Optimization of Process Parameters for Adsorption of Phenol from Aqueous Solution Using Unripe Plantain Peels Activated Carbon

Abstract

The study investigated the optimum conditions for the adsorption of phenol from aqueous solution using plantain peels activated carbon. Low-cost adsorbents were produced from unripe plantain peel by both physical and chemical activation processes at carbonization temperature of 400oC for 2 hrs. The chemical activated unwashed carbon (UPPAC) was activated with ZnCl2 at impregnation ratio of 1:2 while the physical activated carbon (NAPPC) was not impregnated with any chemical. The produced carbons were characterized in terms of surface area, porosity, iodine number, ash content, carbon yield and pH. The result showed that the physicochemical properties of UPPAC were significantly higher than those of NAPPC having surface area of 957 m2/g, porosity of 32.2%, iodine number of 736 mg/g, ash content of 9.02% and carbon yield of 65%. The optimum conditions for the adsorption of phenol from the aqueous solution using UPPAC was based on three variables, contact time, adsorbate concentration and adsorbate pH. A total of 27 experimental runs were used to study the effects of these parameters using the response surface methodology (RSM) as the experimental design. The result of the batch adsorption was found to increase with initial adsorbate concentration and contact time but decreases with increase adsorbate pH. UPPAC achieved optimum percentage removal of 91% at initial phenol concentration of 21 mg/g and its removal was pH dependent (pH 2), better at acidic conditions. The amount adsorbed also increased with contact time until equilibrium was reached at 150 mins. Thus, chemically activated unripe plantain peel can be used for the removal of phenol from aqueous solution.