Electro-deionization

A second place where membrane contactors are often used is before the electro deionization (EDI) step in UPW plants to remove residual CO2 gas. Removal of CO2 improves efficiency of EDI unit. Membrane contactors allow the opportunity to decarbonate water inline and under pressure just prior to EDI. 

Walters et at. (Wl), have proposed an electro-deionization process for radioactive waste treatment. The process consists of partial deionization in a multi-compartment, permselective, membrane cell, and is similar to the production of potable water from sea water. This first step is followed by final deionization of the partially demineralized effluent in a multi-compartment, permselective, membrane cell employing mixed anion exchange and cation exchange granules in the deionization compartment. This process would permit higher volume reductions than for chemically regenerated ion exchangers. 

Ion conductivity Electrodialysis Concentration or desalination of electrolytes, separation between electrolyte and non-electrolyte, bipolar ion exchange membrane process to produce acid and alkali, ion-exchange reaction across the membrane, electro-deionization (EDI, CDI), etc. 

W.R. Walters, D.W. Wieser and L.J. Marek, Concentration of radioactive aqueous wastes, Electromigration through ion-exchange membranes, Ind. Eng. Chem., 1955, 47, 61-67 E. Glueckauf, Electro-deionization through a packed bed, Br. Chem. Eng., 1955, 646-651. 

Chemical Separation of oxalic acid from glyoxal,44 separation of sodium formate from pentaerythritol,45 preparation of aminoethane sulfonic acid (taurine),46 production of acids and alkalis from neutral salts by water-splitting using a bipolar ion exchange membrane,47 production of pure water by electro-deionization,48 utilization of double decomposition of salt49... 

Figure 6.15 Example of the electro-deionization method (EDI). First, anions are removed in the compartment packed with anion exchange resin, and second, both cations and remaining anions are removed in the compartment packed with cation and anion exchange resins (mixed bed).

Glueckauf, E. (1959). Electro-deionization through a packed bed. Br. Chem. Eng. 646 651, December. 

Electro dialysis is used widely to desalinate brackish water, but this is by no means its only significant appHcation. In Japan, which has no readily available natural salt brines, electro dialysis is used to concentrate salt from seawater. The process is also used in the food industry to deionize cheese whey, and in a number of poUution-control appHcations. 

The washing of capillaries with dilute alkaline solution is advisable before analysis. The alkaline solution can be followed by deionized water and buffer. Capillaries can be washed between runs too. Samples can be introduced into the capillary by hydrodynamic and electro-kinetic methods. The hydrodynamic method applies a pressure difference (5-10 sec) between the two ends of the capillary. The pressure difference can be achieved by overpressure, vacuum or by creating a height difference between the levels of the buffer and sample reservoirs. In the case of electrokinetic injection, the injection end of the capillary is dipped into the sample for a few seconds and a voltage of some thousand volts is applied. 

Pavlik and Sansone [81] found that the size distribution of spherical particles, in the size range 5 to 40 pm, obtained by sedimentation in double-distilled deionized water plus a wetting agent was significantly different from that obtained in O.IN KCI plus a wetting agent. Coulter Counter data agreed with the tatter data. These results were later confirmed [82]. The electro-viscous effect needs to be eliminated, for Stokes law to apply, by the addition of non-ionic sedimentation liquids. 

Wang, G. etal.. Activated carbon nanofiber webs made by electro spinning for capacitive deionization. Electrochimica Acta. 2012, 69, 65-70. 

Figure 3 presents the frequency dependence of the electro-optical effects for suspensions of different volume fractions of spherical particles. The stock solution (8% sphere volume fraction) is highly deionized, and dilution is carried out with deionized water. Thus the highly dilute samples are in the liquid-phase state. Modulated responses are detected at low frequencies —- for highly dilute samples... 

FIG 11 Frequency dependence of the ELS responses of a dilute palygorskite suspension (volume fraction 0.01%) for different ionic strengths of the sample ([B,D] dc compound [A, A] ac compound filled symbols, 10 M NaCl open symbols, about 10 M NaCl). Upper diagram Electro-optical responses of the sample at field frequency 1 kHz (dotted line, deionized). 

Another interesting possibility is die selective deposition of copper on the structures. We are using an electro less deposition process for this purpose. First of all we have to define the parts of the copper deposition by activating them with palladium, i ch acts as a catalyst. Because palladium is not able to coordinate direcdy to hydroxy groups it is necessary to heat the surface with a SnCla solution. In a first step Sn will coordinate to the hydroxy groups and then it will reduce the PdCl2-solution in a second step. After the selective deposition of the catalyst the substrate is exposed to a mixture of a solution consistent of potasium-sodium tartrat copper(II)sulfate and potassium hydroxide in deionized water and a solution of formaldehyde in water for the reduction of the copper solution. The deposition of the copper is very fast and so tiie substrate has to be removed fixim the solution after 30 seconds (Figure 7). 

Complexes of PEOi77-b-PMAA23/polycation were prepared in aqueous solution (deionized water) by electro-... 

Aqueous solutions of cationic polyacrylamide (0.25 wt. % in deionized water) were prepared by rolling for 48 hours. Suspensions of 0.2 wt. % clay in deionized water were similarly prepared. Each 10 x 10 cm piece of PET film, rinsed with methanol and deionized water, was corona treated with a BD-20C Corona Treater (Electro-Technic Products Inc., Chicago, IL), prior to LbL deposition. The substrate was initially dipped in the C-491 solution for 5 minutes, followed by rinsing with de-ionized water and blow drying with air. This same procedure was followed with the clay solution, followed by one minute of deposition for all subsequent dips. The entire dipping procedure was accomplished with a home-built robotic system (12). 

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