Nickel Cyanide Complex Research Articles

Mechanism of Ni Removal from Si Materials Using Hydrogen Cyanide Aqueous Solutions

The mechanism of Ni removal from -covered Si specimens by HCN aqueous solutions has been investigated by means of total reflection X-ray fluorescence spectroscopy and X-ray photoelectron spectroscopy measurements. Ni contaminants on the surface are present in the form of SiO-NiOH. The removal mechanism consists of two steps, i.e., an initial fast process followed by a slow process. The rate-determining steps of both the processes are of the first order with respect to the concentration of cyanide ions . The fast and slow processes are tentatively attributed to the removal of SiO-NiOH on terraces and in sub-nanometer pores, respectively. The cleaning ability of the HCN aqueous solutions is much better than ammonia aqueous solutions, because of high reactivity to form nickel-cyanide complex ions and avoidance of readsorption of complex ions in the solutions.

The dependence of sorbed copper and nickel cyanide speciation on ion exchange resin type

The present study investigates the influence of functional group structure and resin matrix on the speciation of copper and nickel cyanides sorbed onto two commercially available ion exchange resins. Batch experiments were performed using synthetic copper and nickel solutions containing 50 and 200 mg/L free cyanide, respectively. Despite the presence of Cu(CN) 3 2− and Cu(CN) 4 3− in solution, it has been found using Raman spectroscopy that the Imac HP555s resin, which has a polystyrene–divinylbenzene matrix, loads predominantly the Cu(CN) 3 2− complex. In contrast, the polyacrylic resin, Amberlite IRA958, sorbed significant amounts of both Cu(CN) 3 2− and Cu(CN) 4 3−. It has been found that the speciation of nickel cyanide sorbed onto each resin was the same. A recently developed mathematical model based on statistical thermodynamic principles has been used as a tool to understand further the equilibrium sorption of copper and nickel cyanide complexes onto each resin studied. A higher sorption energy for nickel compared to copper has been observed for the sorption onto Imac HP555s. In contrast, the sorption energy for copper was found to be higher than for nickel for the polyacrylic resin, Amberlite IRA958. The values of the model parameters obtained were correlated with the chemical features of each complex in solution as well as sorbed onto the resins.

Photocatalytic production of hydrogen from aqueous solution containing CN − as a hole scavenger

The effect of CN − as a hole scavenger on the photocatalytic hydrogen evolution from water was investigated over NiO/TiO 2. A considerable amount of hydrogen was produced in the presence of CN −; the total amount of hydrogen evolved was proportional to the total amount of CN − ion in the solution. Quantum yield was 0.12 at 25°C and 0.32 at 75°C; the increment of quantum yield was about 0.048 per 10°C increase of the reaction temperature. Nickel cyanide complex, Ni(CN) 4 2−, was generated from NiO/TiO 2 in the presence of CN −. The Ni complex decomposed under UV light in the course of hydrogen evolution, resulting in OCN − formation. In addition to producing valuable hydrogen, this complex decomposition under UV light might be a valuable process to treat wastewater containing harmful cyanide complexes. Heat treatment of NiO/TiO 2 catalyst at 700°C was effective for reducing nickel dissolution significantly.

Spectroscopic Characterization of Ethyl Xanthate Oxidation Products and Analysis by Ion Interaction Chromatography

An ion interaction chromatographic separation method, coupled with UV spectroscopic detection, has been developed for the analysis of ethyl xanthate (O-ethyl dithiocarbonate) and its oxidative decomposition products in mineral flotation systems. The effects of the ion-pairing agent (tetrabutylammonium ion), pH modifier (phosphoric acid), and organic modifier (acetonitrile) in the eluant upon the retention characteristics of the ethyl xanthate oxidation products have been determined. The optimized separation procedure has been successfully applied to the analysis of ethyl xanthate and its oxidation products in a nickel-iron sulfide mineral suspension containing a number of other anionic species, including cyanide complexes of nickel and iron, as well as sulfur-oxy anions. The ethyl xanthate oxidation products investigated in this study have been isolated as pure compounds and characterized by UV-visible, FT-IR, and NMR spectroscopies. The UV-visible and FT-IR spectroscopic properties of these species are discussed in terms of the chemical modifications of the thiocarbonate group.

