Cyanide Ion Concentration Research Articles

Electronic tongue for simultaneous determination of cyanide, thiocyanate and iodide

Five cross selective electrodes comprising cyanide, thiocyanate, and iodide coated graphite electrodes CGEs were used as sensing parts of an electronic tongue for simultaneous determination of cyanide, thiocyanate, and iodide ions in the presence and the absence of chloride ion as a coexisting ion. The CGEs were constructed using poly(vinyl chloride) (PVC), o-nitrophenyl octyl ether (o-NPOE), cetyltrimethylammonium bromide (CTAB), and metal–porphyrin complexes as ionophores. The constructed electrodes were characterized to obtain their calibration curve, response time, and repeatability.A programmed switching system combined with an array of the five potentiometric coated graphite electrodes (i.e., ion-selective or cross-selective electrodes) were connected directly to a pH/potentiometer and a computer to sequentially acquire the potential corresponding to water sample mixtures. The acquired potentials were recorded and saved on the computer and were used as input variables for an artificial neural network to simultaneously yield the concentrations of cyanide, thiocyanate and iodide ions in simple and complex mixtures. A feed-forward, back propagation network with a Levenburg–Maquart algorithm was employed to optimize the network parameters.

Removal of Cyanide from Liquid Waste by Electrochemical Oxidation in a New Cell Design Employing a Graphite Anode

Removal of CN− from liquid solutions was studied experimentally by an anodic oxidation technique under various operating conditions. A new cell configuration was used, the cell consists of four vertical graphite rod anodes distributed at 90° on the circular circumference at a distance of 3 cm from the wall and surrounded by two cylindrical stainless steel screen cathodes from the inner and the outer side. Parameters investigated are the initial concentration of cyanide ions, applied current density, initial pH of the electrolyte, and electrolyte conductivity. All parameters were investigated at an operating time of 3 h. The % removal increased upon increasing the applied current density, increasing the electrolyte conductivity, and decreasing the initial concentration of CN−. Increasing initial pH from 4 to 8 increased the % removal by a factor ranging from 55 to 73%, further increase of pH up to 12 slightly increased the % removal (3–8%).Application of the present electrochemical reactor in treating cyanide containing effluents from different industries was highlighted.

Efficient ensemble system based on the copper binding motif for highly sensitive and selective detection of cyanide ions in 100% aqueous solutions by fluorescent and colorimetric changes.

A peptide-based ensemble for the detection of cyanide ions in 100% aqueous solutions was designed on the basis of the copper binding motif. 7-Nitro-2,1,3-benzoxadiazole-labeled tripeptide (NBD-SSH, NBD-SerSerHis) formed the ensemble with Cu(2+), leading to a change in the color of the solution from yellow to orange and a complete decrease of fluorescence emission. The ensemble (NBD-SSH-Cu(2+)) sensitively and selectively detected a low concentration of cyanide ions in 100% aqueous solutions by a colorimetric change as well as a fluorescent change. The addition of cyanide ions instantly removed Cu(2+) from the ensemble (NBD-SSH-Cu(2+)) in 100% aqueous solutions, resulting in a color change of the solution from orange to yellow and a "turn-on" fluorescent response. The detection limits for cyanide ions were lower than the maximum allowable level of cyanide ions in drinking water set by the World Health Organization. The peptide-based ensemble system is expected to be a potential and practical way for the detection of submicromolar concentrations of cyanide ions in 100% aqueous solutions.

Bicinchoninic acid-based colorimetric chemosensor for detection of low concentrations of cyanide

