From e-waste to eco-sensors: synthesis of reduced graphene oxide/ZnO from discarded batteries for a rapid electrochemical bisphenol A sensor

Improper disposal of used dry cell batteries and the leaching of bisphenol A (BPA), a prevalent endocrine disruptor present in food packaging, into surface water pose a significant threat to both the environment and drinking water, threatening the sustainability of the ecosystem. Thus, it is imperative to manage detrimental e-waste and regularly monitor BPA using a sensitive and reliable technique. This study proposes a cost-effective reduced graphene oxide/zinc oxide (rGO/ZnO) nanohybrid, entirely synthesized from electronic waste, for electrochemically detecting BPA in an aqueous medium. Graphite and metallic Zn precursors obtained from discarded batteries were employed to synthesize rGO/ZnO. The successful characterization of the prepared rGO and rGO/ZnO nanohybrid was conducted through different state-of-the-art techniques. An rGO/ZnO-modified glassy carbon electrode (GCE) exhibited superior conductivity and a larger surface area. Voltammetric study at the rGO/ZnO-modified GCE successfully detected BPA in an aqueous medium, demonstrating a one-electron and proton pathway for BPA oxidation. The sensor demonstrated a linear response within the concentration range of 1–30 μM, with a limit of detection of 0.98 nM and sensitivity of 0.055 μA μM⁻¹. The developed electrode could also detect BPA in real water samples with reasonable recovery. These findings imply that the developed sensor has the potential to be a sensitive, practical, and economical monitoring system for BPA in water.