Ferric hydrous oxide sols I. Monodispersed basic iron(III) sulfate particles

The methods of preparation of basic ferric sulfate sols consisting of particles uniform in shape of extremely narrow size distribution are described in detail. To produce such sols, acidic solutions containing ferric ions and sulfate ions were aged at elevated temperatures for a few hours. Solids formed from solutions containing a mixture of a ferric salt with a metal sulfate consisted of Fe₃(SO₄)₂(OH)₅· 2H₂O, which is the basic formulation for the alunite mineral group, whereas particles formed from ferric sulfate solutions also included Fe₄(SO₄)-(OH)₁₀ in varying proportions. The morphology of the particles was strongly dependent on the [Fe³⁺]: [SO₄²⁻] ratio in solution. Changes in the cation (K⁺, NH₄⁺, Na⁺) of the sulfate salt used in the mixture with ferric nitrate solutions greatly affected the particle size and also exhibited some effect on the lattice parameters. Certain cations (Mg²⁺, Ni²⁺, Cu²⁺) completely inhibited particle formation. During the first few hours of growth of the Fe₃(SO₄)₂-(OH)₅· 2H₂0 particles their diameters increased essentially linearly with time, indicating that the rate determining step was the surface reaction. The relevance of these systems to the study of corrosion of iron and steel is discussed.     

Effects of Cs and Na ions on the interfacial properties of dodecyl sulfate solutions

The competitive binding of counterions to anionic dodecyl sulfate ions in aqueous solutions of cesium dodecyl sulfate (CsDS) and sodium dodecyl sulfate (SDS) mixtures, which significantly influences the critical micelle concentration (cmc) and surface (or interfacial) tension of surfactant solutions, was investigated. The cmc and degree of counterion binding were obtained through electrical conductivity measurements. The curve of cmc versus the mole fraction of CsDS in the surfactant mixture was simulated by Rubingh's equations, which enabled us to estimate the interaction parameter in micelles (W _R) based on the regular solution approximation. The curve-fitting exhibited a slightly negative value (W _R=−0.1), indicating that the mixing (SDS+CsDS) enhances micelle formation owing to a greater interaction between surfactant molecules and counterions than in pure systems (SDS). On going from SDS, SDS:CsDS(75:25), SDS:CsDS(50:50), SDS:CsDS(25:75) to CsDS, interfacial tension at the hexadecane/surfactant-solution interface showed a negative deviation from the mixing rule (interaction parameter in adsorbed film W _A=−0.38), indicating the replacement of Na⁺ bound to anionic dodecyl sulfate by Cs⁺ ions owing to the stronger interaction between the Cs⁺ and the dodecyl sulfate ions. Droplet sizes of emulsion formed with hexadecane and aqueous dodecyl sulfate solutions were investigated using the light scattering spectrophotometer. The higher binding capacity of Cs⁺, having a smaller hydrated ionic size than Na⁺, also resulted in a negative deviation in emulsion droplet size in mixed systems. Received: 10 May 2000/Accepted: 11 August 2000     

Stability of Ultradisperse Copper in a Sulfo Cation Exchanger Matrix

The recrystallization of ultradisperse copper chemically deposited onto a sulfo cation exchanger matrix was studied by the potentiometric method. The stationary value of the electrode potential of the copper-sulfo cation exchanger composite was established during a long period of time, which depended on the ionic form of the composite (H⁺, Cu²⁺, or Na⁺), solution composition (CuSO₄, H₂SO₄, and Na₂SO₄), and solution concentration. Recrystallization was favored by copper(II) counterions, which entered the composite as a result of ion exchange, nonexchange absorption of copper sulfate, or preliminary composite transformation into the Cu²⁺ form. In the quasi-equilibrium state, the concentration of copper(II) counterions was maintained at a high level by the Donnan interfacial potential. At all the copper(II) sulfate concentrations used, the potential of the Cu²⁺/Cu ion—metal pair in the ion-exchange matrix remained at virtually the same level, which was indicative of the stable state of copper particles. In the absence of an external source of copper ions, recrystallization was significantly hindered; therefore, the potential exhibited only a slight drift. Copper ions formed in the solution of small crystals were localized in the vicinity of ionogenic matrix centers, which decreased the mobility of these particles as counterions; therefore, the dispersity of particles remained unchanged.     

