Aqueous Thiocyanate Solutions Research Articles

Redetermination of the crystal structure of K2Hg(SCN)4.

Single crystals of K2Hg(SCN)4 [dipotassium tetra-thio-cyanato-mercurate(II)] were grown from aqueous solutions of potassium thio-cyanate and mercury(II) thio-cyanate and studied by single-crystal X-ray diffraction. In comparison with the previously reported structure model [Zvonkova (1952 ▸). Zh. Fiz. Khim. 26, 1798-1803], all atoms in the crystal structure were located, with lattice parameters and fractional coordinates determined to a much higher precision. In the (crystal) structure, the HgII atom is located on a twofold rotation axis and is coordinated in the form of a distorted tetra-hedron by four S atoms of the thio-cyanate anions. The K+ cation shows a coordination number of eight.

Aqueous RAFT Polymerization of Acrylonitrile

Controlled radical polymerization of acrylonitrile (AN) in concentrated aqueous solutions of sodium thiocyanate (NaSCN, 50 wt %) and zinc chloride (ZnCl2, 60 wt %) is reported. Reversible addition–fragmentation chain transfer (RAFT) polymerization was successfully accomplished with 4-cyano-4-(phenylcarbonothioylthio)pentanoic acid (CPAD) as a chain transfer agent (CTA) and AIBN as a radical initiator at 65 °C. First-order linear kinetic plots were observed in aqueous NaSCN with molecular weights (MW) between 3000 and 60 000 and relatively narrow molecular weight distributions (Mw/Mn = 1.2–1.4). Chain extension of the synthesized PAN macroinitiator with AN in aqueous NaSCN showed a clear shift in MWs which indicated high retention of chain end functionality. Furthermore, RAFT polymerization of AN in aqueous ZnCl2 (60 wt %) was conducted with CPAD and 2,2′-azobis(4-methoxy-2,4-dimethylvaleronitrile) (V-70) as radical initiator at 30 °C. This system also exhibited linear kinetics and produced PAN with Mn = 1...

Aqueous ammonium thiocyanate solutions as refractive index-matching fluids with low density and viscosity

We show that aqueous solutions of ammonium thiocyanate (NH4SCN) can be used to match the index of refraction of several transparent materials commonly used in experiments, while maintaining low viscosity and density compared to other common refractive index-matching liquids. We present empirical models for estimating the index of refraction, density, and kinematic viscosity of these solutions as a function of temperature and concentration. Finally, we summarize the chemical compatibility of ammonium thiocyanate with materials commonly used in apparatus.

Thin layer chromatographic separation of cobalt from nickel on impregnated silica gel layers: quantitative determination by digital image analysis

Thin layer chromatography (TLC) of cobalt and nickel has been performed on silica gel layers induced with alkali mediated cellulose extract. A novel combination of 10% aqueous solutions of Tween-20 and potassium thiocyanate in 1:1 (v/v) was identified as the best mobile phase for the selective separation of Co2+ from Ni2+ on the impregnated Silica Gel G layers. The chromatographic characteristics of the cations were studied and the limits of detection as well as the limits of quantification for Co2+ and Ni2+ were determined. The quantitative estimation of the cations was achieved from the digital image analysis of respective chromatograms. The proposed quantitative method was successfully applied with 0-0.50% error for the determination of Co2+ from Ni2+ in spiked samples of bauxite, soil and rock containing common cations such as Al3+, Fe2+, Ti4+, Zn2+, Mn2+, Cu2+, Cr6+, Mg2+ etc. under the optimized chromatographic conditions.

A Conductance Study of Guanidinium Chloride, Thiocyanate, Sulfate, and Carbonate in Dilute Aqueous Solutions: Ion-Association and Carbonate Hydrolysis Effects

We study the conductance of dilute aqueous solutions for a series of guandinium salts at 298.15 K. The experimental molar conductivities were analyzed within the framework of the Quint-Viallard theory in combination with Debye-Hückel activity coefficients. From this analysis, we find no evidence for significant ion association in aqueous solutions of guanidinium chloride (GdmCl) and guanidinium thiocyanate (GdmSCN), and the molar conductivity of these electrolytes can be modeled assuming a complete dissociation. The limiting ionic conductivity of the guanidinium ion (Gdm(+)) is accurately determined to λ(Gdm(+)) = 51.45 ± 0.10 S cm(2) mol(-1). For the bivalent salts guanidinium sulfate (Gdm(2)SO(4)) and guanidinium carbonate (Gdm(2)CO(3)), the molar conductivities show small deviations from ideal (fully dissociated electrolyte) behavior, which are related to weak ion association in solution. Furthermore, for solutions of Gdm(2)CO(3), the hydrolysis of the carbonate anion leads to distinctively increased molar conductivities at high dilutions. The observed ion association is rather weak for all studied electrolytes and cannot explain the different protein denaturing activities of the studied guanidinium salts, as has been proposed previously.

