Metal Ferrocyanides Research Articles

Composite sorbents for recovery of cesium radionuclides

Sorption properties of composite sorbents produced by electrochemical deposition of a siloxaneacrylate emulsion impregnated with transition metal ferrocyanides onto a fibrous carbon matrix for cesium radionuclides were studied.

Coprecipitation of microamounts of cesium with precipitates of transition metal ferrocyanides in alkaline solutions

Experiments on coprecipitation of microamounts of Cs with precipitates of copper, nickel, and cobalt ferrocyanides in alkaline solutions showed that the dependences of the distribution coefficients (Kd) of 137Cs on pH of the liquid phase have a pronounced maximum at pH 10.0 ± 0.2 (Kd ≈ 8 × 105), 10.5 ± 0.2 (Kd ≈ 2 × 106), and 10.6 ± 0.3 (Kd ≈ 5 × 105), respectively. This phenomenon is associated with the formation of mixed precipitates of transition metal ferrocyanides and hydroxides, surpassing in the sorption characteristics the phases of the corresponding ferrocyanides. The mechanism of coprecipitation of microamounts of cesium with precipitates of transition metal ferrocyanides in alkaline solutions and the conditions of maximum recovery of cesium from solutions of various compositions were determined.

Synthesis and characterization of cobalt ferrocyanides loaded on organic anion exchanger

Transition metal ferrocyanides have important applications in the selective removal of radioactive caesium from low level and intermediate level radioactive liquid waste streams. The microcrystalline nature of these materials renders them useless for application in column mode operations. Special preparation procedures have been developed to prepare granular solids by in situ precipitation of metal ferrocyanides on organic anion exchangers, which is suitable for column mode operations. The elemental compositions of the metal ferrocyanides precipitated inside the pores of anion exchanger were determined by analysing the dissolved samples using ICP–AES system and flame photometer. From the XRD and EDX analyses and the elemental composition of the synthesized materials, the nature of the compound formed inside the anion exchanger was found to be cobalt ferrocyanide. From SEM analysis of the samples, the particle size of the cobalt ferrocyanide precipitated inside the anion exchanger was found to be much less than that of cobalt ferrocyanide precipitated outside. The efficiency of these materials for removal of Cs was evaluated by measuring the distribution coefficient (Kd), ion exchange capacity and kinetics of Cs uptake. The Kd of the materials loaded on anion exchanger was found to be of the order of 10 5 ml/g. The Cs uptake kinetics of the materials loaded on anion exchanger was slower than that of precipitated materials. The ion exchange capacity of the cobalt ferrocyanide loaded on anion exchanger was found to be much higher than that of the precipitated cobalt ferrocyanide.

Studies in Adsorption: Measurement of External Specific Surface Area of Metal Ferrocyanides by Methylene Blue Dye Adsorption

Studies in Adsorption: Measurement of External Specific Surface Area of Metal Ferrocyanides by Methylene Blue Dye Adsorption

Interaction of Tryptophan and Phenylalanine with Metal Ferrocyanides and Its Relevance in Chemical Evolution

The interaction of two naturally occurring aromatic alpha-amino acids, namely, tryptophan and phenylalanine, with zinc, nickel, cobalt, and copper ferrocyanides has been studied. Both amino acids showed a high adsorption affinity toward metal ferrocyanides at neutral pH (7.0). Adsorption trends followed the Langmuir adsorption isotherm. Values of the Langmuir constants K(L) and X(m) suggest tryptophan is a better adsorbate than phenylalanine. Zinc ferrocyanide showed the highest adsorption, while the minimum adsorption was found in the case of copper ferrocyanide. Infrared spectral studies of adsorbate, adsorbent, and adsorption adducts indicate that adsorption occurs because of the interaction of adsorbate molecules with outer divalent metal ions present in the lattice of metal ferrocyanides. The present investigation supports the hypothesis that metal ferrocyanides might have concentrated the biomonomers on their surface in primeval seas during the course of chemical evolution.

Interaction of ribose nucleotides with metal ferrocyanides and its relevance in chemical evolution

Interaction of ribose nucleotides with cobalt- and cadmium ferrocyanides was found maximum at neutral pH. Adsorption trend followed Langmuir isotherms. The Langmuir constants, X m and K L were calculated. Purine nucleotides adsorbed more than pyrimidine nucleotides on both the metal ferrocyanides. Cobalt ferrocyanide was found a better adsorbent for all the ribose nucleotides studied. Infrared spectral studies of the adsorption adducts suggested that the adsorption occurs due to interaction of ribose nucleotide molecule with outer divalent metal ion present in the lattice of metal ferrocyanides. The results of the present study suggest that the metal ferrocyanides could have concentrated and stabilised the ribose nucleotides on their surface through adsorption processes during the course of chemical evolution.

