The effect of some soluble inorganic admixtures on the early hydration of portland cement

The effects of the soluble chlorides, bromides, nitrates, sulphates and acetates of Ca²⁺, Mg²⁺, Li⁺, Na⁺ and Zn²⁺ as well as the corresponding mineral acids on the early hydration of neat Portland cement pastes have been studied. Both the cations and anions are ranked according to their general effectiveness as accelerators of the hydration of the Ca₃SiO₅ phase: Ca²⁺>Mg²⁺>Li⁺>Na⁺>H₂O>Zn²⁺ and OH^? >Cl^?>Br^? >NO₃^?SO₄²～H₂O > CH₃CO₂^?.     

Ion flotation and solvent sublation of cobalt cyanide complexes

An experimental investigation into the batch ion flotation of cobalt complex anions with the cationic surfactant, cetylpyridinium chloride is described. The concentration ratio of cetyl-pyridinium: cobalt in the foam was determined and found to be 2.0–2.7 for CoCl₂ plus KCN solution and 3.0–3.3 for K₃[Co(CN)₆] solution. Spectroscopic measurements of the former anion show that mainly [Co(CN)₅H₂O]²- anions were floated. The [Co(CN)₆]^3- flotation was established in the presence of Cl^?, Br^?, I^?, CN^?, NO₃^? and SO₄^2- anions. The accelerating influence of the ion flotation produced by the presence of Cl^?, Br^?, I^?, CN^?, NO₃^? and SO₄^2- increased as their partial molal volume increased. The solvent sublation of [Co(CN)₆]^3- anions was established in the presence of these anions.     

A cationic surfactant as a soluble ion exchanger in the continuous foam fractionation of nitrate; iodide,and bromide

An experimental investigation is presented of the continuous foam fractionation of NO₃^? versus Br^? and of T^? versus Br^? with a quaternary ammonium surfactant at concentrations of the order 1.8 × 10^?4M. An equation is derived to enable the computation of anion selectivity coefficients from foam fractionation data. The key assumptions of the derivation are verified experimentally. The selectivity coefficient for NO₃ versus Br^? is 1.56 ± 0.28 and for I^? versus Br^? is 5.85 ± 1.81, established from 40 continuous-flow experiments. Precipitation of EHDA-I is indicated at the highest ratios of the bulk solution concentrations of I^? and Br^?. significantly, both selectivity coefficients are independent of the fraction of the exchanger occupied by the preferred ion, indicating an exchanger activity coefficient ratio of unity, and are independent of ionic strength. The counterion present markedly influences the surfactant distribution coefficient.     

Solvatation des ions par le nitromethane

The direct potentiometric determination of the normal potentials of Cu/Cu⁺, Cu⁺/Cu²⁺, Ag/Ag⁺, Hg/Hg²⁺₂ couples in nitromethane and the comparison of these values with the normal potentials in aqueous solution makes possible the calculation of solvation coefficients γ_(t)(Mⁿ⁺) of the corresponding cations; the Strehlow hypothesis (γ(Fc) = γ(Fc⁺)) has been used. An indirect method using the determination of the solubility constants of alkaline chlorides and alkaline earth chlorides leads to the normal potentials of alkaline and Mg²⁺ cations and thus to the γ_(t) values of these ions.The measures of the AgX^-₂ stability constants and of the AgX solubility constants lead to the γ_(t) values of X^? and AgX^?₂ anions (X^? = Cl^?, Br^?, I^?, Scn^?, CH₃CO^?₂, CN^?, BrO^?₃, (C₆H₅)₄B^?). A comparison of γ_(t)(H⁺) and γ_(t)(Ag⁺) for 20 solvents is given.     

Influence of Some Hofmeister Anions on the Krafft Temperature and Micelle Formation of Cetylpyridinium Bromide in Aqueous Solution

