Research On Preparation And Performance Of Pervaporation Membrane For The Separation Of Acidic Organics/water Mixture

Pervaporation?PV?has received great attention over years,due to the advantages of low consumption,high efficiency,and environmental protection,compared with the traditional separation techniques such as distillation and extraction,However,in acidic condition such as dehydration of acidic ethanol,dehydration of acetic acid and PV-assisted esterification,the separation performance and stability of the membranes would be seriously affected.Therefore,preparation of membrane with high selectivity,high flux and acid-stability is practical significant.In this research,an acid-resistant and hydrophilic material was selected to prepare composite membranes by Layer-by-Layer self-assembly technique.Firstly,?SA/PEI?_1.5/PAN composite membrane was prepared on PAN substrate by dynamic LbL self-assembly technique to separate ethanol/water at pH=3.The assembly progress of composite membrane was characterized by Zeta potential,UV-Vis and ellipsometric.The morphology and structure were characterized by SEM,AFM and FT-IR to illustrate the ionic cross-linking between–COO^-groups in SA and protonated–NH₂ in PEI occurred.CA and DS test were used to characterize the affinities of composite membrane towards water.The effects of assembling and operating conditions on the separation performance were investigated,such as the number of layers,the sodium alginate concentration and the pH.The results showed that with[PEI]=0.25 wt%,[SA]=0.375 wt%,1.5 layers,the water content was 10wt%,the membrane performance achieved optimal with water content in the permeate of 99.42 wt%?a=1542?and flux of 1.203 kg/m²h?pH=3,60 ^oC?.In addition,to modify the NaA zeolite membrane,?SA/CaCl₂?₄/NaA composite membrane was prepared on NaA surface by immersing the substrate into the sodium alginate solution crosslinked with CaCl₂,to separate acidic ethanol/water mixtures.The morphology and structure of?SA/Ca Cl₂?₄/Na A membrane were characterized by SEM,EDX,FT-IR,XRD and nanoindentation,illustrating a dense and acid-resistant separation layer assembled on the NaA membrane.In order to improve the resistance of modified membrane,the effects of SA concentration,assembly method,layer number,pH and operating temperature on separation performances were studies.The obtained?SA/CaCl₂?₄/Na A membrane was used to separate acidic ethanol/water mixture.When[SA]=1 wt%,[CaCl₂]=0.1 mol/L,layer number=4,operation number=75 ^oC,the total permeate flux and water content in permeate were 666g/m²h and 99.94 wt%??=14991?,respectively.Furthermore,the modified?SA/CaCl₂?₄/Na A membrane still had stable separation performance when altering the operation temperature and pH,which illustrated the remarkable improvement of acid-resistant after modification comparing with the PV performance of Na A substrate.