Isotopic exchange of gaseous ammonia 14NH3 and 15NH3 in sulfonated macroreticular ion exchangers

Adsorption and ¹⁵NH₃ isotopic exchange was performed on dry macroreticular polystyrene ion exchanges crosslinked with varying amounts of divinylbenzene and partially neutralized by ¹⁴NH₃. Data on pressure changes and mass spectrometric analyses of isotopic composition of the gaseous phase were used to calculate equilibrium distribution of ¹⁴NH₃ and ¹⁵NH₃ under various dislocation conditions. It was established that along with the exchange of ¹⁴NH₃ to a gaseous phase, ¹⁵NH₃ penetrates to the mass of ion exchanger. This is evidently due to the migration of ammonia among functional groups. It was found that by thermal desorption under reduced pressure ammonia is released only from functional groups located on the surface of ion exchanger.     

Ion exchange extraction of platinum(IV) and palladium(II) from hydrochloric acid solutions

Sorption concentration of platinum(II, IV) and palladium(II) from freshly prepared and aged two-yearold hydrochloric acid solutions by a series of anion exchangers with different functional groups and of different physical structure of Purolite and CYBBER grades was studied. The high sorption ability of the ion exchangers in relation to the extracted chlorocomplexes of noble metals is shown. It was demonstrated that palladium(II) from all tested ion exchangers can be completely desorbed with thiourea solutions acidified with hydrochloric acid, while complete desorption of platinum is achieved only from Purolite S 985 anion exchanger of the complexforming type and Purolite A 111 weak base anion exchanger.     

单功能基叔胺型弱碱树脂的合成及其滴定曲线研究

合成了以苯乙烯－二乙烯苯为骨架的若干叔胺型弱碱性树脂，研究了胺化反应条件，胺化试剂及交联度等对叔胺产碱树脂功能单一性的影响，测定了强碱交换量低的叔胺树脂的滴定曲线特征，找到了适合作为热再生树脂弱碱组分的单功能基叔胺树脂的合成条件。     

Dissociation rates of urea in the presence of NiOOH catalyst: a DFT analysis

Single molecule reactions have been studied between nickel oxyhydroxide, urea, and the hydroxide ion to understand the process of urea dissociation into ammonia, isocyanic acid, cyanate ion, carbon dioxide, and nitrogen. In the absence of hydroxide ions, nickel oxyhydroxide will catalyze urea to form ammonia and isocyanic acid with the rate-limiting step being the formation of ammonia with a rate constant of 1.5 × 10?? s?1. In the presence of hydroxide, the evolution of ammonia was also the rate-limiting step with a rate constant of 1.4 × 10?2? s?1. In addition, desorption of the cyanate ion presented an energy barrier of 6190 kJ mol?1 suggesting that the cyanate ion cannot be separated from NiOOH unless further reactions occurred. Finally, elementary dissociation reactions with hydroxide ions deprotonating urea to produce nitrogen and carbon dioxide were analyzed. These elementary reactions were investigated along three paths differing in the order that protons were removed and the nitrogen atoms were rotated. The rate-limiting step was found to be the removal of carbon dioxide with a rate constant of 4.3 × 10??? s?1. Therefore, the catalyst could be deactivated by the surface blockage caused by carbon dioxide adsorption.     

Specific features of rhenium desorption from weakly basic anion exchangers Purolite A170 and Purolite A172 with ammonia solutions

Equilibrium, kinetics, and dynamics of rhenium desorption from weakly basic macroporous (Purolite A170) and gel anion (Purolite A172) exchangers with ammonia solutions were studied. The effective diffusion coefficients of rhenium in its desorption from these anion exchangers and the activation energy of rhenium desorption from the gel anion exchanger were estimated.     

