Homogenous and heterogenous advanced oxidation of two commercial reactive dyes

Two commercial reactive dyes, the azo dye Reactive Black 5 and the copper p hythalocyanine dye Reactive Blue 21, have been treated at a concentration o f 75 mg l(-1) by titanium dioxide mediated photocatalytic (TiO2/UV), dark a nd UV-light assisted Fenton (Fe2+/H2O2) and Fenton-like (Fe3+/H2O2) process es in acidic medium. For the treatment of Reactive Black 5, all investigate d advanced oxidation processes were quite effective in terms of colour, COD as well as TOC removal. Moreover, the relative growth inhibition of the az o dye towards the marine algae Dunaliella tertiolecta that was initially 70 %, did not exhibit an increase during the studied advanced oxidation reacti ons and complete detoxification at the end of the treatment period could be achieved for all investigated treatment processes. However, for Reactive B lue 21, abatement in COD and UV-VIS absorbance values was mainly due to the adsorption of the dye on the photocatalyst surface and/or the coagulative effect of Fe3+/Fe2+ ions. Although only a Limited fraction of the copper ph ythalocyanine dye under-went oxidative degradation, 47% of the total copper in the dye was already released after 1 h photocatalytic treatment.