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.