In this work, the effect of some Hofmeister anions on the Krafft temperature (T_K) and micelle formation of cetylpyridinium bromide (CPB) have been studied. The results show that more chaotropic anions increase, while the less chaotropic ones lower the T_K of the surfactant. More chaotropic I^? and SCN^? form contact ion pairs with the cetylpyridinium ion and reduce the electrostatic repulsion between the CPB molecules. As a result, these ions show salting‐out behavior, with a consequent increase in the T_K. In contrast, less chaotropic Cl^? and NO₃^? increase the activity of free water molecules and enhance hydration of CPB molecules, showing a decrease in the T_K. A rather unusual behavior was observed in the case of SO₄^2? and F^?. These strong kosmotropes shift from their usual position in the Hofmeister series and behave like moderate chaotropes, lowering the T_K of the surfactant. Because of the high charge density and the strong tendency for hydration these ions preferentially remain in the bulk. Rather than forming contact ion pairs, these ions stay away from the CPB molecules, decreasing the T_K of the surfactant. In term of decreasing the T_K, the ions follow the order NO₃^? > SO₄^2? > Cl^? > F^? > Br^? > SCN^? > I^?. The critical micelle concentration (CMC) of the surfactant decreases significantly in the presence of these ions due to the screening of the micelle surface charge by the excess counterions. The decreasing trend of the CMC in the presence of the salts follows the order SCN^? > I^? > SO₄^2? > NO₃^? > Br^? > Cl^? > F^?.     

Removal of Dichromate Anions with Nanofiltration‐Complexation by using Amino Calix[4]arene Derivative

Abstract

Herein the removal and recovery of chromium anions from aqueous solutions by using nanofiltration pilot‐scale equipment (Osmonics Sepa CF Membrane Cell) with a water‐soluble amino calix[4]arene derivative was studied. To understand the selectivity, the authors also examined the retention of chromium anions in the presence of Cl^?, NO₃ ^?, SO₄ ^2?, HSO₄ ^?, CO₃ ^2?, PO₄ ^3?, H₂PO₄ ^? anions in nanofiltration‐complexation. From the results water‐soluble amino calix[4]arene was effective and selective ligand for dichromate anions over nitrate anions, in a nanofiltration‐complexation system at pH 2.5. Moreover, the recovery and reusability studies of dichromate and nitrate anions and also ligand were performed.     

Effects of anions on the photocatalytic and photoelectrocatalytic degradation of reactive dye in a packed‐bed reactor

The effects of various anions, Cl^?, ClO₄^?, SO₄^2?, NO₃^?, HCO₃^?, H₂PO₄^? and C₂O₄^2?, on the photocatalytic and photoelectrocatalytic degradation of reactive Brilliant Orange K‐R have been investigated in a packed‐bed photoelectrocatalytic reactor. It was found that the nature and concentrations of these inorganic anions significantly affected the photocatalytic and photoelectrocatalytic degradation performance of the reactive dye. The results indicated that the external electric field was successfully applied to improve the photocatalytic efficiency of reactive Brilliant Orange K‐R in the presence of Cl^?, especially at higher concentrations, while other inorganic anions displayed more or less negative effects on the degradation of the dye. The strongest inhibition effect on photocatalytic and photoelectrocatalytic degradation of the dye was observed in the presence of HCO₃^? ions. Copyright © 2004 Society of Chemical Industry     

Influence of anionic form on thermal degradation of TMAHP–cellulose

Trimethylammoniumhydroxypropyl (TMAHP)–cellulose in 10 anionic forms (F^?, Cl^?, Br^?, I^?, HSO, NO, OH^?, HCO, H₂PO, CH₃COO^?) was prepared, and the influence of each anion on thermal degradation in inert atmosphere was studied. With the help of dynamic and isothermal thermogravimetry (TG) it was found that H₂PO ions had the greatest retarding effect on TMAHP–cellulose degradation. From the values of rate constants it can be seen that all ionic forms of TMAHP–cellulose have the starting rate of thermal degradation greater than unmodified cellulose. The calculated values of activation energy of thermal degradation for different ionic forms are decreasing in following sequence: H₂PO > F^? > NO > I^? > Br^? > HCO > Cl^? > HSO > OH^? > unmodified cellulose > CH₃COO^?. From the results of pyrolyse measurements in combination with gas chromatography and mass spectrometry (Py–GC–MS) it follows that the products of the elimination of quarternary ammonium salts are trimethylamine, 3-hydroxy-2-propanone, and, in the case of OH^? form, water. In all other ionic forms the third product is the corresponding acid.     

