Germanium separation and purification by leaching and precipitation

In this research work, extraction and purification of germanium from zinc leach residues(ZLR) were investigated. The results of ICP, XRF, and atomic adsorption spectroscopy(AAS) tests show that contents of germanium, iron, lead, and zinc within the leaching residue were 105×10^(-6), 3.53%, 10.35%, and 8.8%, respectively. XRD results indicate that the main minerals were in different forms of sulfates(CaSO_4·2H_2O, PbSO_4 and ZnSO_4·6H__2O), silicate(SiO_2), and oxide(Fe_2O_3). Dissolution of leaching filter cake was carried out using 5 parameters and each in 4 levels(acid concentration, temperature, time, liquid-to-solid ratio, and stirring speed) by Taguchi method(L_(16)), and then optimization of the effective parameters by response surface method. Under optimum conditions, zinc and germanium dissolution efficiencies were 88.71% and 8%, respectively. Leaching tests with sulfuric acid(added di-ammonium oxalate monohydrate) and hydrochloric acid(HCl) on the residues obtained from previous-stage sulfuric acid dissolution, yielded germanium and iron recoveries of 83%, 88%, 40%, and 90%, respectively. Thus, leaching experiment with sulfuric acid(added di-ammonium oxalate monohydrate) was superior to that with hydrochloric acid due to high and low extraction amounts of germanium and iron, respectively. Precipitation experiments revealed that germanium purification with tannic acid presented a better result compared to sodium hydroxide and ammonia. Under optimum conditions, contents of germanium and iron in the solution after precipitation were 0.1505% and 14.7% with precipitation yields of 91% and 52%, respectively.

Thermodynamical and catalytic aspects of zinc separation from aqueous solution

The present research work examines extraction mechanism of zinc by D2 EHPA(Di-2-ethyl hexyl phosphoric acid) and comprehensively studies the main effective parameters on the process. Results of thermodynamic experiments showed that zinc extraction by D2 EHPA was endothermic and spontaneous, and thermodynamic parameters including entropy and enthalpy were + 27.37 J·mol^(-1)·K^(-1) and 25.21 kJ·mol^(-1), respectively.Gibbs free energy was varied between-7.21 kJ·mol^(-1) and-8.41 kJ·mol^(-1) with the variation of temperature from 20 °C to 70 °C. Solution ionic strength was increased by addition of potassium and lithium sulfate solution while addition of calcium sulfate decreased ionic strength whereby zinc extraction efficiency was also decreased.TBP showed positive synergism at concentration of 5%(v/v) and negative synergism effect at concentrations of2% and 10%. Simultaneous addition of both TBP and salt caused extraction efficiency to drop significantly and lower both TBP and ionic strength efficiency. Results showed that a continuous addition of TBP tends to effectively improve the zinc extraction efficiency. Experiments in the presence of catalyst Ni-Raney demonstrated that zinc extraction kinetic increases remarkably and due to easy recycling of the catalyst, we can propose a novel idea in solvent extraction field.

化学和物理分离法萃取金、汞、银（英文）

采用搅拌过滤法对Aghdareh金矿样品进行金的萃提。矿物学研究表明,样品中58%的金颗粒小于10μm,该等级的3%属于难熔金。实验结果表明,在最优条件下,金回收率可达91.8%,银和汞分别为41.5%和10.2%。以氰化法测试的6种分次尺寸样品的结果表明,未萃取的金粒子大多小于25μm,还有大约5%的金颗粒大于25μm。因此,对样品要进一步粉碎,这样可使金和银回收率分别提高约3.57%和约5%,进一步粉碎样品并不影响汞的回收率。采用Knelson重力选矿法可提高汞回收率并防止金和汞的混合,利用氰化法检测重力法的尾料。这些方法的结合应用,最终使金回收率达到93.3%,汞回收率增加到42.16%,而银回收率没有明显的变化,为42.17%。