Preparation And Characterization Of The Nanofiltration Membrane For Dye Desalting

Domestic dye production in dye industry contains large quantities of salt and have a lower purity at present.So much of high-purity dyes in domestic market rely largely on imports.Therefore,purification of crude dye is of great significance. Nanofiltration technology is the preferred desalination technology for dye,but most of the desalting effect of nanofiltration membranes is relatively low.By selecting the appropriate responsemonomer,a select layer was fabricated through the interfacial polymerization reaction on the surface of ultrafiltration membrane.The select layer with positive charge and negative charge can improve the transmittance of inorganic ions and retain dye molecules effectively.The main contents are as follows:A new type of flat Nanofiltration membrane was fabricated which used interfacial polymerization(IP) techniques onto a porous support(PES ultrafiltration membrane).2,5-diaminobenzene sulphonic acid(DIA) and polyamine(PECH-amine) mixture solution was chosen as aqueous phase,and trimesoyl chloride(TMC) hexane solution as organic phase.The scanning electron microscopy(SEM) showed that a dense layer of interfacial polymerization product was formed on the surface of the basement membrane.After the interfacial polymerization the surface of nanofiltration membrane is more dense and smooth.The amino and hydroxyl of polyamine participated in interfacial polymerization and the quaternary ammonium salt of polyamine can lead in positively fixed charged groups;The amino of 2,5-diaminobenzene sulphonic acid participated in interfacial polymerization and the sulfonic acid group of 2,5-diaminobenzene sulphonic acid can lead in negative fixed charged groups.In addition,the carboxylic acid group that trimesoyl chloride hydrolysis to generate can lead in negative fixed charged groups for nanofiltration membrane.The separation factor of NaCl and xylenol orange(XO) in the XO/NaCl system was used as the object of study and the uniform design was applied to the preparation process.The experimental data were disposed by SPSS software,and the regression equation was established.And the calculation results of the regression equation agree well with the experimental data.The separation factor can reach 16 at the optimal condition which was obtained by calculation with the regression equation and further experiment as follows:polyamine flocculants 0.68%(wt); 2,5-diaminobenzene sulfonic0.4%(wt);trimesoyl chloride 0.4%(wt);interfacial polymerization(IP) time 2.54 min.Then,the separation factors were investigated for XO,Nitroso-R-salt(NRS),methyl green(MG) with the four salts.The results show that the separation factor of dye/NaCl is more than 13;and the separation factor of dye/MgSO₄ is smallest,but also more than 8.So the optimized composite membrane has the high desalting effects in some dyes and salts solution.The impact of changing experimental conditions about separation performance of XO/NaCl system was studied,It was shown that volume flux inerease with increasing the operation pressure and decrease with the increasing the solute;separation factor inerease with the increasing of the NaCl concentration,and decrease with increasing the operation pressure and XO concentration.A new type of hollow fiber nanofiltration membrane was fabricated onto three holes hollow fiber porous support.The results show that the separation factor of dye/NaCl about hollow fiber nanofiltration membrane is more than 10.So the separation performance of the hollow fiber nanofiltration membrane is aimilar as the flat nanofiltration membrane.