Sodium Thiocyanate Solution Research Articles

On the Use of Pseudo-Protic Ionic Liquids to Extract Gold(III) from HCl Solutions.

Solvent extraction of gold(III) from HCl media using pseudo-protic ionic liquids (PPILs) dissolved in toluene as the extractant phase is investigated. Three PPILs are generated from the reaction of commercially available amines and 1 M HCl solution and named as pri-NH2H+Cl- (derived from the primary amine Primene 81R), sec-NHH+Cl- (derived from the secondary amine Amberlite LA2) and ter-NH+Cl- (derived from the tertiary amine Hostarex A327). In the above structures, -NH2H+Cl-, -NHH+Cl- and -NH+Cl- represented the active groups (anion exchangers) of the respective PPIL. In the case of gold(III) extraction, the experimental variables investigated included the equilibration time (2.5-30 min), temperature (20-60 °C), HCl concentrations (1-10 M) in the aqueous phase, gold(III) concentration (0.005-0.05 g/L) in this same phase, and PPILs concentrations in the organic phase. From the experimental data, and using the Specific Interaction Theory, the interaction coefficients (ε) for the pair AuCl4-, H+ are estimated for the systems involving the three PPILs. Gold(III) is recovered from the metal-loaded organic phases using sodium thiocyanate solutions, and from these, gold is finally recovered by the precipitation of zero-valent gold (ZVG) nanoparticles.

Structure of Polyacrylonitrile Fibers Produced from N-Methylmorpholine-N-Oxide Solutions

Structural and morphological evolution of polyacrylonitrile (PAN) samples from starting powder of a ternary copolymer to fibers produced from concentrated solutions of PAN in N-methylmorpholine-N-oxide (NMMO) was studied using x-ray diffraction for the first time. X-ray exposures in transmission and reflection geometries allowed the structures of outer and inner parts of the PAN fibers to be differentiated. It was shown that a shell—core structure formed in the precipitation bath during fiber spinning. A comparison of x-ray diffraction patterns of fibers spun using the NMMO process and industrial samples spun from DMSO and aqueous sodium thiocyanate solutions did not reveal fundamental structural differences.

Combined technology for gold desorption and ionite regeneration in the conical device

The principal technological scheme of desorption of gold and concomitant metal-impurities from the AM-2B resin phase used for the sorption processing of gold-bearing ores is considered. The proposed combined scheme, involving the use of two traditional, independent from each other methods (thiocyanate and acid-thiourea) for eluting gold, includes desorption of metal impurities from the resin with alkaline solutions of sodium thiocyanate, and gold with sulfuric acid solutions of thiourea. To shorten the duration of the process research of proposed technology was carried out the in a conical apparatus. The results of study of the elution of gold and impurity metals from anionite saturated with the following components, mg/g: Au – 2.6; Cu – 3.5; Zn – 1.3; Ni – 2.9; Co – 3.3, are given. It is shown that the main amount of impurity metals is desorbed from the resin upon its thiocyanate treatment, while the transition of gold into the eluate is negligible. The composition of the eluate in the thiocyanate treatment of saturated resin is, mg/l: Au – 1.7; Cu – 156.0; Zn – 53.0; Ni – 89.0; Co – 102.0. The subsequent treatment of the resin with sulfuric acid solutions of thiourea allows the conversion of 89.32 % of gold from the ion exchanger into the eluate. The resulting eluates containing ~113.0 mg/l gold and a small amount of impurities are target solutions for obtaining a valuable metal. The ion exchanger was regenerated by washing with water and treating with an alkaline solution of sodium to convert it to OH form, since gold sorption is carried out from alkaline cyanide solutions of heap leaching. Residual contents of components in the resin after regeneration were, mg/g: Au – 0.24; Cu – 0.23; Zn – 0.15; Ni – 0.07; Co – 1.29, which allows the successful use of the regenerated resin in the next stage of sorption.

