Competition among metals

DSSCs efficiencies up to 10.4%8 have been reported for devices employing nanocrystalline Ti02 films. Several studies have addressed the use of alternative metal oxides including SnCU,9 10 ZnO,11,12 and Nb205.13 The performance of dye-sensitized solar cells can be understood in view of the kinetic competition among the various redox processes involved in the conversion of light into electricity. Ultrafast electron injection (k2) has been observed in the femtosecond-picosecond (10 l5-... 

If all particles of matter at room temperature have the same average kinetic energy, why are some materials gases while others are liquids or solids The answer lies with the attractive forces within and between particles. The attractive forces that hold particles together in ionic, covalent, and metallic bonds are called intramolecular forces. The prefix intra- means within. For example, intramural sports are competitions among teams from within a single school. The term molecular can refer to atoms, ions, or molecules. Table 13-2 summarizes what you learned about intramolecular forces in Chapters 8 and 9. 

Heavy metals compete for sorption sites on soil components. Reports on competition in the adsorption of two or more heavy metals on variable-charge minerals and humic substances in soils are rare. Benjamin and Leckie (1981) found a nearly complete lack of competition among Cd, Cu, Zn and Pb added to a poorly crystalline Fe- oxyhydroxide. Probably, the lack of competition among the heavy metals could be attributed to low surface coverage effect. Saha et al. 

The adsorption properties of natural clinoptilolite toward Co were investigated by batch equilibration technique [07S2], The kinetic data were fitted by pseudo-second-order reaction model, and the adsorption isotherms were defined by the Langmuir equation. The adsorption capacity of the natural clinoptilolite was decreased by the competition among the metal ions in solution. The adsorption capacity reached 2.34 mg/g for Co. The adsorption of Co was low, at low pH, but increased remarkably with increasing pH and precipitated at pH > 8. The presence of EDTA hindered the adsorption of Co on clinoptiloUte. 

Streptomycin has a complex action on bacteria the general background is given in Section 4.1 (p. 126)5 and the unusual penetration of the plasma membrane is described in Section 14.2. What is of interest here is that streptomycin displaces magnesium from ribosomes as shown in Fig. 11.7. This effect seems to be a case of competition among cations rather than a metal-binding effect. 

This competition for electrons is reminiscent of the competition for protons among acids and bases. The similarity suggests that we might develop a table in which metals and their ions are... 

Water birds have not been shown to be directly affected by acidification. However, the prey of waterbirds may be of concern as these lower food-chain organisms may have elevated levels of toxic metals related to acidification of their habitat. Moreover, most water birds rely on some component of the aquatic food-chain for their high protein diet. Invertebrates that normally supply caJcium to egg-laying birds or their growing chicks are among the first to disappear as lakes acidify. As these food sources are reduced or eliminated due to acidification, bird habitat is reduced and reproductive rate of the birds is affected. The Common Loon is able to raise fewer chicks, or none at all, on acidic lakes where fish populations are reduced 37 and 5S). However, in some isolated cases, food supplies can be increased when competitive species are eliminated (e.g.. Common Goldeneye ducks can better exploit insects as food when competition from fish is eliminated). The collective influences of acidification are difficult to quantify on a specific area basis but for species that rely on a healthy aquatic ecosystem to breed, acidification remains a continuing threat in thousands of lakes across eastern North America 14). 

---