Silver natural resources

Cadmium (Cd) anode cells are at present manufactured based on nickel-cadmium, silver-cadmium, and mercury-cadmium couples. Thus wastewater streams from cadmium-based battery industries carry toxic metals cadmium, nickel, silver, and mercury, of which Cd is regarded the most hazardous. It is estimated that globally, manufacturing activities add about 3-10 times more Cd to the atmosphere than from natural resources such as forest fire and volcanic emissions. As a matter of fact, some studies have shown that NiCd batteries contribute almost 80% of cadmium to the environment,4,23 while the atmosphere is contaminated when cadmium is smelted and released as vapor into the atmosphere4 Consequently, terrestrial, aquatic, and atmospheric environments become contaminated with cadmium and remain reservoirs for human cadmium poisoning. 

Proposed silver criteria for the protection of natural resources and human health... 

Table 7.8 Proposed Silver Criteria for the Protection of Natural Resources and Human Health... 

CLUNiE p and koehn j (2001) Silver perch a recovery plan. Final Report for Natural Resource Management Strategy Project R7002. Canberra Murray-Darling Basin Commission. 

MOSS, S.M., D.R. MOSS, S.M. ARCE, and C.A. OTOSHI. 2003. Disease prevention strategies for penaeid shrimp culture. Pages 34 6 in Y. Sakai, J.P McVey, D. Jang, E. McVey and M. Caesar (editors) Proceedings of the Thirty-second US Japan Symposium on Aquaculture. US-Japan Cooperative Program in Natural Resources (UJNR). US Department of Commerce, N.O.A. A., Silver Spring, MD. http //www.lib.noaa. gov/japan/aquaculture/aquaculture panel.htm... 

Deposits. Selenium forms natural compounds with 16 other elements. It is a main constituent of 39 mineral species and a minor component of 37 others, chiefly sulfides. The minerals are finely disseminated and do not form a selenium ore. Because there are no deposits that can be worked for selenium recovery alone, there are no mine reserves. Nevertheless, the 1995 world reserves, chiefly in nonferrous metals sulfide deposits, are ca 70,000 metric tons and total resources are ca 130,000 t (24). The principal resources of the world are in the base metal sulfide deposits that are mined primarily for copper, zinc, nickel, and silver, and to a lesser extent, lead and mercury, where selenium recovery is secondary. 

The chemical resources of early humans were limited to the metals and compounds on the earth s surface. A few metals (e.g., copper, silver, and gold) were found uncombined (native) in nature, so they have been available for many centuries. It is believed that the iron first used may have been found as uncombined iron that had reached the earth in the form of meteorites. In contrast, elements such as fluorine and sodium are produced by electrochemical reactions, and they have been available a much shorter time. 

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