[show abstract][hide abstract] ABSTRACT: Structural (crystallinity), textural (pore volume, V p , specific surface area, S BET , pore size distribution, PSD) and adsorption characteristics of bleached flax fibres and cotton fibres have been determined using equilibrium adsorption of nitrogen, water, chlorhexidine diacetate (CHX) and methylene blue (MB), adsorption-desorption kinetics of MB and CHX, X-ray diffraction, thermogravimetry, differential 10 scanning calorimetry (DSC) and DSC cryoporometry. Air-dry, degassed, wetted (RH 95%), swollen (24 h in water) and air-dried and heated (120 o C for 1 h) fibres were studied. Flax fibres have higher crystallinity, adsorption capacity (MB, CHX, water), and smaller MB desorption than cotton fibres. Cotton fibres have larger V p value (nitrogen adsorption) and the S BET,N2 similar to that of flax. Water vapour adsorption is higher on flax since the adsorbed water volume is V p,w = 0.19 and 0.14 cm 3 /g for flax 15 and cotton, respectively, at RH 95%. Wetted fibres are characterised by V p,w larger by an order of magnitude than V p,N2 for degassed samples because of swelling effect. However, nanopores at radius R < 1 nm are practically absent in all samples studied regardless of the characterisation technique. The adsorption of MB and CHX on flax fibres is much larger than that for cotton fibres. The specific surface area determined from MB adsorption is 51 m 2 /g (close to S BET,w estimated from water adsorption but 20 larger than S BET,N2) and 8 m 2 /g (much smaller than S BET,N2 and S BET,w) for flax and cotton fibres, respectively.
[show abstract][hide abstract] ABSTRACT: Morphological, structural, adsorption, and catalytic properties of highly disperse titania prepared using sulfate and pyrogenic methods, and fumed titania-containing mixed oxides, were studied using XRD, TG/DTA, nitrogen adsorption, (1)H NMR, FTIR, microcalorimetry on immersion of oxides in water and decane, thermally stimulated depolarization current (TSDC) and catalytic photodecomposition of methylene blue (MB). Phase composition and aggregation characteristics of nanoparticles (pore size distribution) of sulfate and pyrogenically prepared titania are very different; temperature dependent structural properties are thus very different. Catalytic activity for the photodecomposition of MB is greatest (per gram of TiO(2) for the pure oxide materials) for non-treated ultrafine titania PC-500, which has the largest S(BET) value and smallest particle size of the materials studied. However, this activity calculated per m(2) is higher for PC-105, possessing a much smaller S(BET) value than PC-500. The activity per unit surface area of titania is greatest for the fumed silica-titania mixed oxide ST20. Calcination of PC-500 at 650 degrees C leads to enhancement of anatase content and catalytic activity, but heating at 800 and 900 degrees C lowers the anatase content (since rutile appears) and diminishes catalytic activity, as well as the specific surface area because of nanoparticle sintering.
Journal of Colloid and Interface Science 12/2008; 330(1):125-37. · 3.17 Impact Factor