A new method for online measurement of the concentration of working fluids in absorption refrigeration systems

This paper proposes a new method for online measurement of the concentration of working fluids in absorption refrigeration systems: electrical conductivity is measured to determine the concentration of the solution. Compared with the common density-concentration method, electrical conductivity-concentration method has the same accuracy but helps to save cost when applied in absorption systems with ammonia–salt solutions. This novel method is also suitable for systems with traditional working fluids like water–lithium bromide solution. Electrical conductivities of ammonia–lithium nitrate, ammonia–sodium thiocyanate and water–lithium bromide solutions were measured between (293.15 and 333.15) K, using an Industrial Conductivity Meter. The ammonia mass fraction varied from 0.35 to 0.48 for ammonia–lithium nitrate solution and from 0.35 to 0.50 for ammonia–sodium thiocyanate solution. For water–lithium bromide solution, the mass fraction of lithium bromide was within the range of 40%–60%. The experimental data were correlated as a function of temperature and composition using the extended Casteel–Amis equation. In addition, correlations of refrigerant mass concentration as a function of electrical conductivity and temperature of the solution are proposed.

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...

Experimental evaluation on thermal performance of an air-cooled absorption refrigeration cycle with NH3–LiNO3 and NH3–NaSCN refrigerant solutions

This paper experimentally analyzes thermal performance of an air-cooled type single effect absorption refrigeration cycle with ammonia–lithium nitrate and ammonia–sodium thiocyanate solutions as working pairs. Ammonia/salt system has simple construction, low evaporating temperature (<0°C) and high working efficiency. Ammonia is one kind of environment-friendly refrigerants. Hence, ammonia/salt absorption refrigeration cycles are considered to be the most possible ones for practical application in small capacity refrigeration units. An experimental apparatus has been designed and built in Wuhan, China, to evaluate the cycle thermal performance of air-cooled type single effect ammonia/salts absorption refrigeration system. The experimental apparatus operates steadily under different working conditions. A set of tests have been conducted and the corresponding experimental data are measured and recorded to show the variation of the system performances with different system working parameters. For the NH3–LiNO3 system, the measured lowest evaporation temperature reaches −13.1°C with corresponding average system COP of 0.15, and the average refrigerating capacity is about 670W. For the NH3–NaSCN system, with a measured evaporation temperature of −7.5°C, the corresponding average COP is 0.20, and the average refrigerating capacity was about 590W. According to the experimental results, the actual measured COP of NH3–NaSCN system are in the range of 0.20–0.35, which are a little higher than that of NH3–LiNO3 system (actual measured COP ranging from 0.15 to 0.29). Under similar working condition, NH3–LiNO3 system can reach a lower evaporation temperature than that of NH3–NaSCN system. The experimental results of the present study demonstrate the feasibility and capability of ammonia/salt absorption refrigeration cycle for freezing purpose under air cooling conditions. Although the coefficient of performance of the experimental apparatus is below expectation while comparing with the theoretical results, optimization methods are put forward by the present paper for further research.

Use of hypercrosslinked polystyrenes for removing iron complex salts and organic impurities from sodium thiocyanate solution in production of polyacrylonitrile fiber

The main organic impurities in concentrated solutions of sodium thiocyanate in different steps of production of polyacrylonitrile fiber were identified, and the possibility of their efficient removal simultaneously with iron salts by commercial sorbents of neutral hypercrosslinked polystyrene type was demonstrated.

Solid-Phase Extraction of Pt(IV) with Dialkyl-(hexane-1,6-diyl) Phosphate Modified Merrifield Resins from Aqueous Chloride Media in Column Operations

A series of three dialkyl phosphate resins with a Merrifield resin support was used to extract platinum from acidic media. In column operations total capacities of 85-130 mg/g were gained. The presence of palladium and rhodium results in the order: Pt(IV) > Pd(II) >> Rh(III). From a leach liquor gained from spent automotive catalysts metals forming anionic chloro complexes are co-extracted only to a small extent. However, in order to separate and enrich platinum a selective back-extraction can be done with a sodium thiocyanate solution. A second elution step with acidic thiourea leads to a mixed solution of palladium and rhodium.

