New type of the ion-exchange resins – polymers with a space (three-dimensional) globular structure (eco-polymers) were first prepared in the USSR in the middle of 20th century. At present, only EcoFilters use this technique for commercial applications in the EU. Eco-polymers are principally new materials of which three types of filtration are used, namely mechanical, sorption, and ion-change filtration is possible. None of known sorption materials allow treatment to remove such a large assortment of chemical compounds as eco-polymers.
Eco-polymers are macromolecular compounds which can be prepared from various monomers, e.g. resorcin, pyrocatechol, hydroquinone, melamine, carbamide, etc. Micro globules, i.e. long polymeric chains convoluted in clew are formed in the synthesis of the eco-polymers. Being bound together these micro globules provide porously and simultaneously a mechanically rigid structure form. Micro globules posses large internal surface area (up to 500 m2*g-1); their surface is coated with active functional groups participating in the ion- exchange processes. The ions removed directly interact with a chemically-active polymer surface excluding their diffusion into the globule bulk which is typical for ion-exchange resins /Fig. 1a, 1b/. As a result, the rate of the volume filtration of the eco-polymers is greater by a factor of 10-20 as compared to common granulated ion-exchangers. This is a decisive advantage of the eco-polymers.
Mechanical admixtures are predominantly removed in the outer near-surface layers; the pore size can vary in any range from 0.01 to 3.5 mkm. Changing the synthesis conditions the required porosity of the material can be obtained with an accuracy of no more than 10%. At present, nearly 30 modifications of the eco-polymer were studied and the operation procedures for their production were developed. The materials exhibiting both cations- and anion- exchange properties were also synthesized The fields of application of the eco-polymers are very wide and involve purification of: Drinking water and hot water; Juices, vines, sunflower-seed oil; Technical liquids, acids and alkalis; Waste waters, including those contaminated with petroleum products; Gases, including exhausts.
EcoAgua cartridge sorbent based on resorcin exhibits the best results in the complex treatment of water to remove harmful pollutants. This polymer meets the rigid requirements of International (NSF) Standards and can be used in systems for treatment of the drinking water. Dissolved chemical elements (from aluminum to radioactive metals) and their compounds are removed from water according to the ion-exchange and sorption mechanisms. EcoAgua’s filtration cartridge is a combination of usual ion-exchange resin and polymer block impregnated with silver. Hardness salts, dissolved iron, heavy metals are removed due to ion-exchange properties of resin and polymer /Fig. 2/ into the purified water often happened at pressure jumps. The amount of free channels in the material only gradually reduces in the course of its operation decreasing the head of the purified water. This allows prolonged multiple operations of the filtration element based on the eco material. Ion-exchange resin increases a resource of EcoAgua’s drinking filter in regard to hardness salts in 15-20 times if compared with usual materials.
The filter sorption capacity is comparable with the best brand activated carbons which provide removal of active chlorine, chlorine-containing compounds, and organic compounds. All the coarse particles with a size greater than the pore diameter are mechanically filtered off on the sorbent surface. The filtration channel has a complex tortuous profile with a gradient porosity which prevents discharge of removed impurities. The labyrinth structure of the filter sorbent acts as a barrier for microorganisms. The major fraction of bacteria and viruses having the oblong shape (from 0.5 to 20.0 mkm) are trapped in the tortuous sorbent channels. To suppress growing of micro- organisms absorbed in the polymer this material is modified with silver added in the form preventing its migration into the purified water.
Quasi-softening is the unique property of the eco-polymer based material. On water passing through the sorbent material the structure of salts providing water hardness is changed. As a result, no deposits upon boiling is formed and water exhibits the salutary effect on the living organism. The effect of quasi-softening is given in detail here.
This material possesses high strength and allows mechanical treatment (to prepare cylinders, discs, etc. for filtration elements). Compact and efficient filters based on eco-polymer sorbent are unitized in accordance with main international standards. The filter sorbent is successfully used for water treatment in the regions contaminated with various pollutants after the Chernobyl accident.