Ferrocyanide Complex Research Articles

An Evaluation of Long-Term Contaminated Soil from a Manufactured Gas Plant for in Situ Biodegradation Potential and as a Source of Ferrocyanide-Degrading Bacteria

Despite the high abundance and potential toxicity of ferrocyanide in the environment, data on the bioremediation of these complexes in contaminated soils are missing. In this study we isolated forty bacterial species presented in soil highly contaminated with ferrocyanide complexes, originating from a Manufactured Gas Plant (MGP). All bacterial strains were resistant to ferrocyanide (500 mg L−1). Six isolates showed better growth in the presence of ferrocyanide and were able to use it as a sole nitrogen source. One of them was able to assimilate ferrocyanide‐derived nitrogen and carbon. The strains varied in their tolerance to the ferrocyanide. The Minimum Inhibitory Concentration (MIC) values determined in the rich medium ranged from 1400 mg L−1 to 2000 mg L−1 and in all cases were greater than those set on the minimal medium. Molecular analysis revealed that the investigated isolates had the highest similarity to the Bacillus and Rummeliibacillus lineages. Rummeliibacillus was recognized for the first time for its ferrocyanide-degrading potential. Soil samples collected from MGP sites indicated that the overall indigenous population of microorganisms was low. Total cyanide content ranged from 220 mg kg−1 to 346 mg kg−1. Additionally, elevated Pb concentrations and an imbalanced C:N:P ratio were observed. Our study provides new information about the presence of a well-acclimated bacterial community associated with long-term ferrocyanide-contaminated soil. This bacterial community could play an important role in MGP site bioremediation processes and has the potential for application for other bioremediation purposes; however, it is likely limited due to unfavorable environmental conditions.

Prospects for refractory gold-sulfide ore processing

Cyanide-refractory ores constitute 30 % of the world’s gold mineral resource base. With the global decrease in the availability of high-grade and free-milling ores, low-quality ores, including those rich in sulfur and arsenic, are increasingly being processed. The authors have conducted an assessment of the primary factors complicating the leaching process of refractory gold. These factors include the influence of gold distribution within the ore, the presence of preg-robbing effects, and the impact of cyanicidal minerals, notably pyrrhotite, on the leaching process. Sulfide minerals significantly affect the kinetics of gold leaching and associated reagent costs. The behavior of Fe5S6 is elucidated through the concept of “chemical depression”. Under cyanide leaching conditions, pyrrhotite actively and directly reacts with NaCN/KCN, undergoing surface oxidation by dissolved oxygen in the pulp. This leads to the formation of ferrocyanide complexes and rhodanides, which are unable to leach gold. Presently, there are two approaches to enhance the process parameters of refractory ore processing technology. The first approach involves the inclusion of preparation operations for cyanidation, aimed at liberating gold from the sulfide matrix (including hydrometallurgical and pyrometallurgical oxidation technologies and mechanical activation). An alternative approach is to use alternative reagents as leaching agents (notably thiourea, sodium and ammonium thiosulfates, and halides). The article explores means of modifying the technological process for gold extraction when ores contain substantial amounts of pyrrhotite or concentrates.

Compositionally Controlled Electron Transfer in Metallo-Organics.

We demonstrate here the assembly of a nanolayer of electrochromic iron complexes on the top of composite layers of cobalt and ruthenium complexes. Depending on the ratio of the latter two complexes, we can tailor materials that show different electron transport pathways, redox activities, and color transitions. No redox activity of the top layer, consisting of iron complexes, is observable when the relative amount of the ruthenium complexes is low in the underlying composite layer because of the insulating properties of the isostructural cobalt complexes. Increasing the amount of ruthenium complexes opens an electron transport channel, resulting in charge storage in both the cobalt and iron complexes. The trapped charges can be chemically released by redox-active ferrocyanide complexes at the film-water interface.

