Dissertation > Excellent graduate degree dissertation topics show

Preparation and Performance Research of Znmgal-Layered Double Hydroxides and Composites

Author: LiNa
Tutor: ZhangWeiDe
School: South China University of Technology
Course: Physical and chemical
Keywords: Layered double hydroxides (LDHs) Hydroxide Adsorption Hierarchicalheterostructure Photocatalysis
CLC: O611.4
Type: Master's thesis
Year: 2012
Downloads: 202
Quote: 0
Read: Download Dissertation

Abstract


Layered Double Hydroxides (LDHs) are an important class of lamellar functionalmaterials, which consist of Hydrotalcite (HT) and Hydrotalcite-Like Compounds (HTLCs).They have a wide range of applications in many important industry fields, such as medicine,catalysis, adsorption, biology and environmental protection and so on, because of theirsuper-molecule structure, the anion-exchange ability and the controllable size. However, thenaturally occurring example of this class of materials is the mineral hydrotalcite,Mg6Al2(OH)16CO3·4H2O, containing carbonate ions in between the layers and the amount isvery limited. The above drawbacks of natural LDHs impose restrictions on the use of someaspects. Developing artificial methods to design novel LDHs is the key to make full use ofthem, which not only has important academic significance but also has practical value. Inthis dissertation, with the characteristics of exchangeable cations in the layers, weintroduced Zn2+into LDHs since its size matches with that of Mg2+. So, Mg2+can bepartially substituted by Zn2+in the process of coprecipitation, and the ternary threedimensional (3D) ZnMgAl-LDHs microspheres were prepared. In consideration of the largesurface area of the3D LDHs microspheres, the adsorption properties of the preparedsamples were characterized. Meanwhile, with the “edge effect”, the lattice matches betweenZnO and ZnMgAl-LDHs, the heterostructures consist of uniform ZnO nanoparticles orderlystanding at the edges of two-dimensional (2D) surfaces of ZnMgAl-LDHs nanoplatelets.Their application for degradation of organic dyes was also studied. The main points of thisdissertation are summarized as follows:Firstly,3D ZnMgAl-LDHs microspheres consisting of nanoplates were synthesized atlow temperature using urea as a precipitator. This preparation method does not use anyorganic solvent as reaction media. The as-prepared LDHs were characterized by XRD, TG,AAS, SEM, TEM and BET. The possible formation mechanism for the architectures wasdiscussed. It is proposed that the introduction of Zn2+played a key role in the formation ofthe microsphere structure. The adsorption properties of the as-prepared sample wereevaluated by adsorbing methyl orange. The3D LDHs microspheres show high adsorptioncapacity. The optimum pH value for the adsorption of MO onto LDHs is3.0. The adsorption process can be well described by the pseudo-second-order kinetic model and the adsorptionisotherm matches Langmuir model well. In addition, the LDHs microspheres can berecovered and used repeatedly.Secondly, modification of LDHs microspheres by ZnO nanoparticles withheterostructure was successfully conducted using glycol-water mixed solvents as reactionmedia and NH3·H2O as a pH adjustor. The effect of solvent and the pH value on theheterostructures were studied. The photocatalytic activity of the as-prepared composites wasevaluated by degradation of phenol in water under ultraviolet light irradiation. TheZnO/LDHs show enhanced photocatalytic activity when the molar ratio of the two differentcomponents were optimized, which can be attributed to the large surface area of LDHs andthe better dispersity of ZnO nanoparticles. With increasing the ZnO content continuously,the photocatalytic activity of the ZnO/LDHs composite photocatalyst decreases reverselybecause the aggregation of ZnO nanoparticles is prejudicial to separation of thephotoinduced carriers efficiently.The investigation indicates that degree of oxide coverage over other materials plays animportant role on photocatalytic performance of the catalysts. The coupling ofsemiconductors with LDHs can overcome its weakness effectively, and enhance itsphotocatalytic activity. The results reported in this study provide insight to construct othercomplex metal oxides with LDHs to form composite photocatalysts. The as-preparedphotocatalysts exhibit excellent photocatalytic activity for the degradation of the organicdyes. Therefore, it is promising to degrade organic pollutants in the field of wastepurification.

Related Dissertations

  1. Study on the Synthetic Process of Vat Pink R,TQ616.2
  2. Research on the Modified Methods of Fly Ash for Ammonia-nitrogen Wastewater Treatment,X703
  3. Chemical Treatment of Coal Slag and Production of Chemical Products,X705
  4. Preparation of Metal @ TiO2 Core @ Shell Nanoparticles and SERS Research,TB383.1
  5. Study on Enrichment of Low-concentration Methane by Adsorption,O647.3
  6. Study of Crystallization Process of Magnesium Hydroxide,TQ132.2
  7. Chemical Reaction Hysteresis Induced by Capillary Condensation Within the Catalyst Pellets,O643.36
  8. Deactivation Mechanism of Cation Resin Catalyst for Esterification of Acetic Acid and Isopropanol,O643.3
  9. Preparation and Morphology Control of Amino Resin with Micropores and Its Performance of CO2 Adsorption,O647.31
  10. Treatment of Concentrated Ammonia Wastewater by Stripping-absorption Combined Process,X703
  11. Electrostantic Assembled Glass Fiber/Multiwall Carbon Nanotubes Hybrids Reinforced Polymer Composites,TB383.1
  12. Preparation of Hyperdispersant and the Influence of Its Structure to the Properties of UPR/ATH Composites,TB324
  13. Preparation of Platinum Loaded TiO2 Nanotubes and Its Photocatalytic Performance,TB383.1
  14. Supported Co-doped TiO 2 photocatalyst Preparation and Research,O643.36
  15. Influence of Aromatic and Nitrogen Compounds on Desulfurization onto Activated Carbon,TE624.5
  16. Wet Chemical Preparation of 1-D β-FeOOH Nanorods and Nanorod Arrays as Well as Their Photocatalytic Property,TB383.1
  17. Study on UV Spectral Characteristics of Alkylphenol Ethoxylate and Its Affinity Performance to Silk/Cotton,TS195.2
  18. Preparation and Performances of Polypropylene/LDHs Composites,TB332
  19. Metal Nanoparticles on Layered Double Hydroxide: Highly Active Catalyst for Aerobic Oxidation of Alcohols,O643.32
  20. Study on the Preparation of Functionalized Graphene and Adsorption of Heavy Metal and Methylene Blue,O647.3
  21. Immobilized nano- TiO 2 situ preparation and photocatalytic properties of,O643.36

CLC: > Mathematical sciences and chemical > Chemistry > Inorganic Chemistry > Chemical elements and inorganic compounds > Inorganic synthetic chemistry
© 2012 www.DissertationTopic.Net  Mobile