Loading...

Experimental Study and Modelling of Ultrafine Particles Formation by Using the Supercritical Fluids

Karimi Sabet, Javad | 2012

2141 Viewed
  1. Type of Document: Ph.D. Dissertation
  2. Language: Farsi
  3. Document No: 43061 (06)
  4. University: Sharif University of Technology
  5. Department: Chemical and Petroleum Engineering
  6. Advisor(s): Gotbi, Cyrus; Khanchi, AliReza; Farhadpour, Farhad; Dorkoosh, Farid
  7. Abstract:
  8. In this research, we focused on demonstration of features and advantages of supercritical fluids technology to formation of fine particles (nano and micro scales) from bulk materials (solid) and synthesized metal oxides nanoparticles. Therefore, using two different fluids, carbon dioxide and water, and two completely different methods, the Rapid expansion of supercritical solution and supercritical hydrothermal, were used to produce fine particles of drug (acetaminophen) and nano metal oxide (zirconium dioxide and bismuth ferrite). The summary of this research are as follows:1. The solubility of acetaminophen in SuperCritical-Carbon Dioxide (SC-CO2) with and without menthol as a cosolvent was measured at various temperatures (313, 328 and 343) K, and within pressures ranging from (10 to 25) MPa. The menthol has chiral isomers with different melting points. Therefore, the effects of both menthol (I) with a lower melting point and menthol (II) with a higher melting point, as cosolvents on the solubility of acetaminophen in SC-CO2, were studied. The experimental data collected in this work were obtained using a static flow apparatus. Finally, the data reduction for the solubility of cetaminophen in SC-CO2 in the presence and in the absence of menthol (I) and menthol (II), were correlated using the semi-empirical equations proposed by Chrastil and Mendez-Santiago & Teja (acetaminophen without cosolvent) and the modified Mendez-Santiago & Teja (acetaminophen with menthol as a cosolvent). The results obtained from these equations were in good agreement with the experimental data.
    2. Fine particles of acetaminophen were produced by Rapid Expansion of Supercritical Solution (RESS). The experiments were conducted to investigate the effects of extraction temperature, extraction pressure, pre-expansion temperature and post-expansion temperature on particles size and morphology of acetaminophen particles. The characterization of the particles was determined by Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), and Liquid Chromatography/Mass Spectrometry (LC-MS) analysis. The average particle size of the original acetaminophen was 20.8 μm, while the average particle size of acetaminophen after micronization via the RESS process was 0.46 μm (average of all experiments). Moreover, the morphology of the processed particles changed to spherical and regular while the virgin particles of acetaminophen were needle-shape and irregular. Response surface methodology (RSM) was used to optimize the process parameters. The extraction temperature, 347 K; extraction pressure, 12 MPa; pre-expansion temperature, 403 K and post-expansion temperature, 322 K was found to be the optimum conditions to achieve the minimum average particle size (129 nm) of acetaminophen. 3. Supercritical Water Hydrothermal Synthesis (ScWHS) of Zirconium dioxide and bismuth ferrite nanoparticles was conducted using a batch type reactor and the effect of operating parameters such as reaction temperature, reaction time, primary concentration of zirconium nitrate solution and the initial aqueous solution pH on the production of zirconium dioxide nanoparticles were investigated. A mathematical model (experimental) was used to estimate specific surface area (SSA) in the range of experimental condition using RSM. Moreover, the effect of parameters and interaction between the parameters on the SSA was demonstrated. The optimal values of the variables to achieve the highest level of SSA (141.25 m2 g-1) obtained by empirical models such as reaction temperature, 405 °C; reaction time, 1.38 h; primary concentration of zirconium nitrate solution, 0.19 M and initial aqueous solution, pH 1.21. Characterization of synthesized particles were performed by X-Ray Diffraction (XRD), TEM, Induced Couple Plasma (ICP) and Brunauer-Emmett-Teller (BET) measurements. Additionally, the nanoparticles of BiFeO3 were synthesized from bismuth nitrate and iron nitrate according to the capability of batch reactor system. 4. In order to better understand the rapid expansion of supercritical solution, the hydrodynamic simulations of RESS process by using Fluent software was performed. Using simulation and modeling, the effects of operating and computational parameters such as expansion system geometry, fluid type, equations of state, adiabatic and isothermal boundary condition on the hydrodynamics, supersaturation and nucleation for both conventional expansion device, capillary tube and nozzle, were investigated.
    Present study is considered to be an attempt to identify better use of supercritical fluid in order to produce nanoparticles and advanced materials which are required for industry
  9. Keywords:
  10. Nanoparticles ; Computational Fluid Dynamics (CFD) ; Supercritical Hydrothermal ; Supercritical Solution Rapid Expansion ; Acetaminophen Solubilities ; Menthol ; Zirconium Dioxide ; Bismuth Ferrite

 Digital Object List

  • محتواي پايان نامه
  •   view