Carbamazepine removal from aqueous solution by synthesized reduced graphene oxide-nano zero valent iron (Fe⁰-rGO) composite: theory, process optimization, and coexisting drugs effects

Synthesized Fe⁰-rGO nanocomposite with ratio of 1/1 (w/w) was prepared and has been used as adsorbent for the removal of Carbamazepine (CBZ) from aqueous solution. The adsorbent was characterized by various techniques such as Fourier-transform infrared spectroscopy (FTIR), energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), and Field Emission Scanning Electron Microscopy (FE-SEM) analyses. Linear experiments were performed to compare the best fitting isotherms and kinetics. The Freundlich isotherm (R²>0.90) and pseudo second order kinetic (R²>0.99) fitted well the experimental data. On the basis of the Langmuir isotherm, the maximum adsorption capacity of Fe⁰-rGO for CBZ was up to 50 mg g^-1 at 30 °C. The pH, adsorbent dose, and initial concentration of CBZ were observed to be the leading parameters that affected the removal of CBZ considering the analysis of variance (ANOVA; p<0.05). The optimum process value of variables obtained by numerical optimization corresponds to pH 3.07, an adsorbent dose of 36.2 mg, an initial CBZ concentration of 5 mg L^-1 and at 30.15 °C. The results of optimum conditions reveal that a maximum of 94% removal efficiency can be achieved; whereas, this phenomenon was independent of temperature (p-value>0.05). Moreover, Fe⁰-rGO can be used to remove diclofenac (DIC) and cetirizine (CTZ) simultaneously. To sum up, the Fe⁰-rGO is a promising adsorbent not only for the efficient removal of CBZ but also for the reduction of coexisting drugs in aqueous solution.