Preparation of poly(glycidylmethacrylate‐divinylbenzene) weak acid cation exchange stationary phases with succinic anhydride,phthalic anhydride,and maleic anhydride for ion chromatography

In this work, poly(glycidylmethacrylate‐divinylbenzene) microspheres were prepared and applied for the preparation of weak acid cation exchange stationary phases. Succinic anhydride, phthalic anhydride, and maleic anhydride were selected as carboxylation reagents to prepare three weak acid cation exchangers by direct chemical derivatization reaction without solvent or catalyst. The diameters and dispersity of the microspheres were characterized by scanning electron microscopy; the amount of accessible epoxy groups and mechanical stability were also measured. The weak acid cation exchangers were characterized by Fourier transform infrared spectroscopy; the content of carboxyl groups was measured by traditional acid base titration method. The chromatographic properties were characterized and compared by separating alkali, alkaline earth metal ions and ammonium and polar amines. The separation properties enhanced in the order of succinic anhydride, phthalic anhydride, and maleic anhydride modified poly(glycidylmethacrylate‐divinylbenzene) cation exchangers.     

Composite ion exchangers of redox type for cesium separation. Sorption-desorption-regeneration cycle with cupric ferrocyanide impregnated macroporous anion-exchange resins of strongly basic type

Cupric ferrocyanide impregnated Bio-Rad AGMP-1 or Amberlite IRA-904 exhibited an excellent performance and could be repeatedly used for cesium sorption from 3M nitric acid in the presence of trace hydrazine and subsequent cesium desorption with 3–5M nitric acid containing a slight amount of nitrous acid when regeneration of the composite ion exchanger after the desorption was conducted with an acidic hydrazine solution containing cupric ion above 200–250 ppm.     

Synthesis of polymeric anion exchangers bearing dimethylhydrazine and alkylammonium functional groups and comparison of their chromatographic properties

A new anion exchanger for ion chromatography bearing an N,N-dimethylhydrazine functional group was synthesized by chloromethylation followed by the amination of a copolymer of styrene and divinylbenzene with a crosslinking degree of 50%. Its chromatographic properties were studied in a two-column mode of ion chromatography with conductometric detection. The anion exchanger obtained is characterized by better selectivity and efficiency than ion exchangers bearing alkylammonium functional groups, namely, trimethylamine, triethylamine, N,N,N′,N′-tetramethyldiaminomethane, N,N,N′,N′-tetramethylethylenediamine, and pyridine. Addition of p-hydroxybenzonitrile in the eluant improved the shape of the peak of the nitrate ion and allowed the simultaneous determination of fluoride, chloride, nitrate, phosphate, and sulfate ions.     

Evidences for the relationship between surface structure and reactivity of goethite nanoparticles based on advanced molecular-probe methods

Surface properties of two goethites have been studied in order to compare the amount of acid surface sites and their distribution over the various surface domains. For this purpose, ammonia, pyridine and nitrogen were used as basic molecular probes. Calorimetry measurements of ammonia adsorption provided the image of the average surface acidity being moderate. This conclusion was supported by the moderate resistance of the adsorbed pyridine molecules to degassing conditions. Adsorption and desorption of pyridine prior to gaseous nitrogen adsorption resulting in masking/unmasking of acid surface sites on the goethite surface allowed confirmation of the acid character of the specific adsorption sites characterized by the high-energy adsorption of electron-donating molecular nitrogen. The amount of acid sites probed by nitrogen and ammonia were of the same order of magnitude but systematically higher for ammonia. The subsequent analysis of the argon and nitrogen derivatives of first-layer adsorption isotherm led to determine the distribution of {101} and {121} crystallographic faces and discuss the location of acid sites on these surface domains.     

Ion-exchange high-performance liquid chromatography of nucleotides and polypeptides on new types of ion-exchange sorbents, based on polystyrene-coated silicas.

