Adsorption of Ga(III) by Zn2+, quaternary ammonium and polyamine embellished lignin with the crosslinking agent of epichlorohydrin.

Cost-effective and eco-friendly extraction of gallium is a technical challenge. Gallium-containing anions can be effectively adsorbed by Zn2+, quaternary ammonium and polyamine. Polyamine can be grafted into adsorbent by formaldehyde and the crosslinking agent of epichlorohydrin. Zn2+/quaternary ammonium/polyamine lignin was constructed for adsorption of Ga(III) through embellishing of Zn2+, quaternary ammonium and polyamine and crosslinking of epichlorohydrin. The adsorbent was characterized by SEM, ICP-MS, BET, BJH, LDM, FTIR and XRD. The effects of pH, initial gallium concentration, adsorption time, dosage of adsorbent and number of cycles on adsorption properties were investigated. The adsorption mechanism was elucidated by SEM, ICP-MS, FTIR and XPS. The results showed that the adsorbent was coarse and contained hydroxyl, polyamine, quaternary ammonium and Zn2+. The adsorption capacity of 0.5 g·L-1 adsorbent for Ga(III) reached 289.20 mg·g-1 at 25 °C, pH of 9, oscillation rate of 200 r/min, initial gallium concentration of 400 mg·L-1 and adsorption time of 540 min. Adsorption followed Langmuir model and quasi-second-order kinetic model. The adsorption capacity decreased by only 10.57 % after five cycles, implying its strong stability and potential reuse. Ga(III) was adsorbed through electrostatic attraction of hydrogen bond and Zn2+, coordination with -NH- and ion exchange between Cl- and Ga(OH)4-.