Electrodeposition of silver from dense gaseous solutions of silver nitrate in ammonia

Abstract

Silver was electrodeposited on platinum electrodes from solutions of AgNO₃ in NH₃ at temperatures from ?70°C. to 140°C. The solutions were 0.036 molar in AgNO₃ at ? 78°C. In the dense gaseous region, the concentrations of AgNO₃ and NH₃ were 0.018 and 22 moles/liter respectively.

The deposit was observed to become more and more crystalline in appearance as the temperature approached the critical temperature of NH₃(133°C). All electrodeposits at temperatures above 133°C were characterized by either dendritic or needle-like growths on sharp edges and corners. These were not observed at lower temperatures. Both three- and four-sided symmetries were observed, suggesting that the deposits were growing in the [111] and [100] directions, respectively.     

Synthesis of ditopic ligands for the selective extraction of copper(II) nitrate and crystal structures of their Cu(II) complexes

We have synthesized two ditopic ligands for selective extraction of copper(II) nitrate. We also synthesized one cation-only binding analog for comparison. All three ligands were characterized by conventional techniques. Competitive two-phase metal ion solvent extraction experiments were performed at 25 °C over a period of 24 h. These ligands showed significant selectivity for Cu(II) ions, having the ditopic ligands extract 81 and 73% of the Cu(II) ions in a solution of different metal ions {Ni(II), Co(II), Cu(II), Zn(II), Cd(II), Pb(II)} at pH 5.09. Competitive transport experiments (water/chloroform/water) were undertaken employing each ligand separately as the ionophore in the membrane (chloroform) phase. No metal ion transport was observed, but a large concentration of Cu(II) was present in the membrane phase. Competitive anion extraction and transport were carried out with the ditopic ligands, yielding selective extraction and transport of nitrate. Furthermore, a pH isotherm of the best ditopic ligand (H₂L²) with Cu(II) was determined from pH 1.0 to 6.0, producing a pH_½ value of approximately 2.6. Finally, crystal structures of the ditopic ligands complexed with Cu(II) were determined and refined. The coordination geometry around the metal centers are distorted square planar and the Cu(II)-donor bond lengths fall within the normal range.     

Study of the Contents and Speciation of Heavy Metals in River sediments By Factor Analysis

Abstract

Heavy metals Zn, Cd, Pb, Cu, Ni and Co from two spanish river sediments have been determined by voltammetric techniques, along with % CaCO₃ and % organic matter, and the whole data set examined by means of Factor Analysis, finding a different behaviour of the metals in each river.

Heavy metal speciation in the sediments was carried out by using the Tessier's scheme: Zn and Pb were mainly associated to ‘reducible phases’, Cd and Cu bound to ‘organic matter and sulphides’, and Ni and Co were distributed between the above fractions. The ‘residual’ metals were used as pollution indicators from the rivers, finding a similar behaviour to other industrialized river systems.     

Kinetics of aluminum extraction from aluminum ash by leaching with sulfuric acid

Abstract

To explore the high value of aluminum ash development and utilization, factors (granularity of aluminum ash, leaching temperature, leaching time, sulfuric acid concentration, and liquid solid ratio) affecting the leaching rate of aluminum were evaluated. The kinetics of the leaching process was also investigated. The results indicate that the leaching rate of aluminum in aluminum ash can reach 88.9% under the following conditions: leaching temperature, 100?°C; leaching time, 120?min; sulfuric acid concentration, 2.5?mol/L; and liquid–solid ratio (mass ratio), 1.3:1. Studies on the leaching dynamics of aluminum in aluminum ash showed that leaching was divided into two stages. At the initial stage (i.e. at the leaching rate x?≤?0.3), the external diffusion resistance and the diffusion resistance of the solid product layer are negligible, and leaching is controlled by chemical reaction at the interface. The apparent activation energy was 5733.25?J/mol. At the leaching rate x?=?0.3–0.9, the leaching rate was controlled by the non-steady diffusion of the liquid film in the porous solid by the fluid reactant H₂SO₄. The apparent activation energy was 25390.87?J/mol.     