Separation and concentration of cobalt from aqueous thiocyanate solutions containing cobalt–nickel by emulsion liquid membranes using TBP as extractant

In this work, the zinc plant copper cake (CINKUR Co., Turkey) was leached with hydrochloric acid and main acidic leach solution containing Zn(II), Fe(II), Pb(II), Al(III), Cu(II), Co(II) and Ni(II) ions was obtained. Except for cadmium, cobalt and nickel, the other metals were precipitated by adding various reagents and adjusting the pH of the solution. Then, cadmium was separated by solvent extraction process. After these separation processes, ammonium thiocyanate and water were added to remaining leach solution. Thus, acidic thiocyanate leach solutions used in ELM process were obtained. ELM consists of kerosene as diluent, tributyl phosphate as extractant, sorbitan monooleate (SPAN 80) as surfactant, and 6 M ammonia solution as the stripping solution. Separation and concentration of cobalt by ELM from acidic thiocyanate leach solution containing cobalt and nickel was performed. The important parameters governing the extraction behavior of cobalt have been investigated. These parameters were mixing speed, surfactant concentration, extractant concentration, phase ratio, treatment ratio, stripping solution base concentration, initial cobalt concentration in feed solution, thiocyanate concentration in the feed solution, and the feed solution pH. The results obtained showed that by appropriate selection of the extraction and stability conditions, nearly all of the cobalt ions present in the feed solution were extracted within 10 min. The separation factors of cobalt with respect to nickel, based on initial feed concentration, have experimentally found to be of as high as 310 for non-equimolar Co–Ni feed solutions.

Electropolishing of Silver in Water-Organic Solutions of Potassium Thiocyanate

The anodic behavior of silver in aqueous and water-glycerol solutions of potassium thiocyanate is studied on motionless and rotating-disk electrode. The appearance of the limiting current is explained. Optimal solution compositions and conditions for the process (which ensure metal polishing) are suggested.

Ultrasonic and Raman Scattering Spectroscopy of Zinc Thiocyanate Complexes in Water at 25∘C: Kinetics of Complex Formation Determined by Multivariate Analysis

Advances have been made recently in broadening the accessible ultrasonic absorption frequency range and improving the detectability of minor species present in solution using Raman spectroscopy. Development of chemometric techniques in these areas needs to keep pace with the improvement of these experimental methods. Refinements in the analysis of ultrasonic and Raman data based on multivariable least squares and factor analysis, respectively, are examined to investigate the kinetics of zinc thiocyanate complex formation in water. Analysis of ultrasonic absorption relaxation spectra verified that the observed process in aqueous Zn(SCN)2 involves substitution of water from the first coordination shell of Zn2+. Use of a multivariable least-squares error surface is described that enhances the reliability of assigned frequencies of ultrasonic absorption maxima. Factor analysis of Raman scattering data provided direct evidence that at least four complex species, such as Zn(SCN)+ and Zn(SCN)2, are simultaneously present in the aqueous zinc thiocyanate solutions.

Thiocyanate Wet Oxidation

Aqueous solutions of thiocyanate were oxidized in a semi-batch reactor at temperatures between 170 and 210 °C and system total pressures ranging from 70 to 100 atm. The initial pH of the solution was set at 12, while initial concentrations have ranged between 20 and 1000 ppm according to the typical concentrations of thiocyanate-containing wastewater. The kinetic data discussion was based on the establishment of a kinetic regime control that guaranteed the validity of the experimental data and that oxygen excess was assured for all the runs. An attempt to establish a thiocyanate wet oxidation pathway has been made on the basis of the reaction intermediates and final oxidation products identified during the experimental work. SO42- and CO3- have been pointed out as the main final reaction products whereas (SCN)2 and SCNO- are suggested as possible short-life oxidation intermediates. The oxidation reaction results were fitted to a first-order kinetic equation with respect to thiocyanate and to 0.81 with respect to oxygen, with an activation energy of 84.4 kJ mol-1.

