Preparation and evaluation of germanium concentrate by ultrasonic purification of tannin germanium residue.

Germanium (Ge) is a dispersed metal primarily recovered from secondary Ge-containing resources. The traditional treatment method is hindered by incomplete impurity removal, resulting in a low grade of tannin germanium residue (TGR) and Ge concentrate, high production costs, and significant hazardous waste. This study proposes a new technology involving ultrasonic pre-purification of TGR to enhance the quality of Ge concentrate prepared by roasting. Under optimal conditions (ultrasonic power 225 W, liquid-solid ratio 7:1, H2SO4 concentration 20 g/L, reaction time 30 min, and reaction temperature 40 °C), the removal efficiencies of impurities Zn, Mg, Fe, As, and S from purified tannin germanium residue (PTGR) increased by 4.2%, 4.2%, 17.4%, 8.7%, and 2.9% respectively. Moreover, the Ge content in PTGR increased from 2.9% to 4.1%. The mechanism of ultrasonic action indicated the ultrasonic energy reduced the particle size of the reactants from 67.698 µm to 31.768 µm, thereby accelerating impurity removal. Roasting ultrasonic-purified tannin germanium residue (U-PTGR) at 650 °C with 40 L/h air flow for 120 min produced Ge concentrate with a Ge grade of 33.26%, which is 6.11% higher than the regular method. Analysis using XRD and HRTEM, combined with crystallite size calculation, revealed that the Ge concentrate prepared by U-PTGR exhibited low sintering degree, good crystal properties, and high crystallinity. Implementing this technology could save enterprises approximately $57,412 annually in production costs. Additionally, it holds significant practical importance in reducing hazardous waste emissions and promoting the high-quality development of the Ge industry.

Mechanism of Germanium Adsorption by Iron Hydroxide Colloids during the Leaching Process of Secondary Zinc Oxide.

In the leaching process of secondary zinc oxide, there is a problem of germanium loss caused by the colloidal adsorption of germanium by iron hydroxide (Fe(OH)3) formed by Fe3+ hydrolysis. In response to this, this article elucidates the hydrolysis conditions of Fe3+ and the adsorption mechanism of the Fe(OH)3 colloid on germanium through theoretical analysis and simulation of the adsorption process. The coexistence of Fe3+ and H2GeO3 requires high acidity conditions (pH < 1.53 at 25 °C). The adsorption of germanium by the Fe(OH)3 colloid is a spontaneous exothermic entropy reduction process, which conforms to a pseudo-second-order kinetic model and includes three stages: fast, slow, and equilibrium. In addition, the adsorption process can be fitted by the Langmuir isotherm adsorption model, mainly consisting of monolayer and chemical adsorption. The Fe(OH)3 colloid has a great adsorption capacity for germanium at 328 K, and the equilibrium adsorption capacity is 261.15 mg/g in 40 min. During leaching, the adsorption of germanium by Fe(OH)3 colloids can be inhibited by increasing the reaction temperature, controlling the pH value of the solution system, and suppressing the formation of Fe3+ at the source. This study provides direction for how to suppress the adsorption of germanium by Fe(OH)3 colloids during the leaching process of secondary zinc oxide, which is of great significance for improving the germanium leaching efficiency and fully utilizing limited germanium resources.