Determimation of Cu and Fe in Hobium by Electrolytic Dissolution and Atomic Absorption Spectroscopy

Abstract

The method of electrolytic dissolution in organic solvents (saturated with NH₁Cl) followed by atomic absorption spectroscopy was applied to the determination of Fe and Cu impurities in niobium metal. It was found that a previously reported decrease in sensitivity could be attributed to precipitation of NH₄Cl on the walls of the feeding chamber of the spectrometer and could be avoided by diluting the solution before measurement.     

Phase equilibria and extraction of metal cations in the systems based on synergistic mixtures of potassium bis(alkylpolyoxyethylene)phosphate and alkylbenzyldimethylammonium chloride

The solubility in the system formed by the oxyethylated anionic surfactant potassium bis(alkylpolyoxyethylene)phosphate (oxyphos B), the cationic surfactant alkyldimethylbenz- ylammonium chloride (cathamine AB), and water was studied. The optimal parameters of the extraction process in the systems based on the mixture of surfactants, whose aqueous solutions have the lowest phase-separation temperatures, without a salting-out agent and in the presence of (NH₄)₂SO₄ were established. A possibility of the extraction of metal cations in the oxyphos B—cathamine AB—water system at 50 °С, and the (NH₄)₂SO₄—oxyphos B—cathamine AB—water system at 25 °С was demonstrated. The advantages of application of a mixture of ionic surfactants as compared to the systems based on individual surfactants were revealed.     

Synthesis and Characterization of Na And Mg Containing Carbonatefluorapatites

Abstract

The apatites were precipitated in an aqueous NH₄OH-NH₄NO₃ solution with pH 9–10 at temperatures 20°C and 80°C. The synthesized materials were studied by chemical and thermal analyses (TG/DTG/DTA, TG/ETIR-EGA), IR-spectroscopy, XRD-powder analysis and specific area measurements.     

SOME METAL COMPLEXES OF α, β, γ, δ-TETRA-(4-PYRIDYL) PORPHINE

Abstract

The zinc (II), copper (II), nickel (II), cobalt (II), chloromanganese (III), and chloroiron (III) complexes of α, β, γ, δ-tetra-(4-pyridyl)-porphine (4-TPyP) were prepared. The magnetic susceptibilities from near 0° to 90° K and at room temperature were measured for solid Cu(4-TPyp), Ni(4-TPyP), Co-(4-TPyP), ClMn(4-TPyP) · H₂ O and ClFe(4-TPyP). The Mössbauer spectra of ClFe(4-TPyP) were obtained at several temperatures. The infrared spectra and d-spacings were obtained for all of the solids. Electronic spectra of the complexes in pyridine and, where possible, in 0.1 N HCl solution were recorded. Evidence of intermolecular interaction was found for Co(4-TPyP), Ni(4-TPyP), and ClFe(4-TPyP).     

Comparison of Conventional,Ultrasound- and Microwave-Assisted Extraction Techniques Applied for the Determination of Metals in Spruce Needles

In the present study the extraction of trace and major elements (Al, B, Ba, Ca, Cd, Cr, Cu, Fe, Mg, Mn, Ni, Pb, Sr, Ti, V and Zn) from spruce (Picea) needle samples under various experimental conditions, i.e., extractant, temperature and time of extraction, was examined. The effectiveness of conventional, ultrasound- and microwave-assisted extraction techniques was investigated. The replacement of a sample decomposition procedure by leaching prior to multielemental analysis by ICP-AES as well as the aspect of fractionation analysis is discussed. Standard Reference Material (CRM 101-Norway spruce needles) was used for validation of the applied analytical procedures.     

