Synthesis Of Polyamide Membrane And Its Application In Organic Solvent Nanofiltration

As one of the most energy consumption process in chemical industry,chemical separation consumes 50%of the industrial energy use,accounting for 10-15%of the world's total energy consumption.However,80%of the separation process still relies heavily on energy intensive heat-driven process such as distillation,drying and evaporation,nonthermal-based separations make up only 20%.Membrane based process could be one order of magnitude more energy efficient than heat-driven process,membrane separation technology is gradually replacing traditional separation techniques.As a burgeoning technology of membrane science,nanofiltration can effectively separate organic molecules with at least one order of magnitude difference.Nanofiltration is a pressure-driven membrane separation process between ultrafiltration and reverse osmosis,which is used widely in the wastewater treatment,food industries and pharmaceutical industries.In this thesis,the interfacial polymerization method was used to synthesis the membrane,the pore size of the membrane and the surface properties of the membrane were controlled by using different monomer,Finally,the effects of monomer concentration and reaction time on the flux and rejection of membrane were studied.A large area membranes without any defect were prepared on the surface of polyacrylonitrile by using m-phenylenediamine and trimesoyl chloride.Fourier infrared spectroscopy and scanning electron microscopy proved that the membrane was synthesized successfully.The acetonitrile flux of the m-phenylenediamine polyamide membrane was up to 20.3 L·m^-2·h^-1·bar^-1 when the concentration of m-phenylenediamine is 0.1%w/v and the reaction time is 10 s,and the fluxes of methanol,acetone,ethanol,n-propanol and n-heptane are sequentially decreased due to the difference of viscosity and solubility parameters between different solvents.The rejection of the bright blue was 92.7%of the m-phenylenediamine polyamide membrane.As the molecular weight of the dye molecules gradually decreased,the rejection rate gradually decreased.Subsequently,p-phenylenediamine and o-phenylenediamine were used as active monomers to adjust the pore size of the polyamide membrane.Under the same test conditions,experiments showed that the acetonitrile flux was 23.1 L·m^-2·h^-1·bar^-1 of the p-phenylenediamine polyamide membrane,the rejection of bright blue was 90.5%,the acetonitrile flux of o-phenylenediamine polyamide membrane is 18.5 L·m^-2·h^-1·bar^-1,and the rejection of bright blue reaches 95.2%.The effect of pore size on the flux and rejection of the polyamide nanofiltration membrane was demonstrated.Finally,a freestanding charged polyamide nanofiltration membrane was prepared by using ethidium bromide which is ionic monomer.The flux of the ethidium bromide nanofiltration membrane to the aprotic solvent such as acetone and acetonitrile were up to 20.8 and 20.3 L·m^-2·h^-1·bar^-11 respectively,the flux of the protic solvent decreased,and the flux of the pure water was 5.1 L·m^-2·h^-1·bar^-1.In addition,the rejection of the anionic dye such as bright blue was 98.0%of the ethidium bromide nanofiltration membrane,and the rejection of the neutral dye such as calcein was 88.6%,and the rejection of the cationic dye such as methylene blue only was 47.5%.In this thesis,a series of polyamide nanofiltration membranes were prepared by using interfacial polymerization method,polyamide nanofiltration membranes with high flux and rejection were obtained by control of the pore size of the nanofiltration membrane.This work suggest that polyamide membranes have an enormous potential in the wastewater treatment,food and pharmaceutical industry application.