Thermodynamic analysis of a novel air-cooled non-adiabatic absorption refrigeration cycle driven by low grade energy

An air-cooled type absorption refrigeration cycle using ammonia–lithium nitrate and ammonia–sodium thiocyanate solutions as working fluids are thermodynamically studied in this paper. In the case of many occasions especially small cooling capacity occasion where water cooling is restricted or inconvenient, application of conventional adiabatic absorbers in air-cooled type absorption refrigeration system has been studied by many investigators. Comparing to the adiabatic absorber, a novel air-cooled non-adiabatic absorber is applied to the absorption refrigeration system in this study to improve system performance. It is shown that, system performance has a significant improvement when temperatures of rich ammonia solution at the outlet of absorber decrease under the effect of the heat dissipation capacity of the non-adiabatic absorber. Another advantage is that heat load of the system heat exchangers including generator, solution heat exchanger and air-cooler, decreases with the solution temperature decrease at the outlet of the absorber under the same system cooling capacity condition, which brings benefits to the system cost reduction. Variation of system performance and other system operation parameters with generator temperature, absorption temperature and absorption efficiency has been carried out. Effects of the self-circulation flow rate of the absorber have been studied. A datasheet of system operation parameters has been proposed.

Dissolution Properties of Silk Cocoon Shells and Degummed Fibers from African Wild Silkmoths

Silk cocoon shells and degummed fibers from four African wild silkmoth species were studied and compared with the industrial standard, Bombyx mori, for their dissolution properties. Nine M aqueous Lithium bromide, Calcium chloride and Sodium thiocyanate solution systems were used. Efficiency of the solvent systems was determined by the percentage of dissolved silk cocoon shells and degummed fibers after three hours of treatment. Degummed fibers were more readily soluble than the cocoon shells. B. mori cocoon shells (51.5%) and fibers (59.3%) had higher solubility than their wild counterparts. Among the wild species, Gonometa postica cocoon shells and degummed fibers had the highest solubility (37.3 and 51.7%, respectively). Lithium bromide was the most effective dissolving agent for both the cocoon shells and fibers (41.2 and 84.5%, respectively). Argema mimosae, Anaphe panda and Epiphora bauhiniae showed lower solubility across the solution systems used. The Scanning Electron micrographs showed A. panda fibers exhibited gelling property after dissolution while E. bauhiniae and A. mimosae had cracked and broken fibers exposing the fibriliar structures. The difference in the chemical orientation and composition of the fibers might have contributed to the variability in the dissolution behaviour.

Amplification of the STOML3, FREM2, and LHFP Genes Is Associated with Mesenchymal Differentiation in Gliosarcoma

Gliosarcoma is a rare glioblastoma variant characterized by a biphasic tissue pattern with alternating areas that display either glial (glial fibrillary acidic protein-positive) or mesenchymal (reticulin-positive) differentiation. Previous analyses have shown identical genetic alterations in glial and mesenchymal tumor areas, suggesting that gliosarcomas are genetically monoclonal, and mesenchymal differentiation was considered to reflect the elevated genomic instability of glioblastomas. In the present study, we compared genome-wide chromosomal imbalances using array comparative genomic hybridization in glial and mesenchymal tumor areas of 13 gliosarcomas. The patterns of gain and loss were similar, except that the gain at 13q13.3-q14.1 (log(2) ratio >3.0), containing the STOML3, FREM2, and LHFP genes, which was restricted to the mesenchymal tumor area of a gliosarcoma. Further analyses of 64 cases of gliosarcoma using quantitative PCR showed amplification of the STOML3, FREM2, and LHFP genes in 14 (22%), 10 (16%), and 7 (11%) mesenchymal tumor areas, respectively, but not in glial tumor areas. Results of IHC analysis confirmed that overexpression of STOML3 and FREM2 was more extensive in mesenchymal than in glial tumor areas. These results suggest that the mesenchymal components in a small fraction of gliosarcomas may be derived from glial cells with additional genetic alterations.

