Romuald Bogoczek

Studies on the thermal stability of the perfluorinated cation-exchange membrane Nafion-417

The thermal stability of the perfluorinated cationexchange membrane Nafion-417 was determined by means of simultaneous TG-DTA. The individual decomposition stages were studied via IR spectroscopy and ion-exchange capacity determinations. Nafion-417 is thermally stable up to 280 ‡C. Above this temperature, sulfonic groups present in the membrane are split off (Tmax= 345 ‡C. In the temperature range 420–590 ‡C, oxidative destruction of the perfluorinated matrix occurs, which is accompanied by practically total weight loss.ZusammenfassungDie thermische Stabilität der perfluorierten Kationenaustauscher-Membran Nafion 417 wurde durch simultane TG-DTA untersucht. Die einzelnen Zwischenstufen der Zersetzung wurden durch IR-Spektroskopie und Messung der Ionenaustauschkapazität charakterisiert. Nafion 417 ist thermisch stabil bis 280 ‡C. Oberhalb dieser Temperatur werden die vorhandenen Sulfonsäuregruppen abgespalten (Maximum bei 345 ‡C). Im Temperaturbereich 420–590 ‡C findet oxidativer Abbau, verbunden mit völliger Gewichtsabnahme, statt.РЕжУМЕДль ОпРЕДЕлЕНИь тЕРМ ОУстОИЧИВОстИ пОлНО стьУ ФтОРИРОВАННОИ кАтИО НО-ОБМЕННОИ МЕМБРАНы НАФОИН-147 Был И спОльжОВАН тЕРМИЧЕс кИИ АНАлИж. Дль ИжУЧЕНИь ОтДЕльН ых стАДИИ РАжлОжЕНИь БылИ пРИМ ЕНЕНы МЕтОД Ик спЕктР ОскОпИИ И ИОНООБМЕННОИ хРОМАт ОгРАФИИ. УстАНОВлЕНО, ЧтО НАФИОН-147 тЕРМИЧЕск И УстОИЧИВ ДО тЕМпЕРА тУРы 280‡. ВышЕ ЁтОИ тЕМпРЕРАтУ Ры (тМАкс.=345‡) пРОИсхОДИт ОтЩЕплЕНИЕ сУльФОгР Уппы, А жАтЕМ В тЕМпЕРАтУРНО М ИНтЕРВАлЕ 420–590‡ пРОИсхОДИт ОкИсл ИтЕльНО-ВОсстАНОВИт ЕльНыИ РАспАД пЕРФтОРИРОВА ННОгО ОБРАжцА, сОпРОВОжДАУЩИИсь пР АктИЧЕскИ пОлНОИ пОт ЕРЕИ ВЕсА.

Chemical modification of styrene-divinylbenzene copolymers by dialkyl phosphites

Abstract Chloromethylated styrene-divinylbenzene copolymers were treated with dialkyl phosphites to obtain cation exchangers with phosphorus-containing acid groups. The gel and macroporous styrene-divinylbenzene (St-DVB) copolymers of Wofatit type were used. The influence of the phosphite (R=CH 3 , C 2 H 5 ) as well as of the copolymer structure (gel, macroporous) on the course of the phosphorylation and of the ester bond hydrolysis was investigated. The cation exchangers with -PO(OH)(OR) functional groups were obtained and their main properties (density, swelling, ion exchange capacity, p K a , thermal stability, i.r. spectra) were determined.

Dissolution and mineralization of ion exchange resins: differentiation between heterogeneous and homogeneous (photo-)Fenton processes

Fenton and photo-Fenton processes lead under defined experimental conditions to the oxidative degradation and complete apparent dissolution of ion exchange resins (IER) based on copolymers of sulfonated styrene and divinylbenzene, as well as to the mineralization of the dissolved organic fragments. Using the optimal experimental design methodology (OED), the initial Fe(II)-concentration ([Fe(II)]0) was found to control the time needed to completely degrade the IER into soluble fragments, whereas the H2O2 concentration was of minor impact. The photo-Fenton process enhanced primarily the rate of mineralization compared to the dark reaction. The results of process modeling for Fenton and photo-Fenton processes, investigations on the evolution of sulfate (SO42−), CO2, formic and oxalic acids, as well as the comparison between results of photo-Fenton and VUV-photolysis experiments confirm: (i) the existence of two distinct Fenton processes taking place at the surface of the IER beads and in the aqueous bulk, (ii) the desulfonation as the reaction triggering the oxidative degradation and apparent dissolution of IER, (iii) the release of Fe(III) into the aqueous medium and its subsequent reduction, as well as the recycling of the Fe(II)-complexes at the surface of the IER, (iv) the low reactivity of HO˙ generated in solution toward the solid organic substrate, and (v) the important effect of Fe(III)-complexation by oxalic acid. Results also support the hypothesis that formic and oxalic acids are of different origin, and their probing might prove useful for other degradation processes as well.

