Innovative Amidoxime Nanofiber Membranes for Highly Effective Adsorption of Ga(III) from Waste Bayer Solution

The effective treatment of Ga-containing wastewater from the Bayer process is a promising strategy for the sustainable development of the gallium resource. Among the adsorption materials, nanofibers play indispensable roles in the recovery of gallium with their adsorption capacity. However, developing facile, easy scale-up, and low-cost grafting methods for polyacrylonitrile nanofiber membranes (PAN NFs) is still challenging in view of the traditional grafting methods with lower grafting rates and strict requirement of fiber flexibility. In this study, a newly and highly efficient amidoxime nanofiber membrane preparation method with electrostatic spinning technology was explored to apply in the Ga­(III) adsorption from Ga-containing wastewater. The results of Ga­(III) adsorption studies by amidoxime polyacrylonitrile nanofiber membranes (AOPAN NFs) showed that Ga­(III) was remarkably consistent with the Langmuir isotherm, with a maximum adsorption capacity of 39.80 mg/g of Ga­(III) at 30 °C, a gallium concentration of 200 mg/L, a solid to liquid ratio of 1.0 mg/mL, and a solution pH of 12, which is generally higher than those of other materials. The kinetic adsorption experiment demonstrated that the adsorption process was controlled by a chemical reaction and followed the pseudo-second-order kinetic model. Furthermore, the adsorption mechanism of AOPAN NFs was proposed, and the oxime group played an essential role in the adsorption process. This strategy combines the advantages of AOPAN NFs to open up a new way to develop the next generation of gallium adsorption materials.