Water by reverse osmosis

Lynch, S. C. Smith, J. K. McTopy, J. Collect and Concentrate Drinking and/or Waste Waters by Reverse Osmosis—Jefferson Parish Disinfection Pilot Plant October 1983 Report to EPA Health Effects Research Laboratory January 1984 Contract No. 68-03-3164. 

Polyamides and their analogue are also effective for the selective membranes and there have been developed many kinds of permselective membranes. In early 1960 s, du Pont started to investigate the membranes for demineralization of water by reverse osmosis. After screening polymers, aromatic polyamides and polyhydrazides were shown to have superior properties9-11. In the present review various polyamides and their analogue are in focus as barrier materials for membranes, and their permeative characteristics will be discussed from the view point of their chemical structures. 

In the case of desalination of water by reverse osmosis illustrated in Figure 4.3(a), the salt concentration cio adjacent to the membrane surface is higher than the bulk solution concentration c, because reverse osmosis membranes preferentially permeate water and retain salt. Water and salt are brought toward the membrane surface by the flow of solution through the membrane J,.1 Water and a little salt permeate the membrane, but most of the salt is rejected by the membrane and retained at the membrane surface. Salt accumulates at the membrane surface until a sufficient gradient has formed to allow the salt to diffuse to the bulk solution. Steady state is then reached. 

Reverse osmosis is a process whereby seawater can be purified by passing the water molecules through a semipermeable membrane. What is the minimum amount of work that must be done to obtain 1.0 L of pure water by reverse osmosis, starting with seawater that is 0.7M NaCl Compare this work with the energy required to vaporize the water in a distillation process. 

A water desalination plant is set up near a salt marsh containing water that is 0.10 M NaCl. Calculate the minimum pressure that must be applied at 20.°C to purify the water by reverse osmosis. Assume that NaCl is completely dissociated. 

Coconut water is a sterile liquid. From mature nuts, it has the following constituents in percent total solids 4.7, fat 0.74, protein 0.55, ash 0.46, and reducing sugar 1. The liquid has a pH of 5.6 (14). It is a coproduct of desiccated coconut and considered a health beverage. Concentration of coconut water by reverse osmosis may further expand its use in the fermentation and food industries. 

X. J. Chai, G. H. Chen, P. L. Yue, and Y. L. Mi, Pilot scale membrane separation of electroplating waste water by reverse osmosis. Journal of Membrane Science 123,235-242 (1997). J. D. Seader and E. J. Henley, Separation Process Principles, John Wiley Sons, New York, 1998. 

Semipermeable membranes play important roles in the normal functioning of many living systems. In addition, they are used in a wide variety of industrial and medical applications. Membranes with different permeability characteristics have been developed for many different purposes. One of these is the purification of water by reverse osmosis. 

Odegaard, H. and Koottatep, S. (1982). Removal of humic substances from natural waters by reverse osmosis. Water Res. 16, 613-620. 

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. 

Dresner, L., "Boundary Layer Buildup in the Demineralization of Salt Water by Reverse Osmosis," Oak Ridge National Laboratory Report 3621, 1964. 

R. Rautenbach, W. Kopp, G. van Opbergen and R. Hellekes, Nitrate reduction of well water by reverse osmosis and electrodialysis - studies on plant performance and costs, Desalination, 1988, 65, 241. 

The following processes were all discussed in Chapter 18, Chemistry of the Environment Estimate whether the entropy of the system increases or decreases during each process (a) photodissociation of 02(g), (b) formation of ozone from oxygen molecules and oxygen atoms, (c) diffusion of CFCs into the stratosphere, (d) desalination of water by reverse osmosis. 

The seminal discovery that transformed membrane separation fi-om a laboratory to an industrial process was the development in the 1960s of the Loeb-Sourirajan process to make defect-free ultrathin cellulose acetate membranes [1]. Loeb and Sourirajan were trying to use membranes to desalt water by reverse osmosis (RO). The concept of using a membrane permeable to water and impermeable to salt to remove salt from water had been known for a long time, but the fluxes of aU the membranes then available were far too low for a practical process. The Loeb-Sourirajan breakthrough was the development of an anisotropic membrane. The membrane consisted of a thin, dense polymer skin 0.2-0.5 pm thick sup-... 

Desalination The process of removing salts from water by reverse osmosis or distillation. 

The process of reverse osmosis is used to purify water because it removes many contaminants at relatively low cost. The osmosis process can be reversed by applying a pressure greater than the osmotic pressure to an aqueous solution. This causes the water, but not the dissolved solutes, to flow from the solution through the semipermeable membrane. The largest municipal desalination plant in the United States is in Sarasota, Florida. It treats salt water by reverse osmosis to produce more than 12 million gallons of fresh water per day. Other applications include the desalination of sea water on ocean-going vessels and wastewater purification. 

Osmotic pressure. Estimate the osmotic pressure of sea water at 25°C. Assume that it contains 36 g NaCl (a strong electrolyte) per liter. What is the minimum pressure needed to purify sea water by reverse osmosis (page 188) ... 

Teychene, B., Collet, G., Gallard, H. Croue, J.R (2013) A comparative study of boron and arsenic (III) rejection from brackish water by reverse osmosis membranes. Desalination, 310,109-114. 

Instead of drawing off juice, it is now possible to eliminate water directly from the grape must (Section 11.5.1). Two methods currently exist the first circulates the must across membranes which retain water by reverse osmosis (Degre-mont, Inc.) the second evaporates water in a low-temperature (20-24°C) forced vacuum (Entropie, Inc.). These techniques have the additional advantage of increasing the sugar concentration, thns eliminating the need for chaptaUzation in some cases. 

Applications -182 MW(e) of electricity plus 102 000 m7day of potable water by reverse osmosis - Applicable to district heating Electricity production oidy... 

The pH of the aqueous solution will determine the extent of ionization of solutes like phenol, 2-chlorophenol or acetic acid in the solution. If such a solute is ionized, the separation of such a solute from water by reverse osmosis through a membrane will be changed since the ionized solute and the nonionized solute have different solute rejections through the membrane. Consider an ionizable acidic solute species 1 ionization leads to a negatively charged species 2 (see equation (5.2.57)). The total feed solute concentration, Cy., is then given by... 

First we will illustrate the minimum energy required to separate a small amount of mixture for the following processes evaporation of water from a saline solution recovery of water by reverse osmosis separation of an ideal binary gas mixture by membrane permeation. Then we will consider the definition of net work consumption for thermally driven processes. Next we will consider a variety of separation processes vis-k-vis their minimum energy requirement for separation. 

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