Synthesis and main properties of uniformly chlorosulfonyl-substituted styrene-divinylbenzene resins

Cinetique de la chloruration de resines commerciale echangeuses de cation styrenesulfonate-divinylbenzene

Using macroporous N-chlorosulfonamide S/DVB copolymer as an aid to iron removal from water*

The de-ironing of water is a basic stage in water-treating technology. Consequently, the oxidation of easily soluble Fe(II) to poorly soluble Fe(III) compounds is indispensible. In order to oxidize Fe(II) ions to Fe(III), a macromolecular and macroporous product in bead form was used: polystyrene cross-linked by divinylbenzene, which contains pendant N-chlorosulfonamide groups in both the sodium and hydrogen forms. To assist the process of removing residual iron from water, this polymer - a macromolecular analog of Chloramine T, containing more than 4.0 mequiv of active chlorine/g - was prepared, starting from the sulfonate cation exchanger Amberlyst 15 by a three-step transformation of its functional groups. The investigations were carried out using both the batchwise and column methods, and 0.0025 M as well as 0.02 M FeSO4 solutions with different acidity were used. We found that the oxidation of ferrous ions to ferric by N-chlorosulfonamide copolymer was effective and was favored by a low pH. The oxidative ability of the copolymer was 225 mg Fe(II)/g. We established that the oxidation reaction could be operated in two directions. In acidic media (pH < 2.5), Fe(III) ions remained in the solution as products of the reaction. The higher the pH, the more the poorly soluble ferric compounds sedimented in the inner structure of the copolymer beads. In this way, new hybrid materials were obtained, i.e., by ferrous/ferric oxides and hydroxides, by nanoparticles, modified materials which can serve as specific reacting sorbents and catalysts.

Thermal analysis of macromolecular “Haloamines”

The TG, DTG and DTA curves of macromolecular macroporous N-halogeno- and N,N-dihalogenosulfonamides are reported and interpreted. To compare their thermal behaviour with that of their unfunctionalized matrices, analogous studies were performed on the porous styrene-divinylbenzene(20%)copolymer and its sulfonamide derivative.ZusammenfassungDie TG-, DTG- und DTA-Kurven makromolekularer makroporöser N-Halogen- und N,N-Dihalogensulfonamide werden beschrieben und gedeutet. Zum Vergleich wurde das thermische Verhalten des unsubstituierten porösen Styren-(20%)Divinylbenzen-Copolymeren und seines Sulfonamids in gleicher Weise untersucht.РЕжУМЕпРИВЕДЕНы И ОБсУжДЕН ы тг, Дтг И ДTA кРИВыЕ Дль МАкРОМОлЕкУльРНых М АкРОпОРИстых N-гОлОгЕН- И N,N-ДИгАлОкЕН сУльФАМИДОВ. с цЕльУ сОпОстАВлЕНИь Их тЕР МИЧЕскОгО пОВЕДЕНИь с Их НЕАктИВНыМИ НЕжА МЕЩЕННыМИ пРОИжВОДН ыМИ, БылИ пРОВЕДЕНы АНАлОгИЧН ыЕ ИсслЕДОВАНИь пОРИстОгО сОпОлИМЕР А стИРОлА И ДИВИНИлБЕ НжОлА И ЕгО сУльФАМИДНОгО пРОИж ВОДНОгО.

Covalent reactions on carboxylic cation exchangers poly(acrylic acid-dvb/esters)

Abstract In this basic research—possibly qualifying for practical application—ionic bonds were replaced with covalent bonds in carboxylic cation-exchange resins, taken as examples of crosslinked reactive polymers. To achieve this aim we applied esterification reactions, comprising several modifications. The said reactive polymers were used in the macroporous and gel states and in a part of the study they had previously been dehydrated to contain acid anhydride groups. It was found that the best conversion of the carboxylic to ester groups was ∼80%. The products can be used for example in nucleophilic substitutions, giving rise to a number of derivative crosslinked reactive copolymers.

