Treatment of effluents from wool dyeing process by photo-Fenton at solar pilot plant

The decolourization and mineralization of simulated wastewaters from wool dyeing tanks were investigated by Fenton and photo-Fenton processes. Yellow, red and blue dyebaths with azo-type and anthraquinone dyes and additives were selected as colored effluents. Photo-Fenton reaction was much more efficient than the respective dark reaction under identical experimental conditions. The effect of H2O2 and Fe(II) dosage and fractional or initial addition of these reagents on the photo-mineralization processes were studied and the optimal conditions found. Experiments at a pilot plant based on compound parabolic collectors (CPCs) confirmed that, under optimal conditions, 100% of color removal was obtained requiring low accumulated energy. No toxic effects on marine bacteria Vibrio fischeri were observed at the end of photo-Fenton treatment for all studied effluents. High concentrations of sodium acetate are used as additive in the wool dying process. HPLC and TOC analysis of the effluents after photo-Fenton process confirmed that the remaining organic carbon is due to the presence of acetates. The obtained results showed the feasibility of photo-Fenton process to achieve suitable water qualities for internal reuse.