| In the development of the coal chemical industry,wastewater treatment has always been a difficult problem that hinders its development.As energy conservation and environmental protection become the theme of sustainable development in today’s society,and the country makes great efforts to control pollutant emissions,this problem has become increasingly prominent.In the wastewater produced by the coal chemical industry,the content of phenol is relatively high,and phenol is highly toxic.At the same time,it is an important chemical raw material.Therefore,it is of great significance to separate and recover it from industrial wastewater.At present,the common methods for separating phenol from industrial wastewater include extraction,adsorption,chemical oxidation and membrane separation.Among those methods,the extractant used in the extraction method is often toxic and usually causes secondary pollution.The adsorbent is difficult to regenerate.The chemical oxidation method decomposes phenol,and thus phenol cannot be recovered.However,the energy consumption is less in the membrane separation process,the membrane materials need not been regenerated and there is no secondary pollution produced in the process.Membrane separation technology has become one of the most promising technologies for the separation and recovery of phenol from wastewater owing to the advantages mentioned above.The separation performance of membranes depends on the nature of the membrane material.As a new type of additive used in mixed matrix membranes,metal organic framework materials(MOFs)have a strong interaction between their organic ligands and polymer matrix,which makes them more uniformly distributed in the organic matrix and better combined with the organic matrix,and hence,the mixed matrix membranes with MOF as additive possess more excellent separation performance.In thesis,by introducing strong hydrophobic metal-organic framework material ZIF-L crystals into organic matrix PEBA2533,a series of ZIF-L/PEBA2533 mixed matrix membranes were prepared;then the PTFE support layer is introduced into the membranes to prepare ZIF-L/PEBA2533/PTFE composite membranes;Finally,the ZIF-L/PEBA2533/PTFE composite membrane with oriented ZIF-L crystals was prepared.The ZIF-L crystals and membranes as synthesized were characterized by SEM,XRD,ATR-FTIR,contact angle,thermogravimetric and mechanical property testing,and the three kinds of membranes were used to separate and recover phenol from phenol solution.The specific research content is as follows:1.ZIF-L/PEBA2533 mixed matrix membranes with different amount of ZIF-L were prepared.The influence of additive content on membrane structure and membrane separation performance were investigated,and the influence of operating temperature and feed concentration on the separation effect were also investigated.The results show that with the increase of the loading amount of ZIF-L crystals(0-50 wt.%),the hydrophobic property of the membranes gradually increase,but the agglomeration degree of ZIF-L crystals also gradually increases,resulting in an increase in the interface defects between the crystals and the matirx.As the defects increase,the separation performance of the mixed matrix membranes for phenol solution first increases and then decreases.When the ZIF-L crystal content is 30 wt.%in the membrane,the membrane shows the best separation performance for phenol.At the same operating temperature,the concentration of phenol solution has little effect on the total flux.The flux of phenol increases with the concentration of phenol solution,while the water flux presents the opposite trend.The separation factor is larger for a more dilute phenol solution,and it decreases as the concentration of the phenol solution increases,until the concentration of the phenol solution increases to 2000 ppm.After that,continue to increase the concentration of the phenol solution(2000～12000 ppm),the separation factor is almost constant.When the concentration of the phenol solution reaches 15000 ppm,the membrane is broken.When the concentration of the phenol solution is constant,the total flux,phenol flux,water flux and separation factor all increase with the increase of the operating temperature.On the membrane with the best separation performance,when the feed concentration increases from 80 ppm to12000 ppm at 80℃,the total flux increases from 1439.14 g/(m~2·h)to 1681.93 g/(m~2·h),and the separation factor reduces from 281.16 to 120.95.2.A ZIF-L/PEBA2533/PTFE composite membrane with 30 wt.%ZIF-L crystals and PTFE as support layer was prepared.The effects of the support layer,operating temperature and feed concentration on the separation performance of the membrane were investigated.The results show that after the introduction of PTFE support layer,the total flux and separation factor increase,and the membrane can be used in solution with bigger phenol concentration(12000～18000 ppm).The introduction of the support layer basically does not change the influence of the operating temperature and the concentration of the phenol solution on the total flux,the phenol flux,the water flux and the separation factor.When the phenol solution concentration increases from 15000 to 18000 ppm,the separation performance of the membrane decreases.At 80℃,when the feed concentration increases from 80 ppm to 15000 ppm,the total flux increases from 3118.86 g/(m~2·h)to 3799.21 g/(m~2·h),and the separation factor decreases from 280.90 to 160.25.3.The ZIF-L/PEBA2533/PTFE composite membrane with oriented ZIF-L crystals was prepared,and the influence of operating temperature and feed concentration on the separation effect of phenol solution was investigated.When ZIF-L crystals orient in the matrix,the crystals distribute in the organic matrix more uniformly,the agglomeration of the crystals is restrained,and the combination of the crystals with the organic matrix is improved,so that the separation ability of the membrane is enhanced.The orientation of ZIF-L crystals in the membrane does not change the influence of operating temperature and phenol solution concentration on the total flux,phenol flux,water flux and separation factor,either.At 80℃,when the feed concentration increases from 80 ppm to 15000 ppm,the total flux increases from 5302.01g/(m~2·h)to 5301.34 g/(m~2·h),and the separation factor decreases from 282.60 to 163.38. |
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