Bicinchoninic acid (BCA) is reagent that is widely used to determine the concentration of proteins in solutions through the colored complex it forms with Cu(I) and the proteins. In this report, we present a new use for BCA, where a highly sensitive method for detection of cyanide ions in solutions by using Cu2+–BCA complex as the chemosensing agent is demonstrated. The detection of cyanide ions is achieved by taking advantage of the nucleophilic attack of the Cu2+–BCA complex by cyanide ions. Upon the addition of cyanide ions, the Cu2+–BCA complex undergoes transformations to free BCA via a series of equilibriums and, as a result, forms different Cu(II)–(BCA)x(CN)y species depending on the concentrations of cyanide ions in the solution. These different Cu(II)–(BCA)x(CN)y species, in turn, give different metal-to-ligand charge transfer electronic spectra and colors that are easily detectable both with naked eyes and UV–vis spectroscopy. As the cyanide ion concentration increases, the color of the solution containing the complexes changes from green to purple, red, yellow, and finally colorless, giving a corresponding blue shift in the absorption maxima on their UV–vis spectra. Through this process, the complexes enable detection of cyanide ions with a detection level of up to 0.06ppm in solutions. Thus, this colorimetric technique based on Cu2+–BCA can make low concentrations of cyanide detectable, well before the concentrations possibly reach lethal amounts. Furthermore, the method is shown to give fast detection response with no interference from other anionic and cationic species and has the potential to be adopted for accurate and convenient analysis of cyanide ions in drinking water sources as well as industrial effluents.

Highly selective colorimetric/fluorometric chemodosimeters for cyanide ions in aqueous solution based on Michael addition to C-atom possessing different polar substituents

Two simple chemosensors, 3-(4-aminophenyl)-2-cyanoacrylic acid (1) and 3-(3-aminophenyl)-2-cyanoacrylic acid (2), exhibited visual colour and fluorescence changes selectively with cyanide ions in aqueous solution. Their anion sensing properties were investigated using UV–vis, fluorescence and 1H &13C NMR spectral studies and theoretical studies. The mechanism of sensing involves Michael addition of CN− to CC bond. The addition reaction was found to occur relatively easier with p-NH2C6H4 group (Taft’s σ∗ 0.16) substituted CC bond than that with m-NH2C6H4 group (σ∗ 0.58) substituted compound. The detection limits were calculated to be 33pM and 0.2nM for the receptors 1 and 2, respectively, which are lower than the maximum permissible concentration of cyanide ion in drinking water (1.9μM) set by the World Health Organization (WHO).

Polyamine Type IEF’s Adsorption Efficiency to Cyanide and Copper

The adsorption capacity of two kinds of Ion exchange fiber (IEF) was compared to treat the wastewater contained CNT and Cu, then adsorption efficiency of Poly Acrylo-amidino Triethylene tetramine Fiber (PATAF) was studied under different pH (7.5-9.0) and flow rate (80.4-160.8 BV⋅h-1). The concentration of cyanide and complex ion were measured at pH=8, flow rate=126.0 BV⋅h-1, and the desorption conditions were studied under different concentration and flow rate.

A New Method for the Determination of Cyanide Ions and Their Quantification in Some Senegalese Cassava Varieties

Cassava (Manihot esculenta Crantz) is a starchy staple food that previous researches have showed to contain cyanogenic compounds, precursors of hydrocyanic acid, undoubtedly toxic for humans. With the aim to determine food security in cassava, this study developed a simple, fast and less expensive step for quantifying cyanide ions by using micro-diffusion with modified Conway cells. After an enzymatic degradation, the cyanide ions were quantified by electrochemical procedures. The validation of this method is estimated. The concentration of cyanide ions at different part of the samples was determined. The results showed high toxicity in some fresh Senegalese consumed cassava varieties (>100 mg HCN·kg﹣1). However, in the processed cassava products, less than 10 mg HCN·kg﹣1 was found in the different varieties studied except for the chips where the levels of CN﹣ contents were important (>49 mg HCN·kg﹣1).

Pure zinc sulfide quantum dot as highly selective luminescent probe for determination of hazardous cyanide ion

A rapid and simple fluorescence method is presented for selective and sensitive determination of hazardous cyanide ion in aqueous solution based on functionalized zinc sulfide (ZnS) quantum dot (QD) as luminescent prob. The ultra-small ZnS QDs were synthesized using a chemical co-precipitation method in the presence of 2-mercaptoethanol (ME) as an efficient capping agent. The prepared pure ZnS QDs was applied as an optical sensor for determination of cyanide ions in aqueous solutions. ZnS nanoparticles have exhibited a strong fluorescent emission at about 424nm. The fluorescence intensity of QDs is linearly proportional to the cyanide ion concentration in the range 2.44×10−6 to 2.59×10−5M with a detection limit of 1.70×10−7M at pH11. The designed fluorescent sensor possesses remarkable selectivity for cyanide ion over other anions such as Cl−, Br−, F−, I−, IO3−, ClO4−, BrO3−, CO32−, NO2−, NO3−, SO42−, S2O42−, C2O42−, SCN−, N3−, citrate and tartarate with negligible influences on the cyanide detection by fluorescence spectroscopy.

