Search results for "CADMIUM"
showing 10 items of 431 documents
Identification of inorganic pigments from paintings and polychromed sculptures immobilized into polymer film electrodes by stripping differential pul…
2000
Abstract Inorganic pigments in paintings and polychromed sculptures are studied by cyclic voltammetry and differential pulse stripping voltammetry using micro-sample coatings in Paraloid B72-film modified electrodes. Characteristic cathodic and anodic differential pulse profiles were obtained in the +0.4 to −1.0 V vs. SCE potential range for different cadmium, copper, lead, mercury and zinc pigments used in traditional colour palettes. Under optimized conditions, excellent reproducibility was obtained. Microsamples extracted from polychromed sculptures, wall paintings, canvas paintings, panel paintings and altarpieces from Spain, Ethiopia and Italy from the 12th to the 20th centuries have b…
Antioxidant Enzymes inOncopeltus fasciatus(Heteroptera: Lygaeidae) Exposed to Cadmium
2003
Abstract Catalase (CAT), glutathione reductase (GR), glutathione S-transferase (GST), and thiobarbituric acid reactive substances (TBARS) were measured together with cadmium (Cd) toxicity and accumulation in newly molted adults of Oncopeltus fasciatus (Dallas) exposed to the metal in drinking water. Insects were provided with either 200 or 20 mg Cd/liter (96-h LC30 and LC10, respectively) or with tap water for 1, 3, 5, and 7 d. Insects exposed to either concentration accumulated Cd in a time-dependent manner. Peroxilipids measured as TBARS were significantly elevated (1.7- to 1.9-fold) from day 3 in insects exposed to 200 mg Cd/liter, whereas TBARS levels of insects exposed to 20 mg Cd/lite…
Optical mercury sensing using a benzothiazolium hemicyanine dye.
2006
[structure: see text] The selectivity and sensitivity of a benzothiazolium hemicyanine dye toward mercury(II) in aqueous solutions are described. Mercury ions coordinate to the dye forming a 1:1 complex. This interaction induces a color change in the dye at micromolar concentrations of mercury. Furthermore, the color change and quenching of the dye emission are selective for mercury when compared with other ions such as lead(II), cadmium(II), zinc(II), or iron(II).
Modelling Cd(II) removal from aqueous solutions by adsorption on a highly mineralized peat. Batch and fixed-bed column experiments
2006
This paper evaluates the potential use of a locally available organic soil amendment as a low-cost adsorbent. The removal of cadmium from aqueous solutions was studied by means of kinetic, batch and fixed-bed experiments. Batch experiments were conducted to evaluate the process kinetics and the removal equilibrium over a broad pH range. Pseudo-second-order kinetics and Freundlich equilibrium parameters were obtained. Six column experiments were carried out at different flow-rates and feed concentrations. Breakthrough curves showed higher metal retention than expected from the batch adsorption isotherms. Column modelling assuming rate-controlled pore diffusion was successfully performed. The…
Sorption properties of algae Spirogyra sp. and their use for determination of heavy metal ions concentrations in surface water.
2010
Abstract Kinetics of heavy-metal ions sorption by alga Spirogyra sp. was evaluated experimentally in the laboratory, using both the static and the dynamic approach. The metal ions – Mn2+, Cu2+, Zn2+ and Cd2+ – were sorbed from aqueous solutions of their salts. The static experiments showed that the sorption equilibria were attained in 30 min, with 90-95% of metal ions sorbed in first 10 min of each process. The sorption equilibria were approximated with the Langmuir isotherm model. The algae sorbed each heavy metal ions proportionally to the amount of this metal ions in solution. The experiments confirmed that after 30 min of exposition to contaminated water, the concentration of heavy meta…
Cadmium and Copper Removal by a Granular Activated Carbon in Laboratory Column Systems
2000
Single and competitive removal of Cd and Cu from aqueous solutions by using Darco 12–20 mesh granular activated carbon in column systems has been investigated. Seven experiments modifying the initial pH and the flow rate were performed. Results showed the efficiency of activated carbon as a sorbent for both metals. pH is shown to be the decisive parameter on metal removal in the column; metal removal increases when the influent pH value is raised. The influence of the flow rate for the experimental conditions is negligible. Batch adsorption and column data are compared. Column modeling assuming local equilibrium and rate-controlled pore diffusion was performed.
Formation and Stability of Cadmium(II)/Phytate Complexes by Different Electrochemical Techniques. Critical Analysis of Results
2010
In the present work the stability constants of various cadmium(II)/phytate (Phy) species were determined at T = 298.15 K in NaNO3(aq) at I = 0.1 mol·L−1 by DP-ASV (Differential Pulse Anodic Stripping Voltammetry) and by potentiometric titrations using an ISE-Cd2+. Cyclic voltammograms were also recorded to check the electrochemical behavior of cadmium in the presence of phytate. The results were analyzed together with previous data determined by ISE-H+ measurements. Data obtained were used to provide an exhaustive speciation scheme for the phytate/cadmium(II) system at different conditions, as well as a comprehensive representation of the binding ability of phytate toward cadmium(II). Diffe…
Studien zum Vorgang der Wasserstoffübertragung, 54. Mechanismus und Grenzen der Clemmensen-Reduktion des Acetophenons und verwandter Verbindungen
1978
Bei der Reduktion von Acetophenon nach Clemmensen entstehen auser Ethylbenzol (1; Vier-Elektronen-Ubergang) in von den Reaktionsbedingungen abhangigen Mengen das Hydrodimerisierungsprodukt 2,3-Diphenyl-2,3-butandiol (2; Ein-Elektronen-Ubergang) und dessen Umlagerungsverbindungen 3 und 4, aber weder 1-Phenylethanol noch Styrol (Zwei-Elektronen-Ubergang). Temperatur, Saurekonzentration, Saureart, Reduktionsmittel (amalgamiertes Zink, Zinkamalgam, Cadmium, Zink-Cadmium-Legierung, Cadmiumamalgam, Magnesiumamalgam, Blei, Zink, Blei-Legierung) bestimmen die Anteile der gebildeten Reduktionsprodukte 1 — 4. 1-Phenylethanol und Styrol konnen unter Clemmensen-Bedingungen partiell in Ethylbenzol (1) u…
Cadmium and Zinc Adsorption onto Activated Carbon: Influence of Temperature, pH and Metal/Carbon Ratio
1996
The adsorption characteristics of cadmium and zinc onto a granular activated carbon were studied. Cadmium and zinc removals increased on raising pH and temperature, and decreased on raising the molar metal/carbon ratio. The adsorption processes were modelled using the surface complex formation (SCF) Triple Layer Model (TLM) with an overall bidentate species. A dependence of the SCF constant on pH, the molar metal/carbon ratio and temperature was observed, and a correlation for log K ads was determined. The SCF model successfully predicted cadmium and zinc removals.
Apoptosis in marine sponges: a biomarker for environmental stress (cadmium and bacteria)
1998
The marine demosponge Suberites domuncula is abundantly present on muddy sand bottoms, both in the open sea and in harbors. In the present study it is shown that exposure of S. domuncula to cadmium (CdCl2) in concentrations ranging from 0.01 to 5.0 g ml−1 for up to 5 d results in apoptotic fragmentation of DNA. Kinetics experiments revealed that after 24 h a significant increase of DNA fragmentation already occurred. Besides cadmium a second stimulus was identified to also cause apoptosis in this species, namely exposure to heat-treated Escherichia coli. In order to support the finding that both cadmium and E. coli induce apoptosis in the sponge, expression of the apoptotic gene MA-3 was st…