Adsorption Of Ferrocyanide Research Articles

Study of Ferrocyanide Adsorption onto Different Minerals as Prebiotic Chemistry Assays.

Considered one of the most promising building blocks of life on primitive Earth, cyanide and its complexes are likely to have played an important role in the emergence of life on the planet. Investigation into cyanide on Earth has primarily considered high concentrations, but the cyanide concentration in the oceans of prebiotic Earth was exceptionally low. Thus, Bernal's hypothesis has allowed investigators to work around this problem. We observed, however, that cyanide does not adsorb onto several minerals; therefore, ferrocyanide could be used as a cyanide source when adsorbed onto mineral surfaces to promote the synthesis of molecules of biological significance. When adsorbed onto bentonite, a mineral that has Fe3+ atoms in its interlayers, the formation of Prussian blue analog complexes occurs through endothermic reaction and with increased entropy. The adsorption of ferrocyanide onto kaolinite indicates an exothermic and outer-sphere interaction, which results in degeneracy breakdown for C ≡ N stretch energy into two new bands of FTIR-ATR spectrum. Magnetite, which has iron atoms in its structure, and ferrocyanide interactions have been observed by outer-sphere coordination as well as the formation of Prussian blue analogs, as confirmed by the appearance of a new doublet in the Mössbauer spectra and a broadband close to 750 nm at UV-visible spectroscopy. Magnetite and kaolinite experiments presented relevant results only when performed in seawater, which suggests the importance of seawater composition for prebiotic experiments. These obtained results prove that ferrocyanide interacts with minerals differently according to structure and composition and show that this complex, like the Prussian blue analogs, may have played a crucial role as a source of cyanide on primitive Earth.

Ferrocyanide removal from solution by aluminum-based drinking water treatment residue

This study proposes the use of an aluminum-based drinking water treatment residue (DWTR) to adsorb ferrocyanide. The batch tests and chemical characterization results showed that ferrocyanide adsorption increased as the pH, ion strength, and the solid and solution ratio decreased, and as the initial ferrocyanide concentration increased. The pseudo-first (R2 = 0.906) and pseudo-second-order (R2 = 0.966) kinetic models well described the adsorption kinetics, and the adsorption isotherm was also well fittted by Langmuir (R2 = 0.989) and Freundlich (R2 = 0.989) models. The calculated initial ferrocyanide adsorption rate by the pseudo-second-order kinetic model was 0.0190 mg-CN g−1 h−1, and the estimated maximum adsorption capacity determined by the Langmuir model was 20.9 mg-CN g−1. The main structure and elemental distributions showed nearly no change in DWTR after adsorption. Adsorption involved electrostatic interactions and ligand exchanges with Al in DWTR, as evidenced by the 1.40 eV increase in the Al binding energy after adsorption. Furthermore, ferrocyanide adsorption had a dual effect on the DWTR porosity (including both increase and decrease effect), resulting in a slight increase in the specific surface area and total pore volume of DWTR after adsorption. This dual effect was likely related to Fe present in ferrocyanide, which introduced new vacant sites on DWTR. Overall, recycled DWTR is a promising potential adsorbent for ferrocyanide.

Investigation of coagulation as a pretreatment for microfiltration in cesium removal by copper ferrocyanide adsorption

An adsorption–coagulation–microfiltration (A–C–MF) hybrid process using copper ferrocyanide (CuFC) as the adsorbent was developed in this study for the removal of cesium from water. The effect of coagulant on cesium removal by CuFC adsorption was investigated. A simpler calculation method for determining the CuFC dosage was established based on the Freundlich adsorption isotherms. Although the volume of treated water was 1.32 times higher for the A–C–MF process than the adsorption–microfiltration (A–MF) process, the cake layer and membrane pore resistances in the former were both lower than those in the latter due to the coagulation process.

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.