Determination of Cyanide at Trace Levels by Computational Scanning Densitometry

Introduction: Cyanide is one of the most commonly present anions in industrial effluents, highly toxic to human and animal life. Therefore, its determination in aqueous media by simple, portable, and quick methods is required. Objective: This study aims to develop a simple and quick method to determine this anion at the micro level in aqueous media without using any expensive instrument. Method: The method is based on treating the microliter sample of aqueous cyanide with the classical Lassaigne’s reagents on a TLC plate. After heating in an oven for a few minutes, a deep blue spot of ferric ferrocyanide complex appeared on the plate. The color depth of the spots was measured by scanning the TLC plate and analyzing the image with an indigenous software package. Result: As a result of fusion with metallic sodium, carbon and nitrogen of the organic compound combine to form cyanide, which first reacts with Fe(II) to form hexacyanoferrate ion [Fe(CN)6]4- that further combines with Fe(III) to create a neutral deep blue colored coordination complex, ferric ferrocyanide Fe4[Fe(CN)6]3. Discussion: This process converts real-world colors into numeric computer data consisting of rows and columns of pixels. Each pixel will consist of three numeric components, i.e., red, green, and blue. The pixel's color will be one of 16.8 million possible color combinations (256 shades of red, green, and blue each). Conclusion: From the comparison of results obtained by the proposed method and standard ion-selective electrode method, it can be concluded that the former method for determining micro quantities of cyanide in aqueous samples using computational densitometry is a simple, accurate, and adequately precise method without the involvement of sophisticated instrumentation.

Performance Evaluation of Composite Antisalt Agents and the Antisalt Dynamics Simulation Mechanism.

The conventional ferrocyanide complex ([Fe(CN)6]4–) has been widely used as a scale inhibitor under mild conditions, but its oxidation at high temperature compromises the subsequent wastewater treatment processes. To conquer the inadequacies of Fe(CN)6]4–, aminotriacetamide (NTA) was synthesized using chloroacetic acid as an initial material and its molecular structure was characterized using FT-IR spectroscopy, H-NMR, and TGA. NTA was exploited in combination with polyaspartic acid (PASP) and sodium dodecyl benzene sulfonate (SDBS) to prepare a high-performance antisalt composite, and the scaling inhibitor performance was evaluated. The results revealed that as the concentration of the antisalt composite increased from 0.5 to 1.2 wt %, the solubility and inhibition rate increased by 95.6 and 12.33%, respectively, at 100 °C. The results from molecular simulation evidenced that the order of binding energy between a unit mass of the salt inhibitor and sodium chloride crystal increased in the following order; SDBS > NTA > PASP. The deformation strength between the salt inhibitor and sodium chloride crystal increased as follows: NTA > PASP > SDBS. In addition, the antisalt composite mainly hampered salt precipitation through strong adsorptions arising from both the nitrogen atom of NTA and oxygen atom of SDBS with the sodium atom of sodium chloride crystals, and as a result, it not only altered the crystalline form of sodium chloride but also reduced the adsorption of sodium atoms and eventually improved the salt solubility.

Metal-water covalency in the photo-aquated ferrocyanide complex as seen by multi-edge picosecond X-ray absorption.

In this work, we investigate the photo-aquation reaction of the ferrocyanide anion with multi-edge picosecond soft X-ray spectroscopy. Combining the information of the iron L-edge with nitrogen and oxygen K-edges, we carry out a complete characterization of the bonding channels in the [Fe(CN)5(H2O)]3- photo-product. We observe clear spectral signatures of covalent bonding between water and the metal, reflecting the mixing of the Fe dz2 orbital with the 3a1 and 4a1 orbitals of H2O. Additional fingerprints related to the symmetry reduction and the resulting loss in orbital degeneracy are also reported. The implications of the elucidated fingerprints in the context of future ultra-fast experiments are also discussed.

Weakly Ordered Nanostructured Silver Disilicate and Its Colloidal Solutions: Preparation and Properties

It was shown that the interaction of silver cations in alkaline aqueous solutions with various kinds of silicates, regardless of their chemical and aggregation state, leads to the formation of an exclusively disilicate form of silver salt. We develop procedures for synthesis of nanostructured weakly ordered nonstoichiometric silver disilicate Ag6 –xHxSi2O7 capable of forming aqueous colloids. We study the micellular structure of colloidal particles in these solutions and demonstrate that permeability of silicic acid layers enveloping nanosized salt cores of these micelles depends on pH. Colloidal silver disilicate is found to exhibit a high catalytic activity in photoinduced oxidation of a broad spectrum of different compounds, which is demonstrated for compounds stable in aqueous solutions such as some organic dies and ferrocyanide complex ([Fe(CN $$)_{6}^{{ - 4}}$$ ).

