New chitosan microspheres supported [bis(2-methylallyl)(1,5-cyclooctadienne)ruthenium(II)] as efficient catalysts for colour degradation in the presence of hydrogen peroxide

Abstract

Abstract This paper concerns the immobilisation of either [bis(2-methylallyl)(1,5-cyclooctadienne)ruthenium(II)] (I) or ruthenium chloride (RuCl3) (II) on chitosan microspheres (catalyst I and catalyst II, respectively). These heterogenised catalysts were used for the oxidative degradation of two acid dyes, i.e. [Calmagite (Calma) and Acid Blue 25 (AB25)] in aqueous solution at pH 7.0 in the presence of hydrogen peroxide (H2O2). Prepared solid supports were characterised by Fourier transform infrared (FTIR) spectral study, thermogravimetry (TG), differential thermogravimetry (DTG) and differential scanning calorimetry (DSC) analyses. The efficiency of decolourisation was justified using UV–visible spectroscopic analysis. The factors affecting dye degradation were studied. Some tests for Calma decolourisation achieved up to 100% colour removal using catalyst I. The pseudo first-order equation was shown to fit degradation kinetics in most cases. However, for some cases, it was necessary to use a reversible equation. The energetic parameters were determined and the activation energy (E a) was found to be low, between 11 and 36 kJ mol−1, confirming that these catalysts were very efficient for the degradation of anionic dyes using H2O2. The interpretation of the equilibrium sorption data complies well with the Freundlich adsorption model. The combination of adsorption process and catalytic oxidation made the new developed catalyst systems to achieve a simple and efficient water treatment. Keywords: [bis(2-methylallyl)(1,5-cyclooctadienne)ruthenium(II)]oxidative degradationCalmaAB25energy of activationsorptionFreundlich Acknowledgements We are grateful to the DGRSRT (Direction Générale de la Recherche Scientifique et de la Rénovation Technologique) of the Tunisian Ministry of Higher Education, Scientific Research and Technology for the financial support of this study. We also thank Olivier Gain and Walid Bahloul (Laboratoire des Matériaux Polymères et des Biomatériaux, Bât. ISTIL, Université Claude Bernard LYON 1, UMR CNRS 5627 15, Boulevard Latarjet, 69622, Villeurbanne, France) for FTIR, TG and DSC analysis.