Gas Chromatographic Analysis of Cholesterol Oxidation Products on a Thermostable Medium Polarity Capillary Column

The performance of a fused silica column coated with 50% phenyl-/50% dimethyl-polysiloxane, characterized by a high thermal stability, was evaluated for the gas chromatographic determination of cholesterol oxidation products. A silylated mixture of eighteen oxysterol standards (0.1 mg/ml of each compound) was injected into the gas chromatographic system. The temperature was programmed from 230 to 260°C at 2.5°/min and then to 290°C at 1°/min; the injector and detector temperatures were set at 325°C, and the gas linear velocity was 22.8 cm/s. The column gave a fast (15 min) and satisfactory resolution of the main cholesterol oxides. Good separation of the hydroxy from the epoxy derivatives was achieved.The suitability of the method for the determination of oxysterols in food matrices was successfully tested on a saponified lipid extract from egg yolk powder, previously enriched and purified by NH₂ solid phase extraction.     

Uptake of Divalent Metal Ions (Cu2+, Zn2+ and Cd2+) by Polysiloxane Immobilized Monoamine Ligand System

ABSTRACT

Porous solid siloxane polymers carrying a monoamine functional group of formula P-(CH₂)₃NH₂ (Where P- represents a siloxane framework silica like ) has been prepared by polycondensation of Si(OEt)₄ and (MeO)₃Si(CH₂)₃-NH₂. Treatment of aqueous solutions of divalent metal ions with the polysiloxane monoamine ligand system demonstrates that this material has high potential for preconcentration of metal ions (Cu²⁺, Zn²⁺ and Cd²⁺). The tendency of these divalent metal ions to chemisorb by the monoamine ligand system at the optimum conditions increases in the order: Cd²⁺ <Zn²⁺ <Cu²⁺. The optimum pH is 5.5 for copper and 6-7 for zinc and cadmium. The ammonia/ ammonium chloride buffer solution gave maximum uptake for all metal ions. It is also found that the uptake of copper ions is concentration dependent and is independent of the presence of other competing ions. The monoamine ligand system suffers from leaching of ligand containing groups upon treatment with acidic solutions. The highest leaching occurs at low pH.     

Optimization of a Sequential Extraction Scheme for the Characterization of Heavy Metal Mobility in Iron Oxide Rich Sediments

Abstract

Several parameters governing the extraction of metals from iron oxide rich sediments, using sequential extraction schemes were optimized. The mode of shaking, soil/extractant ratio and concentrations of MgCl₂ and NH₂OH·HCl, for samples collected in the Odiel Marshes Natural Park (SW Spain), were considered. The concentration of NH₂OH·HCl deserved particular attention due to the nature of the studied sediments. A 0.4 M concentration of this extractant was needed to avoid readsorption of Cu and As in the samples. In addition, readsorption processes were studied using a candidate to reference material with a high organic matter content that was previously analyzed in an interlaboratory study.     

Polarographic Behaviour of Copper Complex with 3-(2′-Thiazolylazo)-2,6-diaminopyridine at Dropping Mercury Electrode

Abstract

The polarographic behaviour of Cu(II) has been investigated in the presence of increasing concentration of 3-(2′-Thiazolylazo)-2,6-Diaminopyridine (2,6-TADAP) at different pH values and in 50% ethanol. At all pH's the waves were found to be diffusion controlled and irreversible. The values of the kinetic parameters n_a, K_o and ? have been evaluated as a function of the ligand concentration. The maximum half-wave potential shifts were observed for the Cu(II) complex at pH 3.37. The polarographic wave height was proportional to the concentration of Cu(II). The method has also been applied to the determination of Cu(II) in aluminium alloys.     

Synthesis and luminescence of polymeric metal complexes based on 1,10-phenanthroline and 8-hydroxyquinoline

A ligand containing different coordination groups, 5-([1,10]phenanthroline-[4,5-f]imidazo-2-yl)-8-hydroxyquinoline (PhenI8Q) has been synthesized and two corresponding polymeric metal complexes Cu(II) (1) and Zn(II) (2) were prepared by coordination polymerization of the ligand with copper(II) and zinc(II) halides, respectively. The ligand was characterized by ¹H-NMR, ¹³C-NMR, and Fourier transform-infrared (FT-IR) and its corresponding polymeric metal complexes 1 and 2 were characterized by FT-IR, UV-Vis, elemental analysis, thermal gravimetric analysis, and conductivity measurements. The absorption spectra and luminescence of the ligand, 1, and 2 were investigated by UV-Vis and fluorescence spectroscopy at room temperature. Compared with the ligand, the fluorescence spectra of the polymeric metal complexes exhibit blue shifts in dimethyl sulfoxide (DMSO) solution and bathochromic shifts in the solid state. Complexes 1 and 2 emit blue light with emission maximum (λ _{f max}) at 449 and 431 nm in DMSO solution and at 485 and 484 nm in the solid state, respectively.     

