Chloramphenicol Removal from Aqueous Solution Using Sodium Bicarbonate-Impregnated Coconut Husk-Derived Activated Carbon: Optimization and Insight Mechanism Study

The increasing presence of chloramphenicol (CAP) in aquatic environments each year has led to serious concerns regarding potential adverse effects on human health, the environment, and aquatic organisms. If CAP residues are not sufficiently removed during wastewater treatment, they can migrate into the aquatic environment and eventually end up in the food chain. Therefore, the removal of CAP from river bodies is of great importance. In this research study, a novel sodium bicarbonate (NaHCO3)-impregnated coconut husk-activated carbon (CHAC) was developed through an impregnation method for CAP removal. The introduction of NaHCO3 on the CHAC surfaces results in the formation of OH- and H2O functional groups. The presence of a hydroxyl group appears mainly due to the water molecules found in the middle layer of the adsorbent and might be due to the water molecules that are physically adsorbed. This suggests that OH- groups found on the outer layer of the NaHCO3-impregnated CHAC are the main contributors to the removal of CAP through chemical interaction and electrostatic attraction. Based on the response surface methodology approach, the best preparation conditions for activation temperature, activation time, and IR were identified to be 500 celcius, 1 h, and 0.5, respectively. The optimized CHAC was found to be homogeneous and had a mesoporous type of pores with a BET surface area of 438.2 m(2)/g. In the batch adsorption study, the uptake of CAP onto CHAC increased as both the initial concentration of CAP and contact time increased. In terms of the effect of solution pH, CAP removal was highest at pH 2 and lowest at pH 13. The Langmuir isotherm and pseudo-first-order (PFO) kinetic were the best-fitted models for CAP adsorption. Besides, the adsorption process was mainly governed by the film diffusion mechanism. Based on the thermodynamic study, CAP adsorption onto CHAC was found to be exothermic in nature and spontaneous.