Photocatalytic degradation of Methylene Blue using a mixed catalyst and product analysis by LC/MS

Cr–Ti binary oxide with 10% molar Cr3+ content (Ti–10Cr) was prepared by sol–gel method and characterized by using transmission electron microscope (TEM) and X-ray diffraction analysis (XRD). The photoinduced degradation of Methylene Blue (MB) dye in the presence of Ti–10Cr was studied with UV–vis absorption. The absorption intensity of the dye solution monitored at 668 nm decreased with time upon irradiation in the presence of the catalyst. A maximum degradation efficiency of 70% of the dye was achieved in the presence of Ti–10Cr catalyst at pH 7. Photocatalytic degradation of the dye followed the pseudo-second-order-kinetics. Degradation product analysis was done using the LC–UV/vis–MS technique and the results showed that the dye degradation is initiated by demethylation of the molecule. The intermediates structure was confirmed by tandem mass spectrometric analysis.