Simultaneously removal of Cr(VI) and Cd(II) from water using a flower-like primary battery nanosystem

In this study, a new flower-like primary battery nanosystem termed "Zn/CCP/ZIF-8" was prepared by depositing conductive carbon paint (CCP) and zeolitic imidazolate framework-8 (ZIF-8) on a zinc plate (Zn). Therein, CCP had good conductivity performance and adhesiveness, ZIF-8 and Zn/CCP/ZIF-8 possessed BET specific surface areas of 1909.5 and 1265.4 m²/g respectively. The results showed that the Zn/CCP/ZIF-8 nanosystem could effectively simultaneously adsorb hexavalent chromium (Cr(VI)) and bivalent cadmium (Cd(II)) from water. The system could promote the transfer of electrons from Zn to Cr(VI) and Cd(II) which were effectively reduced to trivalent chromium (Cr(III)) and cadmium (Cd), respectively. The resultant Zn/CCP/ZIF-8/Cr/Cd composite was then easily separated from water. The adsorption isotherm, kinetics, and thermodynamics of the prepared Zn/CCP/ZIF-8 for Cr(VI) and Cd(II) were investigated. An electrochemistry performance test proved that the Zn/CCP/ZIF-8 system was a primary battery. Notably, the Zn/CCP/ZIF-8 system substantially reduced the amounts of Cr(VI) and Cd(II) absorbed by zebrafish and water spinach, thus increasing food safety. The results of a rat test indicated that the Zn/CCP/ZIF-8 system possessed a high biosafety. This study provides a promising, eco-friendly, and facile method for the simultaneously treatment of Cr(VI) and Cd(II) contamination of water.