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Mohammadi, Maryam | 2012

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 42991 (07)
  4. University: Sharif University of Technology
  5. Department: Materials Science and Engineering
  6. Advisor(s): Yoozbashizadeh, Hossein; Moradkhani, Davoud
  7. Abstract:
  8. The environmental pollutions besides wasting the valuable materials as two main challenges in pyrometallurgical processes have brought up the tendency towards the hydrometallurgical processes. In the present study, the recovery of germanium from leaching residues of zinc plant has been investigated. Firstly, the required tests for concentrating the residues through washing of the zinc were designed by taguchi method, and optimum condition for maximum leaching of zinc accompanied by minimum desolution of germanium were obtained. The sulfuric acid concentration, time, termperature of reaction, solid to liquid ratio and rate of stirring are the parameters studied in this research. The obtained results show that the optimum condition for the leaching the maximum zinc solution of 88% is acid concentration of 30g/lit, temperature of 60 0C, solid to liquid ratio of the 1/6, stirring speed of 900rpm and reaction duration of 80 min. Also it is observed that only 8% of initial germanium contents will transfer to the washing solution. Then, the Germanium content of obtained residues was recovered by means of diluted sulfuric acid and hydrochloric acid. In this step, the acid concentration, time and temperature of reaction, the ratio of solid to liquid and the amount of Ammonium oxalate dehydrate added to sulfuric media were probed as studying parameters. The maximum solution of germanium in sulfuric media is obtained at an optimum condition by a temperature of reaction of 900C, acid concentration of 150 g/lit, solid to liquid ratio of 1/8, reaction duration of 3.5 hours and Ammonium oxalate dehydrate amount of 4 gr (0.19 mol/lit). It is seen that under such a condition, 83% of germanium besides 88% of iron enrire the solution dissoluted. At the final step of current research in oder to co-precipotate the germanium content with iron precipitation, the obtained optimum solution containing 17 ppm of germanium and 5.22 gr/lit of iron went under the precipitation process using diluted basic ammonia agents. Moreover, the selective precipitation of germanium through tanic acid usage was investigated. The applied investigated experimental parameters in this step involves the pH pf solution, kind of basic agent, temperature and the amount of tanic acid. At the beginning, the increment of pH to 5.5 and using the diluted acid 800C ended in 98% and 89% precipitation of iron and germanium respectively. This research indicates that 0.2 tanic acid (in 100 ml of solution) by a pH of 1.5 can precipitate the 91% of germanium content of the solution selectively.
  9. Keywords:
  10. Hydrometallurgical Zink Residues ; Washing Process ; Germanium Recovery ; Sulfuric Acid Leaching ; Precipitation by Tannic Acid

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