| Coal-tar wastewater belongs to high COD, high ammonia nitrogen, high phenol wastewater, which contains many kinds of hazardous substances, such as phenolics, oil, cyanide and so on. The phenol, which is hard to be degraded and is poisonous for aquatic organisms, is a kind of strong nerve poison and local corrosive substance. It was listed in the blacklist all over the world.Phenol is Lewis acid, so it should be extracted and separated by Lewis alkaline; N503 is a weak alkaline extractant, and it can generate 1:1 hydrogen bond formation with phenolics, which would be brought into organic phase. Then the extracted phenol was recovery by NaOH solution, and the N503 was reclaimed.The dephenolization characteristics of extraction of N503 were investigated by single factor and response surface method test. The optimal case of extraction were obtained, where the N503 accounted for extracting agent mass was 20%, the oil-water ratio was 1, the pH value was 4, the extraction time was 10 min. And the optimal case of stripping was obtained, where the NaOH solution concentration was 10%, the stripping oil-water ratio was 2.Then, the extraction rate was investigated by extracting kinetic model. The final model was that, R=1.03×10-6·Cphenol·CN5030.18.Furthermore, in order to create favorable conditions for subsequent biotreatment, the series of extraction was determined as three, and the effluent of coal-tar wastewater could be decreased to less than 10 mg/L.Based on the optimal conditions obtained in laboratory tests, we designed the actual application program of phenol removal section in Shandong coal-tar plant. The operation result dictated that N503 was a excellent extraction agent in treating coal-tar wastewater, and the project could make a profit of 15598.38 yuan per cubic metre of sewage by recycling the phenol, which will recover the cost of project within 1.5 years. |
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