Gallium, known as the new grain of the semiconductor industry, has been listed as a strategic reserve metal by the United States, Japan, the European Union, and China. (1−3) With the rapid rise of emerging technologies, especially in the cutting-edge science and technology fields such as communications, integrated circuits, and aerospace, the reserve of gallium elements has increasingly become an essential and urgent task owing to its excellent semiconductor properties. (4) The booming electronic information industry further highlights the strategic position of gallium, and gallium has become a strategic emerging mineral resource. (5−8)

Gallium resources are an associated resource and are the byproduct of aluminum extraction from bauxite ores, (probably more 90%) or zinc extraction from zinc ores. (9,10) The waste Bayer solution, obtained from the seed mother liquor in the Bayer process to produce alumina, typically contains roughly 70% gallium, making it the most economical Ga resource with recovery value. (11,12) It has been reported that amidoxime chelating resin was beneficial to extracting gallium from the waste Bayer solution. (13) Zheng et al. studied the adsorption performance of commercial resin AO on gallium with a maximum adsorption effect of 28.26 mg/g. (14) Zhao et al. investigated the mechanism of gallium adsorption by the commercial resin LSC 700 and showed that the oxygen on the amidoxime group of LSC 700 formed a complex with Ga(III). (15) The density functional theory (DFT) can be used to obtain the energy of the binding model between amidoxime resin and Ga(III). (16) In view of the resin synthesis process, which is typically conducted by suspension polymerization using acrylonitrile or styrene as monomers, it usually suffers a lot from the long synthesis times, low resin qualification rates, and low adsorption capacity, limiting its application in gallium adsorption. Therefore, it is urgent to develop efficient, durable, easy scale-up, and low-cost adsorbents for the economic and highly efficient extraction of gallium.

Owing to the excellent material physical chemistry and structural characteristics, such as a large specific surface area, high adsorption capacity, fast exchange rate, and easy regeneration, ionic fibers have been widely applied in environmental protection, analysis, purification of precious metals, waste gas, and wastewater, and recovery of other substances. (17−19) Chen and Gu et al. reviewed the recovery of radioactive elements from solution by covalent organic materials. (20,21) The study showed that the amidoxime group could recover metal ions from the solution effectively. Polyacrylonitrile (PAN) contains wealthy cyano-functional groups, which can undergo a nucleophilic addition reaction with hydroxylamine reagent to obtain compounds with amidoxime groups. (22) It can be divided into PAN fiber direct modification, chemical grafting, and pre-irradiation grafting according to the different ways of introducing the cyanide group. (23) The proposed lysine-covalently grafted polyacrylonitrile fiber method has been applied in removing U(VI) from seawater. (24) The effect of amidoxime degree of polyacrylonitrile fiber has also been investigated on uranium adsorption. (25)