Adsorptive removal of aqueous fluoride and ferrocyanide by liner minerals from SPL landfill leachate: Effect of pH and adsorptive competition

Soil and water near a spent potliner (SPL) landfill are often found to be highly contaminated with fluoride and ferrocyanide. The liner system, composed of kaolinite and montmorillonite, provides the primary attenuation mechanism for the risk of soluble ferrocyanide and fluoride in the leachate from a SPL landfill. The adsorption of ferrocyanide and fluoride by montmorillonite and kaolinite was investigated in both a single and a binary solute system as a function of the aqueous pH. The adsorption of both solutes was highly pH-dependent, and competed with each of the two liner minerals. In the single solute–montmorillonite system, the adsorption was higher under acidic pH conditions and lower under alkaline pH conditions. For the single solute–kaolinite system, the maximum adsorption appeared near p K a value of the edge functional group. In the binary solute system, the adsorption of solute appeared to be suppressed by the presence of a counterpart, and the competitive adsorption becomes less significant with increasing pH where both adsorptions were minimal. As a result, increasing aqueous pH and the presence of a competitor in SPL-induced leachate can mitigate the attenuation capacity provided by the liner system, thereby, enhancing the leachability of ferrocyanide and fluoride from SPL landfill sites.

Preparation of poly N,N-dimethylaniline/ferrocyanide film modified carbon paste electrode: Application to electrocatalytic oxidation of l-cysteine

Abstract Functionalized poly N,N-dimethylaniline film was prepared by adsorption of ferrocyanide onto the polymer forming at the surface of carbon paste electrode (CPE) in aqueous solution. The electrocatalytic ability of poly N,N-dimethylaniline/ferrocyanide film modified carbon paste electrode (PDMA/FMCPE) was demonstrated by oxidation of l -cysteine. Cyclic voltammetry and chronoamperometry techniques were used to investigate this ability. In the optimum pH (6.00), the electrocatalytic ability about 480 mV and the catalytic reaction rate constant, ( k h ), can be seen 3.08 × 10 3 M −1 s −1 . The catalytic oxidation peak current determined by cyclic voltammetry method was linearly dependent on the l -cysteine concentration and the linearity range obtained was 8.00 × 10 −5 –2.25 × 10 −3 M. Detection limit of this method was determined as 6.17 × 10 −5 M (2 σ ). At a fixed potential under hydrodynamic conditions (stirred solution), the calibration plot was linear over the l -cysteine concentration range 7.40 × 10 −6 M–1.38 × 10 −4 M. The detection limit of the method was 6.38 × 10 −6 M (2 σ ).

Electrocatalytic Oxidation and Determination of Cysteamine by Poly‐N,N‐dimethylaniline/Ferrocyanide Film Modified Carbon Paste Electrode

AbstractFunctionalized poly‐N,N‐dimethylaniline film was prepared by adsorption of ferrocyanide onto the polymer forming at the surface of carbon paste electrode (CPE) in aqueous solution by using potentiostatic method. The electrocatalytic ability of poly‐N,N‐dimethylaniline/ferrocyanide film modified carbon paste electrode (PDMA/FMCPE) was demonstrated by oxidation of cysteamine. Cyclic voltammetry and chronoamperometry techniques were used to investigate this ability. Results showed that pH 7.00 is the most suitable for this purpose. It is found that the catalytic reaction rate constant, (kh), is equal to 2.142×103 M−1 s−1 by the data of chronoamperometry. The catalytic reduction peak current was linearly dependent on the cysteamine concentration and the linearity range obtained was 8.00×10−5 M–1.14×10−2 M. Detection limit was determined 7.97×10−5 M (2σ). This method has been successfully employed for quantification of cysteamine in real sample.

