I use mixed bed demineralization by ionization as part of my RO/DI system.
(I assume so does the unit in question, but buyer beware... it could get very expensive to maintain without the initial RO stage)
(Copied and pasted from an earlier reply of mine on the subject over at ICPS's forum)
Deionization and Demineralization by Ionization both refer to specialized forms of Ion Exchange. (both terms are often used interchangeably, but there is a slight difference...true DI will also remove bacteria)
Deionization removes ions as does Ion Exchange. Ion exchange deionization (DI) columns use synthetic resins similar to those used in water softeners.
Deionization systems use a two-stage process to remove virtually all ionic material remaining in water. That is why we call the process Deionization.
In Deionization two types of synthetic resins are used, one to remove positively charged ions (cations) and another to remove negatively charged ions (anions). Cation deionization (DI) resins ions remove cations, such as calcium, magnesium and sodium and replace them with the hydrogen (H+) ion. Anion deionization resins remove anions, such as chloride, sulfate and bicarbonate and replace them with the hydroxide (OH-) ion.
In Deionization, these displaced H+ and OH- ions combine to form additional H2O
In Mixed-Bed deionization systems, the anion and cation resins are blended into a single tank or vessel. Generally, mixed-bed systems will produce higher quality water with a lower total capacity than two-bed systems. Mixed bed deionization resins have design capacities and must be typically be replaced upon exhaustion. To extend bead life this stage is usually performed after the water has gone through the RO process.
Deionization can produce extremely high-quality water in terms of dissolved ions or minerals, up to the maximum resistance of 18.3 megohms/cm. RO/DI are the standard for the pharmaceutical, Electronic and Nuclear industries.
HTH's
Av
http://icps.proboards.com/index.cgi?board=questions&action=display&thread=1835