Chitosan-based biosorbents: immobilization of metal hexacyanoferrates and application for removal of cesium radionuclide from aqueous solutions

Composite M (M—Cu, Ni) potassium ferrocyanide chitosan-based materials were prepared via co-precipitation methods using chitosan as a matrix for adsorption of cesium from alkaline solutions. The materials were fabricated using a suspension or in situ formation of ferrocyanides of transition metals in a chitosan matrix with simultaneous chitosan deposition. The synthesis products were characterized by the methods of scanning electron microscopy with energy-dispersive analysis (SEM–EDX) and X-ray diffraction (XRD). In the process of sorption of radiocesium from alkaline solutions under static conditions, the stability of composite sorbents compared with the pristine powders of transition metal ferrocyanides was estimated. The boundary values of the pH and time, at which the destruction of the composite sorbent is observed, are determined. The stabilizing effect of chitosan on the resistance of Ni-K ferrocyanide (FCN) complexes in alkaline mineralized solutions has been shown on the example of Ni-K FCN/chitosan composite sorbents.

Слабоупорядоченный наноструктурированный бисиликат серебра и его коллоидные растворы: получение и свойства

AbstractIt was shown that the interaction of silver cations in alkaline aqueous solutions with various kinds of silicates, regardless of their chemical and aggregation state, leads to the formation of an exclusively disilicate form of silver salt. We develop procedures for synthesis of nanostructured weakly ordered nonstoichiometric silver disilicate Ag_6 –_ x H_ x Si_2O_7 capable of forming aqueous colloids. We study the micellular structure of colloidal particles in these solutions and demonstrate that permeability of silicic acid layers enveloping nanosized salt cores of these micelles depends on pH. Colloidal silver disilicate is found to exhibit a high catalytic activity in photoinduced oxidation of a broad spectrum of different compounds, which is demonstrated for compounds stable in aqueous solutions such as some organic dies and ferrocyanide complex ([Fe(CN $$)_{6}^{{ - 4}}$$ ).

Return of the Iron Age

In this issue of Joule, Liu and coworkers present the use of the well-known ferrocyanide complex as an active electrode material for an aqueous organic/organometallic redox flow battery. The ammonium cation was used as counter cation in place of the former-utilized sodium and potassium ions. Interestingly, by this simple cation exchange, remarkable capacity and cycle stability were achieved. A battery system is presented comprising ammonium ferrous hexacyanide and an organo-functionalized viologen compound.

Biomimicry of vascular plants as a means of saline soil remediation

Soil salinization impacts millions of hectares of land around the world and threatens many soil ecosystem services. Impacts of soil salinization are long lasting and impact agriculture productivity, reduce plant diversity and cause increase soil erosion due a reduction or loss in surface vegetation. Generally, remediation of saline soil relies on soil washing methods and phytoremediation to translocate salts below the rooting depth of plants. However, standard methods can often be unsuccessful as leached salts are able to return to the rooting zone through subsequent capillary rise in the soil. Surface application of iron (III) ferrocyanide has been used to remediate salt contaminated soil as the ferrocyanide complex induces salts to efflorescence at the soil surface as water evaporates rather than crystallising within the soil matrix. However, surface application of iron (III) ferrocyanide tends to be less successful in clay textured soil and does not work well when subsequent reapplications of water are made for further salt removal. In this study we investigate a biomimetic approach to desalinate soil by mimicking the capillary transport mechanisms employed by vascular plants.Our approach uses evapotranspiration to translocate saline soil water above the soil surface where it is effloresced with ferrocyanides. After 30 days of treatment, the biomimetic approach used 2.1 pore volume equivalents of water and was able to reduce the concentration of salts from 8% (g·NaCl/g·soil) to 0.8% (g·NaCl/g·soil), resulting in a reduction of soil EC from 120 mS/cm to 14 mS/cm. Our findings indicate that the method, with further refinement and expansion to field based trials, could be an effective tool to desalinate soil and reduce global soil salinization.