A Pretreatment Method for Detection of Cyanide Ion Concentration in Decontamination Wastewater

Three oxidant decontaminants, including NaClO, H2O2 and an organic peroxyl acid, were introduced to destroy the cyanide ion. The residual cyanide ion concentrations in different decontamination water were detected by a cyanide ion selective meter. Before the detection process, the oxidants left in the cyanide decontamination water were pretreated by adding a certain amount of Na2SO3. Results showed that starch-iodide solution indicator method presented a perfect function on determining the dosage of Na2SO3. Values of the relative mean deviations on residual cyanide detection were below 5%. After the decontamination water was deoxidized by Na2SO3, whether the sample distillated or not could not affect the value of CN- quite much. Non-distillation was confirmed alternative in the detection of cyanide ion decontamination water. Too much standing time would lead to a relatively lower CN- concentration, especially in that of non-distillation.

Pretreatment of e-waste and mutation of alkali-tolerant cyanogenic bacteria promote gold biorecovery

Gold was recovered from electronic scrap material (ESM) as gold-cyanide complex by Chromobacterium violaceum which produces cyanide as a secondary metabolite. The effect of pretreatment and mutation of alkali-tolerant bacteria was examined. Pretreatment dissolved most of the base metals, thereby reducing competition for the cyanide ion from other metals. As the pKa of HCN is 9.3, alkaline pH increases the cyanide ion concentration available for bioleaching, and the bacteria were mutated to grow at pH 9, 9.5 and 10. Results showed that at 0.5% pulp density of pretreated ESM, mutated bacteria attained gold biorecovery of 18% at pH 9, 22.5% at pH 9.5 and 19% at pH 10 while that of unadapted bacteria (at pH 7) yielded only 11% recovery. Results showed that gold bioleaching efficiency from electronic scrap was enhanced under alkaline conditions with mutated bacteria compared to bioleaching at physiological pH (around 7) of C. violaceum.

The extraction of Pt, Pd and Au from an alkaline cyanide simulated heap leachate by granular activated carbon

A two-stage heap leach process to extract base and precious metals from the Platreef low-grade ores is currently being investigated industrially. As part of the investigation, and by analogy with current gold recovery practices, the present study investigates the preferential adsorption of precious metals (Pt, Pd and Au) over base metals (Cu, Ni and Fe) from an alkaline cyanide medium, by means of granular activated carbon. Experiments were designed statistically to optimise the process parameters using synthetic alkaline cyanide solutions similar in composition to those expected from plant leach solutions. Precious metal adsorption efficiency was studied in terms of process kinetics and recovery as a function of solution pH, and the concentrations of copper, nickel, free cyanide, thiocyanate, precious metals (Pt, Pd and Au) and activated carbon. Results of kinetic experiments demonstrated that the adsorption of PGM and Au was effective and rapid. Based on their distribution coefficients, the affinity of activated carbon for metal ions follows the selectivity sequence expressed below. Au(CN)2->Pt(CN)42->Pd(CN)42->Ni(CN)42->Cu(CN)32-It was shown that adsorption rates of precious metals within the first 60min were very high, giving more than 90% extraction. Among the different adsorption parameters, nickel concentration had the most influential effect on the adsorption process followed by the adsorbent concentration. Adsorption of Ni was found to proceed at approximately the same rate as the precious metals, showing a recovery of approximately 90% in 2h. The kinetics of Cu adsorption were slower, with less than 30% being recovered within the 120min period. This suggests that the co-adsorption of Cu can be minimised by shortening the residence time. Adsorption of Fe was found to be less than 5%, while the recovery of Rh was negligibly small. The effect of thiocyanate ion concentration was not as important as the effect of free cyanide ion concentration but still had some influence. Under optimal (best) conditions, for a load cycle time of 2h and 10 discontinuous loading cycles, the loading capacity of the activated carbon for PMs was observed to be 0.64, 0.66, 0.17mg of Pt, Pd and Au/g of carbon, respectively.

