Browsing by Author "Yee, P"
Now showing 1 - 2 of 2
Results Per Page
Sort Options
- ItemGeopolymers as candidates for low/intermediate level highly alkaline waste.(Materials Research Society, 2006-11-27) Perera, DS; Vance, ER; Kiyama, S; Aly, Z; Yee, PGeopolymers should be serious waste form candidates for intermediate level waste (ILW), insofar as they are more durable than Portland cement and can pass the PCT-B test for high-level waste. Thus an alkaline ILW could be considered to be satisfactorily immobilised in a geopolymer formulation. However a simulated Hanford tank waste was found to fail the PCT-B criterion even for a waste loading as low as 5 wt%, very probably due to the formation of a soluble sodium phosphate compound(s). This suggests that it could be worth developing a ìmixedî GP waste form in which the amorphous material can immobilise cations and a zeolitic component to immobilise anions. The PCTñB test is demonstrably subject to significant saturation effects, especially for relatively soluble waste forms.
- ItemSynthesis and characterization of functionalized silica-based nanohybrid materials for oxyanions adsorption(American Chemical Society, 2010-06-01) Karatchevtseva, I; Astoux, M; Cassidy, DJ; Yee, P; Bartlett, JR; Griffith, CSThis study investigates the structural evolution of a series of nanohybrid powders and coatings synthesized by direct co-condensation of amino-functionalized alkyltrialkoxysilanes and tetraalkoxysilanes with an aromatic carboxylic acid (trimesic acid, TMA) as a structure directing agent. Fourier transform infrared spectroscopy (FTIR) and 13C CP-MAS NMR results have suggested the formation of secondary (−CO−NH−) amide linkages upon interaction of TMA with the amino functionalized silane thus creating a “scaffold” around which the silica network is formed and also assisting in more homogeneous distribution of nitrogen sites within the nanohybrid structure. Functionalized silica powders were investigated for their potential to remove toxic oxyanions from mildly acidic or basic solutions. The uptake of Mo(VI), Se(VI), and Cr(VI) oxyanions was investigated as a function of the nanohybrid composition, oxyanion concentration, and solution pH using laser diffraction particle sizing, gas adsorption, and various spectroscopic techniques. The adsorption data obtained for Mo and Se could be adequately described by Langmuir adsorption isotherms, while the Freundlich isotherm is employed to fit the adsorption data for Cr. An easily accessible processing window (of pH, aging time, etc.) has been identified allowing production of continuous and uniform thin nanohybrid coatings on silicon and glass substrates. These coatings were tested as chemical barriers against Mo leaching from specially prepared Mo-doped glass. Leaching studies were conducted over 200 days in water at 90°C and the Mo leaching from coated and uncoated samples compared. © 2010, American Chemical Society