Influence of a soil enzyme on iron-cyanide complex speciation and mineral adsorption

Cyanide is commonly found as ferrocyanide [Fe II(CN) 6] −4 and in the more mobile form, ferricyanide [Fe III(CN) 6] −3 in contaminated soils and sediments. Although soil minerals may influence ferrocyanide speciation, and thus mobility, the possible influence of soil enzymes has not been examined. In a series of experiments conducted under a range of soil-like conditions, laccase, a phenoloxidase enzyme derived from the fungi Trametes versicolor, was found to exert a large influence on iron-cyanide speciation and mobility. In the presence of laccase, up to 93% of ferrocyanide (36–362 ppm) was oxidized to ferricyanide within 4 h. No significant effect of pH (3.6 and 6.2) or initial ferrocyanide concentration on the extent or rate of oxidation was found and ferrocyanide oxidation did not occur in the absence of laccase. Relative to iron-cyanide–mineral systems without laccase, ferrocyanide adsorption to aluminum hydroxide and montmorillonite decreased in the presence of laccase and was similar to or somewhat greater than that of ferricyanide without laccase. Laccase-catalyzed conversion of ferrocyanide to ferricyanide was extensive though up to 33% of the enzyme was mineral-bound. These results demonstrate that soil enzymes can play a major role in ferrocyanide speciation and mobility. Biotic soil components must be considered as highly effective oxidation catalysts that may alter the mobility of metals and metal complexes in soil. Immobilized enzymes should also be considered for use in soil metal remediation efforts.

Ferrocyanide adsorption on aluminum oxides

Ferrocyanide (Fe(CN) 4− 6) adsorption onto γ-alumina ( γ-Al 2O 3( s) ) and gibbsite (Al(OH) 3( s) ) was investigated over a wide pH range and at various solid loadings. Batch experiments were performed using 100-ml solutions ( I=0.01 M NaCl) dosed with 1.0 mg l −1 Fe(CN) 4− 6 as CN. Equilibrium adsorption–pH edges were developed for 0.3, 0.6, 1.2, and 2.0 g l −1 γ-Al 2O 3( s) and 25 g l −1 Al(OH) 3( s) . Ferrocyanide adsorption increased as pH decreased, consistent with the general pH dependence for adsorption of anions onto oxide minerals. Ferrocyanide adsorption onto Al(OH) 3( s) was approximately 300 times lower than onto γ-Al 2O 3( s) on a unit weight basis due to the higher surface reactivity of the γ-Al 2O 3( s) . Ferrocyanide adsorption onto γ-Al 2O 3( s) was significantly greater than has been reported for goethite (FeOOH ( s) ), and both γ-Al 2O 3( s) and FeOOH ( s) adsorbed ferrocyanide to a greater extent than Al(OH) 3( s) . The investigation showed that ferrocyanide can adsorb significantly onto aluminum oxides spanning a range of crystallinity and properties, with the extent of adsorption highly dependent on pH, the solid crystalline structure, and associated surface reactivity.

Adsorption Behavior of Iron–Cyanide onto γ-Al2O3Interface: A Coagulation Approach

Ferrocyanide and ferricyanide ions have strong coagulation ability in a natural water system due to their high valences. Studies with aluminum oxide turbid waters showed significant differences in coagulation between simple ions (Cl−, SO2−4, Fe(CN)3−6, Fe(CN)4−6) and other species (H2PO−4) that interact chemically with the oxide surface. The evidence suggested that the adsorption of ferrocyanide and ferricyanide on aluminum oxide surface is an outer-sphere reaction. The linear relationship between the logarithm of the significant coagulation concentration and Schultz–Hardy ratios indicated that the coagulation obeyed the DLVO rule. Therefore, it is concluded that the coagulation of aluminum oxide by ferrocyanide and ferricyanide is essentially caused by compression of the electric double layer rather than by charge neutralization.

Surface-enhanced Raman scattering from ferrocyanide and ferricyanide ions adsorbed on silver and copper colloids

Surface-enhanced Raman scattering has been observed from the adsorption of ferrocyanide (hexacyanoferrate(II)) and ferricyanide (hexacyanoferrate(III)) ions on Ag and Cu colloids and electrodes. Both ferrocyanide and ferricyanide ions interact strongly with Ag and Cu surfaces, and are bonded to surfaces via the end-on bridging CN σ-bondings. Chemisorption lowers site symmetry of the adsorbed states, resulting in the activation of Raman forbidden modes in the low-frequency as well as the nitrile-stretching regions.