Exchange properties of cyanide complexes

Some heavy metal ferrocyanides were prepared and their selectivity towards cesium was investigated. Many were found to have good ion exchange properties and some can be easily prepared in a granular form suitable for the use in a packed column operation. The ferrocyanides show high cesium uptake in various simulated processing solutions relevant to the treatment of radioactive wastes. The amount of cesium sorbed by these hexacyanoferrates exceeded 99%. They also possess a high selectivity for cesium in solutions of high salt concentration. Desorption of the sorbed cesium at various nitric acid concentrations have been investigated and it is concluded that cesium is eluted by a chemical reaction step as a consequence of the oxidation of the ferrocyanides. It has also been observed that ferrocyanides degrade in solutions of low pH.

Supporting of some ferrocyanides on polyacrylonitrile (PAN) binding polymer and their application for cesium treatment

Abstract Transition metal ferrocyanides were supported on polyacrylonitrile (PAN) as a binding polymer and were used for removal of radiocesium. The sorption capacity was determined to be 1.22 and 0.55 mol g −1 for KZnHCF-PAN and KCuHCF-PAN, respectively. Different parameters affecting the sorption process were studied as chemical nature of the aqueous solution and flow rate of feed solution. The regeneration of the used sorbent was studied and also using the regenerated sorbents in other sorption cycles was studied up to four cycles.

Adsorption and Oxidation of Aniline and Anisidine by Chromium Ferrocyanide

The interaction of aniline and p-anisidine with chromium ferrocyanide has been studied. Maximum uptake of both anilines was observed around pH 7. The adsorption data obtained at neutral pH were found to follow Langmuir adsorption. Anisidine was a better adsorbate because of its higher basicity. In alkaline medium (pH>8) both aniline and anisidine reacted with chromium ferrocyanide to give colored products. Analysis of the products by GC–MS showed benzoquinone and azobenzene as the reaction products of aniline while p-anisidine afforded a dimer. IR analysis of the amine–chromium ferrocyanide adduct suggests that the outer metal ion of chromium ferrocyanide and amino group of amines are responsible for the interaction. A possible reaction mechanism for the product formation in alkaline medium has been proposed. The present study suggests that metal ferrocyanides might have played an important role in the stabilization of organic molecules through their surface activity in the prebiotic condensation reactions.

Interaction of 2-Amino-, 3-Amino-, and 4-Aminopyridines with Chromium and Manganese Ferrocyanides

The present investigation deals with the interaction of 2-aminopyridine, 3-aminopyridine, and 4-aminopyridine with chromium and manganese ferrocyanides. Chromium ferrocyanide possesses better adsorbing properties than manganese ferrocyanide. Maximum uptake was observed at neutral pH (pH 7.0). The adsorption data obtained at neutral pH are fitted in a Langmuir adsorption isotherm. The adsorption behavior of the aminopyridines studied follows the order 3-aminopyridine >4-aminopyridine >2-aminopyridine. The infrared spectral studies of adsorption adducts indicate that adsorption takes place through interactions between the adsorbate molecule and the outer divalent metal ion of metal ferrocyanides. From these studies, it is clear that metal ferrocyanides and metal ions play a major role in the stabilization of organic molecules through their surface activity in the prebiotic environment.

Interaction of 2-amino, 3-amino and 4-aminopyridines with nickel and cobalt ferrocyanides

The present investigations deal with the interaction of 2-aminopyridine (2AP), 3-aminopyridine (3AP) and 4-aminopyridine (4AP) with nickel ferrocyanide (NiFc) and cobalt ferrocyanide (CoFc). Nickel ferrocyanide is found to be a better adsorbent. Maximum uptake was observed at neutral pH (pH, 7.0). The adsorption data obtained at neutral pH is fitted in Langmuir adsorption isotherm. The adsorption behavior of studied aminopyridines followed the order: 3-aminopyridine>4-aminopyridine>2-aminopyridine. The infrared spectral studies of adsorption adducts indicate that adsorption takes place through interaction between adsorbate molecule and outer divalent metal ion of metal ferrocyanides. From these studies, it is clear that metal ferrocyanides and metal ions play major role in stabilisation of aminopyridines through their surface activity in prebiotic environment.