Determination of metallo-cyanides by capillary electrophoresis after concentration on supported liquid membranes

A method for the determination of traces of metallo-cyanide complexes by capillary zone electrophoresis is described. The suitability of preconcentration procedures based on supported liquid membranes in a flow system is investigated. Methyltrioctylammonium chloride in dibutyl ether is used as the active component of the membrane liquid. Due to ion-pairing mechanisms enrichment factors ranging from 50 to 600 can be achieved for cyanide complexes of Fe(II), Fe(III), Ni, Co, Pd, Pt, Cr, Au and Ag. The final capillary electrophoretic separation of the metallo-cyanides is performed off-line with a phosphate-triethanolamine buffer at pH 8.5 as the carrier electrolyte. Its separation selectivity and compatibility with the preconcentration procedure are optimized by addition of hexamethonium bromide, sodium perchlorate and sodium cyanide. Detection limits in the low nmol range can be achieved by direct UV detection at 214 nm. An approach for the analysis of free and labile cyanide is discussed which involves the conversion of these species into the nickel cyanide complex. Applications in the fields of environmental monitoring and industrial process control are possible.

Adsorption of Cu(II) and Ni(II) by pelletized biopolymer

Chitosan and Ca-alginate, derivatives of biopolymer, were separately prepared from crab chitin and algin in pellet form for adsorption of Cu(II) and Ni(II) from aqueous solutions. The capability of these biopolymers was also investigated to remove copper and nickel from aqueous solutions in an immobilization system, along with a comparison made of these biopolymers with other adsorbents. Additionally, the feasibility of alginate/chitosan in pellets to remove nickel ion and nickel cyanide complex from polluted water was investigated. Stabilizing chitosan physically in an alginate support medium was deemed possible, by means of which both free metal and metal cyanide ions could be removed from aqueous solutions in an engineering system. However, the crosslinking reaction during immobilization would result in blocking of some adsorption sites.

Ligand Electronic Effects in Asymmetric Catalysis: Enhanced Enantioselectivity in the Asymmetric Hydrocyanation of Vinylarenes

The enantioselectivity of the nickel-catalyzed, asymmetric hydrocyanation of vinylarenes using glucose- derived, chiral phosphinite ligands, L, increases dramatically when the ligands contain electron-withdrawing P-aryl substituents. The substrate and solvent also strongly influence the enantioselectivity, with the highest ee's (85-91% for 6-methoxy-2-vinylnaphthalene (MVN)) obtained for the hydrocyanation of electron-rich vinylarenes in a nonpolar solvent such as hexane. Mechanistic studies suggest the catalytic cycle consists of an initial HCN oxidative addition or vinylarene coordination to NiL, followed by insertion to form an (q3-benzy1)nickel cyanide complex, and irreversible reductive elimination of the nitrile. A kinetic analysis of the NiL.(COD) (L., P-aryl = 3,5-(CF3)2C6H3) catalyzed hydrocyanation of MVN indicates that as the HCN concentration is increased the catalyst resting state shifts from NiL,(COD) to a complex containing both MVN and HCN, presumably the (q3-benzy1)nickel cyanide intermediate NiL,(q3-CH3CHCloH60CH3)CN. A 31P NMR analysis of the intermediate NiL(MVN) shows little ground state differentiation of the MVN enantiofaces and suggests that the enantioselectivity is determined later in the mechanism. Deuterium labeling studies suggest that electron-withdrawing P-aryl substituents increase the rate of reductive elimination of the product nitrile from the (q3-benzy1)nickel cyanide intermediate and, on this basis, a rationale for the ligand electronic effect is proposed.

