It was not until the mid-1940s that ion exchange resins based on the copolymerization of styrene crosslinked with divinylbenzene were developed. This discovery opened the possibility of obtaining completely pure water without dissolved salts, and not using distillation.

Demineralizers are devices that produce chemically pure water on this principle of ion exchange. The system consists of a cationic and anionic exchanger where the ionic resin in the cationic filter is regenerated by a solution of hydrochloric acid (HCl) and the ionic resin in the anionic filter by a solution of sodium hydroxide (NaOH).

Although the process of ionic demineralization is quite outdated and well-established, it still sometimes finds its application today. The advantages of such a system are relatively low maintenance costs compared to reverse osmosis, but what discourages many customers are frequent concerns about the disposal of waste chemicals, which are increasingly receiving attention in the modern world, so the reverse osmosis system provides a more environmentally friendly alternative in most major modern systems.

After ion exchange (or reverse osmosis) it is common to see the process of so-called. “Water polishing”, ie treatment with a mixed resin filter in order to achieve extremely high purity, ie low electrical conductivity. The most common application of this technology is used for laboratories, turbine plants, pharmaceutical industry, etc. Since the use of ionic resins and their regeneration processes are not limited to water, other possibilities of their application are:

• coloring, softening and demineralization of sugar solutions;
• removal of organic (fulvic and humic acid) substances from water (so-called scavenger);
• condensate treatment;
• whey demineralization;
• removal of heavy metals and NH3 (fertilizer factories), detergents, phenols, surfactants, etc. from wastewater;
• removal of contaminants from chemical processes;
• recovery of precious metals from spent baths;
• removal of heavy metals from acid baths of the galvanic industry;
• catalytic removal of oxygen from the feed water of high pressure boilers;
• catalyst in the production of hydrocarbons (motor fuels).