The Study On Preparation/Properties And Application Of Inorganic-Organic Composite NF Membranes

As a new separation membrane technology developed in recent years, nanofiltration (NF) membrane is the most appealing field of membrane science and technology compared with those traditional membranes, the advantages of NF membranes are as follows: having hole diameters of nanometers, low operation pressure, economic for it can replace many procedures in traditional process and separation technology , having high selectivity to different irons, and so on. Now NF membrane has been applied to many fields, such as medicine, food industries , biologic engineering, metallurgy, and so on.The present work indicates the organic NF membranes and the inorganic NF membranes all have shortages, so develop composite NF membranes that have low cost, mechanically strong and thermally/chemically - resistant, easy to cleanout and good performances is a very important task.In this paper, the preparation of inorganic - organic composite NF membranes were presented. This composite comprise a porous SiO2/Al2O3 support substrate, the pore diameters of which ranging from 10 to 15 nm, this inorganic support substrate having a polymer membrane which comprises an polyvinyl alcohol (PVA) or polyamide (PA) densely deposited on at least one of the face surfaces thereof, the structural porosity of such PVA and PA membrane ranging from 3 to 5 nm. The process employs sol-gel to coat Al2O3 micro porous substrate with a SiO2 thin membrane at first. Than the PVA membranes were prepared by coating porous SiO2/Al2O3 membranes with a PVA layer and further cross-linking its surface, malic acid and 5-sulfosalicylic acid as crosslinking agents. Under the conditions of operation pressure about 0.5MPa and feed temperature 25 C , the rejection performance of NaCl feed solution (500ppm) , is about 35%, while the flux is about 45ml cm-2 h-1. The PA membranes were prepared by interfacial polymerization,usingl,3,5-benzenetricarbonyltrichlori2,4-dichloroterephthalaldehyde, 1, 3-phenylenediamine as monomers. Under the conditions of operation pressure about 0.5MPa and feed temperature 25C, the rejection performance of NaCl feed solution (500ppm) , is about 36%, while the flux is about 40.3ml cm-2 h-1. It is also found that the concentrations of reactant, catalyst , the time and temperature of action and the working conditions have perceptible effects on its membrane performances.In this paper, the application of these membranes is also introduced. Combining SiO2/Al2O3 ultrafiltration (UF) membrane and PVA (PA) / SiO2 - A12O3 NF membrane, the purification and concentration process of erythromycin (Er) could be achieved more efficiently such as, energy saving, higher recovery rate and potency of the product as the lower temperature condition by using the UF-NF composite system. And the experiments showed us that those factors which could make impacts on the result of purification included the feed concentration, operating pressure , concentrating time, and so on. Under the conditions of operation pressure about 0.8MPa and feed temperature 20癈, the rejection performance of Er feed solution is about 98%.Ftir and SEM are used to analyses the structure and component of membranes.