Sorption kinetics of ammonia and ammonium ions on gel and macroporous sulphonic acid cation exchangers

Diffusion of ammonia and ammonium ions in sulphonic acid cation exchangers (gel Purolite SGC 100 × 10 MBH and macroporous Purolite C 160 MBH) from the solutions, representing the composition of “caustic condensate” (waste of nitrogen fertilizers production) is affected by pH of initial solution and structure of the matrix of cation exchanger. In gel matrix the effective intraparticle diffusivity (D_ef) depends greatly on the solution pH because of shrinkage in alkaline and swelling in acidic medium: on decreasing the initial concentration of ammonia from 0.214 to 0.003 and increasing that of ammonium nitrate from 0 to 0.214 mol l⁻¹ instead, the effect of ion exchange leads to a decrease in pH, resulting in swelling and increase in D_ef from 0.1 to 0.34 × 10⁻¹⁰ for gel Purolite SGC 100 × 10 MBH and variation of 0.18–0.11 × 10⁻¹⁰ m² s⁻¹ for macroporous Purolite C 160 MBH (resistant to shrinkage and swelling).

In Purolite C 160 MBH both macropore diffusivity (0.07–0.29 × 10⁻¹⁰ m² s⁻¹) and gel (solid phase) diffusivity (0.06–0.19 × 10⁻¹⁰ m² s⁻¹) are higher than micropore diffusivity (0.28–0.56 × 10⁻¹⁸ m² s⁻¹).

With respect to the effective intraparticle diffusivity, resistance to nitric acid, used for the regeneration, and high concentration of ammonium nitrate in eluate (up to 110 g l⁻¹), Purolite C 160 MBH has been installed for the conversion of ammonia and ammonium ions to ammonium nitrate reusable in the fertilizers production. This allows minimizing the economic loss and preventing the environmental contamination.     

Ionic conductivity of PEO9: Cu(CF3SO3)2: Al2O3 nano-composite solid polymer electrolyte

Cu⁺⁺ ion containing solid polymer electrolytes exhibit interesting electrochemical properties. In particular, the polymer electrolyte PEO₉:Cu(CF₃SO₃)₂ made by complexing copper triflate (CuTf₂) with PEO appears to show scientifically intriguing transport properties. Although some copper ion transport in these systems has been seen from plating stripping processes, the detailed mechanism of ionic transport and the species involved are yet to be established. In order to obtain enhanced ionic conductivities and also to contribute towards understanding the ionic transport process in Cu⁺⁺ ion containing, PEO based composite polymer electrolytes, we have studied the system PEO₉: CuTf₂: Al₂O₃ incorporating 10 wt.% of alumina filler particles of grain size 10 μm, 37 nm, 10–20 nm and also particles of pore size 5.8 nm. Thermal and electrical measurements show that the system remains amorphous down to room temperature. The composite electrolyte is predominantly an ionic conductor with electronic conductivity less than 2%. The triflate (CF₃SO₃⁻) anions appear to be the dominant carriers. The presence of alumina grains has enhanced the conductivity significantly from room temperature up to 100 °C. The nano-porous grains with 5.8 nm pore size and 150 m²/g specific surface area exhibited the maximum conductivity enhancement. This enhancement has been attributed to Lewis acid–base type surface interactions of ionic species with O²⁻ and OH⁻ groups on the filler grain surface.     

Kinetics of the reduction of Mn at the dropping mercury electrode in aqueous-dioxan mixtures

Reduction of Mn²⁺ has been studied in aqueous dioxan mixtures at a dropping mercury electrode. The reduction has been found to be quasi-reversible and hence kinetic parameters (K_s and ) have been calculated by Gellings' method. The K_s values are found to be in the order of 10⁻³ cm/s. The effect of halide ions has also been studied in aqueous dioxan solvent mixtures using sodium chloride and sodium bromide as base electrolytes in place of sodium perchlorate. The effect of temperature has also been studied.     

Methacryl-terminated macromers by living polymerization as precursors of IPN polymer electrolytes

A new class of polymer electrolytes, based on the interpenetrating polymer network approach, was obtained starting from functionalised macromers, of poly-ether nature, in the presence of a lithium salt (LiBF₄, LiClO₄, LiCF₃SO₃) and propylene carbonate (PC) or tetraethyleneglycol dimethylether (TGME), as plasticizers.

