Photocatalysis is a relatively new technique for the decontamination of aqueous and air streams. Typically, photocatalysts are activated by ultraviolet (UV) irradiation because of their wide bandgaps. However, UV light accounts for a small fraction (~4–5%) of solar energy compared to visible light (~45%). A relatively new microporous material, vanadosilicate AM-6, has been shown to be active under visible light irradiation in the gas phase photo-polymerization of ethylene. This makes AM-6 a potentially successful natural sunlight photocatalyst for use in environmental remediation. Hydrothermal syntheses of vanadosilicate AM-6 were carried out in 10 mL Teflon-lined stainless steel autoclaves for 2-7 days at 230 oC under autogenous pressure using mixtures with molar compositions 4.5Na2O:1.3K2O: xSiO2: 0.5V2O5: yTMA : 209H2O, where x= 3.4-6.2 and y=2-4.0. After crystallization, all the samples were characterized by X-ray powder diffraction (XRD), Scanning electron microscopy (SEM), and UV-vis absorption spectroscopy. Results show that with increasing TMA content (0&lt;y≤4.0) the fraction of AM-6 in the product increased. The AM-6 synthesis at 230 oC, y=2.25 TMA, and y= 4.85-5.5 resulted in nearly pure AM-6 products (i.e., ≥ 95%), whereas crystallization with y=3.8-4.3 resulted in slightly less pure AM-6 products. Increasing the TMA content to 4.0 resulted in AM-6 formation at x=4.3. Therefore, the presence of TMA is shown to influence the type of phase being crystallized, while the concentration of TMA affects the nucleation of AM-6. The morphology, degree of crystal development (i.e., crystal quality) and size of AM-6 crystals appear to be affected by varying the mixture composition (Si/V ratio content). Increasing the Si/V ratio resulted in smaller AM-6 crystals. Photocatalytic degradation of a model compound, methylene blue (MB), in a slurry reactor was used to evaluate the effectiveness of these modifications on the photocatalytic performance of AM-6 under both UV and visible light irradiation.

Photocatalytic degradation of methylene blue using vanadosilicate AM-6

254th National Meeting (2017)

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