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.

Title

Journal of Colloid and Interface Science

Publisher

ELSEVIER

Publisher Country

Netherlands

Indexing

Thomson Reuters

Impact Factor

4.233

Publication Type

Prtinted only

Volume

461

Year

2015

Pages

396-408