| The rapid development of the coal chemical industry makes the treatment of highconcentration phenol-containing wastewater a problem,which seriously affects the sustainable development of the industry.Solvent extraction is the mainstream process for the recovery of phenols in such wastewater.However,the commonly used industrial dephenolic extractant is generally expensive and low dephenolic efficiency.In this study,the coal chemical wastewater containing phenol was taken as the research object,and the extractant methyl isobutyl ketone(MIBK),which is widely used in industry,was used as the main extractant,based on the theory of collaborative extraction,the economic and effective mixed extraction agent was selected by the extraction experiment.The effect of different process conditions on the extraction effect of the mixed extractant was investigated through extraction experiments,and the process conditions were optimized through response surface analysis to determine the field test process parameters.On this basis,field experiments on wastewater extraction and solvent recovery were carried out.The results are as follows:(1)The binary mixed extraction agent MIBK+ iso-amyl alcohol,MIBK+ diisopropyl ether,MIBK+ ethyl acetate,MIBK+ butyl acetate was mixed with coal chemical wastewater in a volume ratio of 1:5 for single stage countercurrent extraction experiment,and compared with 5 single extractants.It was found that when the mixing ratio of MIBK and butyl acetate was 9: 1,8: 2 and 7: 3,and the initial concentration of volatile phenol in the wastewater was 1321.32 mg / L,the extraction rates were 90.64%,90.94% and89.93%,respectively.The combination of MIBK and butyl acetate can effectively improve the extraction performance of the extractant,and the extraction efficiency of phenol is obviously higher than that of a single extractant.The effect of the mixing ratio of MIBK + butyl acetate + isoamyl alcohol,MIBK + diisopropyl ether + isoamyl alcohol on the extraction rate of volatile phenol was further analyzed,the results showed that the extraction efficiency of phenol in ternary mixed extraction system was lower than that of MIBK and butyl acetate in binary mixed extraction system.(2)In order to save the consumption of extraction agent,the extraction performance of mixed extraction agent under low comparison conditions was investigated,four kinds of mixed extraction agents were mixed with coal chemical wastewater under the condition of volume ratio of 1:10,1:15 and 1:20,respectively.The results showed that the extraction performance of MIBK+ butyl acetate was better than that of other combinations under low comparison.When the ratio was 1:15 and the initial concentration of phenol in wastewater was 1367.44 mg/L,the extraction rate reached 82.72%.(3)The results of single factor condition experiment on mixed extractant showed that the p H value of wastewater has a significant effect on the extraction rate of volatile phenol,when the initial concentration of phenol in wastewater was 1206.24 mg / L,the p H value increased from 5 to 8,the extraction rate of volatile phenol decreased from78.23% to 68.78%,and when the p H increased to 10,the extraction rate of volatile phenol decreased to 43.52%.The extraction rate of volatile phenol in wastewater decreased with the increase of wastewater temperature.The initial concentration of wastewater has a certain effect on the extraction rate of volatile phenol in wastewater.The higher the initial concentration of wastewater,the higher the extraction rate of volatile phenol.(4)According to the results of response surface analysis of volatile phenol extraction rate,it was found that the ratio of the two phases and the p H value of wastewater significantly affected the extraction rate of volatile phenol in wastewater,the interaction of each factor had no significant effect on the extraction rate of phenolic substances in wastewater.On the premise of high extraction rate and low ratio,the optimal extraction conditions for recovery of phenolic substances by mixed extraction agent(MIBK+ butyl acetate)extraction was obtained by optimizing extraction process conditions by regression model: the p H value of the wastewater was 5,the ratio of the two phases was1:15,the stirring speed was 296.37 r / min,the extraction temperature was 20 ?,and the stirring time was 14.78 min,the maximum extraction rate of MIBK+ butyl acetate was predicted to be 87.25%.(5)The mixed extractant obtained by screening was applied to the field test of extraction and dephenolization,and the results showed that when the initial concentration of phenol and oil in the wastewater was 1180.92 mg/L and 195.67 mg/L,respectively,the ratio was 1:15,and the rotary speed was 200-300 r/min,the removal rates of volatile phenol and oil were 75.34% and 75.54%,respectively.Through the optimization and improvement of the operation method of the test equipment,the removal rates of volatile phenol and oil in the wastewater were significantly improved,reaching 84.66% and78.97%,respectively.The experiment monitored the volatile phenol and oil in the wastewater continuously for one month.The removal rate of volatile phenol was basically stable at about 84%,and the removal rate of oil was about 78%.The concentrations of phenol and oil in the effluent were 210.28 mg / L and 46.49 mg / L,respectively,which can meet the requirements of subsequent biochemical treatment after deamination.(6)The recovery of the mixed extractant and crude phenol adopts the rectification method commonly used in industry,and the recovery rate of the extractant in this test can reach 95.17%.Through economic analysis of the phenol extraction and extractant recovery operation test,it was found that the cost of the reagent required for the extraction and removal of phenol from the wastewater of the test project was 4.13 yuan / ton,compared with the single phenol extraction agent and high ratio extraction process,the cost of mixed extraction agent and low ratio phenol extraction process extraction agent can save about 0.96 yuan/ton,and it has a good production application prospect. |
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