Development of coal fly ash modified graphite-polyurethane composite electrodes for the determination of Cd(II) in batteries and water

Abstract

Coal fly ash (FA), an aluminium silicate by-product and environmental pollutant which is generated during the combustion of coal in coal-fired power stations, was used for the first time as an electrode modifier for the determination of metallic cations. Thus, graphite/polyurethane-based composites containing different amounts of FA were prepared and characterized by SEM, EDX and TGA/DTG. The graphite/polyurethane composite electrodes (GPUE), with and without FA modifier, were evaluated with regard to their performance as voltammetric electrodes in the determination of metallic cations, using Cd(II) as a probe. After optimizing solution and instrumental parameters affecting the voltammetric peak current, a differential pulse anode stripping voltammetry (DPASV) procedure was developed for GPUE modified with 5% FA (m/m), resulting in a linear response for Cd(II) in the range 2.0 x 10‑7 to 1.0 x 10‑6 mol L-1 with a detection limit (LOD) of 6.6 x 10-8 mol L-1. Cd(II) was added to natural water samples and determined in concentrations at 10-7 mol L-1 level, with a mean recovery of 99%. It was also extracted from exhausted rechargeable Ni-Cd batteries and diluted to ca. 0.2 µmol L-1 and determined with the same electrode, with recoveries of 98.7% when compared to FAAS. These results serve as a proof of concept that FA is a useful electrode modifier for determination of cationic species.