Application of a webcam camera as a cost-effective sensor with image processing for dual electrochemical – colorimetric detection system

A webcam camera as an alternative cost-effective colorimetric sensor for the simple dual electrochemical – colorimetric detection system is proposed. Performance test of the system was investigated through electrochemical and colorimetric behaviors of redox reactions of potassium ferrocyanide complex. Image processing with two color systems, RGB and HSV, was applied together with various electrochemical techniques. Color responses obtained from the webcam correlated with electrochemical signals in various electrochemical techniques. The results from the proposed dual detection system agreed well with those obtained using conventional UV–vis spectroelectrochemical system reported previously. The application of proposed system was demonstrated for studying the redox reaction of catechin and electrochemical - colorimetric behaviors of Fe(II) and Fe(III) mixture.

The nature of chemical bonding in actinide and lanthanide ferrocyanides determined by X-ray absorption spectroscopy and density functional theory.

The electronic properties of actinide cations are of fundamental interest to describe intramolecular interactions and chemical bonding in the context of nuclear waste reprocessing or direct storage. The 5f and 6d orbitals are the first partially or totally vacant states in these elements, and the nature of the actinide ligand bonds is related to their ability to overlap with ligand orbitals. Because of its chemical and orbital selectivities, X-ray absorption spectroscopy (XAS) is an effective probe of actinide species frontier orbitals and for understanding actinide cation reactivity toward chelating ligands. The soft X-ray probes of the light elements provide better resolution than actinide L3-edges to obtain electronic information from the ligand. Thus coupling simulations to experimental soft X-ray spectral measurements and complementary quantum chemical calculations yields quantitative information on chemical bonding. In this study, soft X-ray XAS at the K-edges of C and N, and the L2,3-edges of Fe was used to investigate the electronic structures of the well-known ferrocyanide complexes K4Fe(II)(CN)6, thorium hexacyanoferrate Th(IV)Fe(II)(CN)6, and neodymium hexacyanoferrate KNd(III)Fe(II)(CN)6. The soft X-ray spectra were simulated based on quantum chemical calculations. Our results highlight the orbital overlapping effects and atomic effective charges in the Fe(II)(CN)6 building block. In addition to providing a detailed description of the electronic structure of the ferrocyanide complex (K4Fe(II)(CN)6), the results strongly contribute to confirming the actinide 5f and 6d orbital oddity in comparison to lanthanide 4f and 5d.

Adsorption of ferrocyanide onto raw and acid-activated clinoptilolite and sepiolite: equilibrium modelling by error minimization

AbstractThe experimental data on adsorption of Fe and CN of a ferrocyanide complex onto raw and acid-activated clinoptilolite/sepiolite on the basis of detention time and particle size was modelled by a linear and a non-linear approach. The linearized best-fit isotherm selection method and non-linear error minimization was applied through Freundlich, Langmuir and Temkin isotherms. ERRSQ, MPSD, HYBRID and ARE error functions were minimized by a developed MATLAB script to determine the isotherm parameters in non-linear optimization. The complex was not adsorbed as whole anions but the Fe and CN were adsorbed separately. 0.65 mg Fe/L. min and 4.84 mg CN/L. min initial adsorption rates were achieved with acid activated clinoptilolite. The Fe adsorption was not as successful as CN. The adsorption of Fe and CN was described by Freundlich and Langmuir isotherms respectively. The differences between the predicted isotherm parameter sets of linear models and minimized error function models indicated that both the best-fit isotherm selection and the isotherm constant determinations can be performed properly by error minimization as well as by conventional linear best fit modelling approach.

Potassium ferro-cyanide trihydrate complex catalyzed one-pot synthesis of 2-phenylimidazo [4,5-f] [1,10] phenanthroline

Abstract Various 2-phenylimidazo [4,5-f] [1,10] phenanthrolines were synthesized from potassium ferro-cyanide trihydrate (KFCT) complex catalyzed three component reaction of 1,10-phenanthroline-5,6-dione, aromatic aldehydes and ammonium acetate at room temperature in excellent isolated yield. This is a simple and straight forward, high yielding, not involving any hazardous or expensive catalyst method.

