Removal of aromatic amines and decolourisation of azo dye baths by electrochemical treatment

The presence of aromatic amines in effluent from dyeing processes of the textile industry is an added problem to the high coloration typical of this type of effluent. The main objective of the present work was to eliminate these two problems simultaneously by electrochemical treatment using bath solutions containing three azo dyes. For the analysis of amines, a liquid-liquid extraction method was developed as an easier and faster alternative to the method described in the standards and widely used in analytical laboratories. Four amines (aniline, o-toluidine, 4-chloroaniline and 4-aminobiphenyl) were detected by GC-MS in the residual azo dye baths. A total amine concentration of between 2.5 and 1 ppm was detected, 4-aminobiphenyl being the main compound. Both residual colour and amines were removed by electrochemical treatment carried out at three current densities (3, 24 and 40 mA/cm2). At 24 mA/cm2, more than 90% of colour removal was achieved, and the total amine concentration was reduced to below 0.15 ppm. © 2013 Society of Dyers and Colourists.