ADSORPTIVE TREATMENT OF CYANIDE-BEARING WASTEWATER: A PROSPECT FOR SUGAR INDUSTRY WASTE

The biosorption of cyanide ions from aqueous solution by bagasse was studied in a batch adsorption system with pH, contact time, cyanide ion concentration, metal ion concentration, and adsorbent dosage as variables. XRD, FT-IR spectroscopy, CHN, proximate, ultimate, and TG/DTG thermal analyses were used for the characterization of bagasse. The biosorption capacities and rates of biosorption of cyanide ions onto bagasse were evaluated. The Langmuir and Freundlich adsorption models were applied to describe the isotherms and isotherm constants. Biosorption isothermal data were interpreted by the Langmuir model followed by the Freundlich model with maximum adsorption capacity of 98% of cyanide ion on bagasse. The kinetic experimental data were properly correlated with the first- and second-order kinetic model.

“Turn-off-on” fluorescence probe based functionalized InP quantum wires for detection of cyanide anions

Water-soluble fluorescent probe based indium phosphide quantum wires decorated with 6-mercaptohexanoic acid has been particularly designed to monitor cyanide ions at very low concentrations up to 110pM. 6-Mercaptohexanoic acid capped InP quantum wires were prepared by water based route technique at low temperature for the first time. At optimum condition, the emission intensity was found proportional to the concentration of cyanide ions in the range of 0–110×10−12molL−1 with detection limit 2.1×10−15molL−1. The results showed the probe has a prominent dynamic sensing range making it promising candidates for human safeguard enforcements. The emission spectrum of the functionalized quantum wire probe working in the blood and tissues optical window (λ=750±10nm). This enables the prepared functionalized quantum wire to be used for transdermal blood monitoring or even for the enumeration of cyanide levels in fire victims.

生あん中のシアン化合物分析法の性能評価と生あん中のシアン化合物の実態調査

In order to ensure compliance of raw bean paste products with the Japanese Food Sanitation Law, we examined the performance characteristics of an analytic procedure based on steam distillation followed by carbonate-pyrazolone assay to determine cyanogenic compounds in raw bean paste. The present method includes a procedure for decomposition cyanogenic glycosides using linamarase due to the possibility that cyanogenic glycoside-hydrolyzing enzymes might be deactivated in raw bean pastes. The performance of the method was evaluated using two types of bean paste spiked with a cyanogenic glycoside (linamarin) corresponding to cyanide ion concentrations of 5 and 10 mg/kg. The trueness of the method was 86-90%, and the repeatability (RSD) was 1.0-2.4%, while the intermediate precision (RSD) was 2.6% to 4.9%. A surveillance of cyanogenic compounds in 28 raw bean pastes manufactured in Japan was then carried out with the validated method. One sample contained 15 mg/kg (as hydrogen cyanide), while the other samples contained less than 5 mg/kg.

Silver nanoparticles as a cyanide colorimetric sensor in aqueous media

The interaction between aqueous colloidal silver nanoparticles (AgNPs) and cyanide ions was studied using UV-Vis absorption and scanning electron microscopy (SEM) techniques. It was found that AgNPs were oxidized by dissolved oxygen in the presence of cyanide ions, resulting in a considerable decrease in the intensity of the surface plasmon resonance (SPR) absorption band of AgNPs. So, we propose a simple, cost effective, rapid, sensitive and selective colorimetric sensor for the detection of cyanide using AgNPs in aqueous media. There is a linear relationship between the absorbance intensity of AgNPs and the concentration of cyanide ions over the range of 16.7 μmol L−1–133.3 μmol L−1 at 394 nm. The proposed method has been successfully used for the determination of cyanide in water samples.