The macromers were synthesised by living polymerisation employing a HI/I₂ system as the initiator. The macromer has a polymerisable end group, which can undergo radical polymerisation, attached to a monodisperse poly-vinylether, containing suitable ethylene oxide groups for ion coordination. Monomers and macromers were characterised by FTi.r., u.v.–vis, ¹H- and ¹³C-n.m.r.

Self-consistent and easily handled membranes were obtained as thin films by a dry procedure using u.v. radiation to polymerise and crosslink the network precursors, directly on suitable substrates, in the presence of the plasticizer and the lithium salt. The electrolytic membranes were studied by complex impedance and their thermal properties determined by differential scanning calorimetry analysis.

Ionic conductivities (σ) were measured for PC and TGME-based membranes at various plasticizer and salt contents as a function of T (60 to −20°C). LiClO₄/PC/PE electrolytes, with 3.8% (w/w) salt and 63% PC, have the highest σ (1.15×10⁻³ and 3.54×10⁻⁴ S cm⁻¹ at 20°C and −20°C, respectively). One order of magnitude lower conductivities are achieved with TGME; samples with 6% (w/w) LiClO₄ and 45% (w/w) TGME exhibit σ values of 2.7×10⁻⁴ and 2.45×10⁻⁵ S cm⁻¹ at 20°C and −20°C.     

Passivity behavior of melt-spun Mg–Y Alloys

Several Mg–Y binary ribbons with Y content up to 17.9 at.% were fabricated by melt-spinning. X-ray diffraction (XRD) revealed that the phase structure changes with increasing Y content from extended solid solution to partially amorphous, and then fully intermetallic Mg₂₄Y₅. Anodic potentiodynamic polarization performed in 0.01 M NaCl electrolyte (pH=12) revealed improved anodic passivity behavior compared to pure Mg for all the Mg–Y alloys. X-ray photoelectron spectroscopy (XPS) revealed that the improved passivity of Mg–Y was more related to the elemental oxidation state rather than the concentration of the surface components. To study the effect of Cl⁻ ion on the passivity behavior, anodic potentiodynamic and potentiostatic polarization were performed on Mg–17.9 at.% Y in alkaline (pH=12) NaCl electrolytes containing Cl⁻ ion in the concentration range from 0.00 to 0.50 M. The passive films formed in 0.01 M NaCl electrolyte were similar to the native film, which were composed of MgO and Y₂O₃. No CO₃²⁻ and Cl⁻ ions were incorporated into the passive film. The passivity was significantly degraded in the electrolytes containing higher Cl⁻ concentration (0.1 and 0.5 M). Detailed XPS revealed that the surface films under these conditions were composed of much hydrated species Mg(OH)₂ and YOOH and/or Y(OH)₃ and CO₃²⁻ was incorporated into the surface film. The incorporation of Y₂O₃ in the passive film was given as the reason for the enhanced passivity properties of Mg–Y ribbons. The mechanism of Cl⁻ and CO₃²⁻ ions to the degradation of the passivity was discussed.     

Products formed in aged Ca-polyester complexed polymer concrete containing cement paste

Poorly crystallized calcium hydroxide [Ca(OH)₂] yielded from portland cement pastes incorporated in calcium-polyester complexed polymer concrete (Ca-UP PC) was slowly formed during 21 days' exposure in water at 24°C. Crystal growth continued as the hydration reactions proceeded. Ca(OH)₂ formed within the amorphous organic polymer layers after up to 90 days' exposure had little if any effect on the ultimate strength of the PC composites. Ca²⁺ ions increased with exposure time, and they act as strongly nucleophilic agents to enhance the formation of complexed COO⁻(Ca²⁺) groups. These contain an ionic bond between Ca²⁺ ion and carboxylate anion (COO⁻) produced by the hydrolysis of esters in UP polymer.     

Anodic behaviour of titanium in acidic chloride containing media (HCl---NaCl). Influence of the constituents of the medium—I. Study of the stationary current. Calculation of the overall reaction orders

In concentrated hydrochloric acid solutions, the overall dissolution rate depends on the acid concentration. Using mixed electrolytes (HCl---NaCl) we have established the influence on the overall anodic stationary current, of each of the H⁺ and Cl⁻ ions. Considering the logarithmic derivative of the overall current with respect to the activities in the various constituents of the medium reveals the complexity of the reaction mechanism especially in the activity and passivation ranges.     

