Efficient recovery of gallium(Ⅲ) from alkaline solution by electrosorption using biomass-derived carbon aerogel electrodes

Abstract

The effective extraction of gallium(Ⅲ) from alkaline solutions is a crucial strategy for the sustainable development of gallium resources. However, the conventional adsorption method is limited in terms of both the adsorption capacity and adsorption rate of gallium(Ⅲ). In this study, the optimal nitrogen-doped persimmon-powder activated carbon aerogel (NPAC) was prepared via optimizing synthesis conditions such as hydrothermal time, hydrothermal temperature, mass ratio of zinc chloride, and pyrolysis temperature to investigate the electrosorption effect of NPAC on gallium(Ⅲ). The results demonstrated that the electrode prepared from NPAC（NPAC@CF） exhibited exceptional electrochemical performance, attributed to the synergistic effect of reduced impedance, enhanced reversibility, and controlled capacitance (the capacitive contribution can be accurately quantified). At a bias voltage of 1.2 V, a pH of 11 and an initial concentration of NaGaO2 of 160 mg/L, the NPAC@CF electrode reached an outstanding electrosorption capacity of 250.69 mg g−1 for gallium(Ⅲ), which surpassed that of the conventional adsorption by over twofold. Electrosorption not only notably enhanced the adsorption capacity of NPAC for gallium(Ⅲ) but also elevated the adsorption rate, reducing the adsorption equilibrium time to just 40 min. The electrosorption mechanism of GaO2- on the surface of NPAC@CF was further understood by FTIR and XPS analyses, which mainly involved capacitive adsorption and the interaction of N/O-containing functional groups with GaO2-. Consequently, the electrosorption technology emerges as a promising, novel, and efficient approach for gallium extraction from alkaline solutions.