Innovative integrated process for the treatment of azo dyes: coupling of photocatalysis and biological treatment

Tests of the biodegradation of the azo dyes Reactive Black 5 and Reactive Yellow 145 confirmed the low biodegradability of these components in the considered conditions, namely a strain of Pseudomonas fluorescens, cultivated at 25°C, an initial pH of 7 and in presence of a supplementary carbon source, glucose. Indeed, for an initial dye concentration of 40 ppm, the maximum yields of decolouration were 27% and 18% for the two dyes RB5 and RY145. Some tests of biological mineralisation of solutions preliminary photocatalysed demonstrate a mineralisation of the considered solutions for various irradiation times. Identification of the intermediate by-products is in progress to propose a reaction pathway.

The feasibility of the use of an integrated process involving photocatalysis followed by biological treatment for dye degradation is confirmed. A biodegradation of the by-products resulting from the photocatalysis step was also shown. Identification of these intermediate by-products is in progress to propose a reaction pathway. Subsequent work have to be done to select the best microbial species for dye degradation, followed by integrated process optimisation to achieve complete mineralisation of the considered azo dye at minimal cost.