Cyanide Ion Concentration Research Articles

Mode of Action of Cyanohydrins in Insects

Fumigation toxicity of hydrogen cyanide (HCN) was compared to very potent natural and synthetic cyanohydrins against the house fly and the lesser grain borer. The concentration of cyanide ion was much higher in the house flies exposed to HCN fumigation than in the flies that were exposed to cyanohydrin fumigation or to topical application of cyanohydrins. The results indicate that the toxic action of cyanohydrins in insects is due to the combined effects of cyanide ion, the aldehyde or ketone produced by the decomposition of the cyanohydrin, and possibly the intact cyanohydrin molecule. © Presticide Science Society of Japan

The effect of cyanide and lead ions on the cementation rate, stoichiometry and morphology of silver in cementation from cyanide solutions with zinc powder

The cementation of silver on zinc powder from solutions with a wide concentration range of cyanide has been investigated in the absence and presence of lead ions through stirred reactor batch tests and scanning electron microscopy studies on the cementation product. The concentration of cyanide ions affected the morphology of the product, the nature of cementation reaction and the cementation kinetics. Three cyanide-dependent concentration regimes have been identified: a low cyanide concentration regime in which silver cementation followed an ion-exchange type reaction taking place at the zinc/aqueous solution interface, and the silver deposited around the zinc particle in a uniform growth; a high cyanide concentration regime, as in plant practices, in which the cementation of silver followed an overall chemical reaction involving the evolution of hydrogen and a one-to-one molar silver-to-zinc stoichiometry (In this regime, both the anodic oxidation and the cathodic reduction reactions occurred at distinct interfaces and the silver deposited in a dense-branching morphology.), and an intermediate cyanide concentration regime which is a transition between the two previous regimes. In the low and intermediate regimes, lead and cyanide ions did not affect the morphology of the cemented silver, but increased the silver cementation kinetics owing to Zn(OH) 2 instability. Within the high cyanide concentration regime, lead ions did not appreciably change the cementation kinetics. They modified the pattern of the silver deposit from a dense-branching to a dendritic morphology.

Kinetics and mechanism of formation of the platinum-thallium bond: the [(CN)(5)Pt-Tl(CN)(3)](3)(-) complex.

Formation kinetics of the metal-metal bonded [(CN)(5)PtTl(CN)(3)](3)(-) complex from Pt(CN)(4)(2)(-) and Tl(CN)(4)(-) has been studied in the pH range of 5-10, using standard mix-and-measure spectrophotometric technique at pH 5-8 and stopped-flow method at pH > 8. The overall order of the reaction, Pt(CN)(4)(2)(-) + Tl(CN)(4)(-) right harpoon over left harpoon [(CN)(5)PtTl(CN)(3)](3)(-), is 2 in the slightly acidic region and 3 in the alkaline region, which means first order for the two reactants in both cases and also for CN(-) at high pH. The two-term rate law corresponds to two different pathways via the Tl(CN)(3) and Tl(CN)(4)(-) complexes in acidic and alkaline solution, respectively. The two complexes are in fast equilibrium, and their actual concentration ratio is controlled by the concentration of free cyanide ion. The following expression was derived for the pseudo-first-order rate constant of the overall reaction: k(obs) = (k(1)(a)[Tl(CN)(4)(-) + (k(1)(a)/K(f)))(1/(1 + K(p)[H(+)]))[CN(-)](free) + k(1)(b)[Tl(CN)(4)(-)] + (k(1)(b)/K(f)), where k(1)(a) and k(1)(b) are the forward rate constants for the alkaline and slightly acidic paths, K(f) is the stability constant of [(CN)(5)PtTl(CN)(3)](3)(-), and K(p) is the protonation constant of cyanide ion. k(1)(a) = 143 +/- 13 M(-)(2) s(-)(1), k(1)(b) = 0.056 +/- 0.004 M(-)(1) s(-)(1), K(f) = 250 +/- 54 M(-)(1), and log K(p) = 9.15 +/- 0.05 (I = 1 M NaClO(4), T = 298 K). Two possible mechanisms were postulated for the overall reaction in both pH regions, which include a metal-metal bond formation step and the coordination of the axial cyanide ion to the platinum center. The alternative mechanisms are different in the sequence of these steps.

