Treatment Of Acid Orange 7(AO7) Simulated Dye Wastewater By Three-dimensional Electrode Method

The dye wastewater cannot be well treated by the conventional technology due to their inherent properties of high chromaticity,high COD value,strong stability and bio-refractory.Three-dimensional?3D?electrode method owns the superior characteristics of strong oxidative degradation ability,high efficiency,without secondary pollution and can further improve the biodegradability of wastewater.It has been used successfully for the treatment of none biodegradable wastewater and has wide application in the treatment of dye wastewater.In this thesis,the effect of particle electrode with TiO₂ and SnO₂ supported granular activated carbon?Ti/Sn-GAC?on the treatment of AO7 simulated dye wastewater was investigated in the 3D electrode system.The experimental conditions of electrochemical degradation of AO7 were optimized by orthogonal test,and the degradation pathways of AO7 molecules during electrochemical degradation were analyzed,it provides scientific basis for the application of 3D electrode method in practical dye wastewater.The main conclusions of this thesis were as follows:?1?The effects of 3D and two-dimensional?2D?electrode method as well as adsorption method on the treatment of AO7 simulated dye wastewater were evaluated.The results showed that the decolorization rate and COD removal efficiency of AO7 were 57.12%and 30.28%in the 3D system,which were 30.03 and 23.94 percent higher than that in the 2D system respectively.The instantaneous current efficiency?ICE?of the 3D electrode system was higher than that of the 2D electrode system,proving that the packing of the particle electrode effectively improved the current efficiency and was beneficial to the degradation of AO7.The decolorization rate and COD removal efficiency of simulated wastewater after electrolysis by 3D electrode method were 55.66%and 33.55%,which were 35.21 and 14.78 percent higher than adsorption method respectively.The 3D electrode method had a better degradation for AO7 simulated dye wastewater.?2?TiO₂ and SnO₂ was successfully loaded on the GAC to generate Ti/Sn-GAC,being confirmed by SEM and EDX characterization.The AO7 simulated dye wastewater was treated using GAC and Ti/Sn-GAC as particle electrode respectively.Results showed that the decolorization rate and COD removal efficiency were 18.04 and 11.72 percent in the 3D electrode system using Ti/Sn-GAC as the particle electrode,which have a better treatment effect than using GAC as particle electrode.Loading of TiO₂ and SnO₂ on GAC can significantly strengthen the wastewater treatment process in 3D electrode system.?3?The degradation conditions of AO7 were optimized by orthogonal design in a 3D electrode reactor using Ti/Sn-GAC as the particle electrode.Five factors and four levels were selected,including the voltage gradient,amount of packed particle electrode,electrolyte concentration,pH and reaction time.Results showed that the reaction time and amount of packed particles were the most important factors affecting the degradation of AO7.At the same time,the optimum parameters for AO7 degradation were as follows:the voltage gradient was 1 V/cm,particle electrode loading was 200 g/L,electrolyte concentration was 0.07 mol/L,pH=3,and the reaction time was 120 min.Under the optimal conditions,the decolorization rate of AO7 was 84.74%and COD removal efficiency was 51.37%.The process of decolorization and COD removal for AO7 simulated dye wastewater followed first order kinetics.?4?The possible degradation pathways of AO7 molecules in the 3D electrode reactor were analyzed using UV-Vis combined with GC-MS.The results showed that the AO7 molecules were firstly degraded into aromatic compounds followed with ring opening to be small molecules of acids,alcohols and alkanes,and finally mineralized to CO₂,H₂O and inorganic salts.?5?The results showed that the AO7 simulated dye wastewater was difficult to be biodegraded initially with the BOD₅/COD value of 0.07?less than 0.3?.After 120 min of reaction,the value of BOD₅/COD increased to 0.41?more than 0.3?.The biodegradability of the wastewater was improved obviously,which is benefical to the subsequent biological treatment.