Purification of Textile Effluents Containing C.I. Acid Violet 1: Adsorptive Removal versus Hydrogen Peroxide and Peracetic Acid Based Advanced Oxidation

Textile effluent containing azo dyes such as C.I. Acid Violet 1 (AV1) can be degraded to toxic aromatic amines in the environment. Thus, there is a legitimate need to treat such effluents before they are discharged to surface waters. Two methods were proposed to remove AV1 from aqueous solutions: adsorption and advanced oxidation processes (AOPs). The sorption capacity of the strongly basic anion exchanger Purolite A520E of the polystyrene matrix determined from the Langmuir isotherm model was found to be 835 mg/g, while that of Lewatit S5428 of the polyacrylamide matrix Freundlich model seems to be more appropriate for describing the experimental data. The pseudo-second-order kinetic model and external diffusion are the rate limiting steps of adsorption. The removal efficiency of AV1 by the anion exchangers was higher than 99% after 40 min of phase contact time. AOPs involved the usage of hydrogen peroxide and peracetic acid (PAA) as oxidizing agents, while Fe2+ and simulated sunlight were used as oxidizing activators. AV1 oxidation followed the pseudo-first-order kinetics, and the systems with the highest values of the rate constants turned out to be those in which Fe2+ was present. The efficiency of oxidation measured by the degree of decolorization in the systems with Fe2+ was higher than 99% after 10–60 min. AV1 mineralization was slower, but after 120 min of oxidation it was higher than 98% in the H2O2/Fe2+, PAA/Fe2+ and PAA/Fe2+/sunlight systems.