The mechanism of electrode process in the system silver/silver cyanide complexes

The electrode's surface inhomogeneity was taken into account studying the mechanism of process. The effect of CN − adsorption and partial surface coverage was investigated by electrochemical fast Fourier transform (FFT) impedance spectroscopy (0.03–3900 Hz). The isopotential solutions ( E 0=−0.350 V) as well as solutions containing constant silver cyanide complex concentration (0.05 M) and different free cyanide ion concentrations (from 0.01 to 1.0 M) were studied. The exchange current density, re-calculated for only active area, gives electrochemical reaction order ( R CN=1.8 for α=0.5, and R CN=2 for α=0.6) which is independent from CN − concentration and from the composition of complexes prevailing in the bulk of electrolyte. The value of R CN close to 2, obtained in a series of isopotential solutions confirms that in all cases the complex ions Ag(CN) 2 − take direct part in the charge transfer step.

Enhance Cyanide Recovery by UsingAir‐Sparged Hydrocyclone

AbstractHuman health and environmental concerns dictate that industrial processes be improved or replaced. Recovery or recycling is an important activity that allows cyanide residue from the industrial processes to be re‐used, reducing its production cost and disposal problems. In this regard, the air‐sparged hydrocyclone (ASH) has been used as a reactor for the treatment of cyanide solutions for cyanide recycling by acidification/volatilization using the Mexican modification of the Mills‐Crowe process. Aqueous cyanide‐ion concentration can be reduced from 250 ppm to below 20 ppm in the ASH with recoveries greater than 80 % in a single stage.

Specific membrane transport of silver and copper as Ag(CN) 32− and Cu(CN) 43− ions through a supported liquid membrane using K +-crown ether as a carrier

Facilitated transport of silver and copper from cyanide solutions through a supported liquid membrane (SLM) containing K +-crown ether as a carrier is described. The SLM used is a thin porous polypropylene (Celgard 2500, 2400) membrane impregnated with dibenzo-18-crown-6 (DB18C6), diaza-18-crown-6 (DA18C6), hexathia-18- crown-6 (HT18C6) and hexaaza-18-crown-6 (HA18C6) dissolved in a mixture of ethanol/chloroform (v/v). K − +-crown ether showed a high efficiency to carry silver and copper as Ag(CN) 3 2− and Cu(CN) 4 3− species through the SLM. However, the mass flux of both silver and copper ions decreases when concentration of cyanide ions in the feed phase increases due to the difference in stability of the complexes M( CN) n n− ( M= Ag, Cu) when n increases from 2 to 4. This was related to the partition of the species in the aqueous phase using a theoretical model.

Spectrophotometric determination of cyanide ion in waste water using copper(II) and N,N-diethyl-p-phenylenediamine

Spectrophotometric determination of cyanide ions in water was studied using Cu(II) ions and N,N-diethyl-p-phenylenediamine(DPD). A cyanide ions reacted with Cu(I) ions, producing a stable complex, CuCN (s.p.=3.5×10−20). Then, Cu(II) ions were reduced to Cu(I) ions with DPD owing to a decrease of Cu(I) ions. The concentaration of the coloring oxidant of DPD was proportional to the concentration of cyanide ions between 0.1 and 2.0 mg CN− l−1. The coloring development by this method was attained in one minute. A copper formate was the most suitable copper salt for a reaction in copper chloride, copper sulfate and copper acetate because of its highest sensitivity and lowest blank. The influences of co-existing metal ions [(Cr(III): 40 mg l−1), (Ag(I): 0.3 mg l−1), (Fe(II): 0.4 mg l−1), (Fe(III): 3 mg l−1), (Ni(II): 0.16 mg l−1), (Co(II): 0.01 mg l−1) and (Zn(II): 100 mg l−1)] were less than 10% for 0.4 mg l−1 of cyanide ions. No influences of co-existing metals on the linearity of calibration curve were observed. This method is very simple, and can be used for the pre-detection of cyanide ions in waste water.

