ADSORPTION AND RECOVERY OF Ag(I) FROM AQUEOUS SOLUTIONS USING SPENT GRAIN

摘要

The brewing industry byproduct, spent grain (SG), was evaluated for its ability to adsorb Ag(I) from aqueous solutions. Ag(I) adsorption was dependent on solution pH, contact time, adsorbent dose, initial Ag(I) concentration and temperature. The kinetic data were well described by pseudo-second-order kinetic model, indicating that chemical adsorption was the rate-controlling step. The equilibrium data followed Freundlich isotherm rather than Langmuir isotherm, suggesting heterogenity of the adsorption sites on spent grain. Ag(I) desorbed from Ag(I)-loaded spent grain was also evaluated in this study. HCl, NaOH, Na_2S_2O_3 and ultrapure water were chosen as eluants and desorbed Ag(I)-loaded spent grain for 30min, Ag(I)-loaded spent grain desorbed in 0.1 M Na_2S_2O_3 exhibited higher elution efficiency as compared with other eluants. The results indicated that application of spent grain for adsorption and recovery of silver from aqueous solutions was feasible.