부산대학교 도서관

Chromium(VI) should be monitored and controlled in the environment since it is introduced into the environment from several sources and it is both toxic and carcinogenic being harmful to the health of humans and animals. This work examined the conversion of hexavalent chromium (Cr(VI)) to tetravalent chromium (Cr(III)) via electrochemical reduction using the carbon paste electrode (CPE) modified with clay sintered at 1000 °C (CPE/clay@1000 °C) and Fe/ZSM-5 zeolite (CPE/Fe/ZSM-5). Fe/ZSM-5 zeolite was synthesized by the hydrothermal method at 170 °C for 72 h. Raw clay, clay sintered at 1000 °C, and Fe/ZSM-5 zeolite materials were comprehensively characterized by XRD, FTIR, and SEM-EDS. Using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) of 5.0 mM of [Fe(CN)6]3−/4−, CPE/20wt.%/clay, and CPE/40wt.%/Fe/ZSM-5 were found to perform the best. Normal pulse voltammetry (NPV) yields the highest current density compared to other voltammetric techniques, with optimal parameters of 120 s preconditioning time, − 1.0 V preconditioning potential, and 0.08 V potential increment. The NPV of Cr(VI) on CPE/40wt.%/Fe/ZSM-5 electrode produces a linear response of peak current versus Cr(VI) concentration in the range of 0.3–20 μM with a regression coefficient R2 = 0.991 and lower limits of detection (LOD), and limit of quantification (LOQ) of 0.67 μM and 2.02 μM, respectively. Recovery percentages of Cr(VI) in tertiary wastewater were obtained in the range of 88.0% ± 0.9–104.0% ± 1.1. This study innovatively incorporates iron into zeolite and employs clay structural iron as an auxiliary reducing agent to efficiently convert chromium(VI) to chromium(III), enhancing sensitivity in Cr(VI) detection using the CPE/Fe/ZSM-5 composite.