A New Route for the Synthesis of Alkali Polyphosphate from Economical Starting Materials: Preparation and Characterization of Sodium Cyclotriphosphate

Abstract

Thermal synthesis of sodium cyclotriphosphate (SCTP) – Na₃P₃O₉ was investigated in the temperature range of 150 °C to 750 °C using sodium chloride (NaCl) and 85 wt% orthophosphoric acid (H₃PO₄) as economical starting materials. Reaction temperature had a crucial impact on the chloride elimination rate and the formation of SCTP. The best result was obtained at 600 °C with 96% of elimination of the initial chloride as hydrochloric acid and 84% of selectivity in SCTP. At lower temperatures, residual chloride contents were high. At higher temperatures (650 °C and 750 °C), SCTP was melted and transformed into glassy products.     

Indirect mineral carbonation of blast furnace slag with(NH_4)_2SO_4 as a recyclable extractant

Large quantities of CO_2 and blast furnace slag are discharged in the iron and steel industry. Mineral carbonation of blast furnace slag can offer substantial CO_2 emission reduction and comprehensive utilisation of the solid waste. In this study, a recyclable extractant,(NH_4)_2SO_4, was used to extract calcium and magnesium from blast furnace slag(main phases of gehlenite and akermanite) by using low-temperature roasting to fix CO_2 through aqueous carbonation. The process parameters and efficiency of the roasting extraction, mineralisation, and Al recovery were investigated in detail. The results showed that the extractions of Ca, Mg, and Al can reach almost 100% at an(NH4)_2SO_4-to-slag mass ratio of 3:1 and at 370°C in 1 h. Adjusting the p H value of the leaching solution of the roasted slag to 5.5 with the NH_3 released during the roasting resulted in 99% Al precipitation, while co-precipitation of Mg was lower than 2%. The Mg-rich leachate after the depletion of Al and the leaching residue(main phases of CaSO_4 and SiO_2) were carbonated using(NH_4)_2CO_3 and NH_4HCO_3 solutions, respectively, under mild conditions. Approximately 99% of Ca and 89% of Mg in the blast furnace slag were converted into CaCO_3 and(NH_4)_2 Mg(CO_3)_2·4 H_2O,respectively. The latter can be selectively decomposed to magnesium carbonate at 100-200 °C to recover the NH_3 for reuse. In the present route, the total CO_2 sequestration capacity per tonne of blast furnace slag reached up to 316 kg, and 313 kg of Al-rich precipitate, 1000 kg of carbonated product containing CaCO_3 and SiO_2, and 304 kg of carbonated product containing calcium carbonate and magnesium carbonate were recovered simultaneously. These products can be used, respectively, as raw materials for the production of electrolytic aluminium, cement, and light magnesium carbonate to replace natural resources.     

Viscosity of molten NaCI,NaBF4 and KBF4

Abstract

The viscosities of molten NaBF₄ and KBF₄ were determined over a 120°C interval and the viscosity of molten NaCl was redetermined over a 200°C interval by use of an oscillating cup viscometer. The viscosities of all three samples followed an Arrhenius type temperature dependence. The measured viscosity for NaCl agreed better with predicted values and the trend established by the other sodium and potassium halides than did previous determinations. The Batchinskii free volume concept of viscosity held for the sodium and potassium halides and the two MBF₄ salts. An equation based upon a hard-sphere model predicted viscosity values in agreement with experimental values for the alkali metal halides and KBF₄ but was not suitable for NaBF₄.     

