The Treatment Of Dye Wastewater By Catalytic Multi-electrodes

China is the main country of producing dyes. A large quantity of wastewater is discharged in the process of dye producing and it has reached 157 million tons per year, which causes considerable environmental pollution problems. Dye wastewater is known to contain large quantity of unbiodegradable organic substances and inorganic salts, strong color, high COD, complex composition and low biodegradability. Besides, there have been more and more new types of dye which are more resistant to be broken down in the condition of sunlight, oxidation and biochemical reaction. So it becames more difficult to treat the wastewater of dye efficiently and attracted more attention in the industrial wastewater pollution control.In this paper, activated carbon loaded manganese was used as multi-electrodes and the removal processes of colority and COD_Cr of simulated Reactive Light Yellow K-4G dyestuff were investigated. Meanwhile, the effects of activated carbon with and without manganese were compared. The results showed that catalytic multi-electrodes could increase the removal rates of decoloration and CODcr more efficiently in comparison with activated carbon multi-electrodes. When it was treated under the condition of current density 1.4mA/cm², they were increased by 10% —15 % at the same time. The final removal results at 90 minutes reached 84% and 69%, respectively. The influences of current density, time and mass transfer on theremoval results were also discussed. From the experimental results, increasing of current density and improving the condition of mass transfer were helpful to treat Reactive Light Yellow K-4G in wastewater. In our experiment, current density of 1.4mA/cm2 and velocity of 55Or/min were the optimal.In experiments of treating single-composition and double-composition dye wastewater by the method of catalytic multi-electrodes, the decoloration and CODo removal rates were compared and analyzed. Moreover, dye wastewater from an actual dye production process in Zhejiang province was treated and the effect was studied. According to the results, CODcr removal rates of the simulated mixed dyestuff were lower than mean removal rates of single-composition dye treated at the same time or close to those. Howerer, decoloration has a quite different results. When actual dye wastewater was treated in 90 minutes under the condition of current density of 1.4mA/cm2, the decoloration and CODcr removal rates reached 40% and 58%, respectively.By means of UV-Vis spectra, it was found that chromophores and benzenoid structures were destroyed evidently by the method of catalytic multi-electrodes. Under the condition of current density of 1.4mA/cm2, wave crests of visible light and ultraviolet area of Reactive Light Yellow K-4G dye almost disappeared completely in 90 minutes. The wave crests of visible light area of Disperse Blue 2BLN almost disappeared completely and that of ultraviolet area declined remarkably.In this paper, the electrochemical regeneration, primary factors influencing regeneration results and the changes of adsorptive isotherm of activated carbon after being regenerated were also studied. From the experiment results, electrochemical regeneration could renew adsorptive capacity of activated carbon partly. Regeneration results could be improved through prolonging treatment time, increasing current density, enhancing electrolyte concentration or selecting NaCl as electrolyte instead of NaiSCU. The types of adsorptive isotherm of activated carbon regenerated changed a little. However, the adsorptive capacity and adsorptive abilitywere getting drop.According to the result of power X-ray diffraction, the manganese loaded on activated carbon was Mn3C>4. Possible mechanism was also discussed.The main innovation points of this paper were as follows.(a) Catalytic multi-electrodes of activated carbon loaded with manganese were made. The possible mechanism of the processes for the treatment of dye wastewater by the catalytic multi-electrodes was studied.(b) It was more difficult to remove CODcr in mixed dye wastewater than that in wastewater with single type of dye. But it was possible to improve the removal results of colority in mixed dye wastewater. By means of UV-Vis spectra, The possible mechanism of the phenomenon was investigated.(c) The electrochemical regeneration, primary factors influencing regeneration results and the changes of adsorptive isotherm of activated carbon after being regenerated were studied more comprehensively.Results from the study offer theoretic basis to further investigate treatment of dye wastewater by Catalytic multi-electrodes.