The Multi-phase Fenton Method Degradation Of Methyl Orange Dye Wastewater

With the rapid development of technology, printing and dyeing industry is developing rapidly, dye not only influences the people' lives, but also bring some big changes to people and pollute the environment. The dyeing wastewater is known to have strong color, a big volume, high content of toxic organic compounds and non-biodegradable matter. Direct discharge of these effluents can cause formation of toxic aromatic amines under anaerobic conditions and contaminate the soil and groundwater. So it is necessary to proper treatment before discharge into the environment. The azo dyes, containing azo groups (—N=N—) and other functional groups, has a character of high stability, so is widely used in the dyeing industry and is the major source of pollution caused by azo wastewater. Degradation of azo dye—methyl orange (MO) dye wastewater by heterogeneous Fenton-like process was studied. Catalyst was prepared by deposition and impregnation methods, respectively. On this basis, green and non-polluting energy—sunlight which promoted photocatalytic degradation of MO by photo-Fenton-like process was studied. The color removal efficiency, COD removal efficiency and the change of structure reflected by UV spectra were studied.In the first part, the main features of wastewater and status were introduced, followed by analysis of the harm of the wastewater to the environment, having pointed out that the dyeing wastewater has brought safe trouble on human being's and living environment. Followed by the overview of the current treatment situation for dyeing wastewater, the current wastewater treatment methods were mainly introduced, such as, traditional water treatment methods and advanced oxidation process. In addition, we pointed that the character and current treatment situation for MO wastewater. Finally, we presented the purpose, content and innovation of this study.In the second part, the experimental reagents, instruments and experimental methods were presented.In the third and forth part, the degradation of azo dye MO was studied by a heterogeneous Fenton-like oxidation process. Fe2O3-modified activated clay catalyst was prepared by deposition and impregnation methods named FAC-1 and FAC-2, respectively. Meanwhile, the effect of various parameters such as amount of hydrogen peroxide, catalyst loading, pH and temperature on decolorization and COD removal of MO dye have been studied. In addition, the catalyst life was investigated. At the optimal operating conditions, the final color and COD removal from the effluent reached 99.6% and 67.2% by FAC-1 catalyst which Fe modified catalyst with deposition methord. However,99.1% and 52.8% of the final color and COD removal were abtained by FAC-2 catalyst which Fe modified catalyst with precipitation methord. After that, the catalyst can be reused 6 times, with relatively higher activity and stability. This shows that the catalytic degration efficiency of the FAC-1 catalyst with deposition methord is better than the FAC-2 catalyst with precipitation methord's.In the fifth part, on the basis of the Fenton-like process, the green, non-pollution natural resource-solar promoted photocatalytic degradation of MO by photo-Fenton-like process was studied. In this part, four different reaction systems(light/catalyst-FAC-l/H2O2,dark/ catalyst-FAC-1/H202,light/catalyst-FAC-1,light/H2O2) have been investigated. The results showed that the optimal condition was light/catalyst-FAC-1/H2O2 system in deal with 100 mg/L MO dye solution. The optimal experimental conditions for the degradation of 100 mg/L MO dye solution, were determined to be:catalyst-FAC-1 dose,9.9 g/L; initial H2O2 concentration,1800 mg/L; initial pH=3.0. The MO dyes were pretreated 10 minutes under above conditions and then at 4 hour exposure,99.8% decolorization and 91.3% COD removal can be obtained. In addition, the treated dye samples in the light conditions have no any peaks. The results indicated that solar promoted photocatalytic degradation of MO by photo-Fenton-like process can remarkably promote the degradation of MO dye and high removal of COD indicated that mineralization was achieved satisfactory results.