A set of studies necessary to determine the suitability of a fibrous anion exchanger with ternary amino groups based on industrial polyacrylonitrile fiber Nitron C as a component of ion substrates was carried out. A laboratory-prepared ion exchanger sample had a working exchange capacity equal to 0.9 meq/g for the nitrate anion, which limits the biological productivity of the substrate for growing plants, in the physiological pH range = 5.5–7.5 and the concentration of the equilibrium nutrient solution is 0.02 eq/l. This capacity is at the level of the best granular ion exchangers and significantly exceeds the capacity of the previously used fibrous ion exchangers for growing plants in zero gravity conditions on space stations in 1970–1994 (Mir, Soyuz TM-10 – TM-17). The synthesized ion exchanger is a polyampholyte and contains three types of ion exchange groups, has high hydrophilicity and mechanical properties that allow it to be processed into textiles and used for any purpose, in which fibrous ion exchangers can be used (air and water purification, human protection means, etc.).

Titration curves of H-forms of the fibrous chelating sorbent with iminodiacetic groups based on industrial polyacrylonitrile fiber Nitron with potassium hydroxide in 1M KCl solution in the presence of Ni2+, Co2+, Cu2+ and Ca2+ chlorides were obtained. The method used made it possible to simultaneously measure the pH of the solution and the concentration of the divalent cation at each point of the titration curve. From these data, the dependences of their sorption values on the pH of the equilibrium solution were calculated. The curves of direct and back titration practically coincided in all cases. As the pH changed during titration, precipitation was observed at pH values of precipitation of the corresponding hydroxides. In this case, the increase in pH was suspended or greatly slowed down by adding alkali to the titration cell. The formation of a precipitate occurred mainly in a solution for Co2+ and Ni2+ (pH 8), when the ion exchanger was saturated with a metal ion. In the case of Cu2+ (precipitate formation pH 4), Cu2+ sorption occurs at both lower and higher pH due to ionization of carboxyl groups and partial dissolution of the precipitate. In all cases, the maximum sorption of Ni2+, Co2+, Cu2+, Ca2+ corresponded to the formation of sorption complexes of the R–N(CH2COO-)2Me2+ type.

Structural and electronic characteristics of molecular models of swollen polyacrylic and sulfostyrene-type cation exchangers in sodium and potassium ionic forms are calculated within the non-empirical HF/basis set method using the MINI Huzinaga basis set and the Firefly program. The obtained data are compared with those for water clusters of a comparable size. The molecular models include four and two monomeric units of corresponding polymers with ten water molecules per functional group; the water clusters contain 20 and 40 water molecules. The following characteristics of the model structure are obtained: the number and the types of the nearest neighbors of cations and water molecules; the distances between the interacting ions and the atoms; the orders of interionic and ion-molecular bonds; binding energy distribution of water molecules in the systems; number and length distributions of hydrogen bonds; the number and character of RCO_2^-⋯I^+, RSO_3^-⋯I^+ and H_2O⋯I^+ bonds. The lengths of hydrogen bonds and the total number of intermolecular and ion-molecular bonds per water molecule in water clusters are established to be similar to those in Na+ and K+ molecular models of ion exchangers. The first coordination layer around both ions is filled with oxygen atoms of water molecules and fixed anions. The coordination numbers of Na + and K + are almost equal to those in aqueous solutions. The calculations indicate that direct interaction of Na + and K + with the anionic groups is responsible for the difference between their ion exchange selectivities on carboxylic and sulfostyrene ion exchangers. The Na + ion forms direct largely covalent chemical bonds with the fixed carboxylate anion. The K + ion forms long electrostatic bonds with the carboxylate group. This accounts for a higher selectivity of Na + on carboxylic ion exchangers than that of K + . The K + ion forms long direct electrostatic bonds with the fixed sulfonate anion. The Na + ion does not form direct bonds with the sulfonate due to strong hydration of the former. This accounts for a higher selectivity of K + on sulfonic acid resins that that of Na + .

Структурные и электронные характеристики молекулярных моделей набухших катионитов полиакрилового и сульфостирольного типа в натриевой и калиевой ионных формах рассчитаны неэмпирическим методом HF/basis set с использованием базиса MINI Huzi­naga и программного пакета Firefly. Полученные результаты сопоставлены с такими же данными для кластеров молекул воды соизмеримого размера. Молекулярные модели включали четыре и две мономерные единицы соответствующих полимеров с десятью молекулами воды на функциональную группу; кластеры воды содержали 20 и 40 молекул. получены следующие характеристики модельной структуры: число и тип ближайших соседей катионов и молекул воды; расстояния между взаимодействующими ионами и атомами; порядок межионных и ион-молекулярных связей; распределение молекул воды в кластерах по энергии связи; распределение водородных связей по числу и длине, а также количество и характер связей RCO2–⋯I+, RSO3–⋯I+ и H2O⋯I+. Длина водородных связей и общее число межмолекулярных и ион-молекулярных связей на молекулу воды в кластерах воды и в молекулярных моделях ионитов в ионных формах Na+ и K+ оказались одинаковыми. Первый координационный слой вокруг обоих ионов заполнен атомами кислорода молекул воды и фиксированных анионов. Координационные числа Na+ и K+ оказались практически такими же, как и в водных растворах. Из результатов расчетов следует, что прямое взаимодействие Na+ и K+ с фиксированными анионными группами обусловливает разницу в их ионообменной селективности на карбоксильных и сульфостирольных ионитах. Ион Na+ образует прямые химические связи с фиксированным карбоксилатным анионом, имеющие заметную долю ковалентности. Ион K+ — длинные электростатические связи с карбоксилатной группой. Это объясняет более высокую селективность Na+ по сравнению с K+ на карбоксильных ионитах. K+ образует длинные прямые электростатические связи с фиксированным сульфонат-анионом, а у Na+ нет прямых связей с сульфогруппой из-за его сильной гидратации. Это объясняет более высокую селективность K+ по сравнению с Na+ на сульфостирольных смолах.

