| With the development of economy,industrial and domestic water consumption is increasing rapidly.Water pollution is one of the most urgent problems in the world.According to statistics,the global industrial water consumption in 2006 has reached 2.07 trillion cubic meters,while 420 billion cubic meters of sewage and industrial wastewater discharged into the natural water,more than 38%of fresh water resources were polluted,so the management of water pollution is particularly important.Coal is the main energy in China,the environmental problems caused by the use of coal and its related technology should not be underestimated,especially the wastewater of coal in the high-temperature distillation and gas purification,chemical products refined process.Wastewater contains phenol,cyanide,ammonia,tar and other pollutants and wastewater has high concentration of pollutants,color and biological toxicity,it is a typical refractory organic wastewater.In the process of measuring COD of coal gasification wastewater,the measurement is not allowed and the data is fluctuate by the national standard "Water quality-Determination of chemical oxygen demand-fast digestion spectrophotometric method".This article explains the phenomenon.In this paper,the research content includes:(1)The changes of the COD value of the liquefied water after ultrasonic treatment were investigated under different initial pH,different ultrasonic power,different ultrasonic frequency and different solution concentration.The results show that CODcr has a significant fluctuation in the reaction of CODcr under different initial pH conditions of ultrasonic degradation of coal gasification.In addition,during the experiment,it was found that the reaction solution was not treated with ultrasonic,and the pH value did not change obviously.The effect of ultrasonic degradation on the pH of the reaction solution was not significant.In different ultrasonic power,Different ultrasonic frequency,different solution concentration after ultrasonic treatment,the reaction process of CODcr determination,CODcr value still showed significant fluctuations.(2)The change of COD after filtration of coal gasification water by different pore size filters was investigated.The results showed that the COD of the wastewater was filtered down by ordinary filter paper and 0.45um filter,respectively,and the COD decreased gradually after the 0.22um filter,but the COD value after filtration was 0.45um.The speculation might be:Coking wastewater is filtered through the 0.22um filter and reacts with the filter so that the substance that can not be digested by potassium dichromate can be digested by potassium dichromate.(3)Explore the ultrasonic/electrochemical degradation of coal gasification.The results showed that the COD value of the reaction solution reached the maximum value at 30 min,and the COD value decreased gradually with the passage of time.In order to investigate the fluctuation of COD values during the process of ultrasonic treatment of coal gasification,we speculate that the complex organic matter in coal gasification is converted into other organic matter during the reaction process due to the cavitation of ultrasonic waves.In order to verify the idea,the composition of the organic matter in the coal gasification water before and after the ultrasonic reaction was qualitatively analyzed.The water samples were characterized by GC-MS and analyzed by the spectra.To see whether the composition of the organic matter in the coalified water after the ultrasonic reaction is increased.(4)The GC/MS spectra of coal gasification after ultrasonic treatment and the GC/MS spectra of coal gasification water were compared and analyzed.It was found that the number of organic matter in the water after ultrasonic treatment increased,indicating that under the effect of ultrasonic cavitation,The chain bonds between organic matter are broken or degraded,resulting in new substances.Compared with the GC/MS spectra of coal gasification bef-ore and after ultrasonic,it was found that the peak area of organic matter in the same retention time was reduced to some extent,which indicated that the ultrasonic cavitation effect was not selective and had universal application value.(5)In view of the above situation,the COD value is not accurate,the fluctuation is easy to explain the above reasons,select the typical organic matter in coal gasification,select the high content of coal gasification of phenolic compounds,phenol as an example;select typical miscellaneous Organic compounds,pyridine as an example;select a typical polycyclic organic material,quinoline as an example.Using the national standard "water quality chemical oxygen demand determination-rapid digestion spectrophotometry",with potassium dichromate on phenol,pyridine,quinoline these organic matter digestion,measured the equivalent of COD value.The results showed that pyridine could not be digested with potassium dichromate,and it was explained that the COD measurement fluctuation and COD measurement data were not accurate during the above experiment.(6)Explore the digested pyridine solution for band scanning.The results show that the digested pyridine solution produces two peaks at about 200 nm and about 350 nm,respectively.The peak at 200 nm represents the total nitrogen of the solution after digestion,and the magnitude of the absorbance represents the amount of total nitrogen in the solution after digestion.The peaks present at 350 nm represent the generation of flavonoids.Flavonoids refer to a series of compounds in which two phenolic hydroxyl groups of benzene rings(A-and B-rings)are interconnected by a central tri-carbon atom.(7)GC/MS analysis of effluent from different time periods for the treatment of pyridine by ultrasonic/electrochemical techniques.The results show that the content of pyridine in the solution decreases with the progress of the ultrasonic/electrochemical reaction and is accompanied by the production of new substances during the reaction.As shown in Figure 5.1,the peak at 4.26 min represents pyridine,and as the reaction time progresses,a new substance is produced in the solution.We can see that in the process of treating the pyridine solution by ultrasonic/electrochemical,Pyridine into a number of new substances,we speculated that the cavitation in the ultrasonic cavitation,the pyridine ring open,so that it is converted into other substances,and then detected a small molecular material,so that by ultrasound/electrochemistry can make pyridine This toxic,difficult to degrade the material to the effective degradation. |
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