Effects Of Chemical Methods On Structure And Performance Of Phase Inversion Membrane

The preparation of high quality antifouling membrane is one of the most efficient methods to improvement antifouling characteristics of the membrane. PVDF/PMMA/CA blend UF membrane was prepared by chemical reaction way is based on the traditional phase-inversion method. The antifouling characteristics of the membrane is enhanced due to the uniformity of the membrane pore size, which is modulated by the carbon dioxide (CO2) gas, produced by a chemical reaction between glacial acetic acid (CH3COOH) in the casting solution and sodium carbonate (Na2CO3) as category of coagulation medium.At first, an orthogonal table with nine factors and four levels L32 (49) was designed to confirm the feasibility of linear multi-regression model by study the influence degree of factors on characteristics of PVDF/CA blend microfiltration membrane. Secondly, the pure water flux, the feed solution flux of BSA and the observed retention of BSA had been used to estimate the characteristics of the PVDF/PMMA/CA blend UF membrane, the steps is as follows: (1) An orthogonal table with eight factors and three levels L18 (2×37) was designed and the influence degree of factors on characteristics of membrane had been determined by range analysis method and linear multi-regression model. (2) On this basis, the orthogonal table L27 (310) was designed to study both the interaction between additive content and additive species, additive species and solvent species. The linear multi-regression model was analyzed with the data collected by the orthogonal test. (3) The pore size distribution and SEM images of the membranes was compared, respectively. (4) By using optical microscope observed the process of membrane formation under optimum condition for preparing the PVDF/PMMA/CA blend UF membrane.The results showed that: (1) The combination of orthogonal table and linear multi-regression model is an efficient method to ascertain the optimum preparation conditions for the porous membrane-making process; (2) Solid content, solvent species, additive species, additive content, category of coagulation medium are influencing factors on the characteristics of the PVDF/PMMA/CA blend UF membrane, and among which solid content and additive species are remarkable influencing factors; The relationship is as follows: , where, Y4 is a function that simultaneity consider the influence of the pure water flux, feed solution flux and observed retention, X1 is solid content, X2 is solvent species, X3 is additive species, X4 is additive content, X7 is the interaction between additive content and additive species; (3) When solid content of PVDF/PMMA/CA is 16%, using DMF as solvent, PEG2000 with 2% as additive, content of glacial acetic acid (CH3COOH) is 10%, category of coagulation medium is aqueous solution of sodium carbonate (Na2CO3), gelation time is 30 minutes; (4) The gelation rate decreased as the gelation time increasing. Chemical reaction affect gelation rate intensively, can increase gelation rate obviously.Under this optimization condition of the membrane preparation, the PVDF/PMMA/CA blend UF membranes with uniform membrane pore size distribution and high pure water flux could be prepared, which pore size distribution is 0.07 ~ 0.10μm; the pure water flux is 197.26 ~ 265.24 mL·cm-2·h-1; the protein flux is 14.87 ~ 15.96 mL·cm-2·h-1 and the observed retention is 89.73 ~ 93.91%. The three parameters above are all measured under the 0.1MPa pressure at room temperature.