Demineralization, water

The success of EDR ia water demineralization has appareatly resulted from its greater tolerance of particulate and fouling matter compared to reverse osmosis greater forgivingness of process upsets greater tolerance for unskilled operators simplicity ia desiga and constmction of EDR stacks compared to reverse osmosis modules the abiHty to iaspect, clean, or replace one membrane at a time the existence of a comprehensive global sales and... 

Chioride Cl- Adds to solids content and Increases corrosive character of water Demineralization, distillation, reverse osmosis, electrodialysis... 

R is the gas constant, T is the absolute temperature, o is the surface tension of the solution, a is the activity of the solute, and Ar is the area of the surface of the solution. According to this equation, brines in contact with air or other hydrophobic surfaces, will have a layer of relatively pure water, 3 or 4 Angstroms thick, adjacent to the interface. Therefore it should be possible to skim off this fresh water, and in fact the project was called "Sea Water Demineralization by the Surface-Skimming Process" until 1960. 

Sourirajan, S., "Sea Water Demineralization by the Surface Skimming Process , UCLAD )t of Bn2iTieer May,1958, Sea Water Research Quarterly Progress Repts. 58-46, 48, 50, 51 (Collected in one report)-... 

Sourirajan,S., "Sea Water Demineralization by the Surface Skimming Process", UCLA Dept, of Engineering,June-Aug,1958,... 

Loeb, S. Sourirajan, S. In Sea Water Demineralization by Means of an Osmotic Membrane Advances in Chemistry 38 American Chemical Society Washington, DC, 1963 p 17. 

Sea water demineralization research has largely been of a developmental nature. Processes already known to be workable, if not economical, have been chosen, then debugged or in some cases radically modified in order to adapt them to the peculiarities of the desalinization problem. In contrast to this approach, the work reported here has been an endeavor to explore unknown areas, and to investigate the mere scientific possibility of various methods. 

Growing scarcity of fresh water in many places in this country and the rest of the world has stimulated the development of several potentially useful processes for saline water demineralization. Because fresh water is such a cheap commodity, these processes must demonstrate the maximum conceivable economy to compete with even the most expensive natural fresh water sources. Nearly all of these methods require considerable energy, either as heat or as electric power. Since this is a large cost item in these processes, solar distillation offers substantial operating economies, but at the expense of large investment requirement. 

Since the advent of the resins capable of being regenerated with acids and alkalies, respectively, exchanging cations for the hydrogen ions and anions for the hydroxyl ion, it has been realized that ion exchange processing is a possible route to water demineralization. The cost of the regenerant chemical, acid and base, has prevented the use of the process except in certain clean-up applications where the quantity of ionic materials to be removed is extremely small. 

Figure 7. Flow diagram of sea water demineralization by ammonium bicarbonate...

Of the possible thermolytic ammonium salt ion exchange processes for sea water demineralization, the ammonium bicarbonate process appears to be the best. But it appears inferior to multiple-effect evaporation processes on the sole basis of the amount of distillation required for the regenerant recovery. 

Figure 6. Reverse osmosis sea water demineralization pilot plant...

The basic elements of a new electrochemical approach to saline water demineralization under study at the University of Oklahoma for the past three years are two porous electrodes, one of which is responsive to cations and the other to anions. When an appropriate voltage is applied to such an electrode pair immersed in saline water, cations are removed by the former and anions by the latter. In the regeneration phase, reversal of voltage gives up these ions to a reject solution. 

The proposed electrochemical method of saline water demineralization is similar to electrodialysis, in that ions are removed from a solution by electrical transference. If the electrodes are porous, oppositely charged ions will be attracted to them and thus... 

During 1959 several important advances have increased the efficiency and lowered the costs of electric membrane demineralization development of an improved permselective membrane which has a lower electrical resistance than those formerly used but retains the structural, mechanical, ana chemical stability characteristics for successful demineralization under the high rate of flow necessary for economic operation a practical membrane stack with available membrane area over three times that of stacks formerly used and a continuous-flow, two-stage, single-stack brackish water demineralizer to provide 65 to over 90% demineralization on flows of I to 20 gallons per minute. Formerly batch recirculating—type units were standard for this range of operation. The new units are simpler in construction and more efficient in the use of membrane area. 

Development of a continuous-flow, two-stage, single-stack brackish water demineralizer. This equipment, operating at higher current densities than formerly, provides greater simplicity of construction and better use of membrane area than the batch-type equipment which has been standard for similar service. It provides up to 93% demineralization of a brackish water without recirculation. 

While use of thin membranes, subject to bowing, has so far not been successful for use in brackish water demineralizers operating near polarization, such membranes offer more promise in treating solutions of high concentration such as sea water where polarization is less likely to be encountered. 

Evans, R. B., Crellin, G. L., and Tribus, M., "Thermo-economic Consideration of Sea Water Demineralization," Chapter 2, in Principles of Desalination, K. S. Spiegler, Editor, Academic Press, New York (1966). 

Figure 22 A scheme for bicarbonate water demineralization (cation exchanger Amberlite IRC-50).

Figure 23 A scheme for water demineralization by treatment with weak-acid and weak-base exchangers.

An industrial unit [46] consisting of several countercurrent columns has been described. In the first stage water is treated with a weak carboxylic acid exchanger in the H form (see Ref 9). Next, after removing CO2, the water, demineralized to a considerable extent, is treated with a mixed bed. Demineralization processes with a mixed bed are described in Refs. 48 and 54. 

Figure 6.10 A linear nomography representation of cojlow column operating capacity for cation exchange (Ca, Mg, Na) against a standard form styrene sulfonic acid resin (8% DVB) as applied to water demineralization (By permission of The Permutit Company Ltd)...

Turbine A Make-up Water Demineralization and colloids removal... 

Water pipes, water demineralization, waste-water treatment plant, site drainage, and sewers ... 

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