Iron environmental significance

Nealson KH, Saffarini D (1994) Iron and manganese in anaerobic respiration environmental significance, phylogeny, and regulation. Ann Rev Microbio 48 311-343 Nealson KH, Stahl DA (1997) Microorganisms and biogeochemical cycles what can we learn from layered microbial communities Rev Mineral 35 5-34... 

Nealson KH, Saffarini D. 1994. Iron and manganese in anaerobic respiration Environmental significance, physiology and regulation. Annu Rev Microbiol 48 311 3. 

Bigham J. M. and Nordstrom D. K. (2000) Iron and aluminum hydroxysulfates from acid sulfate waters. In Sulfate Minerals—Crystallography, Geochemistry, and Environmental Significance, Rev. Min. Geochem. (eds. C. N. Alpers, J. L. Jambor and D. K. Nordstrom). Mineralogical Society of America, Washington DC, vol. 40, pp. 352—403. 

Both iron and manganese change their oxidation status depending on redox conditions in soils and sediments. The ecological and environmental significance of iron and manganese oxidation and reduction reactions can be summarized as follows ... 

The Behavior of Iron and Aluminum in Acid Mine Drainage Speciation, Mineralogy, and Environmental Significance... 

The yield of hydroquinone is 85 to 90% based on aniline. The process is mainly a batch process where significant amounts of soHds must be handled (manganese dioxide as well as metal iron finely divided). However, the principal drawback of this process resides in the massive coproduction of mineral products such as manganese sulfate, ammonium sulfate, or iron oxides which are environmentally not friendly. Even though purified manganese sulfate is used in the agricultural field, few solutions have been developed to dispose of this unsuitable coproduct. Such methods include MnSO reoxidation to MnO (1), or MnSO electrochemical reduction to metal manganese (2). None of these methods has found appHcations on an industrial scale. In addition, since 1980, few innovative studies have been pubUshed on this process (3). 

Environmental. The toxicity of cyanide in the aquatic environment or natural waters is a result of free cyanide, ie, as HCN and CN . These forms, rather than complexed forms such as iron cyanides, determine the lethal toxicity to fish. Complexed cyanides may revert to free cyanide under uv radiation, but the rate is too slow to be a significant toxicity factor. Much work has been done to estabhsh stream and effluent limits for cyanide to avoid harmful effects on aquatic life. Fish are extremely sensitive to cyanide, and the many tests indicate that a free cyanide stream concentration of 0.05 mg/L is acceptable (46), but some species are sensitive to even lower concentrations. 

Precious metals have faced a significant price increase and the fear of depletion. By contrast, iron is a highly abundant metal in the crust of the earth (4.7 wt%) of low toxicity and price. Thus, it can be defined as an environmentally friendly material. Therefore, iron complexes have been studied intensively as an alternative for precious-metal catalysts within recent years (for reviews of iron-catalyzed organic reactions, see [12-20]). The chemistry of iron complexes continues to expand rapidly because these catalysts play indispensable roles in today s academic study as well as chemical industry. 

Due to the environmental and industrial significance of the reaction, the most thorough studies were reported on the iron(III) catalyzed oxidation of sulfur(IV). As shown in Fig. 4, the kinetic traces are distinctively different in the presence and absence of dioxygen. 

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