A novel type of ion exchanger was prepared by multipoint covalent binding of polystyrene chains onto the surface of porous silica followed by polymer-analogous modification of the bonded layer. Both anion and cation exchangers were synthesized and examined in the separation of nucleotides and proteins. Rapid and efficient separation of basic polypeptides on strong anion exchangers and that of acidic polypeptides on strong cation exchangers could be achieved. For the separation of complete mixtures of polypeptides the application of zwitter-ionic ion exchangers can be recommended.     

Polystyrene immobilized ionenes as novel stationary phase for ion chromatography

Several aliphatic ionenes (2-6-, 6-6-, 10-6-ionene) have been prepared as ion exchangers for the development of novel high-performance stationary phases for anion chromatography (IC). A macroporous polystyrene/divinylbenzene (PS/DVB) resin with adjusted cation exchange capacity was used as support. Therefore the immobilization of ionenes to polystyrene carriers with remaining positive surface charge became possible for the first time. Strong ion-exchange interactions, resulting in high retention times, between the stationary phase and inorganic as well as organic anionic analytes have been observed. The influence of different ionenes on the retention behaviour during the ion chromatographic separation was investigated. Additionally, partly aromatic and polar ionene backbones were prepared and their retention behaviour as anion exchanger was investigated. The highest number of theoretical plates obtained was about 90.000 per meter. The signal asymmetries were generally lower than obtained for surface functionalized anion exchangers.     

The Effects of Polymer Properties and Solution Composition on the Distribution,Properties, and Amount of Water in Swollen Ion Exchangers

The effects of the composition and concentration of an external solution on the swelling degree of polystyrene-based ion exchangers crosslinked with different amounts of divinylbenzene have been analyzed within the heterophase model of polymer gel structure. It has been confirmed experimentally that, upon variations in the composition of the external solution, the swelling degree of polymers is determined by the content of “sorbed” water alone. Therewith, the volume of the external solution incorporated into the swollen polymer remains constant; i.e., it depends neither on an ionic form of an ion exchanger nor the concentration and composition of the external solution, but rather depends linearly on the polymer crosslinking degree. An algorithm has been proposed for calculating the volume of water in a polymer gel and some quantitative estimates have been presented.     

Preparation of Organic-Inorganic Composite Adsorbent Beads for Removal of Radionuclides and Heavy Metal Ions

Composite ion exchanger beads were prepared to remove the strontium and silver ions in acidic solution. Potassium titanate and nickelferrocyanate powder, which are acid resistant inorganic ion exchangers were synthesized and then mixed with polyacrylonitrile (PAN) binder to form a PAN-potassium titanate and a PAN-nickelferrocyanate composite ion exchanger beads. Spherical composite beads could be obtained by adjusting the viscosities of the composite dope in the range of 700–1000 cP. The composite beads porosities such as macropore volume and pore size were increased in proportion to the contents of PVP (polyvinylpyrrolidone) which was used as the porosity modifying chemical. The synthesized composite ion exchangers were evaluated on their adsorption characteristics for the Ag¹ and Sr²¹ ion solutions of pH 2.     

Separation of -amino acids using a series of zwitterionic sulfobetaine exchangers

A set of five new covalently bond sulfobetaine exchangers with inner quaternary amines and outer sulfonic acids have been prepared by attachment of a series of zwitterionic precursors to hyperporous divinylbenzene polymers using a grafting reaction. The series of zwitterionic exchangers have the same backbone and identical spacers to the polymeric backbone, as well as comparable capacities. The only difference is the chain length for one to five methylene groups between the charged functional groups. Chromatographic properties are examined by separation of α-amino acids using sodium acetate and nitric acid eluents. The separation mechanism is explored by varying eluent ionic strength and eluent pH, resulting in the conclusion that amino acids are separated due to cation exchange interactions. This is a behavior never before observed using zwitterionic exchangers. It contradicts the fact that sulfobetaine-type materials used in zwitterionic ion chromatography (ZIC) usually are well suited for anion separation and only poorly for cation separation. Contrary to anion separations using the identical set of exchangers, the materials with three and four methylene groups between the charges give the highest retention factors. Materials showing the high potential in ZIC separations of inorganic anions give low retention factors for amino acids and vice versa.     

