Photocatalytic oxidation of phenolic compounds by using a carbon nanotube-titanium dioxide composite catalyst.
A nanostructured multiwalled carbon nanotube (CNT) and titanium dioxide composite catalyst is prepared by a modified acid-catalyzed sol-gel method. Pure anatase TiO(2) and the CNT-TiO(2) composite are tested in the photocatalytic degradation of four para-substituted phenols: 4-chlorophenol, 4-aminophenol, 4-hydroxybenzoic acid and 4-nitrophenol. The effect of several operational parameters on the photoefficiency of the composite catalyst is studied by using 4-chlorophenol as model compound, namely catalyst loading, pH of the medium, hydrogen peroxide concentration, substrate concentration. A relationship between the Hammett constant of each para-substituted phenolic compound and its degradability by the photocatalysts is found. The effect of the carbon phase in the catalyst is ascribed to its photosensitizer action. A clear beneficial effect is observed for the degradation of 4-aminophenol and 4-chlorophenol. For the molecules with stronger electron-withdrawing (deactivating) groups, such as 4-hydroxybenzoic acid and 4-nitrophenol, no synergy effect is observed.
Silva
Cláudia Gomes
CG
Laboratório de Catálise e Materiais, Laboratório Associado LSRE/LCM, Departamento de Engenharia Química-Faculdade de Engenharia, Universidade do Porto, Portugal.
Faria
Joaquim Luís
JL
D002384:Catalysis; D002733:Chlorophenols / Q000737:chemistry; D004583:Electrons; D006861:Hydrogen Peroxide / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D037742:Nanotubes, Carbon / Q000737:chemistry*; D010084:Oxidation-Reduction; D019800:Phenol / Q000737:chemistry*; D010782:Photolysis; D014025:Titanium / Q000737:chemistry*; D014466:Ultraviolet Rays
D002733:Chlorophenols; D037742:Nanotubes, Carbon; C009495:titanium dioxide; D019800:Phenol; C029107:4-chlorophenol; D006861:Hydrogen Peroxide; D014025:Titanium