Germanium extraction from lignite using gravity separation combined with Low-Temperature sintering and chlorinated distillation

Abstract

As a critical metal, germanium (Ge) is widely used as a semi-conductor, a catalyst, and an optical material. Generally, smelting method is used to extract Ge from the coal burned in chain stoves. However, because of the high SiO2 content in coal, Ge tends to form a GeO2-SiO2 solid solution at high temperatures, which is difficult to extract using conventional chlorinated distillation. Thus, herein, a new method for the pre-enrichment of Ge in lignite using gravity separation combined with low-temperature sintering. The SiO2 content in lignite can be effectively pre-discarded, and the formation of the GeO2–SiO2 solid solution during burning process can be avoided. Results revealed that the Ge enrichment factor in lignite can reach 2.0 after gravity separation. Furthermore, the low-temperature sintering treatment at 300 °C and 500 °C can produce residual ash with a Ge content of 1811.4 mg/kg, and the enrichment factor further reached 10.6. After pre-enrichment, ＞ 90 % of Ge in lignite can be extracted in the chlorinated distillation process. Therefore, gravity separation combined with low-temperature sintering is an excellent pre-enrichment method for Ge in lignite, avoiding the thermal pre-treatment at high temperatures and the formation of a stable solid solution.