Optimized Fabrication Of PDMS/PVDF Composite Membrane And Its Application In Biobutanol Separation

In recent years,the shortage of traditional fossil fuels and the environmental pollution problems caused by them have become more and more serious.The production of biobutanol by bio-fermentation has become the focus of researchers.The butanol yield is lower due to the inhibitory effect of the product butanol on the strain in the current ABE fermentation process.Therefore,in order to reduce the inhibition of butanol and increase the yield of butanol,the pervaporation membrane separation technology is used to improve the production efficiency of product butanol in the subsequent fermentation separation coupling experiment.Choosing the right pervaporation membrane is the key to pervaporation technology.Due to the shortcomings of pure PDMS homogeneous membrane with poor mechanical properties and poor film formation,PDMS/PVDF composite membranes were prepared by spraying technology with PVDF as support layer,aiming to improve the separation efficiency of butanol under the premise of ensuring the mechanical properties of the membrane..In this paper,the effects of cross-linking agent dosage and PDMS viscosity on the pervaporation performance of the composite membrane were investigated in turn.The effects of PDMS concentration(wt.%)and spraying time on the pervaporation performance of the composite membrane were further investigated by response surface methodology.The interaction effect exists,and the composite membrane with better separation performance is prepared by changing the membrane forming conditions.In order to better study the separation performance of the composite membrane and analyze the structural characteristics of the composite membrane,it is characterized by scanning electron microscopy,infrared spectroscopy and energy dispersive X-ray spectroscopy.Finally,the surface of the composite membrane is smooth,uniform,compact and defect-free.The PDMS selective layer and the support layer in the cross section of the composite membrane are well combined,and no obvious delamination and leakage occur.From the infrared spectrum,it was found that the composite membranes prepared by five different molecular weights had obvious cross-linking reaction,and the cross-linking degree of PDMS and TEOS was the best at the mass ratio PDMS:TEOS=1:0.3.Through the energy spectrum analysis of the composite membrane,it is found that the ultrafiltration membrane is more suitable as a support layer than the microfiltration membrane.The PVDF membrane in the ultrafiltration membrane has the advantages of good hydrophobic property and good thermal stability,and is more suitable for the support layer.The 15 g/L aqueous solution of butanol was used as the raw material to be separated,and the influence of the amount of crosslinking agent and the viscosity of PDMS on the separation performance of the composite membrane was investigated in order.The conclusions of the cross-linking agent experiment are consistent with the conclusions obtained by infrared spectroscopy,that is,the composite membrane with the best crosslinking agent dosage of 0.3(TEOS and PDMS mass ratio)has the best separation effect,its permeation flux and separation factor.They were 213.8 g/(m~2·h)and 38.9,respectively.With the increase of the viscosity of PDMS,the separation factor of the composite membrane increased,the permeation flux decreased,and the separation factor reached the maximum when the PDMS viscosity was 155,000 cst,which was 51.1.Then,based on the raw material liquid,the influence of temperature and concentration on the separation performance of PDMS/PVDF composite membrane was tested.The results showed that the temperature and concentration increased,the total flux increased,and the separation factor increased first and then decreased.Finally,in order to get closer to the fermentation separation coupling experiment,the effect of ABE aqueous solution and fermentation broth on the separation performance of the composite membrane was explored.When the fermentation liquid is finally obtained as a raw material liquid,the selectivity of butanol is slightly improved.Moreover,when the 7 g/L butanol aqueous solution at the time of the inhibition of butanol was used as the raw material liquid,the concentration of butanol obtained by the membrane separation experiment was0.41 g/h,indicating that the membrane can be used for the butanol fermentation coupling.And have a certain value for it.