Recovery of pure germanium oxide from Zener diodes using a recyclable ionic liquid Cyphos IL 104

A novel process is developed for the recovery of germanium from the leach liquor of Zener diodes using solvent extraction. Extraction is carried out using a phosphonium ionic liquid, Cyphos IL 104, as an extractant. Preliminary investigations carried out on Ge(IV) extraction using Cyphos IL 104 include influence of various parameters like temperature, equilibration time, and concentration of extractant, chloride ion, and acid on the distribution of Ge(IV). NMR spectrum of Ge(IV)-extractant complex was analyzed to support the proposed extracting species of germanium. Quantitative extraction of germanium is achieved from 7 mol/L HCl onwards using 0.1 mol/L Cyphos IL 104. Optimum conditions for quantitative extraction of Ge from leach liquor of Zener diodes were developed. McCabe-Thiele plots were constructed for the extraction and stripping of Ge(IV) from leach liquor to determine the number of stages required at a particular aqueous/organic phase ratio. Separation of germanium from copper, mercury and iron has been achieved by selective stripping of these metal ions. Germanium is recovered as germanium oxide from the strip solution using NaOH as a precipitating agent. The synthesized germanium oxide is characterized by XRD, FE-SEM and EDX techniques.