Study Of A Novel Process By Combined Oxidation For Removal Of COD_Cr From Printing Works Wastewater

Printing works wastewater contains complicated organism and is highly colored and difficult to degradate bio-chemically, so it pollutes the environment seriously. According to the printing works wastewater character of high-salt, CODMn<5000mg·L-1 and CODCr< 7000mg·L-1，we propose a novel process to treat the printing works wastewater by combined extraction, hydrated MnO2 oxidation and electrochemical oxidation. It means, firstly, using castor-oil acid extraction wastewater separation of organic matter, and then using hydrated MnO2 oxidation part of the COD, lastly, using electrochemical catalytic oxidation to remove COD by advanced oxidation to blow 1000mg·L-1 to transfer to secondary sewage treatment plants for advanced treatment.The process of combining combined extraction, hydrated MnO2 oxidation and electrochemical oxidation was applied to romove CODCr from the printing works wastewater. The impacts of different factors on the treatment of the printing works wastewater with this technology were investigated. The results showed that when the hydrated MnO2 was used separately to treat the printing works wastewater, it achieved a highest CODCr remove rate of 40% under the condition of hydrated MnO2 dosage of 44g/L, H2SO4 dosage of 65.32g/L and oxidation time of 9h. And when the electrochemical oxidation was used separately, it achieved a highest CODCr remove rate of 72.22% with the energy consumption of 48.07kWh/kgCODCr under the condition of cell voltage of 4.3V and the time of 18h. After the separation pretreatment by the castor-oil acid extraction, the wastewater was then oxided by the hydrated MnO2. The process need no H2SO4, dosage of hydrated MnO2 of 22g/L and only take 1h,so it greatly introduces the dosage of H2SO4 and the reaction time. In addition, cyclic utilization of hydrated manganese dioxide to remove CODCr is achieved due to that Mn2+can be oxidized to MnO2 by O2 in alkaline conditions. After the castor-oil acid extraction and hydrated MnO2 oxidation, the printing works wastewater was treated to remove COD to blow 1000mg·L-1 by the electrochemical advanced oxidation under the condition of cell voltage of 4.3V and the time of 9h. In this way, it significantly reduces the work load and energy consumption of the electrochemical oxidation to romove CODCr. Overrall, after the treatment by combined extraction, hydrated MnO2 oxidation and electrochemical oxidation, the CODCr concentration decreased from the initial about 6800mg·L-1 to about 1000mg·L-1, and the removal rate reached 85.3%.