Spectrophotometric Determination of Sulfate Ion Through Copper(II)-azide System

Abstract

An indirect and alternative method for the determination of sulfate ion has been established by spectrophotometry. The procedure is based on the formation of copper(II) monoazido species, in water/acetone medium, in which a discoloration effect of system is caused by sulfate presence. In the recommended conditions, sulfate ions can be determined in the concentration range from 40 to 5000 mg/l (ppm), at 375 nm, in natural samples of waters. The best experimental conditions were determined analysing the different factors involved. Studies about the formation equilibria of the CuN₃ ⁺ and CuSO₄ species were realized in water and their respective stability constants (β₁ = 225 M^?1 and 7.15 M^?1) were determined by spectrophotometry at 25.0° C and ionic strength 1.0 M (NaClO₄). Equilibrium investigations were also made in presence of acetone. Additional studies on the ternary system Cu(II)/N₃ ^?/SO₄ ^2-) indicated some evidences of mixed complexes.     

Syntheses and Structures of Na2Mg3(OH)2(SO4)3·4H2O and K2Mg3(OH)2(SO4)3·2H2O

The crystal structures of Na₂Mg₃(OH)₂(SO₄)₃ · 4H₂O and K₂Mg₃(OH)₂(SO₄)₃ · 2H₂O, were determined from conventional laboratory X‐ray powder diffraction data. Synthesis and crystal growth were made by mixing alkali metal sulfate, magnesium sulfate hydrate, and magnesium oxide with small amounts of water followed by heating at 150 °C. The compounds crystallize in space group Cmc2₁ (No. 36) with lattice parameters of a = 19.7351(3), b = 7.2228(2), c = 10.0285(2) Å for the sodium and a = 17.9427(2), b = 7.5184(1), c = 9.7945(1) Å for the potassium sample. The crystal structure consists of a linked MgO₆–SO₄ layered network, where the space between the layers is filled with either potassium (K⁺) or Na⁺‐2H₂O units. The potassium‐bearing structure is isostructural to K₂Co₃(OH)₂(SO₄)₃ · 2(H₂O). The sodium compound has a similar crystal structure, where the bigger potassium ion is replaced by sodium ions and twice as many water molecules. Geometry optimization of the hydrogen positions were made with an empirical energy code.     

Diffusion with hydrolysis and ion association in aqueous solutions of beryllium sulfate

Taylor dispersion is used to measure mutual diffusion coefficients for aqueous solutions of beryllium sulfate at concentrations from 0.005 to 1 mol-L^–1 at 25°C. Least-squares analysis of the dispersion profiles shows that diffusion of the partially hydrolyzed salt produces a small additional flow of sulfuric acid, about 0.04 mol sulfuric acid per mole of total beryllium sulfate. Ternary diffusion coefficients measured for the aqueous BeSO₄–H₂SO₄ system are qualitatively consistent with Nernst-Planck predictions based on the formation of beryllium sulfate ion pairs, bisulfate ions, and the hydrolysis equilibria 2Be²⁺+H₂O= Be₂OH³⁺+H⁺, 3Be²⁺+2H₂O=Be₃(OH) ₂ ⁴⁺ +2H⁺. Except for very dilute solutions, the predicted flow of sulfuric acid is small compared to the flow of beryllium sulfate because most of the beryllium ions are protected from hydrolysis by the formation of BeSO₄ ion pairs, and most of the hydrogen ions produced by hydrolysis are converted to less-mobile bisulfate ions.     

Characterization and reactivity of nanoscale La(Co,Cu)O3 perovskite catalyst precursors for CO hydrogenation

The characterization of La(Co,Cu)O₃ perovskites has been performed by several techniques including XRD, BET, H₂-TPR, O₂-TPO, TPRS, and the solids tested as catalysts for the hydrogenation of CO. The reducibility of the perovskites is strongly affected by the preparation route, calcination temperature, catalyst morphology, and the amount of remnant alkali. Compared with the citrate-derived perovskite, LaCoO₃ sample prepared by mechano-synthesis has various distinct Co³⁺ ions in perovskite lattice, which are reduced at different temperatures. Under typical conditions, the reduction of cobalt ions occurs in two consecutive steps: Co³⁺/Co²⁺ and Co²⁺/Co⁰, while the intra-lattice copper ions are directly reduced from Cu²⁺ to Cu⁰. The reducibility of cobalt ions is promoted by the presence of metallic copper, which is formed at a lower reduction temperature. The re-oxidation of the reduced lanthanum cobaltite perovskite could regenerate the original structure, whereas that of the reduced Co-Cu-based samples is less reversible under the same experimental conditions.The cobalt atom in the reduced perovskites plays an important role in the dissociation of CO, but the presence of a neighboring copper along with remnant sodium ions on the catalyst surface has remarkably affected the reactivity of cobalt for CO hydrogenation. The addition of copper into the perovskite framework leads to a change in the product distribution of CO hydrogenation and a decrease in reaction temperature. An increased copper content leads to a substantial decline in the rate of methanation and an increase in the formation of higher alcohols. A close proximity between cobalt and copper sites on the Na⁺-modified catalyst surface of the reduced nanocrystalline Co-Cu-based perovskites plays a crucial role in the synthesis of higher alcohols from syngas.     