Co-axial electrospinning with sodium thiocyanate solution for preparing polyacrylonitrile nanofibers

A modified co-axial electrospinning process including electrolyte solution as sheath fluid for preparing high quality polymer nanofibers is investigated. A series of polyacrylonitrile (PAN) nanofibers were fabricated utilizing the modified process with sodium thiocyanate solutions in N, N-dimethylacetamide (DMAc) as sheath fluids. Field-emission scanning electron microscopy results demonstrated that the sheath sodium thiocyanate solutions had significant influence on the quality of PAN nanofibers. High quality PAN nanofibers in terms of fiber diameters and their distributions, surface morphology and structure have been successfully produced. The diameters of nanofibers (D, nm) could be manipulated simply by adjusting the concentrations of sodium thiocyanate (C, mg ml-1) in the sheath fluids with a scaling law of D = 324 C-0.1806. The mechanism about the influence of sodium thiocyanate solutions on the formation of PAN fibers is discussed and it is felt that co-axial electrospinning with electrolyte solution is a facile process for achieving high quality polymer nanofibers.

Separation of m/p‐Aminoacetophenone Using Hydrotropy

The aqueous solubilities of m/p‐aminoacetophenone in different concentrations (0‐3.0 mol/L) of hydrotropes such as diethyl nicotinamide, sodium pseudocumene sulfonate and sodium thiocyanate solutions at different system temperatures (303K to 333K) were studied. The percentage extraction (%E) of m‐ aminoacetophenone from m/p‐aminoacetophenone mixture increases with increase in hydrotrope concentration. A Minimum Hydrotrope Concentration (MHC) in the aqueous phase was required to initiate the significance of the %E of m‐aminoacetophenone. Percentage extraction (%E) is the ratio of moles of m‐aminoacetophenone extracted in presence and absence of a hydrotrope. The sensitivity and feasibility of the proposed process are examined by carrying out solubilization and equilibrium precipitation experiments with the mixtures of various compositions. The effectiveness of hydrotropes was measured in terms of Setschenow constant Ks. The extraction data are also fitted in a polynomial equation as the function of hydrotrope concentration. The solubilized material can be recovered by dilution with water.

Densities, Viscosities, Heat Capacities, and Vapor–Liquid Equilibria of Ammonia + Sodium Thiocyanate Solutions at Several Temperatures

Several thermophysical properties were experimentally measured for the ammonia + sodium thiocyanate mixtures at several temperatures: density from (269.4 to 350.9) K, dynamic viscosity from (269.8 to 369.5) K, and isobaric heat capacity from (304.17 to 364.15) K, all them at a constant pressure of 3 MPa, and vapor–liquid equilibria from (253.1 to 393.1) K. All properties were measured in a range of composition from 0.35 to 0.90 in ammonia mass fraction. The experimental techniques used were a vibrating-tube densimeter, a piston-style viscometer, a heat flux Calvet-type calorimeter, and a static method, respectively. The measured data were correlated as a function of temperature and composition using empirical equations and were compared with literature values.

Highly selective transport of mercury(II) ion through a bulk liquid membrane

In this work carrier-facilitated transport of mercury(II) against its concentration gradient from aqueous 0.04 M hydrochloric acid solution across a liquid membrane containing isopropyl 2-[(isopropoxycarbothiolyl)disulfanyl]ethane thioate (IIDE) as the mobile carrier in chloroform has been investigated. Sodium thiocyanate solution (1.6 M) was the most efficient receiving phase agent among several aqueous reagents tested. Various parameters such as investigated. Under optimum conditions the transport of Hg(II) across the liquid membrane is more than 97% after 2.5 h. The carrier, IIDE, selectively and efficiently could able to transport Hg (II) ions in the presence of other associated metal ions in binary systems.

Preparation and characterization of modified collagen/PAN blending fibers

Graft modification of collagen with acrylonitrile in concentrated aqueous solution of sodium thiocyanate (NaSCN) is developed in this paper. This modification can largely change it’s solubility in water and can be applied in fiber production. Grafting modified collagen is characterized by infrared spectrum and wide angle X-ray diffraction. Wet spinning of PAN fibers containing several content of modified collagen is performed. The tests about these fibers show that breaking strength and sonic orientation decrease as the amount of collagen is raised. The addition of collagen can largely improve the moisture regain of PAN fiber. Micro-appearance of fibers observed under scanning electron microscope (SEM) presents circular cross section and longitudinal grooves on surface, the depth of grooves increases with the increasing draw ratio.

