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    Characterization of $TiO_2$ synthesized in alcohol by a sol-gel process: The effects of annealing temperature and acid catalyst
    (2005) Sayılkan, Funda; Asiltürk, Meltem; Sayılkan, Hikmet; Önal, Yunus; Akarsu, Murat; Arpaç, Ertuğrul
    The effects of annealing temperature and hydrolysis catalyst on the crystalline form and crystallite size of $TiO_2$ prepared by a sol-gel process were investigated. Three types of $TiO_2$ were synthesized by hydrolysis of titanium(IV)-iso-propoxide with water in n-propanol without catalyst (Type-A) and with HCl as catalyst, where the $H^+/Ti^{4+}$ mol ratio was 0.54 for Type-B and 0.2 for Type-C. Hydrolysis products were thermally treated at 100, 200, 300, 400 and 500 °C for 1 h after drying at room temperature. Characterization of the particles was carried out using XRD, BET, TG/DTA and SEM analysis. The pore size distributions were computed by the DFT plus method. The results showed that the acid catalyst and catalyst/alkoxide ratio have a large effect on the formation of anatase $TiO_2$. In particular, it was found that anatase phase $TiO_2$ particles occur at 400 and 500 °C for Type-A $TiO_2$, while they do so at nearly 200 °C for Type-B and Type-C $TiO_2$. The crystallite size of Type-A, Type-B and Type-C increased from 17.96 to 19.24 nm, from 12.38 to 15.12 nm and from 10.60 to 12.20 nm, respectively, when the thermal treatment temperature was raised from 400 to 500 °C.
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    Characterization of TiO_2 synthesized in alcohol by a sol-gel process: The effects of annealing temperature and acid catalyst
    (Turkish Journal of Chemistry, 2005) Sayılkan, Funda; Asiltürk, Meltem; Sayılkan, Hikmet; Önal, Yunus; Akarsu, Murat; Arpaç, Ertuğrul
    Abstract:The effects of annealing temperature and hydrolysis catalyst on the crystalline form and crystallite size of TiO2 prepared by a sol-gel process were investigated. Three types of TiO2 were synthesized by hydrolysis of titanium(IV)-iso-propoxide with water in n-propanol without catalyst (Type-A) and with HCl as catalyst, where the H+/Ti4+ mol ratio was 0.54 for Type-B and 0.2 for Type-C. Hydrolysis products were thermally treated at 100, 200, 300, 400 and 500 °C for 1 h after drying at room temperature. Characterization of the particles was carried out using XRD, BET, TG/DTA and SEM analysis. The pore size distributions were computed by the DFT plus method. The results showed that the acid catalyst and catalyst/alkoxide ratio have a large effect on the formation of anatase TiO2. In particular, it was found that anatase phase TiO2 particles occur at 400 and 500 °C for Type-A TiO2, while they do so at nearly 200 °C for Type-B and Type-C TiO2. The crystallite size of Type-A, Type-B and Type-C increased from 17.96 to 19.24 nm, from 12.38 to 15.12 nm and from 10.60 to 12.20 nm, respectively, when the thermal treatment temperature was raised from 400 to 500 °C.
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    A novel approach to the hydrothermal synthesis of anatase titania nanoparticles and the photocatalytic degradation of rhodamine B
    (Turkish Journal of Chemistry, 2006) Akarsu, Murat; Asiltürk, Meltem; Sayılkan, Funda; Kiraz, Nadir; Arpaç, Ertuğrul; Sayılkan, Hikmet
    Abstract: A novel approach was developed for the synthesis of high-dispersed anatase nano-TiO2 by a hydrothermal process without solvent at 200 °C in 1 h. It was characterized using XRD, TEM, BET and elemental analysis. Nanoparticle-TiO2 was used as a photocatalyst by considering complete degradation of Rhodamine B (RB) dye. The photocatalytic reaction parameters such as photocatalyst amount, irradiation time and dye concentration were optimized and it was found that 0.125 wt% catalyst in 30 mg/L of RB aqueous solution is adequate for full degradation of RB in 50 min with 770 W/m2 irradiation power. Photocatalytic activity of the nanoparticle- TiO2 was compared with Degussa P-25 at optimum catalysis conditions determined for the nanoparticle- TiO2. It was concluded that when compared to Degussa P-25, the nanoparticle- TiO2 can be repeatedly used with increasing photocatalytic activity. The results revealed that the photodegradation of RB proceeds by pseudo first-order reaction kinetics in which the rate constant of the degradation is 0.132 min?1.