Photo-catalytic Degradation Of Azo Dyes By Solar Irradiation And Recycle Of Their Dyeing Effluent

Since discharge limits are becoming stricter for industry wastewater textile manufactures are searching efficient and economical methods of pollution reduction. The technique of pHoto-catalytic oxidation is a new kind of water treatment process with great potential especially in the dyeing wastewaters degradation for its outstanding effect. This paper mainly investigated the pHoto-catalytic degradation of six azo dyes based on ferrioxalate oxalite/H₂O₂. Firstly, study on Fe3+, oxalic acid and H₂O₂ concentration are discussed in details. Secondly, the relation between inorganic salts, surfactants, solar irradiation and discoloration, reaction kinetics value was investigated. The different effect of solar and model solar in the ferrous oxalate complex/H₂O₂ on degradation azo dyes had been contrasted. In addition, the process of degradation was shown by UV-Vis spectrum and TOC. Finally, three reactive dyes containing two reactive groups in aqueous solutions were dyed fabric, the dyeing wastewaters carried out by this solar catalytic degradation technology and recycling of wastewater. The experimentation results indicated that the increase concentration of Fe3+ had accelerated the dyeing degradation, while the oxalic acid and H₂O₂ concentration had an optimization value. The more or less blocked the dye discoloration and degradation. Inorganic salts had restrained the degradation of dyes, the more of its concentration the worse the dyeing degradation. In the same condition, NaCl had the most restrained effect on dyeing degradation, next Na₂SO₄;the least was NaNO₃ Surfactants have a specific affected on dyeing discoloration, if its concentration less than C.M.C, it had a faint control, if its concentration more than C.M.C, it had a prominent control. Generally speaking, the higher the solar irradiance, the faster the discoloration of dyes in water. In the same condition, dyes were more efficiency degradated in sunny than in cloudy. It was found that the degradation of the dyes followed a pseudo-first order kinetic model at different solar irradiance and the inorganically salts in ferrioxalate oxalite/H₂O₂. Reactive dyes dyed fabric and produced wastewaters, which could be degradated by this pHoto catalytic technology, and the gained water (new water â…  and â…¡) can be recycled in the reactive dyes dyeing process. The results DE* less than 1.5, contrasted fabric dyed by new water â…  & â…¡ with tap water, attained commerce requirement. In addition, new water â…  & â…¡ did not affect fabric other fasten and gained four grade standard according to corresponding nation standard.