Dielectric characterization and catalytic activity studies of nickel chloride doped carboxymethyl cellulose films

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• 作者：Zeinhom M. El-Bahy^a ; ¹ ; Khaled H. Mahmoud^b ; ² ; ^{cairouni1@yahoo.com}
• 关键词：CMC ; Dielectric relaxation ; 4-Nitrophenol ; Hydrogenation
• 刊名：Spectrochimica Acta Part A ; Molecular and Biomolecular Spectroscopy
• 出版年：2012
• 期刊代码：99_13861425
• 类别：ch
• 出版时间：15 June, 2012
• 卷：92
• 期：Complete
• 页码：105-112
• 文件大小：638 K

摘要

Cast technique was used to prepare films of sodium carboxymethyl cellulose (CMC) doped with different ratios of NiCl₂路6H₂O in the range of 0-40 Ni²⁺ wt.%. Thermal analysis (DTA) in the range of 25-600 掳C and dielectric properties in the temperature range of 30-150 掳C and frequency range of 0.1-100 kHz were measured for the prepared samples. DTA analysis showed new exothermic peaks which were attributed to structural phase transitions. Different molecular motions are separated via dielectric relaxation spectroscopy. In the high temperature range (higher than 100 掳C), the 蟽-relaxation, which is associated with the hopping motion of ions through polymer material, was detected. The detailed analysis of the results showed that the dielectric dispersion consists of both dipolar and interfacial polarization. Measurements of ac conductivity as a function of frequency at different temperatures indicated that the correlated barrier hopping model (CBH) is the most suitable mechanism for the ac conduction behavior.

The catalytic activity of CMC doped with Ni²⁺ was tested in the reduction of the hazardous pollutant 4-nitrophenol to the functional 4-aminophenol with an excess amount of NaBH₄. Ni-free CMC did not exhibit any catalytic activity for the studied reaction. However, Ni²⁺-doped CMC showed a significant catalytic activity that is proportional to the ratio of Ni²⁺ included in CMC. The activation energy (E_a) was estimated in the temperature range of 25-40 掳C. The estimated value of E_a decreased with increasing the ratio of Ni²⁺. Finally, the optimum catalyst mass was found to be 鈮?.6 g/l.