Modified Preparation Of PDMS/PVDF Composite Membrane And Pervaporative Separation N-Butyl Acetate From Aqueous Solution

The n-butyl acetate as solvent is widely used in chemical,and the wastewater what is generated from the industrial production process contains a small amount of n-butyl acetate.The recovery of organic from aqueous solution is the most important techniques to be tackled in developing green processes.It is difficult for some traditional separation methods to treat azeotropic system formed between ester and water.Because pervaporation technology has many advantages such as low cost,flexible operation,high separation selectivity and low energy consumption,it is especially suitable for the separation of azeotrope system.Polydimethylsiloxane(PDMS)which is known as one of typical organophilic membrane materials has potential application prospects for pervaporation recovery n-butyl acetate from aqueous solution.In this work,PDMS composite membranes were prepared for pervaporation separation n-butyl acetate from aqueous solution using PVDF film as support layer and the hydrophobic nano SiO2 and ZIF-8 as modified filler.The morphology,chemical structure and physciochemical property of membranes were characterized by scanning electron microscope(SEM),fourier transform infrared spectroscopy(FTIR),X-ray diffraction(XRD),tensile testing,contact angle and positron annihilation lifetime spectroscopy(PALS).It is proved that the modified membrane has high selectivity for the adsorption of n-butyl acetate through the calculation of the solubility parameters of the modified membrane,n-butyl acetate and water.The effect of the loading of SiO2 and ZIF-8,feed concentration and feed temperature on swelling behavior and pervaporation performance were studied.The results indicated that SiO2 particles dispersed uniformly in the membrane material and ZIF-8 was mainly distributed at the bottom of the membrane and no chemical interactions occurred between the modifiers and PDMS polymer chain.The mechanical strength and hydrophobic properties of the filled film were obviously improved by incorporation of the SiO2.The hydrophobicity of hybrid membrane was slightly enhanced by ZIF-8 modification.With increase of SiO2 content,the adsorption capacity of n-butyl acetate solution in the hybrid membranes increased first and then decreased,while the permeation flux decreased and the separation factor increased initially and then decreased.When the SiO2 content was 4 wt.%,the maximum values of the separation factor was 542.With increase of ZIF-8 content,the swelling degree of tne hybrid membrane reduced,while the permeation flux was significantly improved,and the separation factor increased first and.then decreased.When ZIF-8 loading content was 6 wt.%,the maximum separation factor was 464.The effects of feed concentration and temperature on separation performances for SiO2 modified membranes were similar to ZIF-8.With the rise of feed concentration,the permeation flux increased while the separation factor increased initially and then decreased.With increase of feed temperature,the permeation flux increased while the separation factor decreased.