Enhanced Photocatalytic Activity for Degradation of Methyl Orange over Silica-Titania

Yaping Guo,Shaogui Yang,Weifeng Zhang,Xuefei Zhou,Chunmian Lin,Yajun Wang

doi:10.1155/2011/296953

Abstract

Silica-modified titania (SMT) powders with different atomic ratios of silica to titanium (Rx) were successfully synthesized by a simple ultrasonic irradiation technique. The prepared samples were characterized by X-ray diffraction (XRD), FT-IR spectroscopy, transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and ultraviolet visible spectroscopy. The specific surface area was measured according to BET theory. Results indicate that the addition of silica to titania can suppress the crystalline size growth and the transformation of anatase phase to rutile phase of titania, enlarge specific surface area of the titania particles, and result in a blue shift of absorption edge compared to pure titania. The photocatalytic activity of the SMT samples was evaluated by decolorizing methyl orange aqueous solutions under UV-visible light irradiation. It was found in our study that this activity was affected by silica content, calcination temperature, H2SO4, and oxidants such as KIO4, (NH4)2S2O8and H2O2. The results reveal that the photocatalytic activity of 0.1-SMT catalyst is the best among all samples calcined at550°C for 1 h and it is 1.56 times higher than that of Degussa P-25 titania, which is a widely used commercial TiO2made by Germany Degussa company and has been most widely used in industry as photocatalyst, antiultraviolet product, and thermal stabilizer. The optimal calcination temperature for preparation was550°C. The photocatalytic activity of SMT samples is significantly enhanced by H2SO4solution treatment and oxidants.

Highlights

As a cost-effective, nontoxic, effective photocatalyst, nanosize TiO2 has received much attention during the past three decades
We found that the photocatalytic activity of the prepared Silica-Modified Titania (SMT) could be greatly improved by H2SO4 solution treatment
Embedding silica into titania matrix increases the thermal stability by suppressing the increase of anatase crystallites and makes it possible to calcine the prepared RxSMT powders at high temperature without reducing surface area

Summary

Introduction

As a cost-effective, nontoxic, effective photocatalyst, nanosize TiO2 has received much attention during the past three decades. One is the synthesis of malodorous titania with high specific surface area resulting in high adsorbability and photocatalytic activity [1], the other is the combination of titania materials with adsorbent [2] For the former strategy, titania mostly exists in an amorphous or semicrystalline phase so it has low photocatalytic activity. Titania-silica mixed oxide has attracted considerable attention as attractive materials for photocatalytic applications because of the synergetic function of the photocatalytic activity, adsorbability, and stability. This may be partially the intimate interaction of titanium dioxide and silica, the new different structural characteristics and physicochemical/reactivity properties of titania-silica complex, such as quantum-sized crystalline, large surface area, high thermal stability, high adsorbability of reactant, or high acidity [3, 4]. Few studies on wastewater treatment with titania-silica have been reported

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