Cross-linked amidoxime porous resin for selective gallium separation in Bayer solutions: Reaction mechanism and kinetic study

The commercial resin suffers from slow diffusion rates and long mass transfer times, limiting its practical application in gallium extraction in Bayer solution. A novel amidoxime grafted polyacrylonitrile-styrene–divinylbenzene (A-PSD) resin was prepared by suspension acrylonitrile-styrene–divinylbenzene resins and subsequent electrophilic addition of hydroxylamine hydrochloride with amidoxime. Adsorption sites and mechanism study proved that the Ga3+ reacted with the amidoxime groups (CNOH) on the A-PSD resins. The A-PSD resins for Ga3+ adsorption followed the Langmuir model and exhibited excellent adsorption performance in Bayer solution with a Ga3+ capacity of 14.67 mg/g at 25 °C. The kinetic adsorption experiment showed that the adsorption process was controlled by chemical reaction and followed the pseudo-second-order kinetic model. The penetration curves of the column experiments indicate the possibility of industrial application of A-PSD resins, which may lay the groundwork for a new alternative to Ga3+ adsorption resins.