Availability of Ferrocyanide and Ferricyanide Complexes as a Nitrogen Source to Cyanogenic Plants

The effects of additional nitrogen on the toxicity and removal of ferrocyanide and ferricyanide by cyanogenic plants were investigated. Maize (Zea mays L. var. ZN 304) seedlings were grown in the hydroponic solutions with or without additional nitrogen, and amended with either potassium ferrocyanide or potassium ferricyanide at 25.0 +/- 0.5 degrees C for 144 h. Various physiological parameters were monitored to determine the responses of the plant seedlings to the exposure of these two chemicals. A remarkable decrease in transpiration rate, biomass, shoot length, chlorophyll contents, and soluble proteins was evident for maize seedlings grown in the N-free hydroponic solutions spiked with either ferrocyanide or ferricyanide (P < 0.01), but slight changes were observed in the selective parameters in the N-containing hydroponic solutions spiked with either of these chemicals (P > 0.05). A higher removal of ferrocyanide than ferricyanide was registered in the N-free hydroponic solutions, but more ferricyanide than ferrocyanide was removed by maize grown in the N-containing nutrient solutions (P < 0.01). Although roots of maize accumulated iron cyanides, more cyanide was recovered in plant materials of those grown in the N-containing hydroponic solutions than the N-free nutrient solutions (P < 0.05). Mass balance analysis indicated that the majority of the iron cyanides removed from solution was assimilated by maize and additional nitrogen had a significantly negative impact on the uptake of both chemicals (P < 0.01). Results of this study suggest that uptake and assimilation mechanisms for ferrocyanide and ferricyanide might be quite different in maize and the application of the external nitrogen has a substantial influence on the removal of both iron cyanides by plants. None of the iron cyanide complexes can serve as a sole nitrogen source to support maize growth.

Detoxification of superoxide without production of H 2 O 2 : Antioxidant activity of superoxide reductase complexed with ferrocyanide

The superoxide radical O(2)(-.) is a toxic by-product of oxygen metabolism. Two O(2)(-.) detoxifying enzymes have been described so far, superoxide dismutase and superoxide reductase (SOR), both forming H2O2 as a reaction product. Recently, the SOR active site, a ferrous iron in a [Fe(2+) (N-His)(4) (S-Cys)] pentacoordination, was shown to have the ability to form a complex with the organometallic compound ferrocyanide. Here, we have investigated in detail the reactivity of the SOR-ferrocyanide complex with O(2)(-.) by pulse and gamma-ray radiolysis, infrared, and UV-visible spectroscopies. The complex reacts very efficiently with O(2)(-.). However, the presence of the ferrocyanide adduct markedly modifies the reaction mechanism of SOR, with the formation of transient intermediates different from those observed for SOR alone. A one-electron redox chemistry appears to be carried out by the ferrocyanide moiety of the complex, whereas the SOR iron site remains in the reduced state. Surprisingly, the toxic H2O2 species is no longer the reaction product. Accordingly, in vivo experiments showed that formation of the SOR-ferrocyanide complex increased the antioxidant capabilities of SOR expressed in an Escherichia coli sodA sodB recA mutant strain. Altogether, these data describe an unprecedented O(2)(-.) detoxification activity, catalyzed by the SOR-ferrocyanide complex, which does not conduct to the production of the toxic H2O2 species.

Refinement of Weak Acid Dissociable (WAD) Method for Measuring Weak Metal Cyanide Complexes in Aqueous Samples