Viscometric Properties of Solutions of Amylose and Amylopectin in Aqueous Potassium Thiocyanate

Solutions of commercial potato amylose (1.65%, w/v) in dimethyl sulfoxide (DMSO) /water mixtures formed gels on standing when the water content was equal to or greater than 60% (w/v). These gels did not form when the water was replaced with aqueous potassium thiocyanate solution (KSCN, 2 mol/L). Commercial amylose did not dissolve completely in aqueous KSCN, unlike commercial potato and corn amylopectins, which formed more stable solutions than those in water alone. Solutions of amylopectin in mixtures of DMSO and aqueous KSCN showed a maximum relative viscosity (flow viscometer) at 80% (v/v) DMSO, like those in DMSO/water. Solutions of amylopectin in 25% (v/v) DMSO/75% (v/v) aqueous KSCN (2 mol/L) could be used for estimation of molecular weight by flow viscometry using the Mark-Houwink-Sakurada Equation. Sigma corn amylopectin gave a weight average molecular weight of 12.1 x 106, lower than that obtained using DMSO alone, and likely to be due to a lower degree of hydrogen bonding in the presence of KSCN, consistent with its chaotropic effect. This effect was also reinforced by the observation that formation of the amylose/iodine complex is inhibited by KSCN at concentrations as low as 0.2 mol/L.

Sorption Properties of Polyacrylonitrile Fibres

As-spun undrawn PAN fibre wet-spun from solutions of the polymer in DMF, DMA, and DMSO are porous with a developed specific surface (up to 80 m2/g for nitrogen), while fibres spun from aqueous solutions of sodium thiocyanate or zinc chloride are nonporous with a specific surface of under 1 m2/g. The finished PAN fibres spun from solutions in different solvents have a closely packed structure, equivalent to highly crystalline, according to the data from sorption of inert gases and water vapors, and according to the results on the kinetics of sorption of vapors of liquids with different molecule sizes, they can be considered ultramicroporous.

Extraction of Ag(I) from aqueous thiocyanate solution with Primene JMT or TOA

Using Primene JMT or TOA, the extraction of thiocyanic acid and of Ag(I) thiocyanato-complex from aqueous thiocyanate solution was studied. On extraction of thiocyanic acid using aqueous phase containing 1.0 M NH 4SCN and an organic phase containing 100–300 kg m −3 Primene JMT or TOA, (RNH 3 +·SCN −) o and (R 3NH +·SCN −) o were formed with apparent equilibrium constants, log K ex,a, of 8.7 and 6.5, respectively. The extraction of 1×10 −3 M Ag(I) from aqueous ammonium thiocyanate solutions by the thiocyanate salts of Primene JMT or TOA at concentrations ranging from 100 to 300 kg·m −3, and in the presence of ammonium thiocyanate at concentrations of 0.5–3.0 M can be summarized as follows: 2( RNH 3 +· SCN −) o + Ag( SCN) 3 2− = K ex,3 (( RNH 3 +) 2· Ag( SCN) 3 2−) o +2 SCN −, logK ex,3 =1.6 2( R 3 NH +· SCN −) o + Ag( SCN) 3 2− = K ex,3 (( R 3 NH +) 2· Ag( SCN) 3 2−) o +2 SCN −, logK ex,3 =2.5.

Coordination of Thiocyanate Ions to Rare Earth Ions in Concentrated Aqueous Rare Earth Thiocyanate Solutions

Coordination of Thiocyanate Ions to Rare Earth Ions in Concentrated Aqueous Rare Earth Thiocyanate Solutions

Extraction, Separation, and Determination of Nickel and Bismuth with 1-(2-Pyridylazo)-2-naphthol in Aqueous Thiocyanate Media

Abstract Nickel(II) and bismuth(III) are quantitatively extracted from aqueous thiocyanate solutions, adjusted to pH 4.0–9.0 and 3.5–5.0, respectively, using solutions of 1-(2-pyridylazo)-2-naphthol (PAN) in tri-n-butyl phosphate (TBP). The extracted species of nickel and bismuth have the formulas [Ni(PAN)SCN]·4TBP and [Bi(PAN)SCN]X·TBP, respectively. Polyurethane foam treated with TBP solution containing PAN is used successfully for the quantitative retention and recovery of nickel and bismuth from aqueous thiocyanate solutions in the column extraction mode. The preconcentration of small amounts (10 mg) of nickel and bismuth from dilute aqueous solutions (1 L) is also possible, with a recovery of 95–97%. The feasibility of using PAN-foam for selective detection and semiquantitative determination of nickel and bismuth in aqueous thiocyanate media is examined. The detection limits of nickel and bismuth by the foam batch method are 0.05 and 0.50 ppm, respectively. Lower concentrations of these metal ions ar...

