Alteration of Tecoma chip wood waste into microwave-irradiated activated carbon for amoxicillin removal: Optimization and batch studies

Abstract

Amoxicillin (AMOX) in wastewater can promote antibiotic resistance in bacteria and affecting aquatic ecosystems, due to inadequate removal by conventional wastewater treatment plants. This study aimed to (i) optimizing Tecoma chip wood based activated carbon (TCAC) to adsorb amoxicillin (AMOX) using response surface methodology (RSM) and (ii) evaluating AMOX adsorption through batch and continuous modes. The RSM revealed the optimum conditions to be 657 W, 20 min and 0.99 g/g for radiation power, radiation time and impregnation ratio (IR), respectively. These optimum conditions resulted in AMOX removal efficiency of 88.07 mg/g and 27.68 % of TCAC’s yield. The BET surface area and total pore volume of TCAC were 924.85 m2/g and 0.3485 cm3/g respectively. The surface of TCAC was occupied with several functional groups namely primary amine, hydroxy, alkyl carbonate and terminal alkyne. These functional groups enhanced the adsorption process by forming hydrogen bond with AMOX molecules. The isotherm study revealed that AMOX-TCAC adsorption system obeyed the Langmuir model and the maximum monolayer adsorption capacity, Qm is 357.14 mg/g. Pseudo-second order (PSO) model fitted the best for the adsorption of AMOX by TCAC in the kinetic studies. Boyd plot divulged that the rate limiting step in the adsorption process was the film diffusion. Thermodynamic study confirmed the adsorption process to be endothermic, spontaneous and controlled by physisorption. In bed column studies, the percentage removal of adsorbates was found to increase when the adsorbates flowrate decreased, adsorbates initial concentration decreased, and bed height increased. For the breakthrough curve model, the adsorption is best fitted to Yoon Nelson model. TCAC demonstrated its efficacy in the removal of AMOX, proving successful in both batch mode and continuous mode operations. These findings suggest the potential for scaling up TCAC production for industrial purposes, indicating its suitability for larger-scale applications.