Materials and Methods
All chemicals, benzothiophene (Merck), n-hexane (Merck) and titanium isopropoxide (Merck) are in analytical grade. FTIR spectra were taken using a Perkin Elmer 65 Model infrared spectrophotometer. XRD patterns were taken by Bruker, D8Advance X-ray diffractometer using CuKa radiation. Benzothiophene concentration was measured by HPLC (Agilent 1200 model) with column of Zorbax, Eclipse XDB-C18. Capillary gas chromatographs (Agilent technologies 7890 A) and GC-MS (Agilent technologies 5975 C) with 30 m HP-5MS capillary column were used to identify reaction products. The enjection port temperature was 250nC. The mass spectra were produced by electron impact (70 ev).
Synthesis of TiO2
Synthesis of TiO2 was carried out using sol-gel technique by hydrolysis and condensation of titanium isopropoxide (Mahshid et al. 2007). The precursor solution was a mixture containing 5 mL titanium isopropoxide (TTIP) and 15 mL isopropanol (99%). 250 mL of distilled water with known pH was used as the hydrolysis catalyst. The desired pH of the solution was adjusted by HNO3 or NH4OH. The gel preparation process started when both solutions were mixed together under vigorous stirring. Hydrolysis of titanium isopropoxide offered a turbid solution which was heated up to 60-70°C for 18-20 h (peptization). After peptization, the volume of the solution was decreased to 50 mL until a suspension was produced. After precipitation, the solid product was filtered and washed with ethanol and dried at 100°C. Finally, the prepared powder was annealed at temperature from 200 to 800°C for 2 h.
Preparation of photocatalyst
Solid state dispersion (SSD) method was used for preparing the zeolite-based photocatalyst. 1g of TiO2 was mixed with 4 g of zeolite by agate pestle and mortar using ethanol as solvent. The solvent was then removed by evaporation. Samples prepared by this method were dried at 110°C and calcined at 450°C for 5 h in air condition to obtain TiO2-supported zeolite catalyst ( Nikazar et al. 2008).
0.2 g of photocatalyst was added to 10 mL of 100mg/L hexane solution of benzothiophene. The mixture was irradiated by a 30W UV source for known period of time at room temperature. The concentration of benzothiophene was measured by HPLC. The effect of different parameters on degradation of the samples was studied and optimized.