Thesis

Nanoparticulate silica : new absorbents for PTE extraction from aqueous media and VOCs from indoor air

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Awarding institution
  • University of Strathclyde
Date of award
  • 2012
Thesis identifier
  • T13168
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Abstract
  • Mesoporous silica samples were synthesised and used as sorbents for VOCs. 4 VOCs were extracted from polluted air streams; toluene, ethylbenzene, cumene and dichlorobenzene. Extraction efficiencies were compared to a commercially available sorbent (Tenax TA) at different relative humidity (25 or 80 % RH) and at different flow rates (25, 50, 100, 150 or 200 cm3 min-1). Silica adsorbents showed efficient performance at low RH, whereas Tenax-TA performed better at high RH. A room temperature method of MCM-41 was developed producing a silica product which exhibited an ordered hexagonal mesostructure, large pore volume (up to 0.99 cm3/g), and unusually large pore size (up to 6.7 nm). Diethylenetriamine functionalised MCM-41 was used to extract Pb (II) ions from solution and showed significant adsorption capacity (up to 1000 μmol g-1). The sorbent was regenerated, and Pb (II) ions recovered, allowing reuse of the sorbent. Mercaptopropyl (MP) functionalised MCM-41 showed extremely efficient and selective adsorption for the removal of Hg (II) ions from water samples doped with a wide range of metal ions. Additionally a method was developed to remove Hg (II) ions from loaded MP-MCM-41. Finally, speciation and separation of Cr (VI) and Cr (III) ions from aqueous solutions was achieved using amino-propyl functionalised MCM-41. The maximum adsorption capacity at 111.1 mg g-1 was calculated according to the Langmuir isotherm model. Silica materials with different pore sizes were used to extract Cr (VI) ions from water and the results were examined using kinetics models. Different adsorption behaviours were observed; of which the most significant conclusion was that MWD-samples of MCM-41 had a 2 step adsorption process; the first related to the diffusion of ions through the liquid to the sorbent surface and the second being the diffusion of ions through the large functionalised pores which explains the increased adsorption performance of MWD-MCM-41.
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  • Strathclyde theses - ask staff. Thesis no. : T13168
DOI
Date Created
  • 2012
Former identifier
  • 947566

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