The primary objective of this study was to correct deficiencies that had been identified in the current weakacid dissociable (WAD) cyanide analytical method. These deficiencies became apparent when the method was applied to groundwater and surface water samples dominated by iron–cyanide complexes (>50% of the total cyanide content); the analytical method, as is, is fine for determining WAD cyanide in any aqueous sample where weak metal cyanide complexes and free cyanide ions dominate the cyanide speciation (i.e., iron–cyanide complexes are <50% of the total cyanide content). It was also determined that the means required to correct these deficiencies depended upon which iron–cyanide complex was present (i.e., ferricyanide/ferrocyanide or an iron–pentacyano methylamino species, [Fe(CN)5NHCH3]4−). For the samples dominated by the ferri- and ferrocyanide complexes, addition of the prescribed amount of zinc acetate under mildly acidic conditions was sufficient to entirely remove these complexes from solution via formation of an iron cyanide precipitate. However, the high-temperature distillation step of the analytical method was found to destabilize the iron–cyanide precipitate thus formed, resulting in the recovery of some of this strong acid dissociable cyanide complex as WAD cyanide. To rectify the method deficiency, an intermediate filtration step using a 0.45-micron filter was introduced to remove the precipitate before distillation is performed. A slightly different modified method was required when the iron–cyanide complexes were dominated by the iron–pentacyano methylamino complex, that is, [Fe(CN)5NHCH3]4−. In this instance, it was necessary to add three times the prescribed amount of zinc acetate to remove the complex from the solution. Also, the precipitate was comprised of smaller size particles, and hence, a smaller filter size (0.2 micron) was required to remove the precipitate before distillation. These modifications to the current WAD method provided a more accurate determination of the WAD cyanide content of the sample that is dominated by iron–cyanide complexes, as verified by the EPA-approved available cyanide method OIA-1677. However, for samples dominated by weak metal–cyanide complexes, the current WAD cyanide analytical method is deemed appropriate.

Vibrational Analysis of Ferrocyanide Complex Ion Based on Density Functional Force Field

Vibrational properties of ferrocyanide complex ion, <TEX>$[Fe(CN)_6]^{4-}$</TEX> , have been studied based on the force constants obtained from the density functional calculations at B3LYP/<TEX>$6-31G^{\ast\ast}$</TEX> level by means of the normal mode analysis using new bond angle and linear angle internal coordinates recently developed. Vibrations of ferrocyanide were manipulated by twenty-three symmetry force constants. The angled bending deformations of C-Fe-C, the linear bending deformations of Fe-C<TEX>${\equiv}$</TEX>N and the stretching vibrations of Fe-C have been quantitatively assigned to the calculated frequencies. The force constants in the internal coordinates employed in the modified Urey-Bradley type potential were evaluated on the density functional force field applied, and better interaction force constants in the internal coordinates have been proposed. The valence force constants in the general quadratic valence force field were also given. The stretch-stretch interaction and stretch-bending interaction constants are not sensitive to the geometrical displacement in the valence force field.

Characterization of Ferricyanide-Humate Complexes by a Voltammetric Approach

The industrial sites that deal with the production and/or use of cyanide in their processes often have contamination problems by cyanide in soils and water. The behavior of these hazardous compounds in soil and the interactions with soil components are mostly unknown. The toxicity of cyanide and its fate in soil are strongly influenced by the formation of complexes with iron, i.e., ferric - and ferrous cyanides (Fuller, W.H., 1994; Theis and West, 1986). These complexes may interact with the soil inorganic fraction containing ferrous or ferric iron, with consequent formation of stable precipitates (ferric ferrocyanide or ferrous ferricyanide, the Prussian Blue and the Turnbull Blue, respectively). However, no information is available on the capacity of humic substances to immobilize the cy-ano-complexes and thus to reduce their toxicity and the leaching, and the consequent risk of contamination of watertable.In fact, one of the most significant properties of humic substances is their ability to interact with xenobiotics to form complexes of different solubility and chemical and biochemical stability.In this paper we report the results obtained in a voltammetric investigation aimed to study the behavior of the ferricyanide/ ferrocyanide redox couple chosen as the indicator of redox system (Hel burn and MacCarthy, 1994) in the absence and in the presence of humic fraction at nominal molecular weight lower than 5 kDa (HSLMW) extracted from a surface horizon of a Haplumbret soil. The results obtained in these investigations, combined with the evidence gained by spectrophotometric measurements carried out in parallel, point out that ferrocyanide-HSLMW and ferricya-nide-HSLMW complexes are more stable than the parent Fe-CN- ones. These complexes undergo electrochemical processes involving a slow homogeneous chemical reaction preceding the electron transfer step and causing their kinetic control (CE processes). The voltammetric measurements allowed the conditional constants K to be determined for ferric- and ferrous cyanide-HSLMW complexes, respectively: they turn out to be about three orders of magnitude higher than those for the ferricyanide and ferrocyanide complexes alone, respectively. From the data treatment we may hypothize that two humate ligands, on average, are accommodated in the coordination sphere of both iron (III) and iron (II) in the corresponding complexes.