Construction of a sensor for the determination of cyanide in industrial effluents: a method based on quartz crystal microbalance

It is the aim of current investigation to develop a method based on quartz crystal microbalance (QCM) system for the detection of cyanide in industrial effluents. A thin layer of nickel was coated on the top of the quartz electrodes. The composite electrode was then used to determine cyanide in solutions. Nickel was reacted with cyanide ions in the presence of oxygen after soaking in cyanide solution. This caused a decrease in electrode mass which is responsible for the frequency shift. The results showed that the corresponding frequency shift was linearly related to the concentration of cyanide ions in solution. Using this method the cyanide ions can be measured in the range of 0–10 ppm. Effect of various factors including solution pH, Ni thickness and the interfering effect of a number of anions and cations was also investigated. No major interference was involved in the performance of the sensor. The lower limit of detection (LLD) of 0.28 ppm obtained for the sensor. A comparative study on the samples of effluent from an electroplating plant revealed no significant difference between ASTM method and the proposed QCM techniques.

Effect of Potassium Cyanide on Electrodeposition of Zinc from Zincate Solutions

With the use of cyclic voltammetry, chronopotentiometry, and a rotating disk electrode, potassium cyanide introduced into tetrahydroxozincate solution is shown to inhibit the process and decrease the limiting current of zinc electrodeposition. An increase in the concentration of cyanide ions in the solution enhances the effect. The impediment to the cathodic process by cyanide is not of a diffusion nature and considerably disturbs the diffusion character of the limiting current. During the aging the zincate solution containing cyanide ions, the deposition kinetics and the quality of zincate deposits change. All results considered, make us conclude that the function of cyanide ions is not to form electroinactive zinc complexes, but to change the properties of difficultly soluble compounds formed on the cathode's interface in the course of electrolysis.

A new spectrophotometric method for the toxicological diagnosis of cyanide poisoning.

A spectrophotometric method for the determination of hydrogen cyanide in biological fluids based on the release of cyanide ion by the addition of a strong acid and its subsequent specific reaction with hydroxocobalamin to give cyanocobalamin is proposed. The release of cyanide ion is accelerated by aeration with a stream of an inert gas (nitrogen) that carries it into the hydroxocobalamin solution. Although the in vitro reaction develops to completion within 20 min, reproducible quantitation in biological media takes 45 min. The cyanocobalamin formed is quantitated by second-derivative visible spectrophotometry from the absorbance difference between 333 and 361 nm, the measured signal being proportional to the cyanide ion concentration in the sample.

Potential use of carbon felt in gold hydrometallurgy

The use of carbon felt as a three-dimensional electrode appears to be very promising for the recovery of heavy metals, and toxic compounds removal from dilute solutions, considering its favourable physico-chemical properties: high specific surface area, good fluid permeability and compressibility, chemical inertness and good electrical conductivity. This work presents the contribution of the carbon felt electrode in two different steps of the gold cyanidation recovery process • - firstly as a cathode for the electrowinning of gold solution obtained after the elution of loaded carbon; • - secondly as an anode for the electro-oxidation of cyanide ions present at low concentration (200–300mg/l) in waste streams. In the first case, more than 10 kg of gold per m 2 of felt (2000 kg of gold per m 3 of felt) can be loaded at 400 A/m 2 from dilute gold solutions (30 mg/l Au) with classic Faradic yields (6–12 %) and high overall extraction efficiency (>90 %). The felt homogeneously loaded with adhesive gold deposit can be smelted in an electric furnace without addition of fluxes since the carbon felt decomposes in gaseous products without formation of ashes. In the second case, the cyanide ion concentration can be lowered to as low as 10 mg/l by electro-oxidation to cyanate form (CNO −) at 400 A/m 2 in the anodic compartment of a divided cell. The presence of copper ion significantly improves the current efficiency of this electro-oxidation and sharply reduces the oxidation of the carbon felt. Copper ions accelerate the oxidation rate of free cyanide ions through the formation of easily oxidizable complexes owing to a mechanism in which the Cull Cu ll redox couple acts as an electron transfer mediator.

Adsorption of Copper Cyanide on Chemically Active Adsorbents

An inorganic chemically active adsorbent (ICAA), SG(1)-TEPA (tetraethylenepentaamine)-propyl, is developed for removal, recovery, and recycling of copper cyanide from industrial waste streams. Equilibrium studies are executed to determine and model adsorption of the copper cyanide complex from aqueous solutions in a batch and packed column. It appears that adsorption is dependent on anionic copper cyanide species and the basicity of the ligand. Aqueous-phase equilibrium modeling shows that monovalent (Cu(CN)2-), divalent (Cu(CN)32-), and trivalent (Cu(CN)43-) species of copper cyanide exist in the solution, depending on the pH and the concentration of total cyanide ions. Batch adsorption data are modeled using a modified multicomponent Langmuir isotherm which includes aqueous-phase speciation and basicity of the SG(1)-TEPA-propyl. This developed model is applied with a mass balance equation to describe the adsorption of copper cyanide complexes in a packed column.

