Nanofiltration -270 membrane

Ultrafiltration may be distinguished from other membrane operations by example When reverse osmosis is used to process whey, it passes only the water and some of the lactic acid (due to the solubihty of lactic acid in RO membranes). Nanofiltration used on whey will pass most of the sodium salts while retaining the calcium salts and most of the lactose. Microfiltration will pass everything except the particulates and the bacteria. 

Nanofiltration membranes usually have good rejections of organic compounds having molecular weights above 200—500 (114,115). NF provides the possibility of selective separation of certain organics from concentrated monovalent salt solutions such as NaCl. The most important nanofiltration membranes are composite membranes made by interfacial polymerization. Polyamides made from piperazine and aromatic acyl chlorides are examples of widely used nanofiltration membrane. Nanofiltration has been used in several commercial applications, among which are demineralization, oiganic removal, heavy-metal removal, and color removal (116). 

Bowen, W.R. and Welfoot, J.S., Modeling the performance of membrane nanofiltration Critical assessment and model development, Chem. Eng. Sci., 57, 1121, 2002. 

Mallubhotla, H. Hoffmann, S. Schmidt, M. Vente, J. Belfort, G. Flux enhancement during Dean vortex membrane nanofiltration. 10. Design, construction and system characterization. J. Membr. Sci. 1998, 141, 183-195. 

Abstract The processes of lactic acid production include two key stages, which are (a) fermentation and (h) product recovery. In this study, fiee cell of Bifidobacterium longum was used to produce lactic acid from cheese whey. The produced lactic acid was then separated and purified from the fermentation broth using combination of nanofiltration and reverse osmosis membranes. Nanofiltration membrane with a molecular weight cutofif of 100-400 Da was used to separate lactic acid from lactose and cells in the cheese whey fermentation broth in the first step. The obtained permeate from the above nanofiltration is mainly composed of lactic acid and water, which was then concentrated with a reverse osmosis membrane in the second step. Among the tested nanofiltration membranes, HL membrane from GE Osmonics has the highest lactose retention (97 1%). In the reverse osmosis process, the ADF membrane could retain 100% of lactic acid to obtain permeate with water only. The effect of membrane and pressure on permeate flux and retention of lactose/lactic acid was also reported in this paper. 

Keywords Cheese whey Lactic acid Membrane Nanofiltration Reverse osmosis... 

Mallubhotla H., Hoffmann S., Schmidt M., Vente J., Belfort G. (1998), Flux enhancement during dean vortex tubular membrane nanofiltration. 10. Design, construction, and system characterisation. 

W atson B.M., Hornburg C.D. (1989), Low energy membrane nanofiltration for removal of color, organics and hardness from drinking water supplies. Desalination, 72,11 22. 

All the aforementioned SILMs were prepared using microflltration membranes and operated with low varying pressure differential (<2 bar). To avoid the pitfaU of liquid instability associated with microporous membranes, nanofiltration membranes were used in SILMs, which greatly reduce the instability problem only at the expense of increased gas transport resistance provided by the nanofiltration (NF) membranes [87]. Experimental stability tests demonstrated that the impregnated ILs did not discharge from the NF membrane structure even under a high transmembrane... 

Reverse osmosis Thermoosmosis Vapor permeation Pervaporation Gas permeation Dialysis Electrodialysis Liquid membranes Nanofiltration... 

---