Catechol-functionalized nanosilica for adsorption of germanium ions from aqueous media

Abstract We prepared the catechol-functionalized nanosilica for adsorption of germanium (Ge) ions from aqueous media. The functionalized nanosilica was characterized by FTIR, TGA, TEM, BET, and XPS. The influence of pH, Ge initial concentration, and time of the adsorption process was investigated. Under the optimum condition, the maximum adsorption capacity of Ge ions was 0.048 mg m −2 at pH 4.5. The adsorption mechanism is the chelating interaction between hydroxyl and Ge(OH) 4 . The functionalized nanosilica was able to selectively adsorb Ge ions from tellurium(IV) and boron. Langmuir isotherm was found to better fit the experiment data rather than Freundlich isotherm. The kinetics of the adsorption process of Ge ions on the functionalized nanosilica was investigated using the pseudo-first-order and pseudo-second-order models, and the results indicated that the pseudo-second order equation model provided the best correlation with the experimental results. Graphical Abstract