In this study, a solid adsorbent based on Chinese gallotannin and chitosan was generated and applied to adsorb rare and scattered metals, including Ge (Ⅳ), Ga (Ⅲ), and In (Ⅲ), from simulated zinc plant leachates. Fourier-transform infrared spectroscopy (FTIR) and solid state nuclear magnetic resonance (SSNMR) were performed to characterize the grafting way of Chinese gallotannin on the chitosan matrix. It was clearly showed that Chinese gallotannin was immobilized on the chitosan by Schiff-base condensation and phenol-formaldehyde reaction at the molar ratio of glutaraldehyde to tannin of 2:1. And the amount of chitosan amino groups was ten times that of tannin, with an initial pH of 4. The adsorption experiments showed that an appropriate increase in pH was more beneficial to enhance the adsorption capacity of immobilized Chinese gallotannin (ICGT). At a temperature exceeding 30 °C, the immobilized tannin became less sensitive to temperature. Adsorption kinetics studies showed that the adsorption of the three scattered metals by ICGT followed a quasi-second-order kinetic equation , with chemisorption as the mechanism. The adsorption isotherm was well fitted by the Langmuir model, indicating uniform adsorption sites on the surface of ICGT. The adsorption capacities of Ge (Ⅳ), Ga (Ⅲ), and In (Ⅲ) in solution by the adsorption model of monolayer were 61.39 mg/g, 63.82 mg/g, and 59.92 mg/g, respectively. Mechanical property and stability tests showed that ICGT had good resistance to harsh adsorption conditions of scattered metal ions .
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 NaGaO 2 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 GaO 2 - 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 GaO 2 - . Consequently, the electrosorption technology emerges as a promising, novel, and efficient approach for gallium extraction from alkaline solutions.
Manman Zhang,Xiaopei Zhang,Chang Liang,Lei Qin,Dongju Fu,Meiling Wang,Yonghui Bai,Weifeng Liu,Xuguang Liu
To meet the requirements of Ga(Ⅲ) selective adsorption from acid leaching of fly ash, a grapheme-based Ga(Ⅲ) imprinted polymer is developed by combining adsorption method with surface ion imprinting technology. The obtained Ga(Ⅲ) imprinted polymer can effectively adsorb Ga(Ⅲ) with a maximum adsorption capacity of 221.56 mg g −1 at an initial concentration of 200 mg/L within 240 min. The pseudo-second order model (R 2 = 0.9882) and Langmuir isotherm (R 2 = 0.9628) fitted the Ga(Ⅲ) adsorption data well. In addition, the imprinted adsorbent exhibits significant selectivity towards Ga(Ⅲ) in a simulated acid leaching of fly ash. The selectivity coefficients of Ga(Ⅲ) with respect to Al(Ⅲ), Fe(Ⅲ), Mg(Ⅱ), and Ca(Ⅱ) are 10.09, 3.36, 18.50, and 55.50, respectively. The synthesized imprinted adsorbent exhibits excellent regeneration ability, maintaining 85.71% of its initial adsorption capacity after 5 adsorption-regeneration cycles. The binding energy of Ga(Ⅲ) to functional monomers is calculated as −16.79 kJ mol −1 , which confirms that Ga(Ⅲ) can be effectively adsorbed. The theoretical simulated calculation results are basically in consistence with the experimental results, which confirms the selective adsorption mechanism of Ga(Ⅲ). Therefore, it provides a new idea for the extraction of Ga(Ⅲ) from acidic environments.
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