Needle-type colloidal copper (II)hydroxide particles

Stable dispersions of fine (< 0.05m) needle-type copper(II) hydroxide particles were prepared at room temperature by admixing sodium acetate and ammonia to copper sulfate solution. The particle length and width could be altered with the concentration of reactants. The rate of dissolution of copper(II) hydroxide particles in doubly distilled water at room temperature is time dependent, which is due in part to the formation of a mononuclear complex solute (CuOH⁺). After extended times (e.g., 18 h), the particles underwent phase transformation, resulting in longer needles of higher degree of crystallinity.Supported by the Griffin Corp., Valdosta, Georgia.     

Etude des complexes sulfosalicylate de cuivre(III), nickel(II), cobalt(II) et uranyle(II) a l'aide d'une resine echangeuse de cations: Study of the sulphosalicylate complexes ofcopper(II), nickel(II), cobalt(II) and uranyl(II) by means of cation-exchange resins.

Study of the sulphosalicylate complexes of copper(II), nickel(II), cobalt(II) and uranyl(II) by means of cation-exchange resins.The conditional stability constants of the 1:1 complexes of the sulphosalicylate ions (L^3-) with copper(II), nickel(II), cobalt(II) and uranyl ions have been determined in a sodium perchlorate solution (0.1 M) and at various pH values by a cation-exchange method based on Schubert's procedure. The limits of application of the method are discussed. The variation with pH of the conditional stability constants can be explained by the existence of the complexes: CuH₂L, CuHL, CuL^-; NiH₂L⁺, NiHL, NiL^-; CoHL, CoL^-; UO₂H₂L⁺, UO₂HL, UO₂L^-, UO₂LOH^2-. The stability constants of these complexes are reported. Distribution diagrams of the various complexes of each element with pH and total concentration of sulphosalicylate parameters are given.     

Reduction from copper(II) to copper(I) upon collisional activation of (pyridine)2CuCl+

Electrospray ionization of dilute aqueous solutions of copper(II) chloride‐containing traces of pyridine (py) as well as ammonia permits the generation of the gaseous ions (py)₂Cu⁺ and (py)₂CuCl⁺, of which the latter is a formal copper(II) compound, whereas the former contains copper(I). Collision‐induced dissociation of the mass‐selected ions in an ion‐trap mass spectrometer (IT‐MS) leads to a loss of pyridine from (py)₂Cu⁺, whereas an expulsion of atomic chlorine largely prevails for (py)₂CuCl⁺. Theoretical studies using density functional theory predict a bond dissociation energy (BDE) of BDE[(py)₂Cu⁺ ‐Cl] = 125 kJ mol^?1, whereas the pyridine ligand is bound significantly stronger, i.e. BDE[(py)CuCl⁺ ‐py] = 194 kJ mol^?1 and BDE[(py)Cu⁺ ‐py] = 242 kJ mol^?1. The results are discussed with regard to the influence of the solvation on the stability of the Cu^I/Cu^II redox couple. Copyright © 2010 John Wiley & Sons, Ltd.     

NMR study of the coordinating behavior of 2,6‐bis(benzimidazol‐2′‐yl)pyridine

The coordination sites of 2,6‐bis(benzimidazol‐2′‐yl)pyridine ( 1 ) toward protons and the diamagnetic metal ions Li⁺, Na⁺, and Co³⁺ were investigated by NMR spectroscopy. Variable temperature ¹H and ¹³C NMR experiments were performed on 1 in order to evaluate the tautomeric equilibrium and hydrogen bonding. Imidazole dicoordinated aromatic nitrogen atoms were protonated by trichloroacetic acid and the three N‐dicoordinated atoms by fuming H₂SO₄. Reactions of the ligand 1 and benzimidazole 2 with metallic sodium or LiH afforded anionic species; the alkali metal ions appeared solvated by THF, but not by the ligands 1 or 2 . In contrast, reaction of 1 with Co(III) produces the stable cation [Co( 1 ‐H)₂]⁺ with cobalt ion coordinated by two molecules of the monodeprotonated ligand. © 2000 John Wiley & Sons, Inc. Heteroatom Chem 11:392–398, 2000     

