ABU VULKANIK GUNUNG KELUD SEBAGAI SUMBER SiO2 PADA PREPARASI FOTOKATALIS TiO2/SiO2 DAN UJI AKTIVITASNYA UNTUK FOTOREDUKSI Cr(VI); KELUD VULCANIC ASH AS SiO2 SOURCE IN THE PREPARATION OF TiO2/SiO2 PHOTOCATALYST AND ITS ACTIVITY ASSAY FOR Cr(VI) PHOTOREDUCTION

Widodo, Agung, Mudasir

2015 | Disertasi | FMIPA

Preparation and characterization of TiO2 into SiO2 from Kelud Mountain vulcanic ash as TiO2/SiO2, as well as its the activities assay as photocatalyst for the Cr(VI) ion photoreduction have been conducted. This research was initiated by dissolution of SiO2 from vulcanic ash using NaOH solution. The dissolved SiO2 was determined using AAS. The preparation of TiO2/SiO2 photocatalycst was carried out by mixing TiO2 powder dispersed in the aquadest medium and sodium silicate solution from the vulcanic ash. The prepared material was dried and calcinated at temperature of 400 ºC for 2 hours. The characterization of the obtained materials was performed using XRD, FTIR, DRUV, and SEM methods to find out the effect of preparation on the particle size and band gap energy. TiO2/SiO2 photocatalyst activity was tested for photoreduction of Cr(VI) ion. The effects of TiO2 content in TiO2/SiO2 photocatalysts, mass of catalyst and time of exposure on the effectiveness of Cr(VI) ion photoreduction have been systematically investigated. The results of the research indicate that SiO2 can be dissolved optimally with 5 M NaOH at solution to form sodium silicates. The results of preparation of TiO2 as TiO2/SiO2 photocatalyst increases band gap energy and decreases crystalline size. The TiO2 content of TiO2/SiO2 photocatalyst influences on photoreduction effectiveness. The increase of TiO2/SiO2 photocatalyst mass up to 30 mg can enhance photoreduction effectivity of Cr(VI) ion as much as 70.86% in 20 mL Cr(VI) solution of 5 ppm. The extension of exposure time until 48 hours increases the effectiveness of Cr(VI) ion photoreduction with result up to 87.76%. Photoreduction of Cr(VI) was relatively constant by using larger photocatalyst mass and longer exposure time.

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