Removing dye Rhodamine B from aqueous medium via wet peroxidation with V-MCM-41 and H2O2

A new heterogeneous Fenton-like system, consisting of V-MCM-41 catalyst and hydrogen peroxide, was proved to be effective in removing recalcitrant dye Rhodamine B (RhB) in aqueous solutions. V-MCM-41 was prepared following a direct hydrothermal procedure with tetraethyl silicate and ammonium metavanadate as precursor. The mesoporous structure has been characterized by XRD, and the specific surface area was determined as x m2 g−1 according to BET method. The catalytic reaction can proceed in a relatively wide pH range from acidic to alkaline. And the visible light irradiation cannot promote the reaction process. In addition, the mechanism implication for V-MCM-41 as a Fenton-like catalyst has been discussed.

Preparation of Silica Microcapsules Containing Phase Change Paraffin Wax

This paper deals with the preparation of silica microcapsules containing phase change paraffin wax for thermal energy storage and the determination of their thermal properties. The spherical microcapsule samples respectively containing two types of paraffin wax (with peak melting temperature of 29.3 °C (type P1) and 35.5 °C (type P2), and the fusion heat of 140 J/g (type P1) and 153 J/g (type P2)) as core and chemically and thermally stable silica as shell, were prepared from O/W emulsion systems in the presence of polyvinyl alcohol as stabilizer, and sorbitan monooleate and poilyoxyethylene(20) sorbitan monooleate as emulsifiers. The silica shell formed via hydrolysis and condensation from tetraethyl silicate with acetate acid as catalyst. The fusion heat of the two samples is 101 J/g and 112 J/g respectively. Property of adaptable temperature of the as-made microcapsules is measured through a self-made cell model. The maximum difference between the temperature of the cell with PCM wallpaper and that of the cell with controlled wallpaper is about 1.1 °C.

Direct Process Metal Alkoxides as Ceramic Precursors

ABSTRACTMetal alkoxides have great promise as oxide ceramic precursors. Direct manufacture from the metal and the alcohol permits the production of high purity materials and of those alkoxides which cannot be easily obtained by other routes. Examples which are of great interest to ceramics are the alkoxides of silicon, aluminum, magnesium and yttrium.Currently, only tetraethyl silicate is produced in large volumes by the direct route, employing a catalytic continuously fed process, yielding a distilled product. The reactivity of silicon, aluminum, magnesium and yttrium is governed by the metal surface state and activation and varies with different catalysts and alcohol chain length and branching.The major use of tetraethyl silicate is in partially hydrolyzed form as binder for precision casting molds and zinc-rich primer coatings. Judicious choice of alkoxide ligands allows the manufacture of soluble or liquid Si, Al, Mg, and Y derivatives. These are especially suitable for molecular doping and mixing in the manufacture of yttriastabilized zirconia, mullite, spinel, cordierite and other oxide ceramic precursors.