WATER ROLE IN THE GASES CHEMOSORPORATION PROCESSES BY SORPTION-ACTIVE MATERIALS

The work summarizes the literature data on the hydration and chemisorption of toxic gases by polymeric sorption-active materials. The mechanisms of absorption by granular and fibrous ion-exchange and impregnated materials and the state of adsorbed water have been studied using various research methods (gravimetric, sorption-thermochemical, derivatographic, IR spectroscopic). The regularities of the hydration processes of granular strongly acidic sulfonic cationexchangers of the brands KU‑2 and KU‑23 (macroporous analogue), fibrous strongly acidic sulfonic cation- exchanger VION KS‑3, fibrous weakly acid carboxylic cation exchanger VION KN‑1 in various ionic forms are considered. Among the anion exchangers, the hydration of granular strongly basic anion- exchangers of the brand AV‑17, granular weakly basic anionexchangers of the brands AN‑25 (AN‑251 macroporous analogue) and ANKB‑35, fibrous strongly basic anion- exchangers of the brands FIBAN A‑6 and FIBAN A‑12, fibrous medium basic anion- exchangers of the brands CM‑2, fibrous weakly basic anion- exchangers of the brands CM-A1, VION AN‑1, VION AN‑3, FIBAN A‑5, FIBAN A‑11 and FIBAN AK‑22 are considered. It has been established that, by nature, the bond with the active centers of water is derided into a «bound» and a ordiner – «free». The first one is a monolayer and the nearest bonded with the ion of the ball; the other is the osmotic swelling water. It has been shown that for the effective absorption of most toxic gases and vapors (SO2, HCl, Cl2, SiF4, HF, NO2, NH3, аміни, COCl2, O3), it is necessary to have «free» water, which is not only a diffusion medium in which mass transfer proceeds, but also is a direct participant in chemisorption.

Weakly Hydrated Anion Exchangers Doped with Cu2O and Cu0 Particles—Thermogravimetric Studies

Hybrid ion exchangers (HIXs) containing fine Cu2O and Cu0 particles were subjected to thermal analysis in order to determine their hygroscopic water content (with regard to their anomalously low porosity) and to determine the effect of the oxidation state of the copper atom in the deposit on the thermal properties of composite materials. Commercially available anion exchangers, Amberlite IRA 900Cl (macroreticular, M) and Amberlite IRA 402OH (gel-like, G), were used as supporting materials. M/Cu2O, G/Cu2O, M/Cu and G/Cu, containing 4.3–8.4 wt% Cu, were subjected to thermal analysis under respectively air and N2. TG/DTG curves revealed that dry M/Cu and G/Cu contained as little as 7.2% and 4.3% hygroscopic water, while M/Cu2O and G/Cu2O contained respectively 10.6% and 9.4% (Cu0 was a stronger water repellent than Cu2O). The oxidation state of the copper atom in the deposit was found to affect the amount of the forming char, and also Cu0 was found to contribute to the formation of more char than in the pyrolysis of the pure resin (the anion exchanger with no copper deposit). Under air the two kinds of particles transformed into CuO, while under N2 metallic copper and char (from the resin phase) made up the solid residue. This means that in the pyrolysis of the HIXs the inorganic phase participated in char formation and it also transformed itself (undergoing reduction when possible). The above findings provide a basis for in-depth research aimed at the innovative use of copper-containing HIXs and at obtaining usable composite materials with a designed (organic-inorganic) composition.

Evaluation of factors affecting the sorption of sulfur dioxide by FIBAN fibrous anion exchangers

The sorption of sulfur dioxide from the air by the fibrous anion exchangers containing amino groups of different structure and basicity has been comparatively investigated. The most effective sorbents of sulfur dioxide are the anion exchangers with ternary amino groups, which have a high exchange capacity (more than 5 meq/g) and additionally contain secondary amino groups. The anion exchangers with high-base amino groups absorb sulfur dioxide at low relative humidity (30 %) but have low dynamic sorption capicity (up to 1.3 meq/g). The anion exchangers with primary and secondary amino groups absorb sulfur dioxide at high relative humidity (more than 54 %) if their cation exchange capacity is several times less than the anion exchange capacity.

Removal of arsenic from aqueous solution containing hexafluoroarsenate

Arsenic removal from aqueous solutions containing hexafluoroarsenate or arsenate by strong and weak base anion exchangers was studied by dynamic column tests that were carried out using solution containing arsenic and accompanying anions (chlorides, sulfates and fluorides). The specific flow rate of solution was 6 BV/h. Desorption of arsenic was carried out by 1 mol/L NaOH or 2 mol/L KSCN. All the studied anion exchangers performed well in the absence of accompanying anions. In the presence of chlorides and sulfates, studied exchangers showed high selectivity towards hexafluoroarsenate.