The elastic modulus of the poly(phosphonitrilic chloride) crystal

The Young's modulus for a crystal of poly(phosphonitrilic chloride) (poly-dichlorophosphazene) (NPCl₂)_n has been calculated using force constants derived from spectroscopy. Assuming that the molecule is a uniform helix the value of the modulus is 1.38 × 10⁹ dyne cm⁻² [dyne cm⁻² = 0.1 N m⁻²]; the result is 1.66 × 10¹⁰ dyne cm⁻² if a cis-planar structure is assumed for the molecule. Neither value is close to those obtained experimentally (1.8 × 10⁶ to 6.5 × 10⁶ dyne cm⁻²). This is because experimental values relate to the amorphous polymer whereas the calculated values are those for the crystal. There is good agreement between the values calculated for the (NPCl₂)_n crystal and those for other polymer crystals.     

Catalytic performance of quaternary ammonium salts in the reaction of butyl glycidyl ether and carbon dioxide

The synthesis of cyclic carbonate from butyl glycidyl ether (BGE) and carbon dioxide was performed in the presence of quaternary ammonium salt catalysts. Quaternary ammonium salts of different alkyl group (C₃, C₄, C₆ and C₈) and anions (Cl⁻, Br⁻ and I⁻) were used for this reaction carried out in a batch autoclave reactor at 60–120 °C. The catalytic activity increased with increasing alkyl chain length in the order of C₃ < C₄ < C₆. But, the quaternary ammonium salt with longer alkyl chain length (C₈) decreased the conversion of BGE because it is too bulky to form an intermediate with BGE. For the counter anion of the tetrabutyl ammonium salt catalysts, the BGE conversion decreased in the order Cl⁻ > Br⁻ > I⁻. The effects of carbon dioxide pressure and reaction temperature on this reaction were also studied to better understand the reaction mechanism.     

Infrared spectroscopic study of the acid properties of dealuminated BEA zeolites

A series of HBEA samples were prepared by dealumination through three different methods (steaming, treatments with hydrochloric acid and ammonium hexafluorosilicate (HFS) solutions) of a parent sample with total and framework Si:Al ratios of 12.5 and 33, respectively, constituted of 20 nm crystallites. The samples were characterized by XRD, nitrogen adsorption and pyridine adsorption–desorption followed by IR spectroscopy. Whereas the three dealumination treatments have practically no effect on crystallinity and nitrogen adsorption properties, they cause large changes in the ranges of the O–H bond stretching modes (3300–3800 cm⁻¹) and of the most intense IR absorption of pyridine (1400–1700 cm⁻¹). Treatments with HCl or HFS cause the most significant changes: disappearance of the 3662 and 3782 cm⁻¹ bands corresponding to extraframework Al species and to tricoordinated Al species partially connected to the framework, respectively, appearance of additional bands at 1603 and 1446 cm⁻¹ ascribed to a new type of pyridine species coordinated to Lewis sites (PyL₂) and for desorption temperatures above 350 °C, of a band at 1462 cm⁻¹ generally ascribed to iminium ions, apparently at the expense of the PyL₂ band. In agreement with this formation of iminium ions, desorption at high temperatures causes the complete disappearance of pyridinium ions without complete restoration of the acidic bridging hydroxyl band. PyL₂ species are proposed to be pyridine molecules coordinated to Lewis sites and interacting through hydrogen bond with protonic sites.     

Differential capacitance of the platinum/aqueous-solution interphase

The differential capacitance of polycrystalline platinum in aqueous H₂SO₄ and NaOH solutions has been investigated as a function of bias potential. A capacitance minimum is observed at 0·56 V in H₂SO₄ and − 0·34 V in NaOH solution. There is strong evidence for the irreversible adsorption of oxygen/OH⁻ ions and oxide-film formation. Addition of n-butylamine hinders the adsorption of oxygen/OH⁻ ions and it is itself strongly adsorbed.     

