Reduction Of Cadmium Ions Research Articles

Eco-friendly synthesis of biosorbent based in chitosan-activated carbon/zinc oxide nanoparticle beads for efficiency reduction of cadmium ions in wastewater

Eco-friendly synthesis of biosorbent based in chitosan-activated carbon/zinc oxide nanoparticle beads for efficiency reduction of cadmium ions in wastewater

Low Wavenumber Raman Modes and Plasmon Resonance in Cd Nanoparticles Obtained in Extract of Opuntia Ficus-Indica Plant

Cadmium colloidal crystalline nanoparticles were obtained by a simple green synthesis method employing the plant extract of Opuntia ficus-indica. The plant extract reduces the Cd ions and stabilizes the size of cadmium colloidal particles at the nanometric level. The size and morphology of agglomerates of nanoparticles of about 100 nm were analyzed by field-emission scanning electron microscopy (FESEM). The size, shape and crystalline structure of the Cd nanoparticles were determined from TEM analysis. The results show that Cd nanoparticles with hexagonal crystalline structure and average size 2–3 nm were obtained by this green synthesis method. The optical absorption spectrum of the colloidal solution containing the cadmium nanoparticles displays an optical absorption band centered at 236 nm, which was attributed to the plasmon resonance of the Cd colloidal nanoparticles. Mie theory for colloidal systems was applied to reproduce theoretically the plasmon resonance absorption data of the Cd colloidal nanoparticles. Furthermore, the Raman spectrum of powder from dried samples after reduction of cadmium ions, displays a low wavenumber vibration mode centered at 114 cm-1, assigned to the Cd nanoparticles. Density functional theory (DFT) calculations at local spin density approximation (LSDA) level were performed to determine the structure and vibrational properties of small clusters of cadmium consisting of 3–10 atoms. Radial breathing modes with frequencies between 90 cm-1 and 120 cm-1 were found to be the most active Raman modes of the low-energy Cd n clusters.

Characterization and seasonal variations of surface active substances in the natural sea surface micro-layers of the coastal Middle Adriatic stations

Surface micro-layer (ML) samples were collected in different seasons over a long time period in the coastal area of the Middle Adriatic Sea including the seawater Rogoznica lake location and the semi-enclosed estuarine Martinska station. Natural surface micro-layers were studied as original samples and as ex-situ reconstructed films after previous extraction by organic solvents of different polarities ( n-hexane and dichloromethane). Using alternating current (AC) voltammetry (out-of-phase mode) the concentration of surface active substances (SAS) in original ML of both locations was determined, and the enrichment factor (EF) in the ML was related to the underlayer water (ULW) samples collected at 0.5 m depth. Seasonal variability of SAS concentrations of the ML was observed at both locations. The ex-situ films were studied using a modified AC voltammetry method (out-of-phase mode) transferring an organic extract of natural micro-layers spread onto electrolyte from the air-water interface to the mercury electrode surface. The comparison of adsorption characteristics for model lipids of different polarities and those of transferred ex-situ reconstructed films has revealed that different types of lipid material were present in each ex-situ film of the same micro-layer. Additional characterization of the surface active material of natural MLs was carried out by AC voltammetry (in-phase mode) using cathodic reduction of cadmium ions as an indicator of permeability of different films adsorbed at the mercury electrode. The SAS of ML of both investigated locations induced an inhibition effect to the reduction of cadmium ions. Seasonal variations of inhibition have also been noticed. The electrochemical study contributed to the physicochemical characterization of the surface active matter of the surface micro-layer with the emphasis to the role of lipids which, although they represent a minor fraction of the total micro-layer organic material, contribute considerably to the micro-layer formation and stabilization at the air–water interface.

Photocatalytic reduction of cadmium on TiO 2 nanoparticles modified with amino acids

The photocatalytic reduction of cadmium ions was investigated using TiO 2 nanoparticles (45 Å in diameter) surface-modified with histidine (His) or alanine (Ala). The X-ray diffraction measurements indicated that illumination of suspension consisting of His- or Ala-modified TiO 2 nanoparticles in the presence of cadmium ions under an anoxic atmosphere lead to the formation of metallic cadmium. The TiO 2 Fermi level upon surface modification with His or Ala must be shifted towards negative potentials at least 400 mV in order to achieve efficient photoreduction of cadmium ions. The surface structure of His- or Ala-modified TiO 2 nanoparticles was proposed based on the changes in the vibration spectrum of His or Ala after adsorption on TiO 2 and after addition of cadmium ions.

Photocatalysis of the Reduction of Cd2+Ions by CdS Nanoparticles in Isopropyl Alcohol

The kinetic relationships governing the photocatalytic reduction of Cd2+ cations with participation of CdS nanoparticles in isopropyl alcohol solutions were investigated. Quantum-dimensional effects that manifest themselves in an increase in the rate of the process with decrease in the average size of the photocatalyst nanoparticles were observed and interpreted. In the light of published data a scheme that agrees satisfactorily with the experimental results is proposed for the mechanism of the photocatalytic reduction of cadmium ions.

