Photocatalytic treatment of colored wastewater from medical laboratories: Photocatalytic oxidation of hematoxylin

The decolorization and organic content reduction of a synthetic Harris’ Hematoxylin (SHH) solution, which is widely used in biochemical and biomedical laboratories, by the use of heterogeneous and homogeneous photocatalytic methods under artificial irradiation has been studied. In the case of heterogeneous photocatalysis the effect of two different commercial TiO2 products with oxidants such as H2O2 on the decolorisation and the organic content reduction (COD) of the wastewater was examined. Reuse experiments had shown that TiO2 P-25 retains its activity nine times concerning the decolorization of the solution and four times concerning the COD reduction. The Photo-Fenton process activated by using UV-A or visible light appears to be more efficient for this type of wastewater in comparison to the TiO2/oxidant system. The apparent initial photonic efficiency (ζ) of decolorization, as well as mineralization under various experimental conditions has been calculated.