Sodium Hydroxide Leaching of Germanium from Lead Slag

In this study, the process of leaching germanium from lead slag by sodium hydroxide solution as a leaching agent was investigated and the leaching kinetics of germanium were studied. Provided that a lead slag raw materials with an average particle size of 101.7 μm is used and that each leaching efficiency data point represents the average of three experiments conducted under the same conditions. The effects of reaction temperature, reaction time sodium hydroxide solution concentration, and liquid–solid ratio on the germanium leaching process were investigated. The results showed that the optimum leaching conditions could be achieved at the leaching temperature of 353 K, the leaching time of 40 min, the liquid–solid ratio of 8:1, and the concentration of sodium hydroxide solution of 5 mol/L, and the optimum leaching efficiency could reach 69.40%. The phenomenon of germanium leaching efficiency greatly reduced in the reaction was explained because a large number of Pb(OH)₂ colloid and NaPb(OH)₃ colloid adsorbed germanium after reaching the critical temperature, resulting in a significant reduction of germanium leaching efficiency. The kinetic germanium leaching reaction process conforms to the shrink core model and is controlled by surface chemical reactions. Based on the experimental data, the macroscopic kinetic model of the reaction was established and the macroscopic kinetic equation was obtained.