Step-Scan FT-IR Spectroelectrochemical Analysis of Surface and Solution Species in the Ferricyanide/Ferrocyanide Redox Couple

Fourier transform infrared (FT-IR) spectrometry adds complementary structural information to sensitive electroanalytical measurements. In this work, in situ, external reflection FT-IR techniques allowed for examination of interfacial electrochemical events through a thin-layer spectroelectrochemical cell in which a sinusoidally modulated potential was applied to the electrode. The infrared spectra of electrochemically modulated species were measured by a step-scan FT-IR spectrometer. The phase-sensitive detection capability of this technique has been used to provide information about dynamic electrode processes and to enhance sensitivity to surface species. The cause of decreases in the heterogeneous rate constant, k°, of the ferricyanide/ferrocyanide redox process with time has been investigated. Previous authors offer a variety of opinions for the variation of k° for this reaction including the adsorption of polymeric hexacyanoferrate complexes, ferrocyanide, or ferricyanide on the electrode surface; other reports indicate that no species adsorb on the electrode during the electron-transfer process. Our results indicate that, with KCl as electrolyte, a hexacyanoferrate complex can form during potential cycling in the ferri-/ferrocyanide redox couple, but only under rather extreme experimental parameters. Measurements made by electrochemical modulation combined with step-scan FT-IR spectrometry show that, under other conditions, the change in rate constant of this redox process can be attributed to the adsorption of ferrocyanide ion.

Adsorption of ferrocyanide and ferricyanide ions at the aluminum oxide‐solution interface

The adsorption of complex ions (ferrocyanide (Fe(CN)4‐ 6) and ferricyanide (Fe(CN)3‐ 6) by aluminum oxide has been investigated at three initial concentrations of complex ions with varying both concentration of background electrolyte and solution pH. In this study, the triple‐layer model has been sucessfully used to simulate ferrocyanide and ferricyanide adsorption on aluminum oxide surface. Evidence for direct coordination of complex ion to the aluminum oxide has been obtained by IR investigation. The results indicate that ferrocyanide is in association with aluminum oxide surface through the outer‐sphere complexation. The ferricyanide, at neutral and alkaline condition (pH > 5), is favor to the outer‐sphere complexation with that surface, but inner‐sphere reaction plays a major role in this interfacial interation at acidic conditions (pH < 5).

Electrochemical and FTIR spectroscopic charactemzation of ferrocyanide-modified TiO 2 electrodes designed for efficient photosensitization

The mechanism of the photosensitization of TiO 2 by adsorbed ferrocyanide has been investigated by electrochemical measurements and surface FTIR spectroscopy. It is shown that surface roughness factors of approximately 100–200 are necessary for efficient light harvesting. Ferrocyanide adsorbates on titania are compared to Ti[Fe(CN) 6 films deposited by a novel electrochemical method onto metallic substrates. Cyclic voltammetry and analysis of the infrared vibrational spectra of TiO 2-Fe(CN) 4− 6 surface complexes and Ti[Fe(CN) 6] indicate significant charge transfer from Fe II to Ti VI. Ferrocyanide adsorption geometries are proposed on the basis of experimental data and geometric considerations of the anatase lattice. Light conversion efficiencies are discussed, and a model energy level diagram for the semiconductor/ sensitizer/electrolyte interface is presented.

A tunneling spectroscopy study of the adsorption of ferrocyanide from water solution by Al2O3

Tunneling spectra of Fe(12C15N)4−6 and Fe(12C14N)4−6 adsorbed on Al2O3 from dilute H216O and 50% H218O solutions are compared to infrared and Raman spectra of the K4Fe(CN)6 salt. C–N stretching frequencies and isotopic shifts indicate that the iron remains in the divalent state after adsorption. IETS provides more information than IR, and somewhat different information than Raman spectroscopy.