Synthesis and basic characterization of a macromolecular dibromoamine: N,N-dibromo-poly(styrene-co-divinylbenzene)sulfonamide

Abstract A macromolecular-pendent-group N,N-dibromosulfonamide ([P]-SO2NBr2) having a macroporous styrene-divinylbenzene matrix structure has been obtained by three methods: by the action of (a) bromine in aqueous medium and (b) aqueous metal hypobromites in acidic medium, on the appropriate macromolecular-pendent-group sulfonamide, and by (c) the action of an aqueous metal bromide on the appropriate macromolecular N,N-dichlorosulfonamide. In the best case the product was obtained with nearly 100% functional yield and it contained 2.4 mmol g−1 -SO2NBr2 groups, i.e. ca. 0.38 g g−1 of active bromine. The stability of the resin was investigated in the range 20–100°C in the dry state as well as in aqueous media. Thermoanalysis (thermogravimetric, differential thermogravimetric and differential thermal analysis curves) was carried out up to 1000°C and its course was interpreted. The resin has brominating, oxidative and microbiocidal properties. It reacts in a reversible way: after loss of the active bromine, it can be reactivated again.

Thermal analysis of 1-Hydroxiethylidenediphosphonic acid and its salts

Abstract1-Hydroxyethylidenediphosphonic acid and its tetrasubstitutcd Li, Na, K, Rb, NH4, Ca and Ba salts were synthcsized and their thermal behaviour was studied under non-isothermal conditions by simultaneous TG-DTG-DTA at 20–1000 ‡C. The following thermal transformations were observed: loss of crystallization water, melting in the case of the acid, and intramolecular dehydration in the case of the salts, leading to the corresponding unsaturated derivatives. From the free acid, its acidic salts and the neutral ammonium salt, long-chain polycondensates are formed through intermolecular dehydration.Zusammenfassung1-Hydroxyethyldiphosphonsäure und ihr Li-, Na-, K-, Rb-, NH4-, Ca- und Ba-Salz wurden dargestellt. Ihr thermisches Verhalten wurde durch simultane TG-DTG-DTA unter nichtisothermen Bedingungen bei 20–1000 ‡C untersucht. Folgende thermische Umwandlungen wurden beobachtet: Verlust von Kristallwasser, Schmelzen (nur bei der freien Säure), intramolekulare Wasserabspaltung (nur bei den Salzen) zu ungesättigten Verbindungen. Die freie Säure, die sauren Salze und das neutrale Ammoniumsalz bilden unter intermolekularer Wasserabspaltung langkettige Polykondensate.РЕжУМЕсИНтЕжИРОВАНы 1-ОксИЁ тИлИДЕНДИФОсФОНОВА ь кИслОтА И ЕЕ ЧЕтыРЕкж АМЕЩЕННыЕ сОлИ лИтИь, НАтРИь, кАлИь, РУ БИДИь, АММОНИь, кАльцИ ь И БАРИь. тЕРМИЧЕскОЕ пОВЕДЕН ИЕ Их БылО ИжУЧЕНО НЕИжОтЕРМИЧЕскИ В тЕ МпЕРАтУРНОМ ИНтЕРВА лЕ с пОМОЩьУ сОВМЕЩЕННОгО МЕтОДА тг-Дтг И ДтА. УстАНОВлЕНы тАкИ Е тЕРМИЧЕскИЕ пРЕВРА ЩЕНИь, кАк пОтЕРь кРИстАллИжАц ИОННОИ ВОДы, плАВлЕНИ Е сВОБОДНОИ кИслОты И В НУтРИМОлЕкУльРНАь Д ЕгИДРАтАцИь сОлЕИ, пРИВОДьЩАь к ОБ РАжОВАНИУ сООтВЕтстВУУЩИх НЕН АсыЩЕННых сОЕДИНЕНИ И. В слУЧАЕ сВОБОРНОИ кИслОты, ЕЕ кИслых сОлЕИ И НЕИтРАльНОИ АММОНИ ЕВОИ сОлИ, ВНУтРИМОлЕ кУльРНАь ДЕгИДРАтАцИь пРИВОД ИлА к ОБРАжОВАНИУ ДлИНИОцЕпОЧЕЧНых пО лИкОНДЕНсАтОВ.