New type of the ion-exchange resins - polymers with a space (three-dimensional) globular structure (SGS-polymers) were first prepared in the USSR in the middle of 20th century.
|At present, only the Geyser Joint-Stock Company can commercially produce these materials. SGS-polymers are principally new materials for which three types of filtration, namely mechanical, sorption, and ion-change filtration are possible. None of known sorption materials allow treatment to remove such a large assortment of chemical compounds as SGS-polymers. |
SGS-polymers are macromolecular compounds which can be prepared from various monomers, e.g. resorcin, pyrocatechol, hydroquinone, melamine, carbamide, etc. Microglobules, i.e. long polymeric chains convoluted in clew are formed in synthesis of the SGS-polymers. Being bound these microglobules provide porous and simultaneously mechanically rigid structure form
Microglobules possess 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. 2a ,2b/. As a result, the rate of the volume filtration of the SGS-polymers is greater by a factor of 10-20 as compared to common granulated ion-exchangers. This is a decisive advantage of the SGS-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 SGS- polymer were studied and the operation proce- dures for their production were developed. The materials exhibiting both cation- and anion- exchange properties were also synthesized.
The fields of application of the SGS-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.
SGS-Polymers in Water Treatment
ARAGON sorbent based on resorcin exhibits the best results in complex treatment of water to remove harmful pollutants. This polymer meets the rigid requirements of the Russian and International (NSF) Standards and can be used in systems for treat- ment 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.
ARAGON 2 is combination of usual ion-exchange resin and ARAGON polymer block impregnated with silver. Hardness salts, dissolved iron, heavy metals are removed due to ion-exchange properties of resin and polymer /Fig. 3/.
into the purified water often happened at pressure jumps. The amount of free channels in the material only gradually decreases in the course of its operation decreasing the head of the purified water. This allows prolonged multiple operation of the filtration element based on the ARAGON material.
Ion-exchange resin increases a resource of ARAGON 2 in regard to hardness salts in 5-7 times if compared with ARAGON material.
The ARAGON sorption capacity is comparable with best brand activated carbons which provides 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 ARAGON 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 sorbed 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 ARAGON 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 in Chapter 2.
This material possesses high strength and allows mechanical treatment (to prepare cylinders, discs, etc. for filtration elements). Compact and efficient filters based on ARAGON sorbent are unitized in accordance with main international standards. The ARAGON sorbent is successfully used for water treatment in the regions contaminated with various pollutants after the Chernobyl accident.