Dual-wavelength β-correction spectrophotometric determination of trace concentrations of cyanide ions based on the nucleophilic addition of cyanide to imine group of the new reagent 4-hydroxy-3-(2-oxoindolin-3-ylideneamino)-2-thioxo-2H-1,3-thiazin-6(3H)-one

A simple, fast, low cost and sensitive direct β-correction spectrophotometric assay of cyanide ions based on its reaction with the reagent 4-hydroxy-3-(2-oxoindolin-3-ylideneamino)-2-thioxo-2H-1,3-thiazin-6(3H)-one, abbreviated as HOTT in aqueous media of pH 7–10 is described. The electronic spectrum of the produced brown-red colored species showed well defined and sharp peak at λ max = 466 nm. The effective molar absorptivity for the produced cyano compound was 2.5 × 10 4 L mol −1 cm −1. Beer's law and Ringbom's plots were obeyed in the concentration range 0.05–2.0 and 0.30–1.5 μg mL −1 cyanide ions, respectively. The proposed method offers 16.0 and 50.3 μg L −1 lower limits of detection (LOD) and quantification (LOQ) of the cyanide ion, respectively. The analytical utility of the method for the analysis of cyanide ions in tap and drinking water samples was demonstrated and the results were compared successfully with the conventional cyanide ion selective electrode. The short time response and the detection by the naked eye make the method available for the detection and quantitative determination of cyanide in a variety of samples e.g. fresh and drinking water. Moreover, the structure of the produced colored species was determined with the aid of spectroscopic measurements (UV–Vis, IR, 1H and 13C NMR) and elemental analysis.

A Highly Selective Cyanide Sensor

The selective detection of low concentrations of cyanide ions in water is of high importance. In order to achieve this goal, the authors synthesized the two sulfonium boranes 3 and 6 and tested their application as hosts for cyanide. Compound 3 was synthesized from the tetra­kis(THF) lithium salt of dimesityl-1,8-naphthalenediylborate (1) by reaction with dimethyldisulfide and methylation of the obtained product 2. Compound 6 was obtained by treating ortho-lithiothioanisole (4) with dimesitylboron fluoride and meth­ylation of the product.

The effect of potential on the gold dissolution in cyanide solutions in the presence of sulfide ions

The effect of potential on the rate of gold dissolution in the cyanide solutions in the presence of sulfide ions is studied. The dependences of current on the time after the electrode surface renewal were measured under the potentiostatic conditions. The majority of experiments were performed in the solution of the following composition, M: 0.1 KCN, 0.1 KOH, 0.01 KAu(CN)2, (1.5–2) × 10−5 Na2S at 23°C. It is shown that, at the potentials more positive than −0.1 V (NHE), the rate of gold dissolution starts to increase as soon as the surface is renewed, which is associated with high-rate chemisorption of catalytically active sulfide ions. At E < −0.1 V, the chemisorption proceeds slowly, and a considerable increase in the current takes much time. Therefore, in the potentiodynamic measurements, at E < −0.1 V, no catalytic effect of sulfide ions is observed. When the ratio between the concentrations of sulfide and cyanide ions is decreased, the potential, which, by convention, bounds the aforementioned ranges, shifts in the positive direction. Plausible explanations for these regularities are proposed.

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.

Simple photometric determination of free cyanide ion in aqueous solution with 2,6-dichlorophenolindophenol

Abstract In this work, a simple photometric method with high accuracy and precision for measuring trace amounts of free cyanide ion in aqueous solution is demonstrated. Under the evaluated conditions, we could determine CN− concentration in the range of 5–70 ppm easily. The work is based upon the photometric titration of CN− with Co(II) in the presence of 2,6-dichlorophenolindophenol (DCPIP) at λmax = 602 nm in aqueous solution. The optimal conditions, such as pH, ionic strength, and concentration of chromopher were evaluated. The interence effect of many other cations and anions studied and the results are given here. The optimized titration was successfully used to determine the concentration of free cyanide ion in aqueous solutions.