Cirrus cloud mimics in the laboratory: an infrared spectroscopy study of thin films of mixed ice of water with organic acids and ammonia

The structures of formic and acetic acids deposited on a thin gold substrate held in vacuum at low temperatures and their related water-ice promoted chemistry have been investigated. The condensed water/guest films were taken to act as cirrus cloud "mimics." Such laboratory representations provide a necessary prelude to understanding how low temperature surfaces can affect chemical composition changes in the upper atmosphere. The systems were characterized by reflection-absorption infrared spectroscopy and temperature-programmed desorption spectrometry. The interaction behavior of the binary acid ices was compared to that observed when ternary mixtures of water, formic acid, and ammonia were deposited. Differences in the chemistry were observed depending on deposition method: layering or mixing. The more atmospherically relevant codeposition approach showed that at low temperatures, amorphous formic acid can be ionized to its monodentate form by water ice within the bulk rather than on the surface. In contrast, the introduction of ammonia leads to full bidentate ionization on the ice surface. The thermal desorption profiles of codeposited films of water, ammonia, and formic acid indicate that desorption occurs in three stages. The first is a slow release of ammonia between 120 and 160 K, then the main water desorption event occurs with a maximum rate close to 180 K, followed by a final release of ammonia and formic acid at about 230 K originating from nonhydrous ammonium formate on the surface. The behavior of acetic acid is similar to formic acid but shows lesser propensity to ionize in bulk water ice.     

Characterization of linear and cyclic polylactic acids and their solvolysis products by electrospray ionization mass spectrometry

Linear and cyclic polylactic acids (PLAs) were characterized using electrospray ionization mass spectrometry (ESI-MS) as part of our ongoing investigation of the hydrolysis mechanism of biodegradable polymers. The condensation oligomers of linear polylactic acid (LPLA) were synthesized by thermal dehydration of L-lactic acid. The trimer and tetramer base polymers of cyclic polylactic acid (CPLA) were obtained by cyclization reactions of lactic acid trimers and tetramers, respectively. In the ESI-MS/MS measurement, LPLA yielded three types of product ion series, while CPLA yielded only one type, from which the repeated units of CPLA were removed. The MS/MS spectrum of the NH4+ adduct ion for both cyclic and linear PLA showed loss of one ammonia molecule. The postsource decay (PSD) spectrum of CPLA by matrix-assisted laser desorption ionization (MALDI) mass spectrometry was similar to the ESI-MS/MS spectrum, while that of LPLA was different. In addition, the degradation of cyclic and linear PLAs by solvolysis was investigated. Solvolysis with anhydrous MeOH was quite feasible, but did not readily occur in the presence of even a small amount of water in the MeOH solvent.     

Sorption of Nickel Ions from Aqueous Solutions by Ion Exchangers

Sorption of Ni²⁺ions from aqueous solutions by ion exchangers differed in their chemical nature and structure was studied. Based on the endothermic curves of ice melting obtained by a differential scanning calorimetry, the amounts of freezing and non-freezing water present in free volumes (pores) of the studied ion exchangers were calculated. Comparison of results obtained from the kinetic curves of nickel ion sorption with data on differential scanning calorimetry indicates a role of structural factor in the sorption of nickel ions. It was found that, depending on the total amount of freezing and non-freezing water, the KU-2-8 sulfonated cationite is the most preferable ion exchanger for the sorption of nickel ions from aqueous solutions. Therefore, sorbent efficiency in this case is determined by its structure rather than by chemical nature.     

