Study On Treatment Of Indigo Carmine Wastewater By Electro-Catalytic Oxidation With Pulse

In present, the annual dyes production of China accounts for over60percents inglobal total production. However, for the reason of small and sporadic production scale,and backward production technology, domestic dyestuff factories are inefficient in use ofdyes that results in large amounts of the Three Wastes including exhaust gas, wastewaterand solid waste. Among of the Three Wastes, the problem of wastewater is especiallyserious. As a typical wastewater, dye wastewater has features of high chroma, complexcomposition, high concentration of organic compounds, high toxicity,less-biodegradability, and large variation in quality and quantity, thereby it will pollutewater environment heavily once discharged directly. Therefore, treatment of dyewastewater has always been a difficult problem for dye industry.As one kind of advanced oxidation processes （AOPs）, electro-catalytic oxidationattracts lots of concern with advantage of good performance and simple operation andenvironment-friendly. However, because of large consumption of energy, electro-catalyticoxidation is restricted during practical application. Consequently, how to reduce powerconsumption and improve of current efficiency becomes one of the hot spots in research ofelectro-catalytic oxidation.To aim at the problem mentioned above, this article utilized electro-catalyticoxidation with pulse to treat synthetic Indigo Carmine dye wastewater. On one hand, bytest method for single factor, the present work studied effects of experimental conditionsincluding initial pH value, concentration of NaCl, voltage of pulse, frequency of pulse,duty ratio and concentration of wastewater. Results indicated that after the treatment of3hours under the optimum condition of initial pH3, concentration of NaCl1.5g/L, voltageof pulse15V, frequency of pulse4kHz, duty ratio0.40and concentration of wastewater220mg/L, the removal efficiency of chroma and TOC of indigo carmine dye wastewaterrespectively reached99%and31.2%, the current efficiency was11.3%, and the unitvolume energy consumption was5kWh/m3. On the other hand, by determination andanalysis of degradation products using LC-MS, the author studied the transformationpathway of Indigo Carmine. The result showed that Indigo Carmine was firstly oxidized into Indirubin-5-Sulfonic acid sodium salt, and then transformed into Oxalic acid andOxalic diamide, and at last completely mineralized into CO₂and H₂O.