EXTRACTION OF INDIUM( III) FROM BROMIDE AND THIOCYANATE MEDIA WITH 1-PHENYL-3-HETHYL-1-BENZOYLPYRAZOL-5-ONE; EFFECT OF LIPOPHILIC AMMONIUM SALTS

1-phenyl-3-methyl-4-benzoylpyrazol-5-one (HL) in toluene extracts In(III) from ClO₄ ^?, (Br^?, CIO ClO₄ ^?, ) and Br^? media according to the extraction equilibria (1) and (2). Tri-n-octylmethylammonium bromide (B⁺Br^?) induces a medium synergic effect for Br^? and (Br^?,NO₃ ^?) media, which is cancelled in ClO₄ ^?medium. It corresponds to the extraction of (B⁺InBr_xL_4-x) ion pairs. On the contrary, from SCN^? or (SCN^?,ClO₄ ^?) media, In is extracted by HL according to only (1) and no synergism is obtained with tri-n-octylammonium salt.

These results are compared with those obtained with Cl^? and (C1^?,ClO₄ ^?) aqueous media. They are to a great extent explained by taking into account the complexing of In³⁺ by aqueous inorganic anions, the lipophilicity of the diverse species and the anionic exchanges in the B⁺X^? ion pairs.     

Selectivity-determining role of C3H8/NO ratio in the reduction of nitric oxide by propane in presence of oxygen over ZSM5 zeolites

The reaction of (NO + C₃H₈ + O₂) can result in selective formation of NO₂ over H-ZSM5, Cu,H-ZSM5, Ag,H-ZSM5, and Li,H-ZSM5 catalysts when the concentrations of NO and O₂ are 0.1 and 9%, SV > 60,000 h⁻¹ (typical for automotive exhausts), and C₃H₈/NO > 1. Despite stoichiometric excess of reductant hydrocarbon below this limit, the in situ formed NO₂ does not react with C₃H₈, thus conversion of NO to N₂ is negligible. NO can be reduced by C₃H₈ selectively to N₂ only when C₃H₈/NO ≧ 1. Contrary to many suggestions the reaction temperature, concentration of oxygen, space velocity, and type of exchange ions have minor influence on the selectivity for N₂. These parameters affect the rates of reactions (NO + ₂), (C₃H₈ + NO_x) and (C₃H₈ + O₂), therefore they also affect the production of N₂ in the HC-SCR process, but only when the ratio of C₃H₈/NO permits. The metal-exchanged zeolites were prepared in situ by solid-state ion exchange from H-ZSM5. Despite the low degree of copper exchange (63%), Cu,H-ZSM5 produces substantially more N₂ than H-ZSM5, Ag,H-ZSM5, or Li,H-ZSM5. However, the selectivity for N₂ is lowest over Cu,H-ZSM5, which also produces considerable NO₂ in the reaction of (NO + C₃H₈ + O₂) even at C₃H₈/NO ≧ 1. Contrary to prior findings, the catalytic activity of Cu,H-ZSM5 for the oxidation of NO by O₂ to NO₂ in absence of hydrocarbon was comparable to that of H-ZSM5 at high space velocities (2.3 l g⁻¹ min⁻¹). By replacing 30 and 40% of the protons of H-ZSM5 by Ag⁺ and Li⁺ ions in Ag,H-ZSM5 and Li,H-ZSM5, respectively, the catalytic activity for this reaction becomes negligible at temperatures ≧100°C. Some mechanistic consequences of these experimental observations are discussed. This revised version was published online in August 2006 with corrections to the Cover Date.     

A chromotropic acid modified SBA-15 as a highly sensitive fluorescent probe for determination of Fe<Superscript>3+</Superscript> and I<Superscript>−</Superscript> ions in water

A novel organic–inorganic hybrid nanomaterial (SBA-15-CA) was prepared by covalent immobilization of chromotropic acid onto the surface of mesoporous silica material SBA-15. Different techniques such as XRD, TEM, FT-IR, N₂ adsorption–desorption and TGA analyses were employed to characterize the grafting process. The data showed that the organic moiety (0.41 mmol g^?1) was successfully grafted to the SBA-15 and the primary hexagonally ordered mesoporous structure of SBA-15 was preserved after the grafting procedure. SBA-15-CA has been realized as a highly sensitive and selective fluorescent probe towards Fe³⁺ and I^? ions in aqueous media. SBA-15-CA exhibited a remarkable fluorescent quenching in the presence of Fe³⁺ ion over other competitive cations including Na⁺, Mg²⁺, Al³⁺, K⁺, Ca²⁺, Cr³⁺, Mn²⁺, Fe²⁺, Co²⁺, Ni²⁺, Cu²⁺, Zn²⁺, Cd²⁺, Hg²⁺, and Pb²⁺ as well as I^? ion among a series of anions including F^?, Cl^?, Br^?, CO₃^2?, HCO₃^?, CN^?, NO₃^?, NO₂^?, SCN^?, SO₄^2?, H₂PO₄^?, HPO₄^2?, and CH₃COO^?. A good linear response was observed between the concentration of the quenchers (Fe³⁺ and I^? ions) and fluorescence intensity of SBA-15-CA with detection limits of 1.5?×?10^?7 M for Fe³⁺ and 0.2?×?10^?7 M for I^?. Moreover, the effects of various pH values on the sensing ability of SBA-15-CA were investigated. Finally, the proposed method was successfully utilized for the determination of Fe³⁺ and I^? ions in river water, well water and tap water samples.     

