| Polyvinylidene fluoride is an excellent raw material for separation membranes.But its hydrophilicity is poor and easy to be contaminated,which is an urgent problem to be solved.Nano-hydroxyapatite has nano-size effect and high biocompatibility,hydrophilicity and excellent adsorption performance,making it widely used in biomedical and adsorption separation fields.This subject uses a new type of nano-hydroxyapatite(n HA)to modify polyvinylidene fluoride(PVDF)to improve the hydrophilic properties,anti-pollution properties,and adsorption properties of the membrane to a certain extent.The prepared Nano-hydroxyapatite/Polyvinylidene fluoride(n HA/PVDF)composite film makes full use of the advantages of both to make up for the shortcomings of single material applications.The thesis mainly studies the preparation and adsorption performance of a new n HA/PVDF composite membrane.First,a new type of n HA was synthesized with different template ionic liquids[Amim]Cl,[Bmim]Cl,etc.Combined with reflux-hydrothermal method,and its crystalline properties and micromorphology were explored.After optimizing the experimental scheme,n HA was compounded with PVDF.The morphology,structure,separation and permeability,mechanical properties,hydrophilicity,thermal stability,and adsorption properties of the dye methylene blue were studied.The results show that:(1)A new type of nano-structured hydroxyapatite was successfully prepared using different types of ionic liquids as templates.The crystalline properties of n HA prepared by using ionic liquid[Amim]Cl as a template are the best;it has a rod-like mesoporous structure with a rod length of 30-50nm and a rod width of 15-25nm;the surface is covered with pits with a diameter of 2-5nm;the specific surface area is 91.425 m~2/g,pore volume is 0.42 cm~3/g;(2)A new type of n HA/PVDF composite membrane was successfully prepared by blending-phase inversion method.With the increase of the amount of n HA added,the pure water flux of the composite membrane increased,the hydrophilic properties became better,the surface pore distribution gradually increased,and the pore size increased accordingly.When the amount of n HA added was 2%,the n HA/PVDF composite membrane had the largest bovine serum protein retention rate was 97.2%.The maximum porosity and pore size were 79%and 48nm,respectively.At this time,the tensile strength reached the best,0.8Mpa.When the amount of n HA was 6%,the maximumelongation at break is 147%;it is known from the infrared spectrum of the composite film that the addition of n HA improves the thermal stability of the composite film to a certain extent.(3)The adsorption performance of n HA/PVDF composite membrane on methylene blue shows that the adsorption effect is the best when the concentration of methylene blue solution is 15mg/L.When the amount of n HA added is 4%,the adsorption capacity of the composite membrane is the best.When the adsorption temperature is 50?,the maximum adsorption capacity is 1.25mg/g;as the mass of the adsorbent composite membrane increases,the adsorption capacity first increases and then decreases.By fitting the adsorption kinetic model,the results show that the adsorption of methylene blue by the n HA/PVDF composite membrane conforms to a pseudo-second-order adsorption kinetic model;by fitting three adsorption thermodynamic curves,the thermodynamic process of methylene blue adsorption by the n HA/PVDF composite membrane is more in line with Freundlich Isothermal model. |
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