Sustainable Removal of Diclofenac from Aqueous Effluents Using PET Waste-Derived Activated Carbon: Experimental and Simulation-Based Process Optimization

Activated carbon was obtained from polyethylene terephthalate (PET). Three activating agents were tested (KOH, ZnCl₂, and H₃PO₄) while evaluating effluents containing sodium diclofenac, and an investigation into the optimal conditions for effluent treatment was conducted. H₃PO₄ showed a higher adsorption capacity (34.06 mg·g^-1) to sodium diclofenac when used in a 2:1 ratio (mass of H₃PO₄: mass of carbon). MEV analyses show that the materials exhibit mesopores and macropores on the surface of the activated carbon obtained (15.3-120 nm). BET analyses revealed that H₃PO₄ activation produced the largest surface area (542.97 m²·g^-1), corroborating the morphological observations and explaining the superior performance in sodium diclofenac adsorption. Four kinetic and two isotherm adsorption models were also tested to fit the experimental data. The kinetic and isotherm adsorption tests indicated that this capacity can be maximized when the process is carried out at 25 °C for 25 min (estimated adsorption capacity of 200 mg·g^-1). The kinetic and isotherm adsorption models enabled simulations to replicate the batch process and to prospect the industrial application of an adsorption column.