Reverse osmosis process

Food and beverage processing, reverse osmosis in, 21 650-651 Food and Drug Administration (FDA), 10 848 11 47 18 682 21 568. See also FDA entries U.S. Food and Drug Administration (FDA) anthropogenic silicas and silicates and, 22 468... 

The range of application of the three pressure-driven membrane water separation processes—reverse osmosis, ultrafiltration and microfiltration—is illustrated in Figure 1.2. Ultrafiltration (Chapter 6) and microfiltration (Chapter 7) are basically similar in that the mode of separation is molecular sieving through increasingly fine pores. Microfiltration membranes filter colloidal particles and bacteria from 0.1 to 10 pm in diameter. Ultrafiltration membranes can be used to filter dissolved macromolecules, such as proteins, from solutions. The mechanism of separation by reverse osmosis membranes is quite different. In reverse osmosis membranes (Chapter 5), the membrane pores are so small, from 3 to 5 A in diameter, that they are within the range of thermal motion of the polymer... 

The traditional membrane separation processes (reverse osmosis, micro-, ultra- and nanofiltration, electrodialysis, perva-poration, etc.), already largely used in many different applications, are today combined with new membrane systems such as CMRs and membrane contactors. Membranes are applied not only in traditional separation processes such as seawater desalination but also in medicine, bioengineering, microelectronics, the life in the space, etc. 

Chemical processing Reverse osmosis membrane, permselective membrane, gas separation membran-lubrication, insolubilization... 

Membrane filters were first commerciafised in 1927 by the Sartorius Company in Germany using the Zigmondy process. Reverse osmosis (RO) was first observed and studied in the 1920s. However, it remained unnoticed until rediscovered by Reid and his co-workers 30 years later. The first practical phenomenon of haemodialysis was demonstrated by Kolff in the 1940s. Membrane milestones are given in Table 1.1. 

Currently, the pressure-driven membrane processes, reverse osmosis (RO), nanofiltration (NF), ultrafiltration (UF), and microfiltration (MF), are widely used in water treatment, biotechnology, food industry, medicine, and other fields (Baker 2004). However, one of the main problems arising from the operation of the manbrane units is membrane fouling, which seriously hampers the applications of manbrane technologies (Scot and Hughes 1996). 

The first separation example is seawater desalination. Traditionally, desahnation was done by distillation or simple evaporation/condensation [55]. Today, thermally driven desalination has been largely replaced by the membrane process reverse osmosis. In reverse osmosis an applied pressure exceeding the osmotic pressure of the salt solution causes water to permeate through a dense membrane. Hydrated salt ions are relatively large compared to water and have a lower permeability through the membrane resulting in relatively salt-free water being collected as the reverse osmosis permeate. 

Seawater or brackish water is used for process applications or as potable water when fresh water is scarce. Six techniques are used for desalination. Five are evaporation processes multiple-effect thermocompression mechanical vapor compression once-through multistage flash and multistage flash with brine recirculation. The sixth process, reverse osmosis, uses membrane technology for desalination. 

An effluent stream of 3 m /h containing 7.6 gd of sodium sulfate at 20 C is treated in a hybrid process reverse osmosis for concentration and production of clean process water and membrane electrolysis for the conversion of sodium sulfate into sulfuric acid (15%) and caustic soda which is used for neutralisation. 

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