Persimmon peel-based ion-imprinted adsorbent with enhanced adsorption performance of gallium ions

A gallium ion-imprinted material (Ga-IIP-PP) was fabricated from persimmon peel using persimmon tannin as a functional monomer. Thereafter, it was applied for the selective adsorption of Ga ions from aqueous solutions containing other metal ions. The sorbent morphology and surface characterization data confirmed the successful loading of a gallium-imprinted layer onto the waste persimmon peel. The imprinted material exhibited a relatively smooth structure with few wrinkles, a negatively charged surface, and a low number of hydroxyl surface functional groups. The results of adsorption experiments revealed that Ga-IIP-PP could be applied in a wide range of Ga concentrations, while its highest adsorption capacity of 128 mg/g and adsorption rate of 0.0081 min-1 were achieved at pH = 3. Moreover, the synthesized Ga-IIP-PP exhibited high selectivity toward Ga ions even in binary systems with similar competitive ions. Finally, Fourier-transform infrared spectroscopy and X-ray photoelectron spectroscopy were performed to elucidate the adsorption mechanism of Ga ions onto the Ga-IIP-PP surface, which primarily involved electrostatic adsorption and the cation exchange between the H+ ions of -OH/-COOH groups and Ga ions. This work demonstrates that the bio-sorbent prepared from waste persimmon peel is a promising adsorbent for recovering Ga ions from aqueous solutions.