Kinetics of electrochemical processes in the system: silver/cyanide solutions

The kinetics and mechanism of electrode reactions of silver in cyanide solutions have been studied. The results of these studies have been compared with the data on cyanide ion adsorption on silver. The values of derivatives of the current with respect to the concentrations of cyanide ions and silver have been obtained both from the direct measurements and on the basis of model calculations taking account of the influence of cyanide and complex ion adsorption and the structure of electric double layers on the rate of electrochemical reaction. Candidates for the limiting stage have been considered.

Determinations of Carboxyhemoglobin, Methemoglobin, and Cyanide in 70 Blood Samples from Victims Suspected of Carbon Monoxide Poisoning.

Carboxyhemoglobin (COHb), methemoglobin (MetHb), and a cyanide ion (CN-) concentrations in the blood taken from 70 victims by fire and auto exhausts were simultaneously determined by our previously described colorimetries using a gas phase mini-circulation apparatus. The simultaneous determination of one sample was performed within 45 min. There existed a difference of hemoglobin derivatives and CN- levels among the each source of carbon monoxide poisoning. In the case of low COHb concentration in blood samples taken from the victims by auto exhausts, it should be considered that the causes of death of the victims might be owing to the combination of carbon monoxide poisoning and hypoxic hypoxia. When MetHb concentration is used as an indicator for vital reactions, the causes of death should be carefully determined because MetHb concentration in the blood is varied by heating the cadaver died by fire or storing even at 4°C. Since CN- was detected from most of the samples and the lethal level of CN- was determined from the some of the samples, CN- concentration in blood samples taken from the fire victims should be certainly determined. From the results, it was shown that the determination of COHb, MetHb, and CN- concentrations was very important for investigating the causes of death of suicides and victims by fire and auto exhausts, and the simultaneous methods used in this study were available for the practice of forensic science.

Cyanide ion minisensor based on methemoglobin incorporated in metal supported self-assembled bilayer lipid membranes and modified with platelet-activating factor

The present paper reports the development of an electrochemical minisensor for the detection of cyanide ions based on methemoglobin, which is incorporated into self-assembled bilayer lipid membranes (s-BLMs) on a metal support. The presence of cyanide in solution was found to modulate the ion permeability of BLMs containing methemoglobin, when using a lipid composition containing egg phosphatidylcholine (egg PC) and semisynthetic platelet-activating factor (PAF; 1- O-alkyl-2-acetyl- sn-glyceryl-3-phosphorylcholine, AGEPC). The cyanide ion sensor exhibited good mechanical stability and longevity (routinely over 48 h) and constant sensitivity and response to a given concentration of cyanide ion in solution. Incorporation of hemoglobin or methemoglobin into s-BLMs was examined, and methemoglobin was found to provide lower (by five-fold) detection limit for cyanide ion determination. The effects of protein concentration and composition of BLMs on sensitivity of response were examined. Selectivity studies of cyanide detection were done in the presence of oxygen, carbon monoxide and dioxide, and other anions. The present cyanide ion sensor based on thin lipid film technology provides advantages of fast response times (in the order of 10 s) to alterations of cyanide ion concentration, low detection limits (ca. 4.9 nM, 0.317 μg l −1), and the capability of analyzing small volumes of samples. Furthermore, a device can now simply and reliably be fabricated at low cost, and therefore can be used as a disposable sensor.

