El-Qanni Amjad, Nassar Nashaat N, Vitale Gerardo, Hassan Azfar
Department of Chemical and Petroleum Engineering, University of Calgary, Calgary, Alberta T2N 1N4, Canada; Department of Chemical Engineering, An-Najah National University, P.O. Box 7, Nablus, Palestine.
Department of Chemical and Petroleum Engineering, University of Calgary, Calgary, Alberta T2N 1N4, Canada.
J Colloid Interface Sci. 2016 Jan 1;461:396-408. doi: 10.1016/j.jcis.2015.09.041. Epub 2015 Sep 21.
In this study methylene blue (MB) has been investigated for its adsorption and subsequent catalytic thermo-oxidative decomposition on surface of maghemite (γ-Fe2O3) nanoparticles. The experimental adsorption isotherm fit well to the Freundlich model, indicating multi-sites adsorption. Computational modeling of the interaction between the MB molecule and γ-Fe2O3 nanoparticle surface was carried out to get more insights into its adsorption behavior. Adsorption energies of MB molecules on the surface indicated that there are different adsorption sites on the surface of γ-Fe2O3 confirming the findings regarding the adsorption isotherm. The catalytic activity of the γ-Fe2O3 nanoparticles toward MB thermo-oxidative decomposition has been confirmed by subjecting the adsorbed MB to a thermo oxidation process up to 600 °C in a thermogravimetric analyzer. The experimental results showed a catalytic activity for post adsorption oxidation. The oxidation kinetics were studied using the Ozawa-Flyn-Wall (OFW) corrected method. The most probable mechanism functions were fifth and third orders for virgin MB and MB adsorbed onto γ-Fe2O3 nanoparticles, respectively. Moreover, the results of thermodynamic transition state parameters, namely changes in Gibbs free energy of activation (ΔG(‡)), enthalpy of activation (ΔH(‡)), and entropy of activation (ΔS(‡)), emphasized the catalytic activity of γ-Fe2O3 nanoparticles toward MB oxidation.
在本研究中，对亚甲基蓝（MB）在磁赤铁矿（γ-Fe2O3）纳米颗粒表面的吸附及其随后的催化热氧化分解进行了研究。实验吸附等温线与弗伦德里希模型拟合良好，表明存在多位点吸附。对MB分子与γ-Fe2O3纳米颗粒表面之间的相互作用进行了计算建模，以更深入地了解其吸附行为。MB分子在表面的吸附能表明，γ-Fe2O3表面存在不同的吸附位点，这证实了关于吸附等温线的研究结果。通过在热重分析仪中将吸附的MB进行高达600°C的热氧化过程，证实了γ-Fe2O3纳米颗粒对MB热氧化分解的催化活性。实验结果显示了吸附后氧化的催化活性。使用小泽-弗林-沃尔（OFW）校正方法研究了氧化动力学。对于原始MB和吸附在γ-Fe2O3纳米颗粒上的MB，最可能的机理函数分别为五级和三级。此外，热力学过渡态参数的结果，即活化吉布斯自由能变化（ΔG(‡)）、活化焓（ΔH(‡)）和活化熵（ΔS(‡)），强调了γ-Fe2O3纳米颗粒对MB氧化的催化活性。
