Ionic liquid modification of zeolite and its removal of chromate from water

This study focused on using imidazolium of different chain lengths to modify the negatively charged zeolite. The modification involves a cation exchange process of the organic cations of ionic liquids (ILs) for the alkali and alkaline earth elements on zeolite surfaces. X-ray diffraction analyses revealed that the uptake of ILs was on the external surfaces. Fourier transform infrared analyses showed that different mechanisms were attributed to IL uptake on zeolite at below and above the external cation exchange capacity. After modification, the zeolite reversed its surface charge to positive, thus enhancing adsorptive removal of anionic contaminants such as chromate from water. At the same time, the modified zeolite increased their total organic carbon content, and thus could promote better adsorptive removal of hydrophobic organic contaminants from water, too. These features enable IL-modified zeolite to be used as inexpensive sorbents for the removal of multi-types of contaminants from water simultaneously.