Chelating ion-exchangers containing n-substituted hydroxylamine functional groups : Part II. N-acylphenylhydroxylamines

The problems associated with the conversion of commercial carboxylic acid ion exchangers to the acid chloride have been studied and a synthesis of a cross-linked poly(acryloyl chloride) is described. Reaction with phenylhydroxylamine produced a chelating ion exchanger, possessing acyl oxime functional groups, whose properties are compared with those of an aroyl oxime exchanger described earlier. Resin capacity from the acyl oxime group was 0.45 mmole g^-1, and the resin had a rapid equilibration rate. A column separation of mercury and lead is discussed.     

Adsorption of ammonia and water on functionalized edge-rich carbon nanofibers

The preparation, characterization and ammonia and water adsorption properties of edge-rich carbon nanofibers (CNFs) were studied, including platelet CNFs (PCNFs) and cup-stacked CNFs (CSCNFs). Since PCNFs and CSCNFs have many chemically active exposed edges, functionalization by oxidizing the edges was carried out by ozone stream and by nitric acid. Transmission electron microscopy, N₂ adsorption isotherms and temperature-programmed desorption analysis showed that the nitric acid treatment partly destroyed the graphite structure of the PCNFs and created acid functional groups and micropores, whereas the ozone treatment created functional groups without damaging the structure. Ammonia adsorption isotherms clarified that NH₃ adsorption on PCNFs and CSCNFs occurred mainly on oxygen-containing groups, whereas the adsorption on activated carbon fibers (ACFs) occurred on both oxygen-containing groups and the carbon surface without the functional groups, and the CSCNFs showed larger amounts of adsorbed ammonia compared to the PCNFs. Especially at a relatively low pressure range (<0.2 atm), the PCNFs/CSCNFs/ACFs showed the same ammonia adsorption mechanism; that is, the one-to-one interaction between oxygen atoms in the functional groups and hydrogen atoms in ammonia molecules. In addition, the adsorption on the ACFs appeared to occur mainly by interaction with the carbon surface at relatively high pressure (0.3–1.0 atm). Our experimental results and previous findings suggest that NH₃ adsorption on PCNFs is due mainly to NH…O hydrogen bonding between oxygen-containing groups and ammonia rather than to chemical bonding.     

Organic Ion Exchangers. Synthesis and Their Behaviour in the Retention of Some Metal Ions

Summary: Three pyridine strong base anion exchangers as beads were obtained by quaternization reactions of a 4-vinylpyridine : 8% divinylbenzene copolymer of gel type. These resins possess methyl / ethyl / butyl radicals as substituents on N⁺ atoms and have exchange capacities of 4.80 mEq/g and 2.10 mEq/mL. For pyridine strong base anion exchangers, the behaviours in the retention processes of Cr(VI) as oxyanions and Ga(III) as [GaCl₄]⁻ complex anion were evaluated with the bath method. All the resins exhibited retention properties, but the retained amounts of the metal cations are different as a function of the alkyl length as substituent on N⁺ atoms and the complex anion nature. Thus, Cr(VI) oxyanions are best retained by the resin with  CH₃ as substituent on N⁺ atoms while [GaCl₄]⁻ complex anion by the resin with  C₄H₉ as substituent on N⁺ atoms. By aminolysis reaction of an ethylacrylate : acrylonitrile : divinylbenzene copolymer as beads of macroporous type with NH₂OH · HCl in the presence of C₂H₅OH a new chelating ion exchanger was performed which contains both amidoxime and hydroxamic acid functional groups. This ion exchanger has the retention property for different metal cations but its retention capacities values are strongly dependent of the nature of metal cation and the counterion as well as pH of the solution. Thus, in the static conditions Zn(II) cation with NOequation/tex2gif-stack-1.gif anion as counterion is retained with the best result at pH = 5. As an example, for the aqueous metal cation solution of 10⁻² M concentration for Zn(NO₃)₂ the resin possess at equilibrium a retention capacity of 6.70 mmol Zn/g dry resin and for Cu(II) from Cu(NO₃)₂ solution of same concentration, the retention capacity is 0.22 mmol Cu/g dry resin and Fe(III) from Fe(NO₃)₃ solution is not retained.