One-pot synthesis of graphene hydrogel/M (M: Cu, Co, Ni) nanocomposites as cathodes for electrochemical removal of rifampicin from polluted water

Nowadays, the removal of pharmaceutical contaminants from water resources and wastewater is of great importance due to environmental and health issues. Over the decades, various methods have been reported to remove pollutants from wastewater. Among the developed methods, advanced oxidation processes (AOPs) have received significant attention from researchers. In this study, we report the one-pot synthesis of graphene hydrogel-metal (GH-M, M: Co, Ni, Cu) nanocomposites via the combination of polyol and hydrothermal methods. The structure of the resulting nanocomposites was examined by transmission electron microscopy (TEM), inductively coupled plasma-mass spectroscopy (ICP-MS), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), and Raman spectroscopy methods. Afterward, as-prepared GH-Cu, GH-Co, and GH-Ni nanocomposites were used to prepare cathodes for the electro-Fenton (EF) process to remove rifampicin (RIF) from polluted water. The effect of operational parameters, including current density (mA/cm2), initial pH, initial RIF concentration (mg/L), and process time (min) was investigated via response surface methodology (RSM). The optimal values for current density, pH, initial RIF concentration, and process time using GH-Ni as cathode were 30 mA/cm2, 5, 30 mg/L, and 90 min, respectively. The results at optimal values showed that the maximum RIF removal efficiency for GH-Cu, GH-Co, and GH-Ni cathodes was 90.47, 92.60, and 93.69%, respectively. Brunauer Emmett Teller (BET), atomic force microscopy (AFM), energy-dispersive X-ray (EDX), and cyclic voltammetry (CV) analyses were performed to investigate the performance of the cathodes for the RIF removal. Finally, total organic carbon (TOC), gas chromatography-mass spectrometry (GC-MS), and atomic absorption spectroscopy (AAS) analyses were performed for further investigation of the RIF removal from polluted water. The results claimed that one-pot synthesized GH-M cathodes can effectively remove RIF from polluted water through EF process.