Predicting the adsorption of organic pollutants from water onto activated carbons based on the pore size distribution and molecular connectivity index

A new model approach is developed to predict the adsorption isotherms of low-molecular-weight nonpolar organic compounds (LMWNPOCs) onto activated carbons (ACs). The model is based on the Polanyi-Dubinin (PD) equation, with the limiting pore volume of adsorbent estimated from the pore size distribution (PSD) data, and the adsorption affinity of adsorbate described by the molecular connectivity index (MCI). To obtain the MCI parameters, the model was first tested for the adsorption of 34 LMWNPOCs primarily on F400 AC from 3 reports. The models fit the experimental data well, with only 39.2% of errors. The approach was further employed to predict the adsorption capacity of 40 LMWNPOCs on F400 AC, 12 LMWNPOCs onto 9 other ACs, and 8 LMWNPOCs onto 5 ACs with unknown PSD, with the errors of 41.9%, showing the model being reasonable. The model approach may provide a simple means for predicting adsorption capacities of LMWNPOCs onto different ACs.