Phosphorus economic importance

Increases in phosphorus export from agricultural landscapes have been measured after the application of phosphorus. Phosphorus losses are influenced by the rate, time, and method of phosphorus application, form of fertilizer or manure applied, amount and time of rainfall after application, and land cover. These losses are often small from the standpoint of farmers (generally less than 200 kg P km-2) and represent a minor proportion of fertilizer or manure phosphorus applied (generally less than 5%). Thus, these losses are not of economic importance to farmers in terms of irreplaceable fertility. However, they can contribute to eutrophication of downstream aquatic ecosystems. 

Extensive areas of phosphorus-deficient soils occur throughout the world, especially in tropical and subtropical areas, and a deficiency of phosphorus can be regarded as the most widespread and economically important of all the mineral disabilities affecting grazing livestock. 

Phosphorus is technologically and economically important in aluminium-silicon alloys. On one hand it regulates the mechanism of solidification of eutectic (12.5 % Si) and nearly eutectic alloys, on the other hand it grain refines the primary silicon in the hypereutectic system (15-25 % Si) When the eutectic or nearly eutectic aluminium-silicon alloys contain less than 5 Mg/g of phosphorus, the alloy solidifies into a lamellar structure. When the phosphorus concentration is above 9 Mg/g a globular structure is obtained. In hypoeutectic alloys with about 7 % of silicon, the solidification is only fine lamellarly at phosphorus contents between 2 ig/g and 4 g/g. When magnesium is present, even below 2 ng/g a globular structure is obtained. 

As in the case of igneous processes, the sedimentary processes of rock formation lead to the formation economic mineral deposits. Many valuable mineral deposits of iron, manganese, copper, phosphorus, sulfur, zirconium, the rare Earths, uranium and vanadium owe their origin to sedimentary processes. Some of these constitute special types of sedimentary rocks, while others form important constituents of sedimentary rocks. 

Phosphorites are hydrogenous precipitates with phosphorus concentrations greater than 5% w/w P2O5. Concentrations as high as 40% have been observed. In comparison the phosphorus content of most sediments is aroimd 0.3%. Phosphorites represent an important economic ore deposit as shown in Table 18.3, supplying phosphorus for fertilizer use. The United States is the leading supplier of processed phosphates in the world, accounting for about 45% of world trade. 

In this important class of additives, the halogen contributes to some extent to the flame retardancy although this contribution is offset by the lower phosphorus content. The halogens generally reduce vapor pressure and water solubility, thus aiding retention of these additives. Thus, more efficient and effective blending/manufacturing processes involved usually lead to a favorable economics of polymer flame retardation.26... 

Some important biogenic elements, such as phosphorus,caIcium and magnesium, have their own characteristic sedimentation cycle. In this type of cycle, elements from biological systems are continuously lost due to erosion and excessive use in economic activities (e.g. phosphorus in the form of industrial fertilizers, detergents, etc.) and they axe finally stored in the sea. 

The wet process is now mostly nsed in preference to the economically less favourable furnace process, but the bioprocesses for obtaining some phosphorus compounds remain industrially very important (Fignre 12.2). There are many direct applications for the acid (Figure 12.3). 

The number of known phosphorus compounds probably now exceeds 10 , and in a book of this kind it is possible to deal with only a small fraction of these. It is nevertheless hoped that adequate coverage of the simpler derivatives has been achieved together with most of the key compounds of economic, sociological and biological importance. Most of the twentieth-century advances in the understanding of biochemical processes have involved phosphorus compounds. 

Ragaini and colleagues recently studied the influences of acid additives [20-22]. Using the palladium-phenanthroline catalyst system for the carbonylation of nitrobenzene to methyl phenylcarbamate, the addition of anthraniUc acid [20] or phosphorus acids [21, 22] can accelerate the reaction. Anthranilic acid produced higher activity compared with the use of simple benzoic acid. The 4-amino isomer does not show the same increased activity. Later on, they established an improved catalytic system for the carbonylation of nitrobenzene by adding phosphoms acids as an additive, for the first time yielding activities and catalyst fife in the range necessary for industrial applications. By pafladium-phenanthroline complexes and phosphorus acids as promoters, nitrobenzene was carbonylated to methyl phenylcarbamate with unprecedented reaction rates (TOP up to 6,000/h) and catalyst sta-bUity (TON up to 10 ). The best promoter was phosphoric acid, which is very cheap, nontoxic and easily separable from the reaction products. The catalyst system was also applied to the economically very important dinitrotoluenes reduction. 

From a mining point of view, deposits of economic interest must contain manganese ores with more than 35 wL% Mn to be considered profitable, although some commercially mined deposits, especially in the CIS, India, and China, are well below this level. As well as the ore grade, mineral hardness and the presence of other elements such as copper, cobalt, phosphorus, sulfur, and arsenic is important in determining the viability of the ore body for development. 

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