Aqueous phase adsorption of cephalexin by walnut shell-based activated carbon: A fixed-bed column study

Abstract

The walnut shell was used as a low cost adsorbent to produce activated carbon (AC) for the removal of cephalexin (CFX) from aqueous solution. A fixed-bed column adsorption was carried out using the walnut shell AC. The effect of various parameters like bed height (1.5, 2 and 2.5cm), flow rate (4.5, 6 and 7.5mL/min) and initial CFX concentration (50, 100 and 150mg/L) on the breakthrough characteristics of the adsorption system was investigated at optimum pH 6.5. The highest bed capacity of 211.78mg/g was obtained using 100mg/L inlet drug concentration, 2cm bed height and 4.5mL/min flow rate. Three kinetic models, namely Adam’s–Bohart, Thomas and Yoon–Nelson were applied for analysis of experimental data. The Thomas and Yoon–Nelson models were appropriate for walnut shell AC column design under various conditions. The experimental adsorption capacity values were fitted to the Bangham and intra-particle diffusion models in order to propose adsorption mechanisms. The effect of temperature on the degradation of CFX was also studied.