Amphiphilic polyelectrolyte networks derived from 2-oxazolines

Ionene graft copolymers and networks containing quaternary ammonium groups as linkages have been prepared by termination of living mono- and bifunctional poly(2-methyl-2-oxazoline) and poly(2-phenyl-2-oxazoline) with poly(dimethylaminoethyl methacrylate). Ionene networks of different density with p,p′-dichloroxylene and poly(2-alkyloxazoline)s as cross-linkers have been synthesized. The obtained graft and crosslinked copolymers are well defined and with controlled hydrophilic–hydrophobic balance. Viscosity examination and potentiometric titration of some of the products were carried out. Sorption ability towards Cu²⁺, Ni²⁺, Mn²⁺, Fe³⁺ and anion-exchange capacity were investigated as well. The pH dependence of the sorption of metal ions was evaluated.     

On the possibility of the application of a radiotracer method for the in situ study of the accumulation of ions in corrosion products adhered to the surface of some steels

The sorption of ³⁶Cl labelled Cl⁻ ions into the layer of corrosion products adhered to the surface of corroding powdered steel samples has been studied as a function of the time at 1.8 × 10⁻² NaCl concentration. The effect of CrO²⁻₄ and SO₂₋₄ ions on the sorption process and the mobility of sorbed species was investigated.     

Elucidation of a preparation method for copper ion-exchanged ZSM-5 samples exhibiting extremely efficient N2-adsorption at room temperature: effect of counter ions in the exchange solution

The adsorption of N₂ on a copper ion-exchanged ZSM-5 sample (CuZSM-5) prepared by ion exchange using an aqueous solution of copper propionate, Cu(C₂H₅COO)₂, was examined at room temperature by measuring the FT-IR spectra, adsorption isotherms and heat of adsorption. This sample was found to be extremely efficient in terms of N₂ adsorption with regard to both the amount and the energy (i.e., heat) of adsorption, compared with samples prepared by a conventional ion-exchange method using an aqueous solution involving Cu²⁺ and simple counter ions, Cl⁻ or NO₃⁻. To clarify the specificity of the newly-prepared sample, the ion-exchange of ZSM-5 with Cu²⁺ was carried out by employing aqueous solutions involving Cu²⁺ and various types of counter ions [propionate (C₂H₅COO⁻), acetate (CH₃COO⁻), formate (HCOO⁻), chloride (Cl⁻) and nitrate (NO₃⁻) ions]. When the ion exchange was performed by using a Cu(C₂H₅COO)₂ or Cu(CH₃COO)₂ solution, the Cu²⁺ species with propionate or acetate ligand (in the monomer state) were ion-exchanged in ZSM-5, as confirmed by the DR, EPR and FT-IR spectra for CuZSM-5. In contrast, Cu²⁺ species were present in the form of aquo-complexes in samples prepared with other solutions. This distinct difference can be ascribed to the difference in the pK_a values of the counter ions; carboxylate ions, with a high pK_a value, are inclined to form a complex with Cu²⁺. Using this newly applied Cu(C₂H₅COO)₂ solution, the present ion-exchange method has the potential to develop new effective materials that possess the specific adsorption and catalytic properties of CuZSM-5.     

NMR measurements of self diffusion in polymer gel electrolytes

The pulsed field gradient NMR spin-echo technique has been used to measure the self diffusion coefficients of solvent molecules, Li⁺ cations and CF₃SO₃⁻¹ anions in polyvinylidene fluoride (PVDF) gel electrolytes incorporating liquid electrolytes based on either N,N-dimethylformamide (DMF) or tetraglyme (TG) and lithium triflate (LiT). Using the Nernst–Einstein equation with the NMR diffusivities, calculated values for the ionic conductivity were obtained and compared with those determined by ac conductivity measurements to provide estimates of ionic association. These results for the gel electrolytes are compared with those for the corresponding liquid electrolytes, over a range of salt concentrations and temperatures. In general terms, the comparisons support the simple conclusion that regions of liquid electrolyte exist within the gel electrolytes, consistent with limited measurements of the transverse relaxation time T₂ on these systems, which are also reported. There are, however, some small but significant differences between the behaviours of the gel electrolytes and the liquid electrolytes and these are discussed.     

