Technology And Mechanism Of Gallium And Germanium Recovery From The Dip Zinc Scrap Iron Powder

As the important raw material of making advanced technological material, gallium and germanium are needed more and more. In this dissertation, the methods of recovering gallium and germanium from various resources are reviewed. Acid leaching, corrosion leaching, NaOH-NaClO leaching, soda roasting followed by caustic soda leaching have been comparably studied, it is found that soda roasting followed by caustic soda leaching is suitable process. On this basis, soda roasting followed by caustic soda leaching are studied systemically in order to recover gallium and germanium from ferrous powder reduced from zinc-leaching residues.The investigation on soda roasting process shows that appropriate roasting conditions are 1.5 of the ratio sodium carbonate to ferrous powder, 1080 C of roasting temperature, 60minutes of roasting time and the method of slow cooling.The investigation on leaching process of the roasted material shows that the leaching recovery of gallium and germanium reaches 91.30% and 90.96% respectively under the leaching conditions of 135 C of temperature, 60minutes of time, 9.09% of sodium hydroxide concentration and 12 of liquid/solid ratio. The process is found controlled by diffusion between 105 and 135 C, the leaching kinetic model of gallium and germanium is found to beAnd the leaching recovery of gallium and germanium is found to be88.73% and 89.10% respectively when the leaching is conducted under the conditions of 90 C , 60minutes, 16.67% sodium hydroxide concentration, 12 of liquid/solid ratio and 1440r/min of stirring speed. When stirring speed is over 750r/min, leaching process is controlled by the chemical reaction in the range of 30~90 C, the kinetic model of gallium and germanium is found to bereaction orders of gallium and germanium to sodium hydroxide are 0.59 and 0.46 respectively.The studies of mechanism show that ferrum is changed into sodium ferrite, gallium is changed into gallium sesquioxide and gallate, germanium is changed into germanous dioxide and germanate in soda roasting process. Some soluble gallium, germanium compounds, for example, gallium sesquioxide, sodium gallate, sodium germanate, germanous dioxide are favored, insoluble gallate and germanate formed in roasting process should be avoided. Gallium and germanium are leached as gallium sesquioxide and sodium germanate respectively. Soda roasting is crucial step in the whole process.