Zinc Ferrocyanides Research Articles

Effect on Cs removal of solid-phase metal oxidation in metal ferrocyanides

Abstract Metal ferrocyanides (MFCs) have been studied for many years and are regarded as efficient adsorbents for the selective removal of radioactive cesium (Cs) from contaminated aqueous solutions. Although their efficiency has been demonstrated, various investigations on the physicochemical, thermal, and radiological stability of the solids of MFCs are required to enhance the applicability of MFCs in the treatment process. We observed that the Cs adsorption efficiencies of cobalt and nickel ferrocyanides decreased as their aging period increased, while the Cs adsorption efficiencies of copper and zinc ferrocyanides did not decrease. The tendencies of these ferrocyanides were accelerated by exposure of the solids at a higher temperature for a longer time. Our comprehensive analyses demonstrated that only the oxidizable metals in the MFCs can be oxidized by aging time and increasing temperature; also, this affects the Cs removal efficiency by decreasing the exchangeable sites in the solids. The chemical stability of MFCs is very important for the optimization of the synthesis and storage conditions.

Preparation and Physicochemical Characterization of Cadmium and Zinc Ferrocyanides as Catalysts and Ion Exchangers

Preparation and Physicochemical Characterization of Cadmium and Zinc Ferrocyanides as Catalysts and Ion Exchangers

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.

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.

Column-usable inorganic fixator preparation by localized growth on a solid alkaline ferrocyanide

Inorganic fixators are selective sorbents which would often be preferred to commercial ion exchangers if they were suitable for column utilization. We present a new preparation method whose principle is a slow growth of an insoluble compound on a soluble-reacting crystal placed in a concentrated solution of another reactant. By this process, it is possible to prepare mixed zinc or nickel ferrocyanides by local growth on sodium or potassium ferrocyanide crystals placed in a concentrated zinc or nickel solution. The particle size is controlled by the size of the starting solid, the solution concentration and temperature. The growth mechanism seems to be a diffusion of water and divalent ions through the film of insoluble product formed around the soluble crystals. The reaction rate is increased by dilution of the solution or increase of its temperature. This method allows the preparation at low cost of insoluble ferrocyanide columns.

Preparation, composition and structure of some nickel and zinc ferrocyanides: Experimental results

Several methods have been used for preparation of nickel and zinc ferrocyanides: precipitation, growth in a gel and a new method based on growth on a solid alkali-metal ferrocyanide. The granulometry, morphology, composition and structure of the compounds were studied. Only the last method of preparation gives products suitable for use as ion fixators in columns on a large scale. The nickel ferrocyanide compositions can be written as M I 2xNi 2− x Fe(CN) 6. yH 2O with M I  Na, K, Cs, H and 0 < x < 0.8. They have a cubic lattice with a partial occupancy of iron sites. For zinc ferrocyanides, rhombohedral M I 2Zn 3[Fe(CN) 6] 2. xH 2O, trigonal Zn 2Fe(Cn) 6.2H 2O and other cubic compounds were found. Products resulting from the fixation of caesium by ion-exchange were also studied.

Exchange mechanism of alkaliions on zinc ferrocyanides

Abstract This work was devoted to the understanding of the fixation mechanisms of alkali ions on two types of zinc ferrocyanides in order to determine the optimal recovery conditions of cesium from radioactive liquid wastes. The studied products were prepared by direct precipitation and were analysed by several methods for their composition. The mixed ferrocyanides belong to the M2IZn3 [Fe(CN)6]2, xH2O series (MI = H, Na, K, Cs) with a rhombohedirc structure R 3 c. Pure zinc ferrocyanide, Zn2Fe(CN)6. 2H2O has a trigonal structure. The kinetics of sodium self-diffusion was studied in Na, Zn3 [Fe(CN)6]2 labelled with the 24Na isotope, and placed in an inactive sodium chloride solution. The equilibrium was reached within ten minutes. The experimental results were compared to different mathematical models related to diffusion into the crystals or through a bounding liquid film. The sodium self-diffusion seems to be controlled by the rate of transfer through the liquid film. The study of Na+ - H+ exchange on this product was performed by a potentiometric method correlated to tracer measurments. H+ fuxation is slower phenomenon and the rate of the process seems to be controlled by H+ diffusion into the particles. Sorption of cesium on Zn2Fe(CN)6 requires more than 70 h, while on M2IZn[Fe(CN)6]2 sorption equilibrium is attained within a few minutes. The capacity reaches 1.6 Cs atoms per one Fe atom in the first product and is limited to one Cs atom per Fe atom in the second product. Cesium is partly retained by cation exchange with the alkali metal or zinc ions and partly by molecular adsorption of a cesium salt. According to the kinetics studies, mixed alkali-zinc ferrocyanides are the most promising products for cesium decontamination.

EXCHANGE MECHANISMS OP SILVER ON NICKEL AND ZINC PERROCYANIDES

ABSTRACT The retention mechanisms of silver ions were studied on some nickel and zinc ferrocyanides Which represent several types of structures. This was performed through the study of the influence of the ferrocyanide composition and structure, a determination of the kinetics and capacity, a study of the modification of the solid at each step of the fixation. All the studied ferrocyanides are able of removing silver from aqueous solutions with a high efficiency. The kinetics is always very fast. It could be interpreted by an intracrystalline diffusion for acid-nickel ferrocyanide, but was too fast for Interpretation in other cases. The main feature is a substitution of all ferrocyanide cations leading to a composition tending to Ag4Fe(CN)6. However, the stability of this compound is questionable. The capacity of fixation exceeds the predicted value and may reach 6 silver atoms per iron atom in the initial product. A possible interpretation is the formation of silver cyanide. The fixation is a complex phenomenon involving structural changes in the crystal lattice.

ChemInform Abstract: ZINC AND NICKEL FERROCYANIDES: PREPARATION, COMPOSITION AND STRUCTURE

Chemischer InformationsdienstVolume 16, Issue 22 Reviews ChemInform Abstract: ZINC AND NICKEL FERROCYANIDES: PREPARATION, COMPOSITION AND STRUCTURE C. LOOS-NESKOVIC, C. LOOS-NESKOVICSearch for more papers by this authorM. FEDOROFF, M. FEDOROFFSearch for more papers by this authorE. GARNIER, E. GARNIERSearch for more papers by this authorP. GRAVEREAU, P. GRAVEREAUSearch for more papers by this author C. LOOS-NESKOVIC, C. LOOS-NESKOVICSearch for more papers by this authorM. FEDOROFF, M. FEDOROFFSearch for more papers by this authorE. GARNIER, E. GARNIERSearch for more papers by this authorP. GRAVEREAU, P. GRAVEREAUSearch for more papers by this author First published: June 4, 1985 https://doi.org/10.1002/chin.198522395AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume16, Issue22June 4, 1985 RelatedInformation

Zinc and nickel ferrocyanides: preparation, composition and structure

A review is given of work on nickel and zinc ferrocyanides during the period 1922–1983 with an emphasis on their compositions and structures in relation to the methods of preparation.