Geopolymer cement–modified carbon paste electrode: application to electroanalysis of traces of lead(II) ions in aqueous solution

Pb 2+ ions were detected on a carbon paste electrode modified with a geopolymer cement. The X-ray pattern and the infrared spectrum of the geopolymer synthesized from metakaolin and phosphoric acid showed a three-dimensional semi-crystalline structure. The obtained geopolymer cement indicates the formation of a broad hump structure between 17 and 40° (2 θ ) ascribed to the poly(phospho-siloxo) network. The electroanalysis of Pb 2+ ions was done in three steps by stripping voltammetry: accumulation of Pb 2+ ions in open circuit at pH 4, detection in NaNO 3 medium, and desorption. The peak current of Pb 2+ ions obtained after 5-min accumulation on the geopolymer cement–modified carbon paste electrode was found to be four times higher than that from the bare carbon paste electrode. After optimization of some parameters related to the detection process (geopolymer cement content in paste, accumulation time, pH of detection medium, detection medium, electrolysis time, potential electrode), a calibration line was drawn in the concentration range from 0.2 × 10 −6 M to 1.4 × 10 −6 M. The detection limit obtained from a signal-to-noise ratio equal to 3 is 2.3 × 10 −9 M. The interferences of some heavy metal ions, such as Hg 2+ , Cd 2+ , and Cu 2+ , and some inorganic ions Al 3+ , Fe 2+ , Zn 2+ , Na + , K + , Ca 2+ , Mg 2+ , Cl − , SO 4 2− , and NO 3 − on CPE/GP-Dib 2 sensor were examined. The results obtained shows that these inorganic ions did not interfere with the determination of Pb 2+ ions. It indicated that the prepared sensor possessed high selectivity for Pb 2+ . Grapical abstract