Determination of Cr(VI) in leather residues using graphite/paraffin composite electrodes modified with reduced graphene oxide nanosheets

• Published in: The Science of the total environment Vol. 834; p. 155318
• Main Authors: de Oliveira, João P.J., Hiranobe, Carlos T., Torres, Giovanni B., dos Santos, Renivaldo J., Paim, Leonardo L.
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 15.08.2022
• Subjects: Chromium; Chromium(VI); Composite electrodes; Differential pulse voltammetry; Electrochemical Techniques - methods; Electrodes; Graphite - chemistry; Limit of Detection; Paraffin; Reduced graphene oxide; Reproducibility of Results; Reduced graphene oxide; Chromium(VI); Composite electrodes; Differential pulse voltammetry
• ISSN: 0048-9697; 1879-1026
• DOI: 10.1016/j.scitotenv.2022.155318

In this study, we determined the Cr(VI) in samples of tanned leather residues by differential pulse voltammetry (DPV) using graphite/paraffin composite electrodes modified with reduced graphene oxide nanosheets (referred to as GPEs/nsRGO). After the modification, the composite electrodes were characterized by two electrochemical techniques (i.e., cyclic voltammetry, CV, and electrochemical impedance spectroscopy, EIS), scanning electron microscopy, and Raman spectroscopy. The electroanalytical method was applied using the GPEs/nsRGO. An analytical curve was obtained in a Clark-Lubs buffer solution (pH = 1), with a linear concentration range from 25.0 to 392.0 μmol L−1 and a limit of detection (LOD) of 1.01 μmol L−1. The GPEs/nsRGO showed good reproducibility in their manufacturing process and good response repeatability with an RSD of 4.59% over twelve measurements. These composite electrodes showed excellent selectivity, which was demonstrated by analyses in the presence of metal ions (Ca2+, Zn2+, Mg2+, Fe3+, Co2+, Na+, and Cu2+) that did not interfere in the analysis of Cr(VI). The GPEs/nsRGO were applied to the determination of Cr(VI) in real samples of wet-blue leather and leather ash using DPV. This approach was validated using the sample recovery method, where it presented values from 95.6 to 108.2%. The proposed method showed satisfactory results compared to the literature and can be considered a good alternative for the determination of Cr(VI) in aqueous samples. [Display omitted] •A simple electrochemical sensor for chromium (VI) determination was developed.•A graphite/paraffin composite electrode was modified with nsRGO by electrodeposition.•The sensor showed good stability and selectivity for chromium(VI) samples.•The nsRGO-modified composite sensor was tested with real leather waste samples.