Prediction of the adsorption capacities for four typical organic pollutants on activated carbons in natural waters

Abstract

A new model is developed to predict the competitive adsorption isotherms of atrazine, methyl tertiary butyl ether (MTBE), 2-methylisoborneol (2-MIB) and 2,4,6-trichlorophenol onto activated carbons (ACs) in natural water. Based on the Polanyi-Dubinin (PD) equation, with the limiting pore volume of adsorbent estimated from the pore size distribution data, and the Ideal adsorbed solution theory - equivalent background compound (IAST-EBC) model approximation, the model takes into account both the properties of ACs and the impact of natural organic matters in water. Only one set of isotherm in deionized water and one set in natural water are needed to obtain the parameters for the prediction of adsorption isotherms onto different ACs in natural water. The model was employed for the predictions of adsorption capacities for atrazine, MTBE, 2-MIB and 2,4,6-trichlorophenol onto 14 ACs in 22 synthetic and natural waters reported in 9 references, with errors between 14.9% and 44.5% SDEV only. The results suggest that in the proposed PD-IAST-EBC approach, prediction of adsorption capacity for organic compounds onto different ACs in the same natural water is feasible, if the ACs are thermally activated with known pore size information. The model may provide a simple approach for the prediction of adsorption of organic compounds in natural water, and thus greatly reduces the effort required for water utilities when change of AC is needed.