Reverse osmosis introduction

Method D in Table 1 represents a case where dry support films were always used because of the need to employ a vacuum and because of the very nature of plasma deposition processes. Yasuda (12) showed that a wide variety of gas phase reactants could be used in this technique. Not only conventional vinyl monomers were used but also any organic compounds with adequate vapor pressure. Further, copolymers could be prepared by introduction of a second reactant such as nitrogen. Wydeven and coworkers (13,14) showed the utility of this method in preparing reverse osmosis membranes from an allylamine plasma. 

This paper has provided the reader with an introduction to a class of polymers that show great potential as reverse osmosis membrane materials — poly(aryl ethers). Resistance to degradation and hydrolysis as well as resistance to stress Induced creep make membranes of these polymers particularly attractive. It has been demonstrated that through sulfonation the hydrophilic/hydrophobic, flux/separation, and structural stability characteristics of these membranes can be altered to suit the specific application. It has been Illustrated that the nature of the counter-ion of the sulfonation plays a role in determining performance characteristics. In the preliminary studies reported here, one particular poly(aryl ether) has been studied — the sulfonated derivative of Blsphenol A - polysulfone. This polymer was selected to serve as a model for the development of experimental techniques as well as to permit the investigation of variables... 

Schmidt number - [ELECTROCHEMICALPROCESSING - INTRODUCTION] (Vol9) - [REVERSE OSMOSIS] (Vol 21) -m absorption [ABSORPTION] (Vol 1)... 

Beaton, N.C., Ultrafiltration and reverse osmosis in the dairy industry—an introduction to sanitary considerations, J. Food Prot., 42, 584, 1979. 

These developments result from the introduction of composite membranes, originally developed in the 1970s primarily, for desalination by reverse osmosis. Application of the same membrane fabrication techniques to pervaporation membranes radically improved their performance and spurred commercial utilization. Today, pervaporation and vapor permeation plants are widely used to dehydrate volatile organics and separate other mixtures, primarily in the pharmaceutical and fine chemical industries. 

Membrane research and development started in Du Pont in 1962 and culminated in the introduction of the first B-9 Permasep permeator for desalination of brackish water by reverse osmosis (RO) in 1969. The membrane in this B-9 Permasep module consisted of aramid hollow fibers. In 1969, proponents of RO technology had ambitious dreams and hopes. Today, RO is a major desalination process used worldwide to provide potable water from brackish and seawater feeds. Du Font s membrane modules for RO are sold under the trademark Permasep permeators. The RO business is a virtually autonomous profit center that resides in the Polymer Products Department. The growth and success of the Permasep products business is a direct result of Du Font s sustained research and development commitment to polyamides, a commitment that dates back to the 1930 s and the classic polymer researches of Wallace H. Carothers. Since 1969, improved and new Permasep permeators have been introduced six times, as shown in Table I. 

We have indicated in the introduction to this chapter that physico-chemical processes related to the diffusion of constituents or to their solubility in the fluid inside a dense membrane should be taken into accoimt in order to model membrane separation of very small particles dispersed in a fluid. We discuss this aspect now, by describing the reverse osmosis process. 

Post-treatment of the desalted permeate from the reverse osmosis unit (Section 7.2.1.2) consists of the addition of CI2 and Ume for disinfection and corrosion protection. If H2S is present, it is eliminated by air stripping. For brackish-water feeds containing hydrocarbons, an activated carbon adsorber is used to remove dissolved hydrocarbons prior to microfiltration, which is followed by steps needed during the pretreatment and post-treatment processes dechlorination is required as a pretreatment if the RO membrane for desalination cannot tolerate residual chlorine dissolved otcygen is often removed to avoid damaging the RO membrane via vacuum based deaeration or addition of sodium bisuMte. An introduction to the pretreatment and post-treatment processes for membrane based sea-water and brackish-water desalination has been provided by Williams et al. (2001). The scale of such desalination plants is quite large, as much as 87 million gallons per day at Ashkelon, Israel, for example. 

Bhattacharyya, D. and Williams, M. Introduction and Definitions-Reverse Osmosis Membrane Handbook W. Ho. Sirkar, K., Eds. VanNostrand Reinhold New York, pp. 265(1992). 

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