Study On Removal Of Phenol From Coal Gasification Wastewater With A/B Composite Membranes And ZIF-71/A/B Mixed Matrix Membranes

The membrane separation process was widely concerned because of its low energy consumption,and no pollution.The membrane separation process was used to treat coal gasification wastewater containing organic pollutants such as phenols and oil,which can realize resource recovery and generate economic benefits.At the same time,it was conducive to the management and protection of the ecological environment and energy conservation and emission reduction in the coal chemical.The separation effect of the membrane process was directly determined by the nature of membrane material.Metal organic frameworks(MOFs)not only have high specific surface area and high porosity,but also have better compatibility with polymers than traditional inorganic materials.Therefore,mixed matrix membranes(MMMs)prepared by doping MOFs into organic polymers have more excellent separation effect.The research group used A/B composite membrane to treat coal gasification wastewater and obtained preliminary research results.Based on the above results,this paper first studied the multi-stage membrane separation process of A/B composite membranes for coal gasification wastewater,and the stability of the membrane performance was investigated.Then ZIF-71 is introduced into the A/B organic polymer matrix to obtain a mixed matrix membrane.The analytical methods including SEM,XRD,ATR-FTIR,contact angle,and DSC were used to characterize the synthesized membranes.The effect of the membranes on the separation of phenol from phenol solution was investigated in detail.The specific research contents are as follows:1.Use A/B composite membranes to treat coal gasification wastewater in multi-stage membrane separation device(phenol 0.5 wt.%,oil 0.12 wt.%).The results showed that after the first-stage membrane was operated for 3 h,the content of phenol and oil in the permeate liquid was high and the oil and water separated in two layers.After the second-stage membrane was operated for 2 h,the phenol and oil concentrations in the permeate liquid decreased,the phenol concentration in the feed liquid fell below 300 ppm,and oil could not been detected.The permeate of the first and second stage membranes can been delivered to the deoiling and coarse phenol recovery device of the factory.After the third-stage membrane was operated for 1 h,the phenol in the feed could not be detected,and the permeate could been delivered into the coarse phenol recovery device of the factory.2.A single-stage A/B composite membrane was used to separate coal gasification wastewater.The stability of the membrane performance was investigated through long-period experiments.The results showed the performance of the membrane decreased at first and after 273 h of operation,it came to a stable situation.3.ZIF-71 with a crystal size of 140 nm,450 nm,and 1?m were synthesized,which were then blended with polymer A as a polymer matrix to prepare a series of ZIF-71/A/B mixed matrix membranes on the support layer B.The effects of ZIF-71 particle size,loading amount,pervaperation temperature and feed concentration on the separation effect of phenol dilute solution were investigated.It was found that additives with large particle size tended to agglomerate in the membranes,while additives with small particle size did not agglomerate and were evenly dispersed.As the particle size of the additive increases,the separation effect of the membrane decreases.Introducing140 nm ZIF-71 into A/B organic polymer matrix reduced the apparent penetration activation energy of phenol and water.With the increase of the doping amount of ZIF-71 at 140 nm(0?30 wt.%),the water contact angle increased,and the Tg decreased first and then increased.The Tg value of membranes with 15 wt.%additive the lowest in all the membranes.Total flux,phenol flux,water flux and PSI increased first and then decreased,and the maximum value is reached on the membrane with 15 wt.%additive.The separation factor increased.Using the membrane with 15 wt.%ZIF-71/A/B crystals as the separation membrane,increased the pervaporation operating temperature(20°C?80°C),the total flux,phenol flux,water flux and separation factor all Increased.At 80°C,increased the concentration of phenol solution(300 ppm to 8000 ppm),the separation factor of phenol decreased from 149.49 to 27.25;the phenol flux increased from125.09 g/(m~2·h)to 606.29 g/(m~2·h).