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

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.