Influence of localized anharmonic vibrations on electron paramagnetic resonance spectroscopy.

We have developed a theory that provides an interpretation for the temperature dependence of the g values measured by electron paramagnetic resonance (EPR) spectroscopy, based on the presence of localized low-frequency anharmonic modes. The model is successfully applied to EPR data on paramagnetic nickel cyanide complexes in NaCl host lattice, for both ${\mathit{d}}_{\mathit{z}}^{2}$ and ${\mathit{d}}_{\mathit{x}}^{2}$-${\mathit{y}}^{2}$ ground states.

Electron Paramagnetic Resonance Studies of Irradiated Single Crystals of Cesium Chloride Doped with Nickel Cyanide Complexes

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Electrochemistry of the nickel-cyanide system at mercury electrodes: Part III. The role of intermediate products in the mechanism of ni(cn) 42− electroreduction at mercury electrodes

The results of a normal pulse and linear potential sweep chronocoulometric study on Ni(CN) 4 2− electroreduction in aqueous media are presented. The existence and stability of the intermediates Ni(CN) 4 3− and Ni(CN) 4 − are discussed and described quantitatively. Using a digital simulation technique, the life-time of Ni(CN) 4 3− was found to be of the order of 10 ms, while the upper limit of the Ni(CN) 4 4− life-time appeared to be equal to 1 ms, in the absence of an excess of cyanides. Mechanisms for the chemical decomposition of both intermediates are suggested and compared with other views about the instability of cyanide complexes of nickel in various media.

Binding of metal cyanide complexes to bovine liver rhodanese in the crystalline state.

Bovine liver rhodanese, which catalyzes the transfer of sulfur atoms between a variety of sulfur donor and sulfur acceptor substrates, is inhibited by metal cyanide complexes [Volini, M., Van Sweringen, B., & Chen, F.-Sh. (1978) Arch. Biochem. Biophys. 191, 205-215]. Crystallographic studies are described which reveal the binding mode of four different metal cyanides to bovine liver rhodanese: Na[Au(CN2], K2[Pt(CN)4], K2[Ni(CN)4], and K2[Zn(CN)4]. It appears that these complexes bind at one common site at the entrance of the active site pocket, interacting with the positively charged side chains of Arg-186 and Lys-249. This observation explains the inhibition of rhodanese by this class of compounds. For the platinum and nickel cyanide complexes virtually no other binding sites are observed. The gold complex binds, however, to three additional cysteine residues, thereby also displacing the extra sulfur atom which was bound to the essential Cys-247 in the sulfur-rhodanese complex. The zinc complex binds to completely different additional sites and forms complexes with the side chains of Asp-101 and His-203. Possible reasons for these different binding modes are discussed in terms of the preference for "hard" and "soft" ligands of these four metal ions.

Electrochemical reactions of nickel cyanide complexes

The reduction of the nickel(II) cyanide complex in aqueous solutions, with and without an excess of free cyanide, was studied using the techniques of cyclic chronopotentiometry aided with computer simulation. The mechanism of reduction is an e.c.e. sequence, the chemical rate determining step being a dissociation reaction. Superimposed onto this reaction sequence is a fast equilibrium disproportionation reaction. The rate coefficient of the chemical reaction was determined by fitting working curves, generated by numerical simulation of the reaction sequence, to experimental data. In solutions containing an excess of free cyanide (0.1 mol l −1 KCN +0.1 mol l −1 KCl) the rate coefficient of the chemical reaction is κ c =0.34 s −1 P2 for any equilibrium constant of the disproportionation reaction, K , between 10 and 100. Corresponding values for 0.1 mol l −1 KCl solutions, in absence of free cyanide, are: κ c =0.03 s −1 , and K =10 −3 . P2

