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Fabrication of Magnetite-based Superparamagnetic Nanoadsorbents Coated with Organic Extractants

Firouzi, Farzad | 2024

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  1. Type of Document: Ph.D. Dissertation
  2. Language: Farsi
  3. Document No: 57371 (07)
  4. University: Sharif University of Technology
  5. Department: Materials Science and Engineering
  6. Advisor(s): Nemati, Ali; Sadrnezhaad, Khatiboleslam
  7. Abstract:
  8. In this study, the fabrication of magnetic nanoadsorbents functionalized with organic extractant compounds has been investigated for potential applications in the hydrometallurgical extraction of metal ions. For this purpose, spherical superparamagnetic magnetite nanoparticles of about 15 nm size were synthesized via the chemical co-precipitation method. Then, an intermediate stearic acid single layer was coated on the surface of nanoparticles, aiming to improve stability and facilitate the subsequent functionalization with organic extractants. The fabrication procedure of nanoadsorbents was completed by physical adsorption of D2EHPA, TBP, and TOA compounds on the intermediate coating. The quality and different physical and chemical properties of nanoadsorbents were evaluated utilizing various characterization techniques. The results of statistical analyses indicated that the adsorption of all three extractants on the stearate coating follows the Langmuir isotherm model. At 25 ˚C, the suitable temperate for fabricating nanoadsorbents, the Langmuir constant KL of 3.718, 4.361, and 9.853 L.mol-1 and the maximum adsorption capacity qm of 400.1, 368.3, and 522.3 mg.g-1 have been obtained for D2EHPA, TBP, and TOA, respectively. According to thermodynamic studies, the standard adsorption enthalpy and entropy changes were determined to be -17.30 kJ.mol-1 and -46.81 J.(mol.K)-1 (for D2EHPA), -22.07 kJ.mol-1 and -61.59 J.(mol.K)-1 (for TBP), and -25.72 kJ.mol-1 and -67.17 J.(mol.K)-1 (for TOA), respectively, implying the exothermic nature of the processes and the decrement of randomness in the studying adsorption systems. Furthermore, the fabrication of nanoadsorbents in the D2EHPA+TBP and TOA+TBP binary systems was investigated to benefit the synergistic effects of the mixed extractants in the future. According to the results, competitive adsorptions of extractants in both binary systems follow the modified Langmuir isotherm model. The corresponding optimal interaction factors of ηD2EHPA = 0.367 and ηTBP = 0.863 for the D2EHPA+TBP, and ηTOA = 1.090 and ηTBP = 0.938 for the TOA+TBP binary systems have been acquired. Based on the resultant adsorption parameters, the surface coverage of extractants on the nanoadsorbents can be determined and accurately adjusted, which is essential for exploring the mechanism of hydrometallurgical extraction of metals
  9. Keywords:
  10. Diethyl Hexyl Phosphoric Acid (DEHPA) ; Tri-butyl Phoaphate ; Tri-N-Octylamine ; Magnetic Nanoadsorbent ; Stearic Acid ; Organic Extractant ; Superparamagnetic Nanoparticles

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