Perparation Of PEBA Hybrid Membrane Filled With ZIF-8and Pervaporative Separation Of Ethyl Acetate From Aqueous Solution

As one of zeolitic imidazolate frameworks (ZIFs), ZIF-8is one of the most potentialapplication of metal organic compounds. It has high surface area, high porosity and strongadsorption capacity of organic molecules. Furthermore, ZIF-8has good compatibility withpolymer membrane materials. This paper aims at studying the influence of ZIF-8onpervaporation (PV) performance of polyether block amide (PEBA) membranes.In this paper, ZIF-8particles had been prepared by the solvothermal method, and thenadded to PEBA membrane. We researched the effect of morphology and specific surface areaof ZIF-8particle on PV performance of PEBA membrane. At the same time, we also deeplystudied the effect of different ZIF-8loading on PV performance of PEBA/ZIF-8membrane.This paper should be divided into the following three parts:1. A series of ZIF-8particles were prepared under the conditions with different molarratios of Hmim/Zn2+and different reaction temperatures, and characterized by scanningelectron microscopy (SEM), X-ray diffraction, specific surface area analysis andthermogravimetric analyzer (TG). SEM figures showed the particle size became smaller witha larger molar ratio of Hmim/Zn2+, ZIF-8particles with the largest specific surface area andmicropore volume were obtained when the mole ratio of Hmim/Zn2+was4:1. At the reactiontemperature of25oC and60oC, the granularity of ZIF-8particles was inhomogenous andpresented a serious agglomeration. The specific surface area and micropore volume of ZIF-8particles was maximum under25oC. The results indicated that different molar ratios ofHmim/Zn2+and reaction temperatures could induce the structure change of particles.2. A series of PEBA/ZIF-8membranes were prepared by adding ZIF-8particles obtainedunder different conditions to PEBA membranes, characterized by SEM, infrared spactroscopy,TG and microcomputer control electronic universal testing machine, and used to separate5wt%ethyl acetate solution by pervaporation. Finally, we discovered that ZIF-8particles withdifferent molar ratios spread evenly in the PEBA membrane, while ZIF-8particles preparedunder different reaction temperature scattered unevenly. When the Hmim/Zn2+mole ratio was1:1, the swelling degree of PEBA/ZIF-8-50membrane was minimum and the tensile strengthwas maximum. The permeability of ethyl acetate and water and the selectivity of ethylacetate/water were maximum. When the reaction temperature reaches140oC, the swellingdegree of PEBA/ZIF-8-50membrane was minimum, however, the tensile strength wasmaximum. The permeability of ethyl acetate was maximum and the water was minimum, theselectivity of ethyl acetate/water was largest simultaneously. The results demonstrated thatZIF-8particles with high specific surface area increased the solubility of ethyl acetate in thePEBA/ZIF-8-50membrane, while decreased its diffusivity. Compared to the solubility ofcomponent in the membrane, the diffusion had greater impact on the pervaporation.3. The PEBA/ZIF-8membranes with different ZIF-8loading were prepared by addingZIF-8particles with Hmim/Zn2+molar ratio of1:1when a reaction temperature was140oC.The PEBA/ZIF-8membranes were characterized by SEM, TG, microcomputer controlelectronic universal testing machine and optical contact angle measurement instrument, and used to separate5wt%ethyl acetate solutions by pervaporation. It was discovered that thecompatibility of ZIF-8and PEBA membrane was good and the thermal stability of PEBAmembrane increased after adding ZIF-8. With the increase of the ZIF-8loading, thepermeability of ethyl acetate improved and the permeability of water remained constant. Theselectivity of ethyl acetate and water presented an increasing trend with the increase of theZIF-8loading.