A mathematical model for description of the sorption capacity of ion exchangers on alkaline compounds protonizable in aqueous solutions (exemplified by ammonia, mono-, diand triethylamine) was proposed. The Henry’s constants for these substances were experimentally determined. The model accounts for the concentration and acid-base properties of the sorbate, relative air humidity, acid-base properties and exchange capacity of the ion exchanger, as well as spatial availability of functional groups for interaction under conditions of limited permeability of polymeric ion exchanger. The applicability of the model is illustrated by processing the experimental results on the sorption of ammonia and ethylamines by fibrous carboxylic and sulfonic cation exchangers. Good agreement between the calculated and experimental data is observed.

С помощью неэмпирических квантово-химических расчетов (в рамках теории функционала плотности с использованием уровня DFT/B3LYP/6-31G(3d,p)) рассчитаны геометрические характеристики сорбционных комплексов диоксида серы с первичными, вторичными и третичными аминогруппами анионитов, которые синтезированы аминированием нитрильных групп полиакрилонитрильного волокна этилендиамином или диметиламинопропиламином, визуализированы их структуры. Установлены основные закономерности сорбции SO2 из воздуха и особенности протекающих взаимодействий в фазе полимеров: 1) SO2 с первичными и вторичными аминогруппами анионита в основном взаимодействует с молекулами воды и практически не образует связей непосредственно с азотом функциональной группы; введение молекулы кислорода не изменяет состояние системы; 2) в фазе анионита с третичными аминогруппами SO2, взаимодействуя с молекулами воды, самопроизвольно трансформируется в гидросульфит-ион с передачей протона на третичный азот; при наличии в системе молекулы кислорода происходит безбарьерное образование аниона пероксокислоты (SO3OO2-) с возможным дальнейшим окислением гидросульфита в гидросульфат.

New ion exchangers based on polyacrylonitrile fiber were obtained by catalytic amination of nitrile groups with tetraethylenepentaamine and pentaethylenehexaamine. Chelating ion exchangers with aminodiacetic functional groups were obtained on the base of these materials. The acid-base parameters of the functional groups of obtained ion exchangers were determined by potentiometric titration: initial polyampholytes have a high anion exchange capacity (E b = 4.5–5.5 m-eq/g) distributed between three types of groups with pK a equal to 3.3, 6.2 and 9.2, and a cation exchange capacity with E a ≈ 1 m-eq/g and pK a ≈ 10.7; chelating ion exchangers on their base contain three types of acid groups with pK a approximately equal to 3.5, 6.0, 10.5 and two types of anion-exchange groups with pK a equal to 2.0 and 6.0. Initial polyampholytes have a high efficiency in the processes of air purification from acidic impurities (experimental data for sulfur dioxide), chelating ion exchangers – in the processes of water purification from heavy metal ions.

A new method for the catalytic preparation (using copper salts) of the anion exchanger with ternary amino groups has been developed. The best conditions for synthesis of this ion exchanger, such as catalyst and aminating agent (dimethylamino propylamine) concentrations and process time, have been found. The acid-base properties of functional groups have been determined by potentiometric titration. By the analysis of isopiestic curves, water-holding capacity of the anion exchanger has been estimated and these results used for determination of the anion exchanger applicability for air purification. The experimental sorption results show the practical applicability of the ion exchanger for air purification from acidic impurities (on the example of sulfur dioxide sorption) in a wide range of relative humidity.

Magnetic composite sorbents based on microporous and biporous hypercrosslinked polystyrenes (HCPs) with inclusions of iron oxide nanoparticles were studied by X-ray diffraction and differential thermal analysis. In microporous composites, the size of impregnated magnetite nanoparticles was less than ∼6 nm, the nanocomposites remaining optically transparent. Biporous HCPs (with micro- and macropores) had larger nanoparticles (∼16 nm). The sorption studies revealed that composite magnetic sorbents, as well as the starting hypercrosslinked polystyrenes, are effective adsorbents with high capacity for many compounds including toxic and physiologically active compounds.

Hydrogen chloride sorption from the air in a wide range of relative humidity and the concentration of the absorbing component was examined under dynamic conditions with fibrous anion exchanger FIBAN distinguishing by basicity and type of functional groups.

The paper presents the results of laboratory studies of ammonia sorption from air by fibrous ion-exchange materials containing acidic groups in concentration of 3-5 mmoles per gram as a function of the ammonia concentration (3-30 ppm), relative air humidity, air flow rate and the thickness of filtering layer. It follows from our experiments that non-woven fabrics with the thickness of above 2 mm and surface density of -0.3 kg m(-2) can efficiently reduce ammonia concentration in air to <1 ppm at flow rates of <0.2 m s(-1). The sorbent can be regenerated with acid solution to obtain salts that can be used as mineral fertilizers.

A new anion exchanger with aminoethylpiperazine functional groups has been synthesized from polyacrylonitrile fiber. The subsequent alkylation with epichlorohydrin afforded another anion exchanger with strong base functional groups. The optimal conditions for synthesis of these ion exchangers have been found, their physical chemical and sorption properties have been investigated. Experimental data of sulfur dioxide sorption on the ion exchanger with aminoethylpiperazine functional groups show its practical applicability for air purification from acidic pollutants.