The synergism of cadmium on the catalytic activity of Cd–Cr–O system: II. Ethanol decomposition, catalysts reducibility, and in situ electrical conductivity measurements

In this paper, the conversion (dehydration/dehydrogenation) of ethanol over a series of chromia as well as cadmium/chromia catalysts calcined in the 400–1000°C temperature range has been studied. The reaction was performed in a fixed-bed reactor at atmospheric pressure and in the 150–400°C temperature range using nitrogen as a carrier gas. The reaction products were ethane, ethylene, and acetaldehyde together with trace amounts of ethyl acetate. The cadmium-containing catalysts, especially those calcined at 400 and 500°C, showed higher dehydrogenation activity. This trend was attributed to the catalyst reducibility, which was correlated with the presence of chromate ions. Such ions enhance the reduction of cadmium ions to zerovalent cadmium. Catalysts reducibility was checked by means of EtOH-temperature-programmed reduction (TPR), XRD, and FT-IR analyses. Moreover, in situ electrical conductivity measurements during alcohol admission were carried out. A good parallelism was found between the catalyst activity and its reducibility. In this way, the presence of Cd0–Cr2O3 mixture, as a result of cadmium chromate reduction, showed a synergistic effect towards ethanol conversion as well as acetaldehyde selectivity. This effect was ascribed to the formation of donor–acceptor pairs as a consequence of Cd0–Cr2O3 mixture formation.

The mechanism of the reduction of cadmium ions at a dropping mercury electrode from NaClO 4 base electrolyte solutions with varied water activity

The reduction of Cd(II) to Cd(Hg) has been studied by means of demodulation voltammetry in a wide potential range and at various water activities using NaClO 4 as the base electrolyte. From this study it is concluded that the reduction proceeds according to: (i) fast loss of 12.5 water molecules in a preceding equilibrium; (ii) a slow “chemical” step, which is not a desolvation; (iii) slow transfer of the first electron; (iv) fast loss of four water molecules; (v) slow transfer of the second electron; and (vi) fast loss of the remaining nine water molecules. These results and the values of the rate constants obtained are compared with results obtained earlier on the reduction of Zn(II).

ChemInform Abstract: Catalysis of the Electrochemical Reduction of Cadmium Ions by Chloride Ions. Mechanistic Study in Mixed 1 M KF + KCl Aqueous Solutions at the Dropping Mercury Electrode.

AbstractAs concluded from rate data measured by impedance and demodulation voltammetry with Cl‐ ion acting as the catalyst, the Cd2‐ reduction proceeds according to a CECEC mechanism (C: chemical conversion; E: single electron transfer).

The catalysis of the electrochemical reduction of cadmium ions by chloride ions: A mechanistic study in mixed 1 M KF + KCl aqueous solutions at the dropping mercury electrode

From the rate data obtained with impedance and demodulation voltammetry at varied concentrations of chloride ion acting as the catalyst, it is concluded that the cadmium ion reduction proceeds according to a CECEC mechanism. The second and third “chemical” steps show up because the catalyst accelerates specifically the first chemical and the first electrochemical step and because it does not affect the other steps to a significant extent. It is argued that the addition of a catalyst may serve as a general tool to unraveling the mechanism of an electrode reaction in a way that has some resemblance to variation of the electrode potential. The rate data, after correction for the Frumkin effect and complex formation, are treated as a function of the concentration, the surface excess and the surface activity of the catalyst, leading to a preference for the latter quantity. The way in which the catalyst exerts its activity is found to be greatly different from the results obtained earlier in this laboratory with thiourea catalyzing the Cd(II) reduction and with iodide ions catalyzing the Zn(II) reduction.

Feasibility of producing cadmium-zinc alloy powders

Electrolytic deposition of cadmium-zinc alloy powders from sulfate solutions is possible provided that the reduction of cadmium ions is performed under limiting diffusion current conditions. Simultaneous discharge of cadmium and zinc ions is not accompanied by super- and depolarization phenomena, which enables the alloy composition to be predicted using polarization curves of reduction of the two kinds of ion in individual solutions. Because of growth of the alloy deposit surface during galvanostatic deposition, the composition of the powder is a function of buildup time, and can be changed only by varying the solution composition. Consequently, it is best to produce such powders either under potentiostatic conditions or under galvanostatic conditions but with continual removal of deposited powder from the basis.

The effect of poly- p-styrenesulphonate ions on the polarographic reduction of cadmium ions

The polarographic reduction of cadmium ions in the presence of ionizable and non-ionizable polymers is studied. It is shown that the limiting reduction currents for Cd 2+ are dependent on the nature of the counter-ion (Li +, Na +, K +), and on the molecular weight of an ionic polymer.

Reduction of cadmium ions at stationary platinum micro-electrodes in fused alkali nitrates

Current-reversal chronopotentiometry was used to investigate the cathodic reduction of Cd2+ ions at platinum micro-electrodes in molten NaNO3-KNO3 at different temperatures. The high rate of the irreversible oxidation of cadmium metal by the nitrate solvent and consequently the difficulties to interpret quantitatively the data obtained are discussed.