Solvent extraction of cerium(III) from aqueous thiocyanate solutions by neutral organophosphorus compounds

The extraction of cerium(III) from aqueous solutions containing potassium thiocyanate by tributyl phosphate (TBP) or trioctyl phosphine oxide (TOPO) in kerosene or benzene has been investigated under different conditions. IR spectral studies have been carried out on the organic extracts. The distribution coefficient of cerium(III) for TBP increases monotonously with increasing aqueous thiocyanate concentration. As a result, it is found that the equilibrium equation for the extraction by TBP can be expressed as follows: Ce 3+(aq) + 3NCS −1(aq) ⇌ Ce(NCS) 3(aq), Ce(NCS) 3(aq) + 4TBP(org) ⇌ Ce(NCS) 3·4TBP(org). A similar result was also obtained for the extraction by TOPO, although the extraction efficiency of TOPO is higher than that of TBP. The IR results indicate that the thiocyanate ion coordinates to the cerium ion through the N atom and that the cerium ion combines with the phosphoryl O atom of the extractants.

Infrared spectroscopic study of acetonitrile in aqueous inorganic salt solutions and comparison with related polyacrylonitrile solutions

The infrared spectra of acetonitrile (CH 3CN) have been obtained in the ν(CN) stretching region for the pure liquid, in water and in aqueous salt solutions of sodium thiocyanate, sodium iodide, lithium iodide calcium iodide and zinc chloride. The CN absorption bands of acetonitrile in aqueous inorganic salt solutions were very similar in character to those found in aqueous solutions of poly(acrylonitrile-co-vinyl acetate) containing inorganic salts. The effect of the salt solutions on the ν(CN) stretching absorptions can be divided into three types: (i) solutions containing NaSCN and NaI which cause a shift in the ν(CN) absorption band relative to that in pure CH 3CN with δν=+6 cm −1, (ii) solutions containing ZnCl 2 which give rise to two absorption bands with shifts of δν=+6 and +60cm −1, and (iii) those containing LiSCN and CaI 2, which also produce two absorption bands but with shifts of δν=+6 and +22cm −1. The spectral data are critically compared with those previously obtained for poly (acrylonitrile-co-vinyl acetate) under a similar range of conditions.

Linkage isomer ratios in thermal and photochemical anation of acidopentacyanocobaltate(III) anions

Photolysis of [Co(CN) 5 X] n− ions, where X=CN − , N 3 − , Cl − , Br − , I − , OH − , and H 2 O, in slightly acidic aqueous thiocyanate solution has been found to give the linkage isomers of [Co(CN) 5 (CNS)] 3− , together with larger amounts of [Co(CN) 5 (H 2 O)] 2− . Photolyses at pH 13 and room temperature, and in acidic medium at −4 o C, demonstrate that direct photoanation occurs in competition with the more efficient aquation reaction

Simultaneous Extraction and Atomic Absorption Spectrometric Determination of IB Group Elements (Cu, Ag, Au) from Aqueous Thiocyanate/2,2′-Dipyridyl-2-Pyridylhydrazone (Dpph) Solutions

Abstract A quantitative simultaneous extraction procedure of copper, silver and gold cations from aqueous thiocyanate solutions into Methyl Isobutyl Ketone (MIBK) is described. the effects of pH, thiocyanate and 2,2′-Dipyridyl-2-py-ridylhydrazone (DPPH) concentration were studied. Tolerance amounts for many diverse cations and anions have been determined. Finally, a procedure for the determination of IB Group elements is recommended, by extaction-AAS.

Solvent extraction and atomic absorption spectrometric determination of cadmium in environmental samples

Abstract Traces of Cadmium can be quantitatively extracted from aqueous thiocyanate solutions into 2‐Benzoylpyridine‐2‐Pyrididylhydrazone (BPPH) Methyl‐Isobutyl‐Ketone (MIBK) solution. Very small amounts of Cadmium can be recovered from a large volume of sample and determined directly by flame Atomic Absorption Spectrometry. A new procedure for Cadmium determination in environmental and biological samples was developed. The proposed scheme for Cadmium determination was found to be simple, selective, sensitive and accurate.

Solvent Extraction of Copper(II) in Aqueous Thiocyanate Solutions with 4-Methyl-2-pentanone

Solvent extractions of copper(II) from aqueous thiocyanate solutions into carbon tetrachloride containing benzoyltrifluoroacetone and into 4-methyl-2-pentanone were studied. From the data of the former extraction system, the stability constants of metal thiocyanate complexes in the aqueous phase were determined. From the data of the latter system, the extraction constants for the CuSCN+ClO4-, Cu(SCN)2 and Na+Cu(SCN)3- species were obtained. The extraction curve of this metal ion as well as those of nickel(II), cobalt(II), zinc(II), cadmium(II), mercury(II) and lead(II) in this liquid-liquid system were considered from the standpoint of the stability and extractability of the complexes.