Showing papers on "Cyanide published in 2003"
TL;DR: The present review describes the advances in the use of biological treatment for the destruction of cyanide in gold mill effluents.
265 citations
TL;DR: Mechanistic data obtained thus far point to a cooperative bimetallic mechanism for nucleophile and electrophile activation.
Abstract: (Salen)Al−Cl complex 1a catalyzes the asymmetric conjugate addition of hydrogen cyanide to α,β-unsaturated imides in high yields and enantioselectivities. The cyanide adducts can readily be converted into a variety of useful chiral building blocks, including α-substituted-β-amino acids and β-substituted-γ-aminobutyric acids. Mechanistic data obtained thus far point to a cooperative bimetallic mechanism for nucleophile and electrophile activation.
231 citations
TL;DR: Studies of the oxidative addition of aryl halides to palladium triphenylphosphine complexes in the presence and absence of amines suggest that the co-catalyst is capable of preventing catalyst deactivation caused by the presence of excess cyanide ions in solution.
Abstract: The development of new palladium catalysts for the cyanation of various aryl and heteroaryl chlorides is described. The combination of amine co-catalysts with chelating phosphine ligands, for example, 1,4-bis(diphenylphosphino)butane (dppb) or 1,5-bis(diphenylphosphino)pentane (dpppe), allows an efficient cyanation of chloroarenes with simple potassium cyanide. General palladium-catalyzed cyanation of nonactivated and deactivated chloroarenes is possible for the first time. Studies of the oxidative addition of aryl halides to palladium triphenylphosphine complexes in the presence and absence of amines suggest that the co-catalyst is capable of preventing catalyst deactivation caused by the presence of excess cyanide ions in solution.
171 citations
TL;DR: This paper presents an overview of the destruction of cyanide in mining related solutions by microbial processes and demonstrates how full-scale bacterial processes have been used effectively for many years in commercial applications in North America.
Abstract: Microbial destruction of cyanide and its related compounds is one of the most important biotechnologies to emerge in the last two decades for treating process and tailings solutions at precious metals mining operations. Hundreds of plant and microbial species (bacteria, fungi and algae) can detoxify cyanide quickly to environmentally acceptable levels and into less harmful by-products. Full-scale bacterial processes have been used effectively for many years in commercial applications in North America. Several species of bacteria can convert cyanide under both aerobic and anaerobic conditions using it as a primary source of nitrogen and carbon. Other organisms are capable of oxidizing the cyanide related compounds of thiocyanate and ammonia under varying conditions of pH, temperature, nutrient levels, oxygen, and metal concentrations. This paper presents an overview of the destruction of cyanide in mining related solutions by microbial processes.
170 citations
TL;DR: In this paper, surface modification of citrate-reduced gold nanoparticles with 2-mercaptosuccinic acid (MSA) was carried out in the aqueous phase.
Abstract: Surface modification of citrate-reduced gold nanoparticles with 2-mercaptosuccinic acid (MSA) was carried out in the aqueous phase. This provides a way to obtain carboxylic acid functionalized gold nanoparticles with diameter above 10 nm. The influence of the protecting MSA layer on the behavior of the modified gold nanoparticles in comparison with that of the traditional citrate-reduced gold colloid was evaluated by HCl titration, cyanide etching, and seeded growth tests. The modified gold nanoparticles show an improved stability against pH changes and cyanide etching. They do show further growth, which appears to be more homogeneous than for the unmodified particles.
155 citations
TL;DR: A convergent diastereo- and enantioselective total synthesis of anti-HIV agent chloropeptin I is reported, performed in the presence of four unprotected phenols, two of which reside on dichlorophenylglycines.
Abstract: A convergent diastereo- and enantioselective total synthesis of anti-HIV agent chloropeptin I is reported. Important features of the total synthesis include: (1) the use of Ti-catalyzed cyanide addition to imines to prepare a requisite amino acid moiety, (2) the discovery of the positive effect of MeOH in the Cu-mediated biaryl ether formation to afford one of the two macrocyclic peptide moieties, and (3) the discovery of the positive influence of collidine in the diastereoselective Pd-mediated cross-coupling to result in efficient formation of another macrocycle within this medicinally important molecule. This key step is performed in the presence of four unprotected phenols, two of which reside on dichlorophenylglycines.
150 citations
147 citations
TL;DR: In this paper, a comparative study of four different polyamide membranes that were tested for their ability to reduce the concentrations of pollutants in a synthetic effluent stream containing acrylnitrile and three inorganic species (sulphate, ammonium and cyanide).
146 citations
TL;DR: Results indicated that biological treatment with Pseudomonas sp.
139 citations
TL;DR: Results from this study show that the processes of cyanide biodegradation and ammonia production by resting cells occurred simultaneously, which suggests that the utilization of cyanides as nitrogen source by K. oxytoca might proceed using ammonia as an assimilatory substrate.
