| As a new class of porous inorganic-organic hybrid crystalline materials,metal-organic frameworks(MOFs)are exploring their applications in storage,separation and sensing,etc.Membrane separation technology with high efficiency,energy saving,economic and other characteristics,is being widely used in the separation and purification of liquid.Polyvinylidene fluoride(PVDF)is a kind of optimizing membrane materials for pressure resistance,high-performance water treatemt,has been widely used in microfiltration,ultrafiltration and other fields.Currently,the researches on the applications of MOF films or membranes are still less,especially the continuous MOF membranes for the liquid separation combined with other membrane is still very small.Studies have shown that the combinning MOF and porous membrane is an effective way to improve the separation permeability and separation performance of MOF mmebrane.Therefore,in this paper combinning the characteristics separation ability of MOF and PVDF to use for oily waste water treatment,PVDF/TIF-A1 and PVDF-g-PAA/ZIF-8 composite membranes were respectively prepared and the separation performance of modified PVDF membrane was systematically studied.The specific contents are as follows:(1)PVDF/TIF-A1 membrane was prepared by blending a novel MOF materials Zn(ad)(int)·(DMF)(TIF-A1)in the casting solution.Then the influence of surface and cross section morphology,the impact of surface hydrophobicity,emphasis on the oil-water separation performance and stability of the membrane were investigated.The results show that TIF-A1 has a very big role on improving the hydrophobicity,flux and change the membrane pore size factors,and the blended membrane obtained a good performance of oil-water separation,the oil content after the separation of n-octane,iso-octane and n-hexane oil-water emulsion has reached more than 95%.The initial contact angle of the film increased by 49.9°,from 102.2 0 to 152.1°,water flux increased by about 10 times.Modified membrane also has a very good flux and separation stability.The results showed that the TIF-A1 improved the hydrophobicity and flux,and endowed a good oil-water separation ability to the blended membrane.(2)PVDF-g-PAA grafted membrane was prepared by physical adsorption radical polymerization process,and then PVDF-g-PAA/ZIF-8 composite membrane was prepared by in situ growth.The effect of different growth conditions inculding solvents and time on the preparation of the membrane were investigated,and the results showed growth for 48 h in methanol was the best conditions after a detailed surface morphology comparison.The surface contact angle of oil and water was tested,the results showed the membrane obtained good lipophilicity and hydrophobicility.The water initial contact angle of the membrane increased from 102.2 °to 136.6 °.The average pore size,surface pore density,porosity,water flux and separation performance of the PVDF-g-PAA/ZIF-8 membrane were investigated after in situ growth of ZIF-8 in methanol at different time,and compared with the PVDF/ZIF-8 prepared under the same condition.The results showed that the hydrophobic and oil-water emulsions flux and separation performance of the PVDF-g-PAA membrane have been significantly improved after situ growth ZIF-8.The emulsion flux of membrane reached 115.4 ± 1.4(L·m-2·h-1),and the flux and separation ablility showed good stability. |