Interaction of 2,4-dinitrophenol and 2,4,6-trinitrophenol with copper, zinc, molybdenum and chromium ferrocyanides

The adsorption of 2,4-dinitrophenol and 2,4,6-trinitrophenol on copper, zinc, molybdenum and chromium ferrocyanides was studied at different pH and temperature. It was observed that the amount of uptake increases with temperature and the percent adsorption on metal ferrocyanides was a maximum for 2,4,6-trinitrophenol. The Langmuir-type of adsorption is followed in the concentration range 10 −3 to 10 −4 M for 2,4-dinitrophenol and 2,4,6-trinitrophenol solutions. Thermodynamic parameters of the process have also been evaluated.

Interaction ofo-Aminophenol ando-Nitrophenol with Copper, Zinc, Molybdenum, and Chromium Ferrocyanides

Removal ofo-aminophenol ando-nitrophenol from aqueous solution through adsorption on copper zinc, molybdenum, and chromium ferrocyanides were studied in pH range 2–10 at 27°C. At pH 7.0o-nitrophenol adsorbed more thano-aminophenol on all the metal ferrocyanides studied. The Langmuir type of adsorption is followed in the concentration range of 10−3to 10−4Mofo-aminophenol ando-nitrophenol solutions.

Studies on metal ferrocyanides as prebiotic catalyst

Processes in chemical evolution must have involved several catalysts multifunctional in nature. Our previous work has demonstrated that metal ferrocyanides posses strong adsorption affinity towards amino acids and nucleotides. It is assumed that during the course of chemical evolution, cyanide could have formed some metal ferrocyanides. As these metal ferrocyanides are mostly insoluble in water, and they are therefore, considered to have settled at the bottom of the primeval ocean or at sea shore. We propose that metal cyanogen complexes might have acted as an important prebiotic catalyst.

Adsorption of protein on metal ferrocyanides

Adsorption of protein on metal ferrocyanides

Role of metal ferrocyanides in chemical evolution

Adsorption of several ribose and 2′-deoxyribose 5′-nucleotides on zinc- and copper ferrocyanides has been studied at a neutral pH of 7.01. The Langmuir adsorption isotherm was used to determine the values of KL and Xm. Both types of nucleotides, ribose and 2′-deoxyribose, showed similar adsorption behavior on zinc- and copper ferrocyanides. Zinc ferrocyanide showed larger adsorption as compared to copper ferrocyanide. Purine nucleotides adsorbed more than pyrimidine nucleotides on both the metal ferrocyanides probably because of an additional binding site in the imidazole ring in purines. Results of the present study suggest the importance of metal ferrocyanides and metal ions in stabilization of nucleotides during processes of prebiotic condensation reactions.

Adsorption of aromatic amines on metal ferrocyanides

Cobalt and zinc ferrocyanides have shown remarkable adsorption of aromatic amines such as aniline, p-chloroaniline, and p-toluidine. Among the two ferrocyanides cobalt ferrocyanide has been found to be a better adsorbent and the observed adsorption trend follows a pattern, p-toluidine > aniline > p-chloroaniline. The infrared spectral studies of the adsorption product suggested that adsorption of amines on metal ferrocyanide is probably taking place due to coordination of amine to the outer metal ions of metal ferrocyanide.

Role of transition metal ferrocyanides (II) in chemical evolution

Due to ease of formation of cyanide under prebiotic conditions, cyanide ion might have formed stable complexes with transition metal ions on the primitive earth. In the course of chemical evolution insoluble metal cyano complexes, which settled at the bottom of primeval sea could have formed peptide and metal amino acid complexes through adsorption processes of amino acids onto these metal cyano complexes.

Adsorption of amino acids on transition metal ferrocyanides and its implications in chemical evolution

Adsorption of amino acids on transition metal ferrocyanides and its implications in chemical evolution

Simultaneous Adsorption of Cs-137 and I-131 from Water and Milk on “Metal Ferrocyanide-Anion Exchange Resin”

“Metal ferrocyanide-anion exchange resin”, which is made by precipitating the metal ferrocyanide in an anion exchange resin matrix, has been used for selective adsorption of Cs ion in a variety of aqueous solutions. The “resin” has both properties of metal ferrocyanide and anion exchange resin. Therefore, we tried simultaneous adsorption of radiocesium and radioiodine from water and milk on the “resin”. Results showed that “metal ferrocyanide-anion exchange resin” such as Cu, Fe and Ni ferrocyanide can be used for a rapid and simple concentration of radiocesium and radioiodine quantitatively from a large volume of sample solutions. This paper also touches upon the removal of 137Cs and 131I in rain water and milk collected in Japan after the Chernobyl accident.