An experimental study of electroreduction of CO2 to HCOOH on SnO2/C in presence of alkali metal cations (Li+, Na+, K+, Rb+ and Cs+) and anions (HCO3−, Cl−, Br− and I−)

It is well-known that the electrolytes can influence the electrochemical reduction of carbon dioxide (ERCO₂) in aqueous media. In this work, we explore the effects of alkali metal cations and anions (Li⁺, Na⁺, K⁺, Rb⁺, Cs⁺, HCO₃⁻, Cl⁻, Br⁻, I⁻) on the current density and product selectivity for the ERCO₂ into formic acid (HCOOH) on the SnO₂/carbon paper (SnO₂/C) electrode. Results of the ERCO₂ experiments show that for the cations, the promotion effects on current density and faradaic efficiencies (FEs) are in the order of Li⁺ < Na⁺ < K⁺ < Cs⁺ < Rb⁺. For the anions, the current density values are in the order of NaHCO₃ < NaCl < NaBr < NaI and KHCO₃ < KCl ≈ KI < KBr, respectively, and that on the FEs for the formation of the HCOOH (FE_HCOOH) is HCO₃⁻ < Cl⁻ < Br⁻ < I⁻. Based on this result, the effects of alkali metal cations and anions on ERCO₂ are discussed.     

Partial oxidation of alkenes by a membrane catalyst conducting H+ and e−

Partial oxidation of C₂H₄ to MeCHO (>95% selectivity) with O₂ by a new type of membrane catalyst was studied at 353 K. Reaction system was (C₂H₄, H₂O | membrane catalyst | O₂, NO). The membrane catalyst was assembled from three sheets, porous catalyst for oxidation of C₂H₄, mixed conductor of H⁺ and e⁻, porous catalyst for the reduction of O₂. NO functioned as a co-catalyst for reduction of O₂ to H₂O. This three-layered membrane catalyst functioned as a hydrogen permeation membrane.     

Ion—solvent interaction: viscosity of ternary electrolytes in dioxane-water mixtures at 35°

The viscosities of the chlorides, bromides and nitrates and perchlorates of Mg²⁺ and Ba²⁺, of the chlorides and nitrates of Ca²⁺ and Sr²⁺, and of the sulphates of Na⁺ and K⁺ at mass fraction of dioxane, 10, 20 and 30% have been measured at 35°. The values of the constant A and B of the viscosity equation indicate ion—ion and ion—solvent interaction respectively. The ion-solvent interaction is found to be of the order NO^?₃ > ClO^?₄ > Br^? > Cl^? and K⁺ > Na⁺.     

SYNTHETIC INORGANIC ION-EXCHANGE MATERIALS. XXXXI. ION EXCHANGE EQUILIBRIA OF ALKALI METAL IONS/HYDROGEN IONS ON TIN(IV) ANTIMONATE

Ion exchange equilibria of alkali metal ions (Li⁺, Na⁺, K⁺,, Rb⁺, and Cs⁺)H⁺, systems have been studied in MNO-j-HNOj media with ionic strength of 0.1 at 30, 45 and 60 °C on tin(IV) antimonate as a cation exchanger. The ion exchange isotherms have been measured for both forward and backward reactions by the batch technique. The isotherms showed S-shaped curves for all exchange systems studied. The selectivity coefficients (logarithmic scale) vary with the equivalent fraction X_M of alkali metal ions in the exchanger and give two linear functions of X_M with a break point (X_M= 0.14, except 0.04 for Li⁺, /H⁺) indicating two different exchanging sites. The selectivity sequence, Na⁺, ? K⁺, ? Rb⁺, ? Cs⁺, ? ? Li, holds in the range of Xu= (0 - 0.04) and the sequence, Cs < Rb ⁺, ? K ⁺, ? Na ⁺, < Li ⁺, applies when X_M is higher than 0.14.

