Optimal isotherm parameters for phenol adsorption from aqueous solutions onto coconut shell based activated carbon: Error analysis of linear and non-linear methods

Abstract

Abstract Removal of phenolic pollutants from wastewaters has become mandatory due to stringent environmental regulations and adverse effects on aquatic marine environment. Adsorption process which is most effective process to remove pollutants, hinders its applications in diverse field due to high cost of adsorbents. In this study, a low cost and easily available agricultural waste of coconut shells based activated carbon were utilized as adsorbent to study its viability and efficiency for phenol removal from wastewater. The efficacy of the phenol removal by adsorption process in a batch reactor is evaluated with respect to contact time for effective adsorption and influence of initial phenol concentration on percentage phenol removal. The experimental adsorption data were examined with conventional isotherms models to describe the equilibrium characteristics of adsorption of phenol. The vigorousity and non-linearity inherent in the isotherm models were validated using various traditional linear and non-linear estimation methods namely gradient method, non-linear least square method and hybrid evolutionary optimization. A novel inverse modeling technique based on differential evolution (DE) optimization which is first of this kind for adsorption applications was implemented to estimate the isotherm parameters in their non-linear form. The model predictions from the DE based optimized parameters provided better predictions and closer to experimental values. The percentage removal of phenol from four different adsorbent dosages with constant initial feed concentrations of phenol found to be varying from 63% to 96% as increase in carbon loading at constant liquid flow rate. These experimental results also revealed that coconut shell based activated carbon is a viable cheaper adsorbent for phenols removal from effluent wastewater.