Chemical Oxidation Of Azo Reactive Dye And Investigation Of The Reaction Mechanism

Effluents from the dyeing and finishing processes in the textile industry are known to contain high levels of chemicals, high biochemical oxygen demand, suspended solids and strong color. In general, conventional biological treatment processes have a certain difficulties in degrading these dye chemicals. Textile wastewater contaminated with these substances has to be treated by physical and chemical means including so-called advanced oxidation processes (AOPs). It is important to investigate the intermediates generated and their potential harmful impacts on the environment.In this study, the azo reactive dye C.I. Reactive Red 120 was selected as a model compounds for ozonation treatment. It showed that additives affected the formation of toxic by-products during short and long-term ozonation. The results also illustrated that the dye additives/impurities in commercial dyes affect the microbial activity as well as the biodegradability.The simultaneous and competitive hydrolysis reaction in the alkaline medium of dyebath resulted in lower fixation with the fiber. A method based on HPLC-MS hyphenation technique for the analysis of hydrolysis products of C.I. Reactive Black 5 was developed. The variation of the toxicity of dyes during hydrolysis process was assessed by bioluminescence. The results showed that some variation of reactive groups may result in the increase of toxicity during hydrolysis process.The pseudo-first order kinetics model of ozonation of azo reactive dyes wasstudied. Bioluminescence test is a standard method for assessment of toxicity of numerous organic compounds. The potential toxicities of the three dyes during ozonation were assessed.C.I. Reactive Red 120 and C.I. Reactive Black 5 were chosen as models to investigate the reaction mechanism of ozonation. HPIC and HPLC-MS were developed as the techniques to identify the degradation intermediates and by-products. Combined with the results of COD, TOC, pH, the reaction mechanisms and degradation pathways of two azo reactive dyes are given.The treatment of reactive azo dyes by photodegradation with UV/H2O2 was studied. The impact factors were explored and the optimum reaction conditions were obtained. The oxidation efficiencies of C.I. Reactive Red 120 with different oxidative method such as UV, O3, UV/H2O2, UV/O3, UV/O3/H2O2 were compared. The combination of O3/H2O2/UV, even at low H2O2 concentrations can effectively improved the decolorization and mineralization.