Coal Fly Ash Modified Graphite-Polyurethane Composite Electrodes for the Electrochemical Determination of Cadmium(II) in Batteries and Water

Abstract

Coal fly ash (FA), an aluminum silicate by-product and environmental pollutant which is generated during the combustion of coal in coal-fired power stations, was used as an electrode modifier for the determination of Cd(II) in aqueous solutions. In this work, graphite/polyurethane-based composites containing different amounts of FA were prepared and characterized by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX) thermogravimetry (TGA), and derivative thermogravimetry (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 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) from 2.0 x 10⁻⁷ to 1.0 x 10⁻⁶mol L⁻¹ with a detection limit (LOD) of 6.6 x 10⁻⁸mol L⁻¹. Cd(II) was added to natural water samples and determined at the 10⁻⁷mol 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.

Keywords:

• Cd(II)
• coal fly ash
• differential pulse anodic stripping voltammetry (DPASV)
• graphite/polyurethane composite electrode (GPUE)

Disclosure statement

No potential conflict of interest was reported by the author(s).

Correction Statement

This article has been corrected with minor changes. These changes do not impact the academic content of the article.

Additional information

Funding

The work was financially supported by the National Research Foundation of South Africa (NRF; Grant number 119223). Support from Brazilian agencies CAPES (CRB master fellowship), CNPq and FAPESP are also acknowledged.