Uranyl Ions Removal by Quercus macrenthera Gall's Extract-Based Cryogels with Extreme Characteristics
In this study, one type of oak galls (galls of Quercus macrenthera, QMG) was used as tannin source for the production of tannic acid-based cryogels (CRGs). QMG-CRGs were characterized with scanning electron microscopy and attenuated total reflectance infrared. The produced CRGs have excellent characteristics such as extreme lightweightness. They look like sponges and are so elastic that they can easily absorb water and the water content can be removed easily by only compressing. These CRGs are able to swell violently immersed in aqueous solution. The prepared CRGs were used in removing uranyl ions from aqueous solutions. Some experimental parameters which affect the adsorption process as pH of the solution, initial uranyl concentration, and sorbent dosage have been investigated. The experimental data were analyzed by the Langmuir and Freundlich isotherm models and kinetic data were treated with pseudo first and second-order models. It is found that the adsorption data of uranium is equally well described by both Langmuir and Freundlich models, besides kinetic data strictly fits the pseudo-second-order rate model.