Statistical analysis of the effect of aromatic, azo and sulphonic acid groups on decolouration of acid dye effluents using advanced oxidation processes

Abstract

In the present study, the effect of advanced oxidation processes such as ozone/UV, ozone/H 2O 2 and ozone/UV/H 2O 2 on decolouration of Acid Red 88, Acid Orange 7, Acid Orange 10 and Acid Red 73 dye effluents in the presence of sodium sulphate salt were considered. Studies were carried out to analyse and compare the effect of aromatic, azo and sulphonic acid groups on decolouration of acid dye effluents. Among the advanced oxidation processes, ozone/UV/H 2O 2 treatment is more efficient for decolouration than other treatments in all the dye effluents except in Acid Red 88, where ozone/UV treatment shows better decolouration than the other processes. Acid dyes possessing only naphthalene rings in its structure undergo faster decolouration than the dyes with the combination of benzene and naphthalene rings. Among the dyes studied, those with higher number of sulphonic acid groups in its structure are easier to decolour. But on increasing the azo groups in its structure, increasing decolouration time was observed. It was also found that acidic pH and lower salt concentration in the effluents are more efficient for decolouration in all the treatment processes.