124 citations
TL;DR: In this article, a non-linear least-squares curve-fitting for a titration curve was developed to establish a standard solution for cyanide ions, and the combined standard uncertainty for a concentration of a 1000mg/kg−1 cyanide solution by this method was 0.079%.
TL;DR: In this paper, a mesoporous silica SBA-15 functionalized with a high density of carboxylate groups has been prepared by a one-pot synthesis of a cyano-functionalized SBA15 followed by treatment with sulfuric acid that removes the template and hydrolyses the cyanide group in one step.
TL;DR: Several methods for the treatment of cyanide solutions are described, and in all cases excellent performance were observed as measured by the extent and of the destruction.
Journal Article•
TL;DR: In suspected cyanide-poisoned patients, it is recommended the use of hydroxocobalamin as first-line antidote, owing to its safety, and in massive cyanide poisoning, continuous infusion of sodium thiosulfate should be associated.
Abstract: Cyanide poisoning may result from different exposures: residential fires, industrial accidents, drug and plant intoxication. Clinical features include coma, respiratory arrest and cardiovascular collapse. The biological hallmark is lactic acidosis. A plasma lactate concentration > or = 10 mmol/L in fire victims without severe burns and > or = 8 mmol/L in pure cyanide poisoned patients is a sensitive and specific indicator of cyanide intoxication. Many antidotes are available and efficient. However, therapeutic strategies are still debated. Our objective was to compare conventional treatments to hydroxocobalamin. This article reviews the literature on cyanide poisoning treatment. Conventional treatment of cyanide poisoning includes decontamination, supportive and specific treatment. Decontamination should be adapted to the route of poisoning and never postpone supportive treatment. Basic life support includes immediate administration of high flow of oxygen, airway protection and cardiopulmonary resuscitation. Advanced life support includes mechanical ventilation, catecholamine and sodium bicarbonate infusion. Supportive treatment is efficient but does not modify the time course or the body burden of cyanide. Numerous antidotes are available. Oxygen counteracts efficiently cyanide action at the mitochondrial level. Sodium thiosulfate, methemoglobin forming agents and cobalt compounds act efficiently by complexing or transforming cyanide into non-toxic stable derivatives. However, regarding the main clinical condition of cyanide poisoning, i.e. smoke inhalation, we should take into account not only the efficiency of antidotes but also their safety. Sodium thiosulfate is both efficient and safe, but acts with delay. Methemoglobin-forming agents are potent, but due to the transformation of hemoglobin into methemoglobin, they impair tissue delivery of oxygen. Experimental data showed increased mortality in carbon monoxide- and cyanide-poisoned rats treated with these agents. Cobalt EDTA and hydroxocobalamin are efficient and act immediately. Cobalt EDTA is more potent on a molar basis; however, numerous side effects limit its use to evidenced cyanide poisoning. In a prospective study, hydroxocobalamin appeared safe in fire victims with or without cyanide poisoning. The only reported side effect was a red coloration of skin and urine. In conclusion, antidotes are beneficial in cyanide poisoning. In suspected cyanide-poisoned patients, we recommend the use of hydroxocobalamin as first-line antidote, owing to its safety. In massive cyanide poisoning, due to the limited potency of hydroxocobalamin, continuous infusion of sodium thiosulfate should be associated.
TL;DR: The data suggest that phytoremediation of cyanide may be possible and ecologically safe due to the lack of cyanine bioaccumulation in aerial tissues, and ferrocyanide uptake and metabolism is suggestive.
Abstract: Cyanide compounds are contaminants of growing importance that could be remediated biologically via phytoremediation, provided the plants possess suitable mechanisms for managing these pollutants without toxicity. The transport and metabolism of two cyanide compounds, potassium cyanide and potassium ferrocyanide, by willow (Salix eriocephala L. var. Michaux) were compared using a hydroponic system that preserved cyanide speciation and solubility. The cyanide compounds were labelled with 15N to quantify transport while a novel tissue extraction procedure was used to relate tissue 15N to cyanide content and speciation. These analyses revealed that although little free cyanide was detected in the aerial tissues of plants exposed to either of these two cyanide compounds, significant enrichments in 15N were observed, suggesting transport and subsequent metabolism of free cyanide as well as ferrocyanide. The results for ferrocyanide are of interest because this molecule is resistant to microbial degradation and if oxidized to ferricyanide is purportedly membrane impermeable. Nevertheless, these results and mass balance calculations for tissue 15N and solution cyanide confirming 100% recovery for the added ferrocyanide are suggestive of ferrocyanide uptake and metabolism. This study provides new information describing the biological transport and metabolism of these two cyanide compounds in plants. Moreover, the data also suggest that phytoremediation of cyanide may be possible and ecologically safe due to the lack of cyanide bioaccumulation in aerial tissues.
