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Mixed Bed - UPW
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Cation and anion resins can be mixed together in a single vessel to produce a very high water quality as a result of the almost infinite number of small ion exchange reaction stages that occur as the water passes through the column of Mixed Bed (MB) resins.
The Mixed Bed typically consists of a Strong Acid Cation (SAC) and a Strong Base Anion (SBA) resin mixed together, usually at a volumetric ratio of 40% Cation to 60% Anion resin. Other ratios can be used depending on the water analysis, the capacity desired, and the required quality of the treated water. Consult with your Purolite representative for more information.
- Purolite Mixed Beds for Ultra Pure Water Production include:
Product Name Application/Description
This form of deionization is typically used when the need for a water quality >18.2 megohm-cm resistivity and <10 ppb or <1ppb Total Organic Carbon (TOC) is required.
A Mixed Bed unit can also be used as a polisher following a Two Bed or a Multi-Bed system.
Typical design for general purpose Mixed Bed units requires that regeneration of the resins be carried out within the same vessel. In this case it is necessary to separate the anion from the cation resin before the acid and caustic regenerants are introduced. This is accomplished by backwashing of the resins, using an adequate velocity of water to fluidize the bed. The cation, being higher in specific gravity, will settle to the bottom of the bed, while the anion, being lighter, will rise to the top of the bed (in some designs, brine is used to assist in this separation).
Each of the separated resin beds are then regenerated. After regenerant chemicals have been introduced, the resins are rinsed and then remixed intimately using oil-free compressed air. |
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