Application Of Silicalite-2Zeolite In Water Treatment

Silicalite-2zeolites were successfully synthesized by steam-assisted dry-gel conversion technique with TBAOH (tetrabutylammonium hydroxide) as structural directing agent and Ludox as silica source. The products were characterized by X-ray diffraction (XRD), N2physical adsorption and Scanning electron microscopy (SEM). XRD pattern and SEM images showed that the silicalite-2nanocrystals with a particle size of about70-90run. The result of adsorption of p-nitrophenol (PNP) onto the samples revealed that the adsorption of p-nitrophenol in aqueous solution is accorded with Freundlich and Langmuir equations. Freundlich equation is suited to describing the adsorpting reaction. Furthermore, the pseudo-second-order kinetic equation can better describe the adsorption kinetics. The adsorption for p-nitrophenol on nanosized silicalite-2zeolites were proved to be a spontaneous, exothermal process with increasing entropy and physical adsorption. The recovery test indicated that NaOH solution could almost completely extract the p-nitrophenol adsorbed by nanosized Silicalite-2zeolitesSilicalite-2zeolite was synthesized by the hydrothermal method with a molar ratio of SiO2:TBAOH:H2O at1:0.35:53. Fe composite catalyst based on the Silicalite-2zeolite carrier were prepared by the mechanical mixing method. The catalyst samples were characterized by XR、SEM、FT-IR、TG-DTA. The effects of initial concentration of the dye wastewater, aqueous solution pH, amounts of catalyst and H2O2used, and reaction time on the degradation efficiency of dye wastewater were investigated. The results showed that the decolorization rate of dye wastewater was97.8%under the optimal conditions which dye concentration was30mg/L and pH was6, catalyst dosing quantity was3.75g/L and30%(ω)H2O2amount was37.5mL/L, reaction time was2.5h.CoFe2O4nanoparticles were prepared by coprecipitation method. The magnetic materials Silicalite-2@CoFe2O4(SC) were prepared by steam-assisted dry-gel conversion technique with TBAOH (tetrabutylammonium hydroxide) as the template, TEOS (tetraethoxysilane)as the silica source, CoFe2O4as the magnetic nucleus. TiO2/Silicalite-2@CoFe2O4(TSC) magnetic photocatalysts were prepared by sol-gel technique with SC particles as support, TBOT (titaium tetrabutaoxide)as the titanium source. The samples were characterized by XRD, SEM,FT-IR,UV-Vis. The reduction of Cr(Ⅵ) in aqueous solution by UV/TSC reduction process was studied under various operating conditions. The results demonstrated that TSC had high photocatalytic activity as result of SC could provide high dispersibility for TiO2;the photocatalytic reaction rate was max under the optimal conditions which pH was2, calcination temperature was350℃; ethanol,acetic acids and citric acid might act as scavenger for holes and promoted the photocatalytic reduction of Cr(VI) by electrons; the photocatalytic reduction of Cr(VI) follows L-H kinetic equation. At the end of the reaction, it was easily collected by an external magnetic field and remained efficient in reuse.