TL;DR: In this article, the authors investigated the kinetics and mechanism of the photocatalytic oxidation of cyanide in the presence of titanium dioxide catalyst and found that cyanide is oxidised via a pure heterogeneous pathway.
Abstract: The kinetics and mechanism of the photocatalytic oxidation of cyanide in the presence titanium dioxide catalyst were investigated in this study. By displacing the surface hydroxyl groups on the surface of titanium dioxide with fluoride ions, it was deduced that cyanide is oxidised via a pure heterogeneous pathway, i.e. oxidised by the holes trapped at the surface hydroxyl groups TiO . The quantum efficiency of the photocatalytic oxidation was found to be low (ca. 0.1–0.2%) and this was mainly due to (1) the low adsorption of cyanide ions onto the titanium dioxide surface, (2) the absence of homogenous reaction between cyanide ions and diffused hydroxyl radicals, and (3) the high electron hole recombination rate within the titanium dioxide photocatalyst. A kinetic model was developed to describe the mechanism involved in the photocatalytic oxidation of cyanide.
TL;DR: The present results appear to explain in part some of the curious biomedical observations reported by other laboratories; for example, the kidneys of cyanide poisoning victims surprisingly exhibit no significant irreversible damage, and lethal doses of potassium cyanide are able to inhibit cytochrome c oxidase activity by only ∼50% in brain mitochondria.
TL;DR: In this article, the chiral 3,3'-dimethyl-2,2'-biquinoline N,N'-dioxide Lewis base promoters have been developed and have for the first time been applied to the asymmetric synthesis of alpha-amino nitriles through cyanide addition to aldimines.
TL;DR: In the presence of MS 4A in DMSO, cyanobenzoylation of various aldehydes with benzoyl cyanide proceeded very smoothly to give the corresponding cyanohydrin benzoates in high to excellent yields without an acid or a base.
TL;DR: In this paper, double metal cyanide (DMC) complexes based on Zn3[Co(CN)6]2 were prepared using different zinc salts and complexing agents and they were characterized by elemental analysis, IR and XRD.
Abstract: Double metal cyanide (DMC) complexes based on Zn3[Co(CN)6]2 were prepared using different zinc salts and complexing agents and They were characterized by elemental analysis, IR and XRD. The catalytic properties of DMC complexes were determined in polymerization of propylene oxide. Great differences in morphology of DMC complexes was were correlated with preparation route as well as with the kind of zinc salts employed. The catalytic activity was strongly dependent on the morphology of DMC complexes and composition of catalysts. The study revealed that the amorphous catalyst made from ZnCl2 and t-BuOH had the highest activity (up to 26 kg polymer/g catalyst). The DMC catalyst was non-stoichiometric. Polymerization of propylene oxide (PO) catalyzed by DMC proceeded in a controlled manner. The molecular weight of each polymer was controlled by the monomer/initiator ratio, the values of molecular weight distribution (MWD) were in the range of 1.23–1.48. The polymer has an atactic structure and a head-to-tail regiosequance.
TL;DR: The hypothesis that the metabolism of cyanide and its main metabolite, thiocyanate, is species-linked is supported, with the goat being more sensitive to the toxic effects of cyanides/thiOCyanate.
Abstract: The aim of the present study was to determine the effect of the species on the toxicokinetics of cyanide and its main metabolite, thiocyanate. Forty-two rats, six pigs and six goats were dosed orally with 3.0 mg KCN/kg body weight, and cyanide and thiocyanate concentrations in blood were measured within 24 h. After the single oral dose, KCN was rapidly absorbed by rats and goats, with a time of peak concentration (T
max) of 15 min. The maximum plasma concentration (C
max) of cyanide was observed in goats (93.5 µmol/l), whereas the C
max of thiocyanate was higher in rats (58.1 µmol/l). The elimination half-life (t
1/2) and volume of distribution (Vdarea) of both cyanide and thiocyanate were higher in goats (1.28 and 13.9 h, and 0.41 and 1.76 l/kg, respectively). Whereas the area under the curve (AUC) of cyanide was significantly higher in goats (234.6 µmol.l/h), the AUC of thiocyanate was higher in rats (846.5 µmol.l/h). In conclusion, the results of the present study support the hypothesis that the metabolism of cyanide and its main metabolite, thiocyanate, is species-linked, with the goat being more sensitive to the toxic effects of cyanide/thiocyanate.
TL;DR: In this article, vanadia-silica xerogel was used as photocatalyst for photodegradation of cyanide from solution, the photoactivity of V 2 O 5 -SiO 2 was 98.5% at surface area 310m 2 /g.
