Insight into the mechanism of heavy metal removal from water by monodisperse ZIF-8 fine particles

Water pollution due to toxic heavy metals discharged by chemical industries and abandoned mines is one of the most serious environmental and public problems. Therefore, the purification of heavy metal-contaminated water has become a major topic in water treatment. Among the metal–organic frameworks used to this aim, zeolitic imidazolate framework 8 (ZIF-8) is particularly promising as a purifying agent for water treatment. Although several reports have dealt with the purification of heavy metal-contaminated water using ZIF-8, the removal mechanism remains controversial. In this study, monodisperse ZIF-8 fine particles were used for the removal of Pb2+ and Cu2+ ions, and the removal mechanisms were investigated. Accordingly, an adsorption mechanism is suggested for the Pb2+ removal, whereas the Cu2+ removal occurs through an ion-exchange phenomenon.