Mass spectra of negative ions in air-like gas mixtures at atmospheric pressure

We have obtained mass spectra of negative ions produced by rays in artificial air at atmospheric pressure (N₂: 80%, O₂: 20%, H₂O: 20–1500 ppm, CO₂: 0.2–300 ppm, NO, NO₂ 0.02 ppm). We observed two main categories: hydrates built on simple ions (O₂⁻, O₃⁻, OH⁻, CO₃⁻, CO₄⁻, HCO₃⁻, NO₂⁻, NO₃⁻), hydrates built on complex ions (NO_x⁻, HNO_γ, HCO₃⁻HNO_x, x = 2,3; Y = 2, 3). For high values of hygrometry, CO₂ content and ageing time (5 msec) we observe the disappearance of O₂⁻, O₃⁻, OH⁻ hydrates whereas the major part of the spectrum consists of complex ions.     

Synthesis, characterization and photophysical properties of benzil-labelled polymers for studies of diffusion-limited interactions by phosphorescence quenching

A new technique for synthesizing benzil-labelled polystyrenes has been developed. This new procedure has advantages over an older synthesis by Horie and Mita in that it involves fewer and less complicated synthetic steps. In addition, the new synthetic pathway should allow for labelling of different sites on the polymer chain and for labelling of different polymers such as poly(methyl methacrylate). The phosphorescence lifetime of terminally benzil-labelled polystyrenes in cyclohexane was found to be approximately 85–90 μs at 25°C with the concentration of benzil at 10⁻⁵ M and was independent of labelled polystyrene molecular weight and polystyrene concentration up to 150gl⁻¹. When used in phosphorescence quenching studies, these materials were found to exhibit non-single-exponential lifetimes in the presence of anthracene and azulene quenchers for a concentration of benzil label 10⁻⁴ M. An explanation for this anomalous behaviour and a technique for decoupling these decays into two lifetimes has been proposed. This technique should allow for the study of diffusion-limited interactions occurring in higher-molecular-weight polymer systems where the label concentration 10⁻⁴ M.     

Isosteric heat of sorption of CO2 in poly(ethylene terephthalate)

Sorption isotherms for carbon dioxide in poly(ethylene terephthalate) have been measured at 35–55°C. The isotherms were measured gravimetrically on a Mettler Thermoanalyzer-1 from vacuum to 1 atmosphere. The sorption data were used to generate sorption isotherms from which the isosteric heat of sorption of CO₂ in PET was determined. At 45°C the isosteric heat of sorption increases from −10 kcal/mole at a concentration of 0.5 cm³ (STP)/cm³ (polymer) to −8 kcal mole⁻¹ at a concentration of 1.5 cm³ (STP)/cm³ (polymer). It has been reported in the literature that the isosteric heat of sorption for this system decreased through a minimum before increasing with increasing concentration. Our measurement of the low-pressure sorption isotherms shows that this is not the case.     

Anodic reactions of several reducing agents on illuminated cadmium sulfide electrode

Anodic reactions of several reducing agents occurring in competition with the electrode dissolution at an illuminated CdS electrode were studied under the potentiostatic condition. S²⁻, SO²⁻₃, and S₂O²⁻₃ ions, which can effectively suppress the photoanodic dissolution of CdS, shift the flatband potential of this electrode to the cathodic direction, leading to the shift of the onset potential for the anodic photocurrent. This shift is attributed to the adsorption of these ions on the electrode surface. Two- or three-step wave appeared in the photoanodic polarization curves in the electrolytes containing low concentration of these ions. The mechanism for these electrodic reactions was discussed in detail in terms of the energy band structure. It can be concluded that the reducing agents which interact so strongly with the CdS electrode surface that the energy band structure at the electrode/electrolyte interface is changed can suppress effectively the photoanodic dissolution of the electrode. The tendency of this interaction was S²⁻ > SO²⁻₃ > S₂O²⁻₃.     

安全固态锂电池室温聚合物基电解质的研究进展

目前,大多数聚合物固态电解质在室温下离子电导率较低,约为10^–8 ~10^-6 S /cm,且对温度存在着较大的依赖性,仍无法满足高性能室温固态锂电池的实际应用需要。基于此,本文先介绍了室温聚合物电解质在锂离子电池中应用的主要研究进展及其优缺点。然后,从物理调控、化学调控等多角度重点阐述了室温聚合物电解质（包括全固态聚合物电解质、准固态聚合物电解质）的制备工艺、优化与改性方法、作用机理等在电池中应用的主要研究进展和现状。最后,对锂离子电池用室温聚合物电解质存在的挑战和未来可能发展趋势进行了展望。