Recovery of germanium from optical fiber industry wastewater using desferroxamine B

Germanium (Ge) is a critical element whose long-term supply to industry is not assured. Thus, recovery of Ge from secondary sources is important. Siderophores-assisted technology could be a solution for recovery of Ge from secondary sources. However, there are no studies on the interaction of Ge with siderophores and subsequent recovery. In the present study, the interaction of Ge with desferrioxamine B (DFOB) was studied to develop Ge recovery technology from its low-concentrated wastewater. Ge-DFOB complexation was studied under varying pH (1.5-9.0), different anion concentrations (chloride, nitrate, sulfate, phosphate) and the presence of other metals (calcium (Ca), magnesium (Mg), copper (Cu), zinc (Zn), silicon (Si). It was observed that Ge-DFOB complexation was preferred at lower pH and increased in the presence of chloride ions. DFOB complexed more than 80.0 % Ge even when Zn, Ca, Cu, and Mg were in 20-fold molar excess. Further, DFOB also favored complexation with Ge (90.1 %) in the presence of equimolar concentration of Si. On increasing pH to 5.0 as well as addition of eight-fold excess ethylenediaminetetraacetic acid (EDTA) at pH 3.5 to Ge-DFOB complex led to more than 95.0 % decomplexation of the Ge-DFOB complex. Through spectroscopy and density functional theory calculations, the hexadentate complex between hydroxamate groups of DFOB and Ge was identified. When this technology was applied to wastewater from the fiber optics industry, more than 80.0 % of Ge-DFOB was recovered with Ge purity of 84.5 % using reversed-phase high performance liquid chromatography.