Activated carbon adsorbent derived from waste biomass, ?Croton caudatus? for efficient removal of 2-chlorophenol from aqueous solution: Kinetics, isotherm, thermodynamics and DFT simulation

The present study aims to prepare an activated carbon (AC) adsorbent developed from Croton caudatus biomass material for the adsorption of 2-chlorophenol (2CP) from wastewater. Activated carbon was prepared by KOH activation at 2:1 impregnation ratio and 700 degrees C temperature using a muffle furnace under self-generated atmosphere for 2 h. Several techniques and methodologies such as proximate analysis, ultimate (CHNS) analysis, BET, SEM, FT-IR, XRD and point of zero charge (pHpzc) have been used to determine physicochemical properties of the activated carbon. Batch adsorption studies were conducted for 2-chlorophenol adsorption and the optimum adsorbent dose, initial concentration, pH, reaction time and temperature were found to be 0.15 g/L, 80 mg/L, 4, 60 min and 298 K, respectively. The equilibrium isotherm study for 2-chlorophenol adsorption was fitted well to the Langmuir model with the adsorption capacity of 53.619 mg/ g, while the adsorption kinetics was best described by pseudo-second order model. Thermodynamic parameters demonstrated a negative Delta H (exothermic) and negative Delta G (spontaneous) values. Studies on regeneration have shown that saturated carbon can be recycled up to five times with considerable removal efficiency. Besides, density functional theory (DFT) simulation revealed that the adsorption of 2-chlorophenol onto AC adsorbent is favorable. Among the oxygen-containing functional groups, the carboxyl group appeared to have a greater influence on the adsorption process than the hydroxyl and carbonyl groups with the highest negative Eadsorption of - 42.16 kJ/mol. Furthermore, the inclusion of three oxygen-containing functional groups improves the adsorption capacity of AC towards 2CP relative to a single functional group. (c) 2023 Institution of Chemical Engineers. Published by Elsevier Ltd. All rights reserved.