Development of chemically engineered porous metal oxides for phosphate removal.

In this study, the application of ordered mesoporous silica (OMS) doped with various metal oxides (Zr, Ti, Fe and Al) were studied for the removal of (ortho) phosphate ions from water by adsorption. The materials were characterized by means of N(2) physisorption (BET), powder X-ray diffraction (PXRD) and transmission electron microscopy (TEM). The doped materials had surface areas between 600 and 700 m(2)g(-1) and exhibited pore sizes of 44-64 Å. Phosphate adsorption was determined by measurement of the aqueous concentration of orthophosphate using ultraviolet-visible (UV-vis) spectroscopy before and after extraction. The effects of different metal oxide loading ratios, initial concentration of phosphate solution, temperature and pH effects on the efficiency of phosphate removal were investigated. The doped mesoporous materials were effective adsorbents of orthophosphate and up to 100% removal was observed under appropriate conditions. 'Back extracting' the phosphate from the doped silica (following water treatment) was also investigated and shown to have little adverse effect on the adsorbent.

Swelling of ionic and nonionic surfactant micelles by high pressure gases.

The influence of different solvent environments on the size, shape, and characteristics of surfactant micelles of Pluronic F127 and CTAB was investigated by small-angle neutron scattering (SANS). SANS experiments were undertaken on dilute micellar surfactant solutions of F127 and CTAB that between them were exposed to liquid and supercritical carbon dioxide, liquid propane, ethane, and heptane under various pressures and temperatures. Swelling of the surfactant micelles could be directly related to the solubility of the solvents within the micelles, especially within their cores. Carbon dioxide produced the largest swelling of the Pluronic F127 micelles, compared to propane and ethane, which mirrors the solubility of the gases in the PPO core of the micelles. Conversely, the extent of swelling of the cores of CTAB micelles was greater with propane compared to carbon dioxide, which again relates to the solubility of the solvents in the alkane core of the CTAB micelles.

Unusual magnetism in templated NiS nanoparticles.

Nanostructured NiS was prepared by inclusion into anodic alumina templates. The resultant particles were found to be stoichiometric and highly crystalline. The particles displayed small particle superparamagnetism, and a low temperature (at 48 K (T(sg))) spin-freezing phenomenon (a spin-glass) and higher temperature (170 K) thermal blocking of small particle magnetic moment fluctuations were both observed for the first time for a sulfide material. Very unusually, these NiS materials are quite distinct from antiferromagnetic nanoparticulate sulfide materials, as they display a high temperature ferromagnetic-like phase. The saturation magnetization, the remanent magnetization, the coercivity and the ferromagnetic mass susceptibility were measured as 0.58 emu g( - 1) (at 100 K), 0.19 emu g( - 1), 219.5 Oe (at 170 K) and ∼ 900 × 10( - 6) emu Oe( - 1) g( - 1) respectively and these are consistent with a moderately strong ferromagnetism. The materials had an unexpectedly high Curie temperature of 390 K. The decrease of the saturation magnetization value at 30 K suggests that the ferromagnetic response is a surface phenomenon and the high coercivity of the paramagnetic component well above T(sg) suggests that the core can be described as superparamagnetic.

Supercritical fluid swelling of liquid crystal films.

The influence of liquid and supercritical carbon dioxide and liquid propane on the structural properties of both ionic and nonionic surfactant-based liquid crystal films is discussed in this paper. Swelling of the films, measured using in situ small-angle neutron scattering (SANS), was found to be dependent on the solubility of the propane/carbon dioxide in the micelles of the respective liquid crystals. Additionally, under certain pressure conditions the structural properties of some of the films were observed to change, ultimately leading to a loss of order in the micellar arrays of the liquid crystals.

Pore size engineering in mesoporous silicas using supercritical CO2.

In this paper we investigate the use of supercritical carbon dioxide (sc-CO(2)) for synthesizing calcined mesoporous silicas with tunable pore sizes, wall thickness, and d spacings. Small angle neutron scattering was used to probe the controlled swelling of the triblock copolymer surfactant templating agents, P123 (PEO(20)PPO(69)PEO(20)), P85 (PEO(26)PPO(39)PEO(26)), and F127 (PEO(106)PPO(70)PEO(106)), as a function of CO(2) pressure. The transition from the liquid crystal phase to the calcined mesoporous silicas, formed upon condensation and drying, was also studied in detail. Powder X-ray diffraction, transmission electron microscopy, and nitrogen adsorption techniques were used to establish pore diameters, silica wall widths, and the hexagonal packing of the pores within the calcined silicas. Using a direct templating method, the diameters of mesopores and the spacing between the pores could be tuned with a high level of precision. The swelling process was observed to have no detrimental effects on the quality of silica formed, a distinct advantage over conventional swelling techniques, and all of the silicas synthesized in this study were highly ordered over distances of at least 2000 A.