Copper-cadmium cells

We construct a standard copper-cadmium cell, close the circuit, and allow the cell to operate. At some later time, the cell voltage reaches zero, and the cell is run down. (a) What will be the ratio of [Cd ] to [Cu ] at that time (b) What will be the concentrations ... 

There are several such toxic agents that cause considerable medical, public and political concern. Two examples are discussed here the heavy metal ions (e.g. lead, mercury, copper, cadmium) and the fluorophosphonates. Heavy metal ions readily form complexes with organic compounds which are lipid soluble so that they readily enter cells, where the ions bind to amino acid groups in the active site of enzymes. These two types of inhibitors are discussed in Boxes 3.5 and 3.6. There is also concern that some chemicals in the environment, (e.g. those found in industrial effluents, rubbish tips and agricultural sprays), although present at very low levels, can react with enhanced reactivity groups in enzymes. Consequently, only minute amounts concentrations are effective inhibitors and therefore can be toxic. It is suggested that they are responsible for some non-specific or even specific diseases (e.g. breast tumours). 

In mammalian cells, some proteins combine with specific metals which are called metal proteins. For instance, transferrin is an iron carrier, ferritin can store iron [9], metallothionein (MT) can hold divalent metals such as zinc, copper, cadmium and so on [10, 11]. In chromosomes, there are some regions where metal proteins combine and regulate gene expressions. Zinc-finger motif proteins are famous for regulating transcriptimi and translation [12]. These metal-related... 

Copper Sulfide—Cadmium Sulfide. This thin-film solar cell was used in early aerospace experiments dating back to 1955. The Cu S band gap is ca 1.2 eV. Various methods of fabricating thin-film solar cells from Cu S/CdS materials exist. The most common method is based on a simple process of serially overcoating a metal substrate, eg, copper (16). The substrate first is coated with zinc which serves as an ohmic contact between the copper and a 30-p.m thick, vapor-deposited layer of polycrystaUine CdS. A layer is then formed on the CdS base by dipping the unit into hot cuprous chloride, followed by heat-treating it in air. A heterojunction then exists between the CdS and Cu S layers. 

StiU another method used to produce PV cells is provided by thin-fiLm technologies. Thin films ate made by depositing semiconductor materials on a sohd substrate such as glass or metal sheet. Among the wide variety of thin-fiLm materials under development ate amorphous siUcon, polycrystaUine sUicon, copper indium diselenide, and cadmium teUuride. Additionally, development of multijunction thin-film PV cells is being explored. These cells use multiple layers of thin-film sUicon alloys or other semiconductors tailored to respond to specific portions of the light spectmm. 

Additional metal layers can create bimetallic corrosion cells if discontinuities appear in service. The layer of copper beneath cadmium plate on aluminium (using a zincate plus cuprocyanide deposit technique) can cause corrosion troubles. When aluminium is plated with nickel and chromium, rapid service corrosion in the zinc layer causes exfoliation. 

The differing malleabilities of metals can be traced to their crystal structures. The crystal structure of a metal typically has slip planes, which are planes of atoms that under stress may slip or slide relative to one another. The slip planes of a ccp structure are the close-packed planes, and careful inspection of a unit cell shows that there are eight sets of slip planes in different directions. As a result, metals with cubic close-packed structures, such as copper, are malleable they can be easily bent, flattened, or pounded into shape. In contrast, a hexagonal close-packed structure has only one set of slip planes, and metals with hexagonal close packing, such as zinc or cadmium, tend to be relatively brittle. 

Metallothioneins are a group of small proteins (about 6.5 kDa), found in the cytosol of cells, particularly of liver, kidney, and intestine. They have a high content of cysteine and can bind copper, zinc, cadmium, and mercury. The SH groups of cysteine are involved in binding the metals. Acute intake (eg, by injection) of copper and of certain other metals increases the amount (induction) of these proteins in tissues, as does administration of certain hormones or cytokines. These proteins may function to store the above metals in a nontoxic form and are involved in their overall metaboHsm in the body. Sequestration of copper also diminishes the amount of this metal available to generate free radicals. 

