Mixed bed

Fig. 1. Demineializei systems consist of various unit processes arranged to meet the system needs. I Lstrong acid cation exchanger I I Strong ha anion exchanger 0 Degasifier I Mixed bed I Weak acid cation exchanger 1 1 Weak base anion exchanger and I IConnterflow cation.

Formamide (specific conductance 2 x 10 ohnr cnr ) of low water content was dried by passage through a column of 3A molecular sieves, then deionized by treatment with a mixed-bed ion-exchange resin loaded with H" " and HCONH" ions (using sodium formamide in formamide)[Notley and Spiro J Chem Soc (B) 362 1966. ... 

Phospholipids. For the removal of ionic contaminants from raw zwitterionic phospholipids, most lipids were purified twice by mixed-bed ionic exchange (Amberlite AB-2) of methanolic solutions. (About Ig of lipid in lOmL of MeOH). With both runs the first ImL of the eluate was discarded. The main fraction of the solution was evaporated at 40°C under dry N2 and recryst three times from n-pentane. The resulting white powder was dried for about 4h at 50° under reduced pressure and stored at 3°. Some samples were purified by mixed-bed ion exchange of aqueous suspensions of the crystal/liquid crystal phase. [Kaatze et al. J Phys Chem 89 2565 7955.]... 

Ammonia NH3 Corrosion of copper and zinc alloys by formation of complex soluble ion Cation exchange with hydrogen zeolite, chlorination, deaeration, mixed-bed demineralization... 

There also exists a type of resin with no functional groups attached. This resin offers no capacity to the system but increases regeneration efficiency in mixed-bed exchangers. These inert resins are of a density between cation and anion resins and when present in... 

In mixed-bed units, both the cation and the anion resins are mixed together thoroughly in the same vessel by compressed air. The cation and the anion resins being next to each other constitute an infinite number of cation and anion exchangers. The effluent quality obtainable from a well-designed and operated mixed-bed exchanger will readily produce demineralized water of conductivity less than 0.5 mmho and silica less than 10 ppb. 

Service Cycle - As far as the mode of operation is concerned, the service cycle of a mixedbed unit is very similar to a conventional two-bed system, in that water flows into the top of the vessel, down through the bed, and the purified effluent comes out the bottom. It is in the regeneration and the preparation of it that the mixed-bed differs from the two-bed equipment. The resins must be separated, regenerated separately, and remixed for the next service cycle. 

Removal of dissolved materials. If operated at ambient temperatures, regenerate mixed bed at least once a week for microbial control. Use 4.5-10 pm absolute filters after mixing bed to stop resins and particulates from entering distribution system. 

Coupling Columns or Using Mixed-Bed Columns to Extend the Molecular Weight Range... 

Discussing pore size selection of columns leads directly to the issue of using single porosity columns or so-called linear or mixed-bed columns, which contain mixtures of different pore sizes in a single column (3,19). Both types of columns have advantages and disadvantages, as shown in Table 9.6. 

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