Research On Preparation And Application Of Superhydrophobic PVDF Membrane

The greenhouse gas of CO₂ has become a hot topic in the world.It has become an urgent problem to promote carbon emission reduction.The characteristics of absorption CO₂ in flue gas by membrane absorption method can avoid secondary pollution to the environment mean while effectively reduce the operating cost,but its carbon removal efficiency is affected by the wetting behavior of membrane.The membrane wetting behavior could be reduced by the superhydrophobic membrane,which has a broad the application of membrane absorption to remove CO₂.The traditional polyvinylidene fluoride?PVDF?membrane has a good hydrophobic,but it can not meet the demand of membrane absorption carbon capture.Therefore,further improving the hydrophobic of PVDF membrane is the key to its application in carbon capture.In this paper,the precursors of superhydrophobic PVDF membrane was prepared by phase inversion method and modified by surface coating,which enhanced the hydrophobic property of PVDF membrane.And it can be operated stably in the carbon capture by membrane absorption method.Firstly,the precursors of superhydrophobic PVDF membrane was prepared by phase inversion method.The effects of the composition of coagulation bath,the type and amount of pore forming agent,PVDF concentration,casting solution extrusion rate on hydrophobic,air flux,pore size and porosity of the precursors of superhydrophobic PVDF membrane were studied.The optimum preparation process of the precursors of superhydrophobic PVDF membrane was determined.Then the precursors of superhydrophobic PVDF membrane with characters of high flux and high hydrophobic was prepared and optimized.The results showed that the precursors of PVDF superhydrophobic membrane with small pore size?0.975?m?and high porosity?75.12%?was successfully prepared.The composition of coagulation bath was ethanol/vinyl acetate at a mass fraction of 60 wt.% ethanol,PVDF concentration was 16 wt.%,addition of pore forming agent PEG-400 was 5wt.%,casting solution rate was 6mL·min-1,the membrane flux was increased to 276.09m3·m^-2·h^-1.The contact angle of membrane owing strong hydrophobic was increased significantly to 131.43°.Secondly,the surface coating method was used to modify the hydrophobic of the precursors of superhydrophobic PVDF membrane.Effects of different dispersing agent,inorganic nano particle,adhesive polydimethylsilane?PDMS?,silane coupling?KH-550?on the properties of superhydrophobic modified PVDF membrane were studied by measuring pore size,porosity,flux and contact angle.Results showed that when the dispersant was isopropanol alcohol,addition of nano-CaCO3 was 1wt.%,PDMS was 1.5wt.%,KH-550 was 1wt.%.The hydrophobic was increased from 131.43° to 147.06°.At the same time,the pore size was 0.959?m,the porosity was 74.88%,the flux was 264.12m3·m^-2·h^-1.The data of these were lower than those before modification.At last,the study of CO₂ removal rate membrane absorption was carried on.The effects of different kinds of absorption,concentration of the absorbed liquid and the flue gas flow on the removal rate of CO₂ was investigated.The research showed that potassium glycine?PG?was the most compliant absorption solution,the removal rate of CO₂ in the same concentration solution was PG>MEA,an optimal value of concentration of absorption solution was 2mol·L-1.The removal rate of CO₂ can be decreased by the increase of gas flow velocity.The removal rate of CO₂ was 81.43% when the concentration of PG solution was 2mol·L-1 and flow rate was 0.06m3·h-1.