High efficiency of the cylindrical mesopores of MWCNTs for the catalytic wet peroxide oxidation of CI. Reactive Red 241 dissolved in water

摘要

A study of the catalytic decolourisation of one textile dye by oxidation with H2O2, using different carbon materials as catalysts, is reported. Ten carbon solids, differing both in their texture-structure features and in their surface chemistry properties, were used for this purpose. These are two activated carbons, a high surface graphite, two structured nanomaterials (carbon nanofibres and carbon nanotubes), and the derivative samples prepared by oxidation of the pristines with nitric acid solutions. All these samples were characterised by determination of the nitrogen adsorption isotherms, thermogravimetric data, transmission electron microscopy, pH at the point of zero charge and chemical composition based on the X-ray photoelectron spectra. These carbon materials were evaluated as catalysts for the catalytic wet peroxide oxidation of C.I. Reactive Red 241 dissolved in water. Carbon nanotubes (CNTs) exhibit the highest performance in terms of activity for the catalytic wet peroxide oxidation, achieving a total removal of the dye after 90 min in process. It appears that catalytic activity for this reaction is improved by the internal cylindrical mesopores of CNTs. However, when these hydrophobic CNTs are treated by incorporation of oxygen surface groups which increase their hydrophilic character, the high catalytic performance of CNTs largely disappears.