Cuculic and Branica [788] applied differential pulse anodic stripping voltammetry to a study of the adsorption of cadmium, copper, and lead in seawater onto electrochemical glass vessels, quartz cells, and Nalgene sample bottles. Nalgene was best for sample storage and quartz was best for electroanalytical vessels. 

Metallothioneins (MT) are unique 7-kDa proteins containing 20 cysteine molecules bounded to seven zinc atoms, which form two clusters with bridging or terminal cysteine thiolates. A main function of MT is to serve as a source for the distribution of zinc in cells, and this function is connected with the MT redox activity, which is responsible for the regulation of binding and release of zinc. It has been shown that the release of zinc is stimulated by MT oxidation in the reaction with glutathione disulfide or other biological disulfides [334]. MT redox properties led to a suggestion that MT may possesses antioxidant activity. The mechanism of MT antioxidant activity is of a special interest in connection with the possible antioxidant effects of zinc. (Zinc can be substituted in MT by some other metals such as copper or cadmium, but Ca MT and Cu MT exhibit manly prooxidant activity.)... 

Larramona, G Chone, C. Jacob, A. Sakakura, D. Delatouche, B. Pere, D. Cieren, X. Nagino, M. Bayon, R. 2006. Nanostructured photovoltaic cell of the type titanium dioxide, cadmium sulfide thin coating, and copper thiocyanate showing high quantum efficiency. Chem. Mater. 18 1688-1696. 

Chromium has proved effective in counteracting the deleterious effects of cadmium in rats and of vanadium in chickens. High mortality rates and testicular atrophy occurred in rats subjected to an intraperitoneal injection of cadmium salts however, pretreatment with chromium ameliorated these effects (Stacey et al. 1983). The Cr-Cd relationship is not simple. In some cases, cadmium is known to suppress adverse effects induced in Chinese hamster (Cricetus spp.) ovary cells by Cr (Shimada et al. 1998). In southwestern Sweden, there was an 80% decline in chromium burdens in liver of the moose (Alces alces) between 1982 and 1992 from 0.21 to 0.07 mg Cr/kg FW (Frank et al. 1994). During this same period in this locale, moose experienced an unknown disease caused by a secondary copper deficiency due to elevated molybdenum levels as well as chromium deficiency and trace element imbalance (Frank et al. 1994). In chickens (Gallus sp.), 10 mg/kg of dietary chromium counteracted adverse effects on albumin metabolism and egg shell quality induced by 10 mg/kg of vanadium salts (Jensen and Maurice 1980). Additional research on the beneficial aspects of chromium in living resources appears warranted, especially where the organism is subjected to complex mixtures containing chromium and other potentially toxic heavy metals. 

Coppellotti, O. 1989. Glutathione, cysteine and acid-soluble thiol levels in Euglena gracilis cells exposed to copper and cadmium. Comp. Biochem. Physiol. 94C 35-40. 

Zaroogian, G., S. Anderson, and R.A. Voyer. 1992. Individual and combined cytotoxic effects of cadmium, copper, and nickel on brown cells of Mercenaria mercenaria. Ecotoxicol. Environ. Safety 24 328-337. 

DSA-02 oxide-coated Ti anode (DSA = Dimensionally Stable Anode) is placed, thus creating a large cathode volume. The effluent solution flows perpendicularly through the electrodes with a typical flow rate of 0.5 dm3 s-1. The flowthrough metal electrodes have an active area approximately 15 times their geometric area. The cell allows air sparging to increase the mass-transfer. The current efficiency is about 40% when the inlet concentration of the metal ions is 150 to 1500 ppm and the concentration at the out-let is about 50 ppm. The cell is currently used for the treatment of recirculated wash-waters from acid copper, copper cyanide, zinc cyanide, zinc chloride, cadmium sulphate, cadmium cyanide and precious metal plating and washwaters from electroless copper deposition. Since the foam metal electrodes are relatively expensive the electrodes... 

Metals are extremely important not only for chemical reactions but also for the health and welfare of plants and animals. Some examples of metals required for good nutrition, even in trace amounts, are iron, copper, cobalt, potassium, sodium, and zinc. Other metals—for example, mercury, lead, cadmium, barium, beryllium, radium, and uranium—are very toxic. Some metals at the atomic and ionic levels are crucial for the oxidation process that metabolizes carbohydrates for all living cells. 

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