Highly effective and selective recovery of germanium from coal acid leaching solution by trihydroxyl functionalized titanium dioxide

In this study, a novel trihydroxyl functionalized titanium dioxide (TiO 2 -NH 2 -3OH) was successfully synthesized by the Schiff base reaction method. TiO 2 -NH 2 -3OH was characterized by Scanning Electron Microscopy (SEM), Fourier Transform Infrared Spectroscopy (FT-IR), x-ray Photoelectron Spectroscopy (XPS), x-ray diffraction techniques (XRD), and further applied to recover germanium (Ge(IV)) from coal acid leaching solution. TiO 2 -NH 2 -3OH exhibited superior capture performance on Ge(IV) at a pH of 3, and the optimal TiO 2 -NH 2 -3OH dosages were 0.8 g L −1 . The distribution coefficients of germanium for coexisting metal ions (Zn 2+ , Co 2+ , Mn 2+ , Ni 2+ and Al 3+ ) were all greater than 1, indicating that TiO 2 -NH 2 -3OH had good selective adsorption performance for Ge(IV) in complex solution environments. Compared with other kinetic models, pseudo-second-order model was more suitable to reveal the absorption of Ge(IV). Moreover, the experiment data were fitted better with Langmuir model at 298 K than the other isothermal models, and the maximum adsorption capacity was up to 72.94 mg g −1 . Thermodynamic data suggesting that the capture of Ge(IV) on TiO 2 -NH 2 -3OH was a spontaneous endothermic process, increasing the temperature was beneficial for the adsorption reaction to proceed. TiO 2 -NH 2 -3OH with saturated adsorption still maintained a high removal rate of 80.55 % of Ge(IV) after five cycles, indicating good stability and recyclability of TiO 2 -NH 2 -3OH. XPS analysis indicated that the capture of germanium by TiO 2 -NH 2 -3OH may be due to the ion exchange interaction between -OH and Ge(OH) 4 on the adsorbent surface. This work indicated that TiO 2 -NH 2 -3OH had great advantages and potential for the recovery of Ge(IV) from coal acid leaching solution.