Particulate cadmium sulfide

Kamat PV, Dimitrijevic NM, Fessenden RW (1987) Photoelectrochemistry in particulate systems. 6. Electron-transfer reactions of smaU cadmium sulfide colloids in acetonitrile. JPhys Chem 91 396-401... 

To date, cadmium sulfide, zinc sulfide, lead sulfide, cadmium selenide, and lead selenide semiconductor particulate films have been grown, in situ, under... 

Cadmium sulfide particulate films, generated in thicknesses of 300 50 A at arachidic acid (AA) monolayer interfaces, have been characterized in situ by STM under potentiostatic control [644], Electrical contact was made between the tip of the STM, acting as the working electrode (WE), which was in contact with the CdS particulate film floating on aqueous 0.30 M NaCl, and the reference (RE) and counter (CE) electrodes, placed in the subphase (Fig. 112) [644]. A well-defined single-reduction wave at about — 1.15 V was observed. Prolonged exposure to room light shifted the reduction peak to — 0.85 V. Electrical and photoelectrical characterizations have also been performed on Ti-foil-supported, 5000-A-thick CdS particulate films in an electrochemical cell (Fig. 113) [644]. The Ti foil was used as the WE, while the RE and CE were placed into 0.50 M... 

In the upper part of the sediment column, total particulate cadmium content is approximately 10 mg/kg, whereas in the deeper anoxic zone 20 mg Cd/kg have been measured. The results of the sequential extractions of the core sediment samples separated at 2-cm levels (Figure 5-8) indicate, that in the anoxic zone cadmium is associated by 60-80% to the sulfidic/organic fraction. In the oxic and transition zone, sulfidic and organic fractions decrease to approximately 30-40%, whereas carbo-natic and exchangeable fractions simultaneously increase up to 40% of total cadmium concentrations. Thus, it is notable that high proportions of mobile cadmium forms correlate with the marked reduction in total cadmium contents. 

Copper smelting Copper concentrate, siliceous flux Sulfur dioxide, particulate matter containing arsenic, antimony, cadmium, lead, mercury, and zinc Acid plant blowdown slurry/sludge, slag containing iron sulfides, silica... 

The metals have the tendency to form compounds of low solubility with the major divalent cations (Pb, Cd being found in natural water. Hydroxide, carbonate, sulfide, and, more rarely, sulfate may act as solubility controls in precipitating metal ions from water. A significant fraction of lead and, to a greater extent, cadmium carried by river water is expected to be in an undissolved form. This can consist of colloidal particles or larger undissolved particles of lead carbonate, lead oxide, lead hydroxide, or other lead compounds incorporated in other components of surface particulate matter from runoff. The ratio of lead in suspended solids to lead in dissolved form has been found to vary from 4 1 in rural streams to 27 1 in urban streams. The US Environmental Protection Agency (USEPA) has reported Maximum Contaminant Levels in water that are permissible to be 0.005 m L for cadmium and 0.015 mg/L of lead. ... 

Iron and manganese occur in a number of soil minerals. Sodium and chlorine (as chloride) occur naturally in soil and are transported as atmospheric particulate matter from marine sprays (see Chapter 10). Some of the other micronutrients and trace elements are found in primary (unweathered) minerals that occur in soil. Boron is substituted isomorphically for Si in some micas and is present in tourmaline, a mineral with the formula NaMg3AlgB3Sig027(0H,F)4. Copper is isomorphically substituted for other elements in feldspars, amphiboles, olivines, p5Toxenes, and micas it also occurs as trace levels of copper sulfides in silicate minerals. Molybdenum occurs as molybdenite (M0S2). Vanadium is isomorphically substituted for Fe or A1 in oxides, pyroxenes, amphiboles, and micas. Zinc is present as the result of isomorphic substitution for Mg, Fe, and Mn in oxides, amphiboles, olivines, and pyroxenes and as trace zinc sulfide in silicates. Other trace elements that occur as specific minerals, sulfide inclusions, or by isomorphic substitution for other elements in minerals are chromium, cobalt, arsenic, selenium, nickel, lead, and cadmium. 

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