Dual-selective silver recovery strategy by simultaneous adsorption-reduction boosted by in-situ magnetic field

Abstract

The mainstream silver recovery has problems such as resource waste, weak silver selectivity, and complicated operation. Here, self-propelled magnetic enhanced capture hydrogel (magnetic NbFeB/MXene/GO, MNMGH) was prepared by self-crosslinking encapsulation method. MNMGH achieved high selectivity (Kd = 23.31 mL/g) in the acidic range, and exhibited ultrahigh silver recovery capacity (1604.8 mg/g), which greatly improved by 66% with the assistance of in-situ magnetic field. The recovered silver crystals could be directly physically exfoliated, without acid/base additions. The selective sieving effect of adsorption, MNMGH preferentially adsorbed Ag(I), and then selectively reduced to Ag(0), realizing dual-selective recovery. The in-situ magnetic field enhanced selective adsorption by enhancing mass transfer, reactivity of oxygen-containing functional groups. Furthermore, density function theory simulations demonstrated that the in-situ magnetic field could lower the silver reduction reaction energy barrier to enhance the selective reduction. Three-drive synergy system (reduction drive, adsorption drive and magnetic drive) achieved ultrahigh silver recovery performance. This study pioneered an in-situ magnetic field assisted enhancement strategy for dual-selective (adsorption/reduction) recovery of precious metal silver, which provided new idea for low-carbon recovery of noble metal from industrial waste liquids.