Hypothetical thermodynamic data on “zero loading” of the ion exchange reaction was evaluated.     

Unique Solubility of Switchable Alkyl-Amine Surfactants in Water

Because many amine surfactants are soluble in both water and CO₂ phases, they attract interest with regard to stabilizing CO₂-in-water dispersion systems. In our recent research, we find that the solubility of alkyl-amine surfactant in water can be significantly enhanced by salts, even though the salts are usually “salting-out” to other surfactants. The influence of various anions (NO₃⁻, Br⁻, Cl⁻, and SO₄²⁻) and cations (Na⁺, Ca²⁺, and Mg²⁺) on the alkyl-amine surfactants is investigated. The results are contrary to Hofmeister series and show that all the anions can enhance the solubility (salting-in) in the order of: NO₃⁻ > Br⁻ > Cl⁻ > SO₄²⁻, while the impact of the cations is insignificant. A physical–chemistry model based on the switchable property of the surfactant is proposed and well explains the experimental results. Therefore, the switchable alkyl-amine surfactants have potential to be applied under high-salinity and high-temperature conditions, for example, in enhanced oil recovery processes for a hot and salty carbonate reservoir.     

Etude voltamperometrique de la n-acetyl l-tyrosine amide sur electrode a pate de graphite en milleux aqueux I—comportement dans les domaines de balayage superieurs a 0,5 v/enh

Graphite paste electrode allows to determine elementary processes of the electrochemical oxidation in aqueous media of an electrochemical probe such as: N-acetyl L-tyrosine amide. Mathematical analysis of voltammograms gives the following EC mechanism: R?C₆H₅OH?R?C₆H₅O^. + H⁺ + e 2 R?C₆H₅O^. → R?C₆H₅O⁺ + R?C₆H₅O^?, R?C₆H₅O^? + H⁺ → R?C₆H₅OH, R?C₆H₅O⁺ → [R?C₆H₄O]^.. + H⁺, n[R?C₆H₄O]^.. → ?[R?C₆H₄O]^?_n.     

The Separation of the Oxidation States of Some Elements with the Use of Tri-n-butyl Orthophosphate

Abstract

The tri-n-butyl orthophosphate:acetic acid:acetone solvent system has been studied for the paper chromatographic separation of the oxidation states of 16 elements. The separation of As³⁺, As⁵⁺; Cr³⁺, Cr⁵⁺; Fe²⁺, Fe³⁺; Hg⁺, Hg²⁺; Mn²⁺, Mn³⁺, and Mn⁷⁺; Sb³⁺, Sb⁵⁺; Tl⁺, Tl³⁺; Cl^?, ClO₃ ^? Br^? BrO₃ ^?; I^?, IO^? ₃; P₂O^4- ₇ PO^3- ₄, and PO^? ₃ has been achieved. Multiple zones obtained with Fe³⁺ and Tl³⁺ species are discussed.     

ION EXCHANGE PROPERTIES OF BiO(NO3) 0.5H2O TOWARDS FLUORIDE IONS

ABSTRACT

We studied the ion exchange behavior of the inorganic anion exchanger BiO(NO₃)0.5H₂O with regard to fluoride ions. The ion exchange reaction was rapid at pH 1, 6.6, and 12. The mechanisms of ion exchange reactions at pH 1 and pH 2-12 were studied in a solution with fluoride ions excess to BiO(NO₃)0.5H₂O. A mixture of the β-phase and an unknown phase was produced in the solution at pH 1. BiOF was produced at pH 2-12. Fluoride ions did not react at pH 13, due to the decomposition of BiO(NO₃) 0.5H₂O at pH 13 to yield Bi₂O₃ (major) and Bi₂O₂CO₃ (minor). The structure of the reaction products depended on the solution pH, mole ratios of BiO(NO₃)0.5H₂O to F’, and the reaction time. We observed that BiO(NO₃)0.5H₂O is capable of removing 99% of the fluoride ions from the solution at pH 1-12 under optimal conditions. The ion exchange reaction of BiO(NO₃)0.5H₂O with fluoride ions was studied under the co-existence of both Cl and Br^?at pH 1, 6.6, 12, and 13. The order of decreasing affinity was found to be (Br^?, Cl^?)> F^?. The reaction product was not a simple mixture of BiOCl, BiOBr, and bismuth oxide fluorides, but an unknown compound.