Chemically modified polymeric resins with catechol derivatives for adsorption, separation and recovery of gallium from acidic solutions

Ion-exchange has been extensively explored for the adsorption, separation, and recovery of metal ions. The use of eco-friendly, low-cost, selective, and reusable resins are important for the development of separation technologies for critical elements. Herein, novel chelating adsorbents were synthesized and studied for the selective extraction, separation, and recovery of gallium (Ga) from acidic solutions. Four chelating adsorbents were prepared using 3,4 dihydroxybenzoic acid, and 3,4,5-trihydroxybenzoic acid to functionalize pre-aminated polymeric resins through amide linkage. Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy analysis confirmed the functionalization of the resins and revealed that their surface morphology was significantly improved after the chemical modification. Their adsorption performance was investigated, and maximum Ga-adsorption capacity was found at pH 3. Equilibrium Ga-adsorption isotherms were better demonstrated by the Langmuir isotherm model, and adsorption kinetics were better explained by Pseudo-second order model. The proposed new adsorbents were 10–4800 times more selective for Ga than Zn, Al, Cd, Sb, Fe, As and Mn in acidic conditions. Moreover, high Ga selectivity (Sel_Ga/M >1.5) was accomplished in the binary solution of Ga:Zn and Ga:As in 1:10, 1:50 and 1:100 metal ratios, which suggests that adsorbents can separate Ga from Zn and As solution effectively. Desorption preliminary experiments showed > 60% desorption of Ga over 4 adsorption/desorption cycles. The adsorption mechanism was confirmed by XPS and FTIR studies. This study indicates that the synthesized adsorbents could be used for industrial applications, due to their low-cost, abundant raw materials, mature synthetic routes, and lower environmental impact.