecone on activated carbon derived from date stones, a mixture of 0.5g of activated carbon and 100 ml of chlordecone concentration 100 µg/l was studied under differentpH values ranging from 2 to 10 andcontact time (15, 30, 45, 60, 90, 120, 150, 180). In addition, 0.5 g of activated carbon were exposed to different initial chlordecone concentration (50, 75, 100, 250, 750) in order to determine the chlordecone concentration effect on the adsorption mechanism. The rate of residual pesticides was determined using liquid chromatography coupled to a UV/visible detector. The kinetic data were analyzed by applying pseudo-first-order and pseudo-second-order models. The applicability of Langmuir and Freundlich adsorption isotherms was evaluated to better understand the adsorption process. The results revealed that the equilibrium data were perfectly represented using Langmuir II and Freundlich isotherms. The maximum multilayer adsorption capacity was found to be at pHZPC and a contact time 90 min. The kinetic data followed closely the pseudo-second-order model. Results from this study suggest that the activated carbon produced from date stones residue is an effective, low cost and locally available adsorbent for removing chlordecone from aqueous systems. This study imposed a conclusion of great concern since activated carbon from natural resources is considered as a renewable and cheaper precursor compared to the commercially available activated carbons