Studies on the solid state reactions of coordination conpounds. XLVIII. The effect of KSCN on the thermal decomposition of cobalt(III)-ammine complexes

The evolved gaseous analysis (EGA), infrared spectra, and XRD have been applied to the study of solid state reactions of KSCN with five cobalt(II)-ammine complexes: [Co-(NH₃)₅N₃]Cl₂. [Co(NH₃)₅(NO₂)]Cl₂. [Co(NH₃)₅(H₂O)]Cl₃. [Co(NH₃)₅Cl]Cl₂, and [Co(NH₃)₆]Cl₃ in a hydrogen atmosphere. It is found that the existence of KSCN shifts the thermal decomposition of these complexes to a lower temperature. The corresponding peak temperatures are near 140°C. The effect of KSCN is discussed and kinetic parameters of deammine reactions are calculated.     

A greener microwave-assisted extraction method for rapid spectroscopic determination of selected metals in river and freshwater sediment certified reference materials

The current study describes development of novel, cost-effective, rapid and greener microwave-assisted extraction (MW-AE) method using diluted hydrogen peroxide (H₂O₂) and 400 µL of concentrated aqua-regia for the extraction of 10 selected metals (Ba, Cr, Cu, Co Fe, Mn, Ni, Pb, V and Zn) in sediment certified reference materials (CRMs), prior to inductively coupled plasma-optical emission spectroscopic analysis. The optimum extraction conditions were achieved when 0.2 g of sediment was extracted with 1 mol L^?1 of H₂O₂ (12.00 mL) and 400 µL of concentrated aqua-regia, at 180°C microwave extraction temperature for 30 min. Accuracy of the proposed MW-AE method was evaluated by using river (LGC6187) and freshwater (CRM015-050) sediment CRMs. Quantitative extraction recoveries of 80–120% in LGC6187 and 74–124% in CRM0150-050 were obtained with acceptable precision (0.4–1.0%). The proposed extraction method has a clear advantage over classical approaches as 1 mol L^?1 H₂O₂ was used instead of notorious acidic mixture (Hydrochloric acid/ nitric acid/ hydrofluoric). The method detection limits (MDLs) of 0.03–0.9 μg g^?1 were obtained for all the investigated metals and were fairly comparable with the MDLs of the published literature reports. Therefore, the proposed MW-AE method can be routinely used for monitoring of metal ions in various river and fresh water sediments.     

Evolved gas analyses on a mixed valence copper(I,II) complex salt with thiosulfate and ammonia by in situ TG-EGA-FTIR and TG/DTA-EGA-MS

Thermal decomposition of a mixed valence copper salt, Na₄[Cu(NH₃)₄][Cu(S₂O₃)₂]₂·0.5NH₃ (1) prepared from pentahydrates of sodium thiosulfate and copper sulphate of various molar ratios in 1:1 v/v aqueous ammonia solution, has been studied up to 1,000 °C in flowing air by simultaneous thermogravimetric and differential thermal analysis coupled online with quadrupole mass spectrometer (TG/DTA-MS) and FTIR spectrometric gas cell (TG-FTIR), in comparison. Compound 1 releases first but very slowly some of the included ammonia till 170 °C, then simultaneously ammonia (NH₃) and sulphur dioxide (SO₂) from 175 to 225 °C, whilst the evolution of SO₂ from thiosulfate ligands continues in several overlapping stages until 410 °C, and is escorted by explicit exothermic heat effects at around 237, 260, 358 and 410 °C. The former two exothermic DTA-peaks correspond to the simultaneous degradation and air oxidation processes of excess thiosulfate anions not reacted by formation of copper sulfides (both digenite, Cu_1.8S and covellite, CuS, checked by XRD) and sodium sulfate, while the last two exothermic peaks are accompanied also by considerable mass gains, as the result of two-step oxidation of copper sulfides into various oxosulfates. The mass increase continues further on until 580 °C, when the sample mass begins to decrease slowly, as a continuous decomposition of the intermediate copper oxosulfates, indicated also by re-evolution of SO₂. At 1,000 °C, a residual mass value of 64.3% represents a stoichiometric formation of Cu^IIO and anhydrous Na₂SO₄.