Persimmon tannin/graphene oxide composites: Fabrication and superior adsorption of germanium ions in aqueous solution

Abstract Herein, a new persimmon tannin/graphene oxide (GO-PT-6Glu) composite was fabricated through one-step cross-linking method. The as-prepared GO-PT-6Glu has substantial phenolic hydroxyl groups (up to 5.23 mmol g−1) by introducing water-soluble PT (up to 5.50 mmol g−1) on the GO, which provides the opportunity to use it as an adsorption material to recover germanium. The GO-PT-6Glu was then used to adsorb germanium from aqueous solution and showed the highest than among currently reported adsorption capacity (117.38 mg g−1). Simultaneously, it exhibits excellent cycle performance to adsorb germanium still with a high adsorption efficiency (up to 81.42%) after 5 adsorption–desorption cycles. More importantly, the GO-PT-6Glu showed superior selectivity towards Ge(IV) as compared to As(III) (Cl−/SO42−/PO43−), in spite of the concentration of As(III) (Cl−/SO42−/PO43−) was 100 times higher than that of Ge(IV). Taking advantages of its low cost, selective adsorption, as well as environmental protection and high adsorption, the GO-PT-6Glu is expected to be the most promising material in recovery of Ge(IV) from water containing As(III).