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Synthesis and Characterization of Graphene-based Material and Investigation of its Adsorption Properties for Radioactive Waste

Tayyebi, Ahmad | 2016

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  1. Type of Document: Ph.D. Dissertation
  2. Language: Farsi
  3. Document No: 48639 (46)
  4. University: Sharif University of Technology
  5. Department: Energy Engineering
  6. Advisor(s): Outokesh, Mohammad
  7. Abstract:
  8. Nuclear power is a prominent alternative of fossil fuels that can effectively solve global warming, acid rains and other consequences of air pollutions, caused by combustion. Despite such obvious advantage, this highly compact form of energy suffers from a big problem corresponding to its nuclear waste. Graphene oxide (GO), a lamellar material with wide range of surface functional groups such as epoxy (C-O-C), hydroxyl, and carboxyl offers large surface area as well as high sorption capacity for the metallic cations. This thesis study presents a supercritical, and co-precipitation synthesis of magnetite- graphene oxide (M-GO) in which Fe3O4 nanoparticles are simultaneously formed, surface modified and decorated on the surface of the reduced graphene oxide. Simulation by density functional theory which was performed using M06-2x/cc-pVDZ level of theory indicates that upon adsorption of Fe3O4 cluster on the graphene, the overall charge on the graphene surface becomes about 0.0236e negative, indicating charge transfer from Fe3O4 cluster to the graphene surface. Instrumental and chemical analyses exhibited formation of strong bonds between Fe3O4 and graphene, through C-O-Fe and C-Fe bridges. Based on this data the study puts forward a formation mechanism for M-RGO. The Langevin equation was successfully applied for estimation of size of Fe3O4 nanoparticles in M-GO hybrid, with maximum error of 17.5%. The study put forward a formation mechanism for M-GO, based on instrumental analyses. The adsorption behaviors of the M-RGO towards Co2+ and Sr2+ ions represented appreciably higher uptake capacity than magnetite- graphene oxide (M-GO), a zero zeta potential point at pHs≈2, endothermic and spontaneous adsorption, and a fast kinetics that was controlled by chemical reaction between ions and surface active sites of Fe3O4 nanoparticles. The material also showed, a good reusability, a quick elution by 0.5 mol.dm-3 HCl, and most importantly, simple separation from the solution by a magnet. Overall, the M-RGO appears to be a promising alternative for current magnetite-graphene oxide hybrids in adsorption of heavy metal ions
  9. Keywords:
  10. Strontium ; Cobalt ; Thorium ; Supercritical Fluid ; Magnetite-Graphene

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