Tecnologia limpa para redução de impacto ambiental do cianeto na mineração de ouro

Esse trabalho discute a aplicação de resinas de troca iônica com matriz poliacrílica para a adsorção de cianocomplexos metálicos. Ensaios em batelada mostraram que as resinas possuem elevada afinidade para os cianocomplexos de ferro e de zinco em relação aos de cobre. Já a eluição, estudada em coluna, indicou que soluções de tiocianato de sódio a 1mol/L são capazes de eluir os ciancomplexos dos três metais. Já soluções de nitrato de sódio, na mesma concentração, não são efetivas para a eluição do cianeto de zinco. Um processo de eluição seletiva é proposto onde os cianocomplexos de cobre e de ferro são eluídos com solução íons NO3-. Em seguida, o zinco é eluído com NaSCN. Ambos eluentes foram capazes de concentrar os cianocomplexos de solução, o que tem efeito benéfico nas etapas subseqüentes de regeneração do cianeto.

Spherulitic Growth of Hen Egg-White Lysozyme Crystals

In protein crystallography, spherulites are considered the result of a failed crystallization experiment. Understanding the formation of these structures may contribute to finding methods to prevent their formation. Here, we present an in situ study on lysozyme spherulites grown from sodium nitrate and sodium thiocyanate solutions, investigating their morphology and growth kinetics using optical microscopy. In a morphodrom, we indicate the conditions at which spherulites form for the lysozyme-nitrate system, showing that liquid-liquid phase separation is not a prerequisite to form sheaflike spherulites and that supersaturation is not the only factor determining their creation. Despite their sheaflike morphology, the spherulites all appear to be formed through heterogeneous nucleation. The spherulites are of a new polymorphic form and are less stable than the monoclinic form. For a single needle, growth kinetics indicate surface processes to be the rate-limiting step during growth, but for an entire spherulite volume, diffusion still plays a role. Spherulites simulated by using a time-dependent, tip-splitting model are found to compare well to experimentally observed spherulites.

超臨界水中におけるチオ硫酸ナトリウムおよびチオシアン酸ナトリウムの分解反応

For the purpose of establishing recycle technology to reduce environmental load, technical and practical development of supercritical water is required. An area of high impact on above purpose is in the recycling of sulfur-containing wastes that are produced in gas clean-up facilities of coal gasification processes. For this purpose, pseudo-first order rate constants were evaluated for thiosulfate ion and thiocyanic ion decomposi-tion in subcritical water and in supercritical water (SCW). Experiments were conducted to decompose so-dium thiosulfate and sodium thiocyanate at 340-400°C and at 25MPa. Thiosulfate ion could be decomposed 100% in 10s reaction time to sulfite, sulfate, and sulfide ions in SCW. Thiocyanic ion could be decomposed 20% in 30s in SCW. When thiosulfate ion was added to sodium thiocyanate solution, however, decomposition rate increased to about 30%. Main reaction pathways and kinetics were determined with a flow reactor. The results show that thiosulfate ion can be completely decomposed in SCW, but that decomposition of thiocyanic ion in SCW requires different conditions, additives, or oxidants.

The Effect of Sodium Thiocyanate on the Corrosion Dissolution Rate of Silver in Thiosemicarbazide Solutions

The effect of thiocyanate on the corrosion dissolution rate of silver in thiosemicarbazide (TSC) ammonium-chloride-bromide solutions was studied by using gravimetry and rotating disc electrode technique. The corrosion dissolution of silver was shown to be preceded by the formation of dithiosemicarbazide molecules due to the oxidation with iron (III) ions. The “second ligand” phenomenon is discussed, which consists in an increase in the corrosion dissolution rate of silver upon adding sodium thiocyanate (STC) to a TSC solution because of the decrease in the adsorption layer thickness. A synergism was discovered in the case of the corrosion dissolution of silver in a solution containing both thiosemicarbazide and sodium thiocyanate. The composition of the adsorption layer formed on a silver electrode and involving silver, sulfur (AgHS and Ag2S), as well as carbon, nitrogen, and oxygen forming the base of adsorption layers, was investigated by means of Auger spectrometry. The kinetic parameters (rate constants and reaction orders) were determined and a mechanism of the corrosion dissolution of silver in TSC, STC, and TSC + STC solutions is proposed.