Leaching, Solvent Extraction and Separation of Cerium, Lanthanum, Neodymium Rare Earth Elements from Apatite Concentrate of Chadormalu Mine

Ferdowsi, Ali | 2017

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  1. Type of Document: Ph.D. Dissertation
  2. Language: Farsi
  3. Document No: 49679 (07)
  4. University: Sharif University of Technology
  5. Department: Materials Science and Engineering
  6. Advisor(s): Youzbashizadeh, Hossein
  7. Abstract:
  8. Waste of iron ore concentrate production plant of Chadormalu contains apatite mineral. The content of rare earths elements (REEs) in apatite concentrate of Chadormalu is about one percent. However, considering apatite deposite and production rate, extraction of REEs from apatite is one of valuable source for production of REEs. Lanthanum, cerium and neodymium which have most application amonge other REEs and have the highest frequency in the apatite. Due to their similar physical and chemical properties, it is difficult to separate individual rare earths from each other and the separation process are too complicated. In this study, in order to extract REEs from apatite, it was leached by nitric acid solution and the effects of main process parameters including acid concentration, solid to liquid ratio and leaching time were investigated and it was found nitric acid concentration and solid to liquid ratio have more effect on the leaching recovery while effect of leaching time is not significant. The optimum condition of leaching were obtained in 24% nitric acid, solid to liquid ratio of 1:20 and 10 minutes as leaching time. Kinetics of REEs dissolution is also investigated and diffusion trough ash layer was determined as controlling mechanism of leaching and the activation energy of leaching was determined equal to 6.54 kj/mol. Solvent extraction of REEs were carried out using tributhyl phosphate (TBP), di-2-ethylhexyl phosphoric acid (D2EHPA) and the mixture of these extractants diluted in kerosen. Effects of different parameters including extractant’s concentration, nitrate ion concentration and pH on extraction recovery, distribution ratio and separation factors of REEs were investigated. In extraction with TBP, maximum value of extraction precentages of REEs were observed in TBP concentration of 1.04 mol/L, nitrate ion concentration of 6.2 mol/L and pH value of 0.1 equal to 67.3, 74.1, 84.8 and 70.3 for La, Ce, Nd and Y, respectively. TBP was found to be suitable for separation of neodymium from other rare earth elements. In solvent extraction by D2EHPA, maximum extraction precentage of REEs were observed in extractant concentration, nitrate ion concentration and pH value equal to 1.04 mol/L, 6.2 mol/L and 0.1, respectively. In this condition the value of precent extractaions for La, Ce, Nd and Y were 100, 67.9, 100 and 70.9, respectively. Separation of yttrium and lanthanum from other REEs is possible using D2EHPA. The extraction equilibria were also studied. Furthermore, synergistic effect in extraction of REEs by mixtures of TBP and D2EHPA is investigated and antagonistic extraction were obsereved in studied conditions. The separation factors of REEs decreases by increasing nitrate ion concentration while by increasing pH, the separation factors for light rare earths decreases and separation factor for yttrium and other rare earhts increases. Increasing concentration of organic phase have an effects similar to effect of increasing pH. The ratio of TBP to D2EHPA in organic phase has no effect on separation factors of light REEs while increasing TBP concentration results a decrease in separation factors of yttrium and other REEs. Finally, according to experimental results a process for extraction and separation of rare earths from apatite is presented
  9. Keywords:
  10. Leaching ; Cerium ; Lanthanum ; Solvent Extraction ; Separation ; Tri-butyl Phoaphate ; Diethyl Hexyl Phosphoric Acid (DEHPA) ; Neodymium Oxide ; Rare Earth Element

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