Coupled Oxidation of Heme without Pyridine. Formation of Cyano Complexes of Iron Oxophlorin and 5-Oxaporphyrin (Verdoheme) from Octaethylheme

Oxidative degradation of iron porphyrins under coupled oxidation conditions, which generally has involved pyridine as solvent and source of axial ligands, results in the production of verdoheme, the iron complex of 5-oxaporphyrin in which an oxygen atom replaces a methine group. Under pyridine-free conditions, ClFeIII(OEP) (OEP is the dianion of octaethylporphyrin) and {FeIII(OEPO)}2 (OEPO is the trianion of octaethyloxophlorin) have been converted into the 5-oxaporphyrin complex (verdoheme) {(NC)2FeIII(OEOP)} (OEOP is the anion of octaethyl-5-oxaporphyrin). Additionally, through control of the cyanide ion concentration, the oxidation of ClFeIII(OEP) can be stopped to produce {FeIII(OEPO)}2 or allowed to proceed to give {(NC)2FeIII(OEOP)}. A convenient method for the preparation of {FeIII(OEPO)}2, and from it the free base H2OEPOH, is reported. Anionic complexes, [(NC)(py)Fe(OEPO)]- and [(NC)2Fe(OEPO)]2-, related to these oxidative degradation processes have been obtained through the addition of bis(triphenylphosphine)iminium cyanide to (py)2Fe(OEPO) in pyridine solution or through cleavage of {FeIII(OEPO)}2 with potassium cyanide in methanol or with tetra(n-butyl)ammonium cyanide in chloroform solution. The products have been characterized principally through their characteristic 1H NMR spectra, which show sizable hyperfine shifts with meso resonances upfield and methylene resonances with both up- and downfield shifts. In the presence of air, [(NC)2Fe(OEPO)]2- undergoes oxidation to form the 5-oxaporphyrin complex (verdoheme) {(NC)2FeIII(OEOP)}. Treatment of BrFeIII(OEPO•) with CN- produces [(NC)2Fe(OEPO)]-, which can also be obtained through oxidation of [(NC)2Fe(OEPO)]2- with diiodine.

凍結時に促進されるシアン化水素による過マンガン酸イオンの還元反応

Reduction of permanganate ion (MnO4-) by hydrogen cyanide (HCN) in aqueous solution was remarkably enhanced under the freezing process, in which permanganate ion was reduced to manganese dioxide (MnO2). As compared with the several freezing speed, the rate of the redox reaction was enhanced with increasing the freezing speed. The redox reaction was found to be strongly dependent on the solution pH and the concentration of cyanide ion added.

Development of a biosensor for gaseous cyanide in solution

A gas-phase biosensor was developed using cyanide degrading bacteria, an oxygen electrode and a gas permeable PTFE membrane. Cyanide degrading bacteria, Pseudomonas fluorescens NCIMB 11764, consume oxygen upon degradation of cyanide. A change in oxygen concentration was detected using a Clark oxygen electrode. A linear relationship was observed between the current decrease and the cyanide ion concentration in the range 0·1–1 mg/l. The optimum working conditions of the sensor were pH 2 and 30°C. The sensor was unaffected by heavy-metal ions and biochemical oxygen demand (glucose, glutamic acid). A good correlation was found between results obtained with the biosensor and those obtained using the Japanese Industrial Standard (JIS) method. The correlation coefficient was 0·995. When the biosensor was stored at 4°C, but operated at 30°C, the sensor was stable for up to 1 month.

Cyanide ion concentration in the effluent from two gold mines in Zimbabwe and in a stream receiving effluent from one of the goldmines

Abstract Cyanide ion levels were measured in the effluent from two gold mines in Zimbabwe where the gold is extracted by the cyanide process, and at points along a stream receiving effluent from one of the Mines. Cyanide ion levels in the mine effluent were 2.1 x 10‐1g/L and 2.6 g/l at the two Mines. The levels in the stream were much lower at 2.6 x 10‐6g/L and <2.6 x 10‐7g/L about 500 meters and 1 km below the point were effluent enters the stream. The plot of log [CN‐] vs sampling point shows a rapid drop in cyanide concentration along the stream. Possible processes leading to the drop in levels of CN in the stream are discussed.

Chemical Oxidation of Thiocyanate Ion by Ozone

Abstract Thiocyanate ion and weak ammonia liquor from a coking operation were ozonated in a semi-batch reactor. In a typical case, 500 mg/L thiocyanate ion disappeared in 8 minutes using an ozone dose of 82 mg/min at pH 7. The cyanide ion concentration was maximized immediately after the thiocyanate ion disappeared. The ozone-to-thiocyanate ion stoichiometric molar ratio was found to be 2.0 ± 0.2. The rate constants for the reaction of thiocyanate ion and cyanide ion with ozone under the typical conditions listed above were 5.4 × 104 L2/(mmole2-min) and 1.5 L/(mmole-min), respectively.