In the present study, optimization of phenol adsorption onto garlic peel (GP) was conducted with process parameters such as initial pH, adsorbent dosage, agitation speed, and contact time. The percentage removal of phenol was optimized based on these process parameters. Response surface methodology was used for optimization as it has many advantages over classical optimization methods. A Box-Behnken experimental design was employed. The optimum conditions for maximum removal of phenol from an aqueous solution of 50 mg L −1 were found as follows: pH: 2, adsorbent dosage: 2.1 g L −1 , contact time: 7 h, and agitation speed: 135 rpm. At these optimized conditions, batch adsorption experiments were conducted to study the effects of initial concentration and temperature on phenol removal. Thermodynamic parameters such as DG ; DH and DS were also evaluated. From the results, the sorption process was found to be spontaneous and exothermic. The equilibrium experimental data were analyzed with several isotherm models. The adsorption kinetics for phenol removal by GP follows the pseudo-second-order kinetic model. The results from the study demonstrated that more than 80% phenol removal is possible at the above-mentioned optimum conditions.

In the quest for eco-friendly and cost-effective adsorbents for the removal of phenol from aqueous systems, garlic peel has been identified as a potential candidate in our earlier study. In the current investigations, we have studied the performance of garlic peel powder in packed fixed-bed column, to assess its potential for real-time deployment for remediation of phenolcontaminated aqueous effluents. Accordingly, parametric studies were carried out with reference to feed concentration, bed height, and flow rate. The experiments indicated the suitability of garlic peel powder-packed columns for remediation of phenol present in aqueous effluents. Salient observations include the improvement of adsorption and remediation efficiency at lower feed flow rates. The assessment of the experimental data using different theoretical models indicated the applicability of Yoon-Nelson model for the adsorption of phenol by garlic peel powder.