Extraktion von alkali- und erdalkalimetallionen mit (sym-dibenzo-14-krone-4-oxy)- und (sym-dibenzo-16-krone-5-oxy)-carbonsäuren

(Extraction of alkali on alkaline earth metal ions with (sym-dibenzo-14-crown-4-oxy)- and (sym-dibenzo-16-crown-5-oxy)-carboxylic acids.)The extraction of lithium, sodium, potassium, calcium and some other metal ions with dibenzo-4-crown-4-oxy- and dibenzo-16-crown-5-oxycarboxylic acids containing the groups -CH₂COOH, -(CH₂)₂COOH, -(CH₂)₃COOH, -CH(C₂H₅)COOH and -CH(C₄H₉)COOH was studied. The extraction increases as a function of the lipophilic character of the carboxylic acid group. Calcium, barium and strontium ions are better extracted than Li⁺, Na⁺ and K⁺; there are only small differences among the alkaline earth metal ions. Evaluated from the extraction data, the composition of the extracted species was 1:1 (metal/ligand) for Li⁺, and 1:2 for CaCa²⁺; Na⁺ and K⁺ favour the formation of 1:2 complexes with dibenzo-14-crown-4-derivatives bbut 1:1 complexes with dibenzo-16-crown-5-oxy-carboxylic acids. The dependence of the distribution ratio on pH does not provide unequivocal evidence for the composition of the extracted compounds.     

Diffusion of ionic species labeled with35S in various aqueous electrolyte solutions at 25°C

Composite diffusion coeffcients have been measured for the various species labeled with³⁵S which are present in a number of aqueous solutions due to the introduction of the labeled material as³⁵SO ₄ ^2– . The solutions were of two components consisting of water and either sodium sulfate. The diffusion coeffcient measured for sodium chloride solutions is similar to literature data for the corresponding diffusion in sodium sulfate solutions. The results for sulfuric acid and ammonium hydrogen sulfate have been interpreted using literature data for the relative concentrations of the hydrogen sulfate and sulfate ions to obtain estimates for the diffusion coefficents of those ions. The results for perchloric acid, regarded as representing the diffusion coefficient of the hydrogen sulfate ion, have a much different concentration dependence to that observed for the estimates for that ion in sulfuric acid and ammonuim hydrogen sulfate. The difference is attributed to the effect of the perchlorate ion on the water structure.     

Aminoacetal derivative of calix[4]resorcinarene. Acid-base properties and reactions with copper(II) and lanthanum(III) in various media

Studies were carried out by means of pH-metry, spectrophotometry, and mathematic simulation of equilibria (program CPESSP) on the state, acid-base properties and complexing ability [with respect to copper(II) and lanthanum(III)] of calix[4]resorcinol with acetal groups in the aminomethyl substituent [H₈L: R¹ = C₇H₁₅, R² = CH₂N(CH₃)CH₂CH₂CH(OCH₃)₂] in water-alcohol solution [80 vol % of i-PrOH] and in solutions of nonionogenic and ionic surfactants [Triton X-100, Brij-35, sodium dodecyl sulfate]. In all environments protonated and deprotonated tetrameric, dimeric, and monomeric species were found (pH range 3–10.6). In the presence of sodium dodecyl sulfate dimer (H₈L)₂ did not form that was the main speciation form in the other solvents. The sodium dodecyl sulfate like also Brij-35 favors formation of a hexadecamer (H₈L)₁₆ (pH about 6.3–6.5) in relatively small maximum accumulation fractions, 20 and 16% respectively. The solubility of H₈L in acid medium in the presence of cetyltrimethylammonium bromide, and in the presence of sodium dodecyl sulfate in alkaline medium, originated from the formation of mixed cationic and mixed anionic aggregates respectively. In a water-alcohol solution six complexes of copper(II) were detected: four mononuclear, one binuclear, and one tetranuclear complex with neutral and deprotonated forms of the ligand. Lanthanum(III) formed nine mononuclear complexes and in general coordinated more ligands than copper(II) favoring association (aggregation) of the compound under study.     

