Reverse osmosis membrane progress

Cadotte, J. E. Kopp, C. V. Cobain, K. E. Rozelle, L. T. Progress Report on In Situ-Formed Condensation Polymers for Reverse Osmosis Membranes North Star Research Institute, Minneapolis, MI. Office of Saline Water Report. U.S. Department of the Interior June 1974, p 92. 

Fisher, R.E., Sherwood, T.K., and Brian, P.L.T., "Salt Concentration at the Surface of Tubular Reverse Osmosis Membranes," Office of Saline Water, U.S. Department of the Interior, Research and Development Progress Report No. 141, 1965. 

I appreciate this opportunity to speak at the same time on the iast day of this symposium just as my close friend and mentor. Dr. Sourirajan spoke on the first day of this symposium. In concluding his talk. Dr. Sourirajan said, "The inherent potential of reverse osmosis processes and reverse osmosis membrane to contribute significantly to the health and welfare of all being and also to the progress of many fields of science, engineering, biology and medicine is far more than what one can comprehend at any time."... 

Polysulfone was recognized as a major improvement in the state-of-the-art of composite membranes at that time. But the broad scope of its usefulness was never fully appreciated until later. It has since become widely useful in its own right as an ultrafiltration membrane. It was subsequently included in a U.S. patent on ultrafiltration membranes by Michaels that issued in 1971.21 Concerning reverse osmosis membranes, it represented a key development that later enabled rapid progress to take place In noncellulosic composite membranes. 

Plasma polymerization has been explored in considerable detail as a potential route to composite reverse osmosis membranes. Yasuda has written an excellent review covering the fundamentals and progress of plasma polymerization through 1974.88 Advances since then have not been particularly promising from a commercial standpoint, with the exception of the Solrox membrane (see below). 

C. Gabelich, K. Ishida, R. Bold, Testing of water treatment copolymers for compatibility with polyamide reverse osmosis membranes. Environmental Progress 2005, 24(4), 410-416. 

The structure of the so-called "composite" membranes used in reverse osmosis is also much more complex than the conventional, simplistic description of the ultrathin semipermeable film deposited on and supported by a porous substrate. Most of these membranes which exhibit high flux and separation are composed of an anisotropic, porous substrate topped by an anisotropic, ultrathin permselective dense layer which is either highly crosslinked, or exhibits a progressively decreased hydrophilicity toward the surface. The basic difference between the conventional anisotropic (asymmetric) membrane and the thin film composite is that the latter might be... 

The progress made in membrane-based desalination has lead to the substitution of evaporation plants with RO systems in different part of the world. For example, the United States holds the second position in worldwide desalination capacity (15.2% of the world production) and the 78% of their production come from RO treatments. Mediterranean countries, including Spain, Malta, Cyprus, and Israel, have also reverted from traditional multistage flash (MSF) to RO during the past two decades. The water production by reverse osmosis desalination plants passed from 36% of the global desalting capacity in 1996 to 42%... 

The treatment so far has heen based on a particular feed concentration, Q , in the reverse osmosis cell (Figure 6.3.28 (a)). As time progresses, water from the feed solution will be removed as permeate therefore the feed concentration of species i, e.g. NaCl, will increase. If we require the process to yield a particular concentration of salt in the permeated water, then the salt rejection required of the membrane, / i,reqd> will have to increase. Further, since the osmotic pressure of the feed solution increases with time, either the solvent flux will go down with time or the driving pressure difference, AP, has to go up. To these factors, one has to add the complication of concentration polarization. To illustrate the effect of increasing feed salt concentration with time, we will ignore first the effect of any concentration polarization and then focus on the consequence of different values of fractional water recovery, re. For the reverse osmosis cell shown in Figure 6.3.28(a), it is defined as... 

Plummer CW, Kimura G, LaConti AB. Development of SPPO membranes for reverse osmosis. Office of Saline Water Research and Development Progress Report No. 551, General Electric Co., Lynn, Mass., 1970. 

C.W. Plummer, G. Kimura and A.B. LaConti, Development of Sulfonated Polyphenylene Oxide Membrane for Reverse Osmosis. In Research and Development Progress Report 557, Office of Saline Water, United States Department of Interior, (1970). 

---