Natural Minerals as Support of Silicotungstic Acid for Photocatalytic Degradation of Methylene Blue in Wastewater
- 7 Downloads
In this paper, silicotungstic acid (HSiW) was impregnated on natural minerals such as clinoptilolite (HSiW/Clin), mordenite (HSiW/Mord), bentonite (HsiW/Bent) and kaolinite (HSiW/Kaoln) and were evaluated towards photocatalytic degradation of methylene blue in wastewater. The as-prepared photocatalysts were characterized by X-ray powder diffraction (XRD), Field Emission Scanning Microscopy (FESEM), Fourier transform infrared (FTIR) and UV–Vis diffuse reflectance spectroscopy (UV–Vis DRS). The results showed that the crystallinty of HSiW was different on above mentioned minerals and HSiW on clinoptilolite had the most crystallinty and the smallest crystallite size. FESEM showed that the supported HSiW had nanometric spherical particles with narrow and uniform distribution. FTIR revealed Keggin structure of HSiW in all photocatalysts and a strong interaction between HSiW and minerals. DRS studies showed HSiW/Clin and HSiW/Mord had photoactivity in both visible and ultraviolet regions while HSiW/Bent and HSiW/Kaoln photocatalysts were just active in UV region. More studies indicated that HSiW/Clin had the lowest band gap of 3.1 eV among studied nano photocatalysts. This sample could degrade 92% of methylene blue after 90 min of UV irradiations and HSiW/Mord, HSiW/Bent and HSiW/Kaoln were in the next positions. Kinetic studies illustrated photocatalytic degradation of methylene blue followed a pseudo first order reaction and the highest rate constant belonged to HSiW/Clin and other photocatalysts had much lower rate constants. Effect of operation parameters like wastewater pH, initial dye concentration, photocatalyst loading and successive runs of HSiW/Clin was investigated and at the end a new mechanism for this photocatalyst was proposed.
KeywordsNanophotocatalyst Wastewater treatment Silicotungstic acid Natural zeolite Clay
The authors gratefully acknowledge Iran Nanotechnology Initiative Council as well as Sahand University of Technology for complementary financial supports.
- 7.N.V.S. Praneeth, S. Paria, Clay-semiconductor nanocomposites for photocatalytic applications, in Clay Minerals: Properties, Occurrence and Uses, ed. by T.K. Sen (Nova Science Publishers, New York, 2017)Google Scholar
- 8.P. Cool, E.F. Vansant, Pillared Clays: Preparation, Characterization and Applications, in Synthesis (Springer, Berlin, 1998), pp. 265–288Google Scholar
- 23.M. Bahrami, A. Nezamzadeh-Ejhieh, Effect of supporting and hybridizing of FeO and ZnO semiconductors onto an Iranian clinoptilolite nano-particles and the effect of ZnO/FeO ratio in the solar photodegradation of fish ponds waste water. Mater. Sci. Semicond. Process. 27, 833–840 (2014)CrossRefGoogle Scholar
- 35.C.L. Hill et al., Catalytic photochemical oxidation of organic substrates by polyoxometalates. Picosecond spectroscopy, photochemistry, and structural properties of charge-transfer complexes between heteropolytungstic acids and dipolar organic compounds. J. Am. Chem. Soc. 110(16), 5471–5479 (1988)CrossRefGoogle Scholar
- 36.Y. Li et al., Effect of preparation method of colloidal platinum on performance of 12-tungstosilicate for photocatalytic hydrogen generation. J. Mol. Catal. A 246(1), 212–217 (2006)Google Scholar