Enhanced recovery of germanium(IV) from zinc residue leachate by tartaric acid functionalized chitosan: Experiments and DFT calculation

Abstract

The recovery of germanium (Ge) from zinc residue leachate has attracted increasing attention. Herein, this study report on the development of a tartaric acid functionalized chitosan (TA-CS) material serving as an efficient adsorbent for Ge(IV). The introduction of TA resulted in abundant protonatable hydroxyl and carboxyl groups, which endows materials with excellent buffering capacity under acidic conditions. Adsorption kinetics and isotherms showed a fast and efficient adsorption capacity of 57.28 mg/g for Ge(IV). In binary systems, Ge(IV) was preferentially adsorbed over Zn(II), a major coexisting ion, with a separation factor of 3.22. The SEM–EDS FT-IR, XPS and DFT results revealed that mechanisms in combination, including electrostatic adsorption, complexation, hydrogen bonding, and ion exchange, promoted the immobilization of Ge(IV) on TA. The TA-CS material also exhibited great reusability with an adsorption efficiency of 70% after 3 recycles. For the recovery of Ge(IV) in practical zinc residue leachate, the TA-CS material showed superior affinity toward Ge(IV) and a 10-fold higher of adsorption capacity compared to that of pristine chitosan. Together, TA-CS demonstrates that it is a viable and economical material for the separation and preconcentration of Ge(IV) from zinc residue leachate.