Abstract: Cyanides used in some chemical synthesis and metallurgical processes are highly toxic and must be destroyed or removed from wastewaters prior to discharge. Vanadia–silica xerogel as photocatalyst has been prepared via sol–gel technique by dissolving ammonium metavanadate (AMV) and tetraethylorthosilicate (TEOS) and applied for photodegradation of cyanide from solution. The optimum conditions for preparation of V 2 O 5 –SiO 2 gel is 1:1 of vanadium/silicon (V/Si) molar ratio and TEOS:H 2 O:C 2 H 5 OH is 1:8:4 mole ratios at 30 °C for 10 min, at these conditions the photoactivity of V 2 O 5 –SiO 2 was 98.5% at surface area 310 m 2 /g. The calculated activation energy of the reaction between AMV and TEOS was found to be −10.81 kcal/g. The optimum loading of vanadia–silica xerogel was 0.166 wt.% that give 98.5% cyanide removal efficiency after 3 h. The overall kinetics of photodegradation of cyanide using vanadia–silica photocatalyst was found to be of first order.
TL;DR: A methodology for the microwave-promoted conversion of triflates to the corresponding nitriles by using 8% equiv of Pd(Ph(3)P)(4) as the catalyst and 2.0 equiv as the cyanide source has been developed and is highly efficient for the preparation of 3-cyano-3-desoxy-10-ketomorphinans.
TL;DR: The anionic ligand bound to zinc in these derivatives, which serve as an anionic polymerization initiator, was shown to be central to the catalytic copolymerization reaction of CO(2)/epoxide to provide polycarbonates and cyclic carbonates.
Abstract: Several synthetic approaches for the preparation of double metal cyanide (DMC) derivatives of iron(II) and zinc(II) are described. These include (1) metathesis reactions of ZnCl2 or ZnI2 with KCpFe(CN)2CO in aqueous solution, (2) reactions of KCpFe(CN)2CO and its phosphine-substituted analogues with Zn(CH3CN)4(BF4)2 and subsequent displacement of acetonitrile at the zinc centers by the addition of a neutral (phosphine) or anionic (phenoxide) ligand, and (3) reactions of the protonated HCpFe(CN)2(phosphine) complexes with Zn(N(SiMe3)2)2, followed by the addition of phenols. All structures are based on a diamond-shaped planar arrangement of the Fe2(CN)4Zn2 core with various appended ligands at the metal sites. Although attempts to replace the iodide ligands in [CpFe(μ-CN)2PPh3ZnI(THF)]2 with acetate using silver acetate failed, two novel cationic mixed-metal cyanide salts based on the [CpFe(PPh3)(μ-CN)2Zn(NC5H5)]22+ framework were isolated from pyridine solution and their structures were defined by X-ray cr...
TL;DR: In this article, the effect of oxygen addition on the kinetics of gold leaching in thiosulfate solutions containing oxygen was studied. But, the effect was not observed when oxygen is excluded from the solution, as experiments performed with the addition of disulfite also resulted in very low gold oxidation rates.
TL;DR: In this article, the use of the electrodialysis technique for the treatment of a synthetic wastewater containing approximately 0.0089 mol L-1 cadmium and 0.081 mol L -1 cyanide was studied using a five-compartment cell.
Abstract: The discharge of galvanic industry wastewaters containing heavy metals and cyanide is one of the largest sources of water pollution. The use of the electrodialysis technique for the treatment of a synthetic wastewater containing approximately 0.0089 mol L-1 cadmium and 0.081 mol L-1 cyanide was studied using a five-compartment electrodialysis cell. The results demonstrate that the removal of cadmium and cyanide depends on the applied current density and it is limited by the precipitation of cadmium on the cation-exchange membrane in the diluate central cell compartment.
TL;DR: In this article, the initial stages of metal deposition from a cyanide electrolyte (pH 14) were investigated using conventional electrochemical techniques combined with AFM and SEM, and relevant kinetic parameters were obtained from analysis of current transients on the basis of existing models for electrochemical nucleation and diffusion controlled growth.
TL;DR: The ternary cyanide complex of P450cam and camphor was determined to 1.8A resolution and found to be identical with the structure of the active oxygen complex, and Notably, cyanide binds in a bent mode and induces the active conformation that is characterized by the presence of two water molecules and a flip of the carbonyl of the conserved Asp251.
TL;DR: In this paper, it has been shown that the thiosulfate leach reaction in the presence of copper(II) and oxygen is very complex with the rates of copper-II and oxygen-based leaching being significantly faster than those in the absence of oxygen.
TL;DR: After fullerenes are heated in the presence of a noble gas or an unreactive molecule at 650 degrees C and 3000 atm pressure, a small fraction of the fullerene molecules contain the atom or molecule.
Abstract: After fullerenes are heated in the presence of a noble gas or an unreactive molecule at 650 °C and 3000 atm pressure, a small fraction of the fullerene molecules contain the atom or molecule. The incorporation fraction is greatly enhanced by adding potassium cyanide to the reaction mixture. The details of the preparation are described here.