Nano silver impregnation on commercial TiO₂ and a comparative photocatalytic account to degrade malachite green

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• 作者：Sandip Saha^a ; J.M. Wang^b ; Anjali Pal^a ; ^{anjalipal@civil.iitkgp.ernet.in}
• 关键词：Commercial TiO2 ; Heat treatment ; P25 TiO2 ; Nano silver impregnation ; Malachite green photodegradation
• 刊名：Separation and Purification Technology
• 出版年：2012
• 期刊代码：78_13835866
• 类别：ce
• 出版时间：22 March, 2012
• 卷：89
• 期：Complete
• 页码：147-159
• 文件大小：1257 K

摘要

Commercial TiO₂ was impregnated with silver nanoparticles at 1 and 2 mol%Ag using a simple 鈥榣iquid impregnation followed by heat treatment鈥?method and the material was characterized using field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM)/energy dispersive X-ray (EDX), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Raman, diffusive reflectance spectroscopy (DRS), and BET surface area/pore volume analysis. Impregnation of silver nanoparticles on P25 TiO₂ was done using the same procedure. Commercial TiO₂ was also modified under simple heat treatment to make combusted TiO₂. To probe the challenge of photodegradation of a known carcinogen, malachite green (MG), we have investigated the UV-induced photodegradation of MG in aqueous medium using all these modified TiO₂ catalysts in order to evaluate the effect of silver impregnation. We report that the presence of silver in TiO₂ enhances the photon induced mineralization of MG but reduces the decolorization efficiency. Based on both decolorization and mineralization, and also on the cost and availability, 1%silver impregnated commercial TiO₂ was found the optimal. The degradation of MG using this catalyst has been investigated in a more detail, and the effect of pH, stirring, initial MG concentration, catalyst dose, nature of light, and the presence of interfering ions/organics are examined. The dye (鈭?5 mg/l) is bleached almost completely upon 1 h of light irradiation under experimental conditions. The degradation follows zero-order kinetics over the entire MG concentration range (25-125 mg/l), and we presume that the degradation occurs via step-wise N-demethylation. Most importantly, we observe high turn over frequency (TOF) for our catalyst. This makes the catalytic process cost-effective and the catalyst recycle able. Further, a cost-analysis is made to evaluate the proper selection of the catalyst in terms of efficiency and economy.