Photocatalytic degradation of commercial dye, CI Reactive Red 35 in aqueous suspension: Degradation pathway and identification of intermediates by LC/MS

• TiO2 is efficient photocatalyst for decolourization of Reactive Red 35 (RR35).
• Degree of decolourization is higher than degree of mineralization.
• LC analysis shows formation of several smaller organic intermediates.
• Six intermediates are formed during 8 h of reaction.
• A detailed reaction mechanism has been established.

The photodegradation of Reactive Red 35 dye by artificial UV light was investigated in the presence of titania P-25. Six reaction intermediates were identified and separated by LC/MS, giving insight into mechanistic details and degradation pathways. The degradation process takes place through competitive reactions such as removal of chromophoric group, hydroxylation of the aromatic ring, substitution on aromatic ring, devinylsulphonation, CN bond cleavage, decarboxylation and further ring opening to give aliphatic compounds. The probable degradation pathways were proposed and discussed.

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