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Solvent Extraction of Leaching Solution Containing Rare Earth Elements from Apatite Concentrate

Shahini, Shahryar | 2018

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 51602 (07)
  4. University: Sharif University of Technology
  5. Department: Materials Science and Engineering
  6. Advisor(s): Yoozbashizadeh, Hossein
  7. Abstract:
  8. In this research, Chadormalou apatite concentrate was dissolved by 40% nitric acid and a solid to liquid ratio of 0.4 at 70 ° C for 2 hours, and its rare earth elements were dissolved. Recovery percents for Cerum, Neodymium and Lanthanum were 62.4, 48.7 and 49.6, respectively. In the solvent extraction step, the effect of HQ concentration as extractant, pH, temperature and phase ratio on the concentration of the adsorbed elements in organic phase, extraction percentage, distribution ratio and separation factor of rare earths were investigated. Organic solutions containing HQ in the kerosene alone pricipitated after contacting with PLS solutions. In order to prevent HQ pricipitation in the experiments, 25% vol. of TBP was added to all organic solutions. To investigate the effect of HQ concentration, concentrations of 0-0.01 molar of HQ were contacted with PLS solutions at pH= -0.55, -0.1, and 0.25. In order to investigate the effect of pH, organic solution with centration of 0.0075 M HQ and 25% volumetric TBP were contacted with PLS solutions at pH= -0.55, -0.3, -0.1, 0.1, 0.2 and 0.25. The pH of the aqueous solutions was increased by dilute ammonia solution. To investigate the effect of temperature, organic solution with a concentration of 0 0075 M HQ and 25% vol. TBP was contacted with the PLS solution at 25, 35 and 45 ° C. To investigate the effect of organic to aqueous ratio, the same organic solution and phase ratios of 1, 2 and 3 was used for solvent extraction. The results of these experiments showed that increasing in HQ concentration increased the extraction percent, distribution coefficient and rare earths’ concentrations in the organic phase. Increasing the concentration of HQ has also reduced the separation factor of rare earth elements. In general, increasing the pH from -0.55 to -0.1 decreases the extraction of rare earths and from -0.1 to -0.25 increases the extraction of the rare earths. In addition, increasing pH increases the calcium extraction. Increasing the temperature reduced the extraction of rare earths. Using the experimental data, the enthalpy value of the adsorption reaction for Cerium, Neodymium and Lanthanum was calculated to be -1.73, -2.14, and -4.84 kJ/mol, respectively. Increasing the organic/aqueous ratio has a positive effect on extraction of rare earths, although it decreases the concentration of rare earths in the organic solution. Finally, an equation for the reaction of extraction of rare earths has been proposed. Using the slope analysis method, stoichiometric coefficients of these equations are estimated for each of the rare earths. Stripping investigation has shown that there is potential for stripping of rare earths and calcium can be washed out of aqueous solution
  9. Keywords:
  10. Solvent Extraction ; 8-Hydroxyquinoline ; Tri-butyl Phoaphate ; Rare Earth Element ; Leaching ; Nitric Acid

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