Bismuth extracted using an environment-friendly aqueous two-phase system from secondary sources applied in the development of an alternative bismuth film electrode for the simultaneous determination of cadmium and lead in water and food samples

The reuse of materials for the development of high-performance electrochemical sensors is explored in this work. Specifically, bismuth (Bi) films were electrodeposited using Bi extracted by using an aqueous two-phase system (ATPS) from discarded fusible plugs (BiSn alloy), which are used as safety valves in gas cylinders. The ATPS is an environmentally friendly strategy for liquid-liquid extraction, and its suitability for obtaining purified Bi for use in electrochemistry is demonstrated. As a proof-of-concept, the bismuth film electrodes obtained from extracted Bi (Bi_ATPS-FE) were applied for the simultaneous voltammetric determination of heavy metal species (Cd²⁺ and Pb²⁺). By applying square-wave anodic stripping voltammetry (SWASV), Bi_ATPS-FE displayed a similar voltammetric response toward both the analytes compared to bismuth film electrodes prepared from standard Bi precursors (Bi-STD). Under optimized conditions, the Bi_ATPS-FE sensor exhibited linear ranges of 0.50 to 7.0 μmol L^-1 and 0.40 to 5.0 μmol L^-1 for Cd²⁺ and Pb²⁺, respectively, with limits of detection of 0.044 μmol L^-1 (Cd²⁺) and 0.019 μmol L^-1 (Pb²⁺). The developed voltammetric method, adopting Bi_ATPS-FE, was successfully applied to lake water and tea drink samples for the simultaneous determination of Cd²⁺ and Pb²⁺, with recovery percentages ranging from 93% to 100%. Furthermore, the proposed sensor (Bi_ATPS-FE) showed good repeatability and reproducibility. The exciting analytical performance verified for the Bi-film electrodes emphasizes the feasibility of combining environmentally friendly materials recovery and electrochemical strategies to propose value-added electrochemical sensors.