Efficient adsorption of the antidiabetic drug metformin from an aqueous medium using a graphene oxide membrane

The presence of micropollutants, such as pharmaceuticals, in aquatic environments is a major concern due to the risks they pose to living organisms. Given the often inadequate management of wastewater, it is crucial to develop reliable and effective methods to eliminate these contaminants, thus ensuring our safety and protecting the ecosystem. This study aims to test the ability of a polyvinyl chloride/graphene oxide (PVC/GO) composite membrane to adsorb metformin (Met) in an aqueous solution. The graphene oxide was synthesized using the Hummers method from recycled graphite obtained from drilling molds, thereby adding an ecological dimension to this research. This graphene oxide was then used to prepare PVC/GO. The resulting materials were characterized using Fourier-transform infrared spectroscopy, thermogravimetric analysis and Brunauer–Emmett–Teller analysis. The following adsorption parameters were investigated: pH (2–8), temperature (25–40 °C), time (5–30 min), GO content in PVC/GO (0–15%) and initial concentration (4, 6, 8, and 10 mg/L). Adsorption experiments revealed that 75% removal of Met was achieved within 15 min at an optimum concentration of 4 mg/L. Maximum adsorption efficiency of Met was obtained at 40 °C in an acidic medium (pH 2); however, adsorption decreased as the pH increased. Thermodynamic studies indicated that Met adsorption was spontaneous (∆ G ° < 0) and exothermic (∆ H ° < 0) at 25, 30, and 35 °C. However, the process was endothermic and non-spontaneous at 40 °C. Based on the obtained results, PVC/GO 5% was found to be an efficient and promising adsorbent for Met.