| Modern coal chemical plants consume a lot of water and discharge a significant amount of wastewater.How to efficiently treat coal chemical wastewater to achieve complete recycling of water resources and "zero discharge" of pollutants is a key problem that needs to be solved.Coal chemical wastewater contains high concentrations of organic matter with a complex composition and is challenging to degrade.Conventional microbiological methods have limited ability to remove these pollutants,which makes biochemical effluent difficult to meet standards.In order to clarify the reasons for the difficult degradation of coal chemical wastewater,investigate the degradation pathway and mechanism of ozone oxidation of chemical pollutants,and solve the current problems of low efficiency of non-homogeneous ozone catalysis and unclear degradation mechanism,we explored the water quality change pattern of coal chemical wastewater on the basis of typical coal chemical projects and water quality analysis,and selected phenol and quinoline,which are the most abundant chemical compounds in fixed-bed gasification wastewater,as the research objects.The degradation mechanism of phenol and quinoline in the ozone-catalyzed oxidation reaction was clarified,and the molecular structure of their intermediate products was clarified,and an ozone catalyst modification method based on the efficient degradation of intermediate products was proposed.Finally,the mechanism of catalyst modification was revealed through extensive experiments and characterization analysis,and the effectiveness of the catalyst for the removal of organic matter from actual coal chemical wastewater was evaluated,forming an efficient ozone-catalytic oxidation process system for the deep treatment of coal chemical wastewater.Among the ozone-catalyzed degradation products of phenol,the percentage of cyclohexanol molecules was found to be about 70%,and the content slowly decreased as the reaction proceeded,while a small amount of 2,2’-methylenebis-(4-methyl-6-tertbutylphenol),a strong antioxidant by-product,was polymerized,and its percentage was about 10%,and its content slowly increased as the reaction proceeded.The content of phenol and phthalic acid increased,accounting for 20.39% and 16.21% of the chemical composition.While they continued to decompose into smaller molecules until they were completely oxidized,they also continued to add and polymerize into long hydrocarbon organic compounds of C16-C24,which was inferred to be one of the main reasons for the difficulty of complete degradation of organic compounds in coal chemical wastewater.The Fe-Ce active component was selected as the dominant ozone catalyst.The best component content of 10% and the optimum roasting temperature of 550 ℃ were determined.Based on the degradation mechanism of phenol and quinoline under nonhomogeneous ozone catalytic oxidation,a catalyst modification idea based on enhanced contact mass transfer of degradation intermediates was proposed.The catalyst was modified with non-polar aromatic solvents using key intermediates,cyclohexanol and phthalic acid.It was inferred that such clusters could help capture similar compounds molecules produced during the degradation of phenol and quinoline.This could improve the contact rate and mass transfer efficiency between organic substances and the catalyst surface.This could improve organic substances removal rates.The modified ozone catalysts were effective,especially for the removal of single-component phenol and quinoline solutions with an average removal rate of 70%,which was more than 220%more efficient than the ozone oxidation reaction without the catalyst and 30%-35%more efficient than the ozone catalyzed oxidation reaction without the modified catalyst.The modified ozone catalyst was used in two scale coal chemical projects(1 t/h)for pilot tests of non-homogeneous ozone catalytic oxidation,and the test results showed that the removal rate could reach more than 50%,and the performance was significantly better than that of ordinary catalysts,and the effluent water quality was stable.The organic removal rate was stabilized at 48%-52%,and the application of the modified catalyst and the complete non-homogeneous ozone catalytic oxidation process system to treat coal chemical wastewater was remarkable. |
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