Degradation And Recycling Of Wastewater Containing Azonic Dyes By Photo-induced Oxidation Based On Ferrioxalate/H₂O₂

In our times the most important matters that the natural environment faces include contamination, shortage of fresh water resources, and exhaustion and pollution of routine energy. In China, the organic dyestuffs have already become one of the most common pollutants.Azoic dyes represent the largest class of textile dyes in industrial use. Current environmental concerned with these dyes revolves around the carcinogenic potential of these dyes and their intermediates. Coagulation/Flocculation, activated carbon adsorption or membrane techniques can only transfer, more or less effectively, the contaminants from one phase to another, leaving the final environmental problem unsolved. From this point of view, advanced oxidation technologies of organic dyestuffs are attractive methods.The UV-Vis photolysis of ferrioxalate in the presence of hydrogen peroxide (the UV-Vis/Ferrioxalate/H₂O₂ process) is investigated for the treatment of contaminated industrial wastewater. This process generates the hydroxyl radical (redox potential = 2.8 V), which is a strong oxidant and reacts rapidly with most organic compounds present in solution. These previous works suggest that the dyes could be mineralized to a great extent by the UV-Vis/Ferrioxalate/H2O2 process, which made it peculiar among AOPs.At present, researches about the environmental behavior of dyestuffs were mostly focused on the basis of the thing that the single pollutant is moved and transformed, still little on combined pollution that made up of many kinds of pollutants. However, Textile finishing mills discharge wastewater containing a great variety of organic contaminants besides many kinds of dyestuffs in a wide range of concentrations, for example, inorganic salts, surfactants. The addition of inorganic salts and surfactants in the dyeing bath increases the pollution load on the effluent generated as well as has an effect on various effluent treatment processes. Furthermore, it was not found that the effect of interactions between azoic dyes on themselves oxidation degradation in previous studies so far.Moreover, the recycling of dyeing wastewater is a developing technology concerning environmental issues and textile industry. This technology nowadays is playing a very important role in saving water and environmental protection.Synthetic effluents prepared using dyes namely, Acid Orange156, Reactive Blue B, ReactiveRed MS, Reactive Yellow MS, Intermedium Black PV and Direct Blue 5B were used in the study. Combined kinetics and spectroscopic investigations have been carried out to examine the influence of inorganic salts and surfactants upon the oxidation of these azoic dyes by the UV-Vis /Ferrioxalate/H2O2 process. Firstly, the oxidizing degradation performance and mechanism of azoic dyes were analyzed. Secondly, this paper describes the effect of presence of inorganic salts namely, sodium chloride, sodium sulphate, sodium nitrate, sodium dihydrogen phosphateand and sodium bicarbonate on decolouration of azoic dye effluents by the UV-Vis /Ferrioxalate/H2O2 process. Thirdly, this work is extended in this paper to include azoic dyes oxidation in the presence of anionic (DBS) and nonionic surfactants (OP-10) in different concentration regions by the UV-Vis /Ferrioxalate/H2O2 process. Fourthly, an evaluating system about the effect of interactions between azoic dyes on oxidation degradation of azoic dyes was established. Lastly, in comparison with previous studies, in this paper the effects of the nature and quantity of the additives in recycling water on reuse were studied by the numbers.The following conclusions can be drawn:(1) Inorganic salts could limit decoloration of azoic dyes to some extent, and sodium chloride shows stronger influence on decoloration than others.(2) Decoloration of azoic dyes could be limited by surfactants, and there is affinity between the CMC of anionic surfactants and decoloration of azoic dyes.(3) There occurs three states in the effect of interactions between azoic dyes on oxidation degradation of azoic dyes as following: Acceleration; Li...