Electrochemical reactions of nickel cyanide complexes

The reduction of the nickel(II) cyanide complex in aqueous solutions, with and without an excess of free cyanide, was studied using the techniques of cyclic chronopotentiometry aided with computer simulation. The mechanism of reduction is an e.c.e. sequence, the chemical rate determining step being a dissociation reaction. Superimposed onto this reaction sequence is a fast equilibrium disproportionation reaction. The rate coefficient of the chemical reaction was determined by fitting working curves, generated by numerical simulation of the reaction sequence, to experimental data. In solutions containing an excess of free cyanide (0.1 mol l −1 KCN +0.1 mol l −1 KCl) the rate coefficient of the chemical reaction is κ c=0.34 s −1 P2 for any equilibrium constant of the disproportionation reaction, K, between 10 and 100. Corresponding values for 0.1 mol l −1 KCl solutions, in absence of free cyanide, are: κ c=0.03 s −1, and K=10 −3. P2

Activated carbon adsorption of cyanide complexes and thiocyanate ion from petrochemical wastewaters

Experimental isotherms indicate that thiocyanate and nickel cyanide complex (tetracyanonicklate (II)) adsorb to an equal extent from synthetic and actual waste solutions at loadings below 10 mg/g carbon. Loading of nickel hexammine complex is an order of magnitude less. Adsorption of the divalent nickel cation is strongly pH dependent and is believed to be a chemisorption by precipitation or reaction on the carbon surface. In pure solution, ferrocyanide (hexacyanoferrate (II)) adsorption was comparable to that of thiocyanate or nickelocyanide, but adsorption from the waste liquor tested was negligible. This difference may be due to solvation of ferrocyanide with methanol in the wastewater to form a species with entirely different adsorption characteristics. Chemical oxygen demand ( COD) values were obtained for several of the pure materials (SCN −, 1.1; Fe(CN) 6 −4, 0.5; Ni(CN) 4 −2, 0.4 mg COD mg ion) and the wastewater to monitor adsorption of organic background materials.

Cyanide complexes of nickel(II) with hybrid bidentate ligands containing phosphorus and nitrogen or sulfur donor atoms

Cyanide complexes of nickel(II) with hybrid bidentate ligands containing phosphorus and nitrogen or sulfur donor atoms

Catalytic effect of nickel cyanide complex and skeletal nickel on addition of hydrogen to 6-methyl-3,5-heptadien-2-ol

1. The complex cyanide K4Ni2(CN)6 catalyzes the hydrogenation of 6-methyl-3,5-heptadien-2-ol, while the divalent nickel cyanide K2Ni(CN)4 is inactive. 2. In the presence of the Ni cyanide complex at CN−/Ni < 5, the same as on skeletal Ni, the dienol is hydrogenated predominantly at the unsaturated bond in the 3,4 position with the formation of 5-hepten-2-ol. At CN−/Ni=5 the hydrogen adds to the dienol at the 5,6 C=C bond. 3. In contrast to skeletal Ni, on Ni cyanide catalyst the formed 5-hepten-2-ol is not reduced further and can be obtained in high yield.

Isomerization and Hydrogenation of Dimethyl Maleate and 1,5-Cyclooctadiene by Nickel Cyanide Complex

Isomerization and Hydrogenation of Dimethyl Maleate and 1,5-Cyclooctadiene by Nickel Cyanide Complex

Hydrogenation, Hydrogenolysis, or Isomerization of Dienes and Monoenes Catalyzed by the Nickel Cyanide Complex

Hydrogenation, Hydrogenolysis, or Isomerization of Dienes and Monoenes Catalyzed by the Nickel Cyanide Complex

809. A magnetic investigation of cyanide complexes of nickel(II) in solution

809. A magnetic investigation of cyanide complexes of nickel(II) in solution

67. Structure of molecular compounds. Part X. Crystal structure of the compound of benzene with an ammonia–nickel cyanide complex

67. Structure of molecular compounds. Part X. Crystal structure of the compound of benzene with an ammonia–nickel cyanide complex