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Ion Exchange Process

In the industry implementing ion exchange to water treatment, you will find a number of essential concepts:

1. The majority of ion exchange systems are pretty straight forward vessels comprising a bed of ion exchange resin controlled downflow on a cyclic basis: a unit is controlled to a established loss level, in which it’s regarded as exhausted, the unit is next regenerated, first through upflow cleaning (backwash) after which by chemical elution, downflow, the resin bed is next washed downflow. Since equally water and regenerant flow in the very same path, water departing the system is connected with the resin obtaining the greatest amount of contaminating ions, so quality and also performance each are affected.

2. The ion exchange bed possesses a substantially greater capacity than is required, simply because uneconomical excesses of regenerating chemical can be necessary to transform the resin completely to the sought after ion form. For instance, the cation resin might possess a capacity of 2 N (about 44 kgr/ft3), but approximately 1 / 2 of it (20 to 22 kgr/ft3) is employed regarding sodium cycle conditioning. Consequently, there’s always a higher concentration of contaminating ions, calcium supplement in this instance, around the resin with a possibility of spoiling the actual treated water level of quality.

3. As a result of cyclic operation with cocurrent flow of water and regenerant, chemical
usage within regenerating ion exchange resins is commonly bad. This particular disadvantage is most obvious with strong resins. For instance, within the sodium cycle, in the event the utilised capability is 21 kgr as CaCO3 per cubic ft . (48 kg/m3) of resin, the sodium necessary is in theory only 58.5/50 X 3 = 3.5 IbNaCl/ft3. The specific salt usage is commonly six to ten Ib NaCl ft3, therefore the proficiency is approximately thirty to fifty %. Acid functionality with regard to hydrogen exchange employing a sulfonic-type resin and H2SO4 for regeneration, and caustic effectiveness with regard to regeneration of strong base anion resins tend to be even worse, around twenty to forty %. Conversely, weak cation resins (carboxylic type) as well as weak anion resins (amine type) are usually controlled at approximately 100% chemical effectiveness.

4. The majority of ion exchange resources employed in water treatment come in the size selection of twenty to fifty mesh, or approximately 0.5 mm efficient size. As a result an ion exchange bed is an effective filtration system, a attribute possessing both pros and cons. This particular filtering capability is coupled with ion exchange properties in creating commercial condensate polishing systems using ion exchange beds. However the filtering capability additionally results in fouling and erratic operating runs. Oftentimes it is due to the build up of excessive microbial populations within an exchanger bed.