Treatment of ferric sulfate waste solutions for the production of ammonium ferric sulfate dodecahydrate

The process of precipitation of ammonium ferric sulfate dodecahydrate (NH₄Fe(SO₄)₂·12H₂O) from waste solutions, obtained during autoclave oxidation of pyrite concentrate has been studied. A special feature of these solutions is the high concentration of Fe(III) ions (>60 g L^–1) and sulfuric acid (> 61 g L^–1). Based on comprehensive laboratory tests, the study determined the optimal conditions for the precipitation process of ammonium ferric sulfate dodecahydrate (AFS) by salting out with ammonium sulfate: reagent excess (100% over stoichiometric, temperature 276 K, time 1 h). The process should be conducted under continuous slow stirring which would not allow forming of large crystals that are difficult to remove from the reactor. The test work confirmed that high quality crystals can be produced by prior oxidation of Fe(II) to Fe(III) ions using hydrogen peroxide and copper removal from the solution.     

Initial stages of copper electrocrystallization from sulfate electrolytes: Cyclic voltammetry on a platinum ring-disk electrode

Initial stages of copper electrocrystallization on platinum rotating and stationary ring-disk electrodes are studied in sulfate electrolytes of different acidities by cyclic voltammetry with a variable cathodic limit. In a weakly acid sodium sulfate solution of pH 3.7, copper deposition occurs at a higher rate than in a sulfuric acid electrolyte, which is due to an acceleration of the discharge of copper ions caused by local electrostatic effects that occur during the specific adsorption of sulfate anions and hydroxyl ions and to alterating nature of electroactive species. The mechanism of the formation of intermediate species (ions Cu⁺) during the deposition and dissolution of copper in solutions of different acidities is established.     

Synthesis,structure, spectroscopic and magnetic properties of a novel two-dimensional copper(II) complex Na2[Cu(pba)] · 6H2O [pba = 1,3-propylenebis(oxamato)]

The copper(II) complex Na₂[Cu(pba)] · 6H₂O has been synthesized and its structure determined. It consists of a novel two-dimensional network of [Cu(pba)]^2– anions connected to each other through the sodium ion as a bridge. Spectroscopic and magnetic properties have been measured and a spin distribution calculation has been carried out with the GAUSSIAN-94. Theoretical calculations indicate the rather larger spin density on nitrogen atoms should be responsible for the satellite lines appearing beside the main hyperfine coupling signs of copper(II). The antiferromagnetic interaction may be due to the intermolecular interaction and/or different copper(II) ions through the Na⁺ bridge in the same layer.     

Emulsion polymerization of styrene. III. Effect of Ti(III) and Cl(1) on the polymerization of styrene initiated by potassium persulfate

The emulsion polymerization of styrene initiated by potassium persulfate catalyzed by Ti⁺³ ions was studied. Two sources of Ti⁺³ ions were used: the titanium trichloride and titanium sulfate. It was found that the titanium ions used in conjunction with potassium persulfate decrease both the reaction rate and the average molecular weight. An even greater drop of reaction rate was noted when chlorine anions (TiCl₃) were present. The presence of these ions had a stabilizing effect on the polydispersity.     

Precipitation and association in a mixture of dodecylammonium chloride and sodium dodecyl sulfate in aqueous medium

The precipitation boundary in aqueous mixtures of dodecylammonium chloride (DDACl) and sodium dodecyl sulfate (NaDS) was determined in the absence and in the presence of 1 mol dm^–3 NaCl. The structure and the composition of the solid phase was characterized by x-ray and chemical analysis, respectively. Activities of Cl^– and Na⁺ ions in the aqueous phase were measured by ion-selective electrodes. As determined by calorimetry, precipitation is an exothermic process.The DDA·DS precipitate was formed in the equimolar region of the precipitation components. Its crystallographic structure is described. In an excess of sodium dodecyl sulfate, the precipitate incorporated substantial amounts of NaDS, as detected by analyses of both solid and liquid phases. X-ray analysis of the dry sample showed peaks of crystalline NaDS. According to the polarization microscopy of wet samples, one may conclude that liquid crystals, containing an excess of NaDS, are incorporated in the solid DDA·DS phase. The same was found in the case of an excess of DDACl; mixed liquid crystals with an excess of DDACl were incorporated in the solid DDA·DS.Interpretation of the solubility boundary points to the presence of DDA⁺·DS^– ion pairs. Formation of these species at low ionic strengths is characterized by the equilibrium constantK _a ⁰ 10⁶. However, in the 1 mol dm^–3 NaCl, the association of DDA⁺ and DS^– ions into pairs is inhibited (K _a ⁰ 0). This finding can be explained in terms of ionic clouds around the charged surfactant heads: if these heads are not in close contact, but separated due to structural effects of the chains, the dense distribution of counterions around them at high ionic strengths may compensate for electrostatic attraction and, thus, inhibit ion-pairing.