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

Abstract

In this study, a novel trihydroxyl functionalized titanium dioxide (TiO2-NH2-3OH) was successfully synthesized by the Schiff base reaction method. TiO2-NH2-3OH 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. TiO2-NH2-3OH exhibited superior capture performance on Ge(IV) at a pH of 3, and the optimal TiO2-NH2-3OH dosages were 0.8 g L−1. The distribution coefficients of germanium for coexisting metal ions (Zn2+, Co2+, Mn2+, Ni2+ and Al3+) were all greater than 1, indicating that TiO2-NH2-3OH 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 TiO2-NH2-3OH was a spontaneous endothermic process, increasing the temperature was beneficial for the adsorption reaction to proceed. TiO2-NH2-3OH with saturated adsorption still maintained a high removal rate of 80.55 % of Ge(IV) after five cycles, indicating good stability and recyclability of TiO2-NH2-3OH. XPS analysis indicated that the capture of germanium by TiO2-NH2-3OH may be due to the ion exchange interaction between -OH and Ge(OH)4 on the adsorbent surface. This work indicated that TiO2-NH2-3OH had great advantages and potential for the recovery of Ge(IV) from coal acid leaching solution.