Natural Deposits and Economic Importance

Bromine occurs in nature mainly as soluble bromides. The concentration of bromine in the Earth s crust is 1.6 lO %. It is contained in  

The most important deposits are in Arkansas (USA) and the Dead Sea (Israel/Jordan). 

The waste solutions from the potash industry contain up to 6 g/L of bromide. 

The world reserves of bromine are virtually unlimited. The bromine content of the Dead Sea alone is estimated to be 10 t. 

The worldwide capacity for bromine in 1993 was 540 10 t/a. Three companies dominate the production and marketing of bromine and bromine compounds Ethyl Corp. and Great Lakes Chemical in the USA and Dead Sea Bromine in Israel. 

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Baddeleyite. Natural zirconia, Zr02 there are deposits of economic importance in Australia, Brazil and Russia. 

Strontianite is the naturally occurring form of strontium carbonate. It has a theoretical strontium oxide content of 70.2%, but no economically workable deposits are known. There are some naturally occurring strontium—barium and strontium—calcium isomorphs, but none has economic importance. 

Just as oil, natural gas is also categorised as conventional and unconventional. Unlike crude oil, however, natural gas deposits are normally classified according to the economic or technical approach, i.e., all occurrences that are currently extract-able under economic conditions are considered conventional, whereas the rest are termed unconventional. Conventional natural gas includes non-associated gas from gas reservoirs in which there is little or no crude oil, as well as associated gas , which is produced from oil wells the latter can exist separately from oil in the formation (free gas, also known as cap gas, as it lies above the oil), or dissolved in the crude oil (dissolved gas). Unconventional gas is the same substance as conventional natural gas, and only the reservoir characteristics are different and make it usually more difficult to produce. Unconventional gas comprises natural gas from coal (also known as coal-bed methane), tight gas, gas in aquifers and gas hydrates (see Fig. 3.17). It is important to mention in this context so-called stranded gas , a term which is applied to occurrences whose extraction would be technically feasible, but which are located in remote areas that at the moment cannot (yet) be economically developed (see Section 3.4.3.1). 

Salt has been of economic importance in India and is produced in laige quantities. About two-thirds of the supply comes from solar evaporation and the remainder from natural salt deposits in dry lake beds. Solar production is carried out in a series of open ponds, using hand labor and making very little effort to purify or recrystallize the salt. In addition, in some desert regions, evaporation of subsoil brine is carried out. The development of the salt industry in India was curbed by the tax on its production in fact, the first confrontation between Gandhi and the British government involved the salt tax. 

Economic Importance The production of sodium hydrogen carbonate is much lower than that of sodium carbonate. The production in the USA in 1995 was 0.454 10 t being only ca. 5% of the sodium carbonate production and corresponding to 50% of the world production of 0.895 10 t. The capacity in the USA has expanded considerably in recent years and as a result production should increase by 2% per year in coming years. A plant for producing sodium hydrogen carbonate from natural deposits came on stream in the USA in 1991. 

Calcium. sulfate occurs naturally as its dihydrate, (natural gypsum) as anhydrous anhydrite and rarely as its hemihydrate in the form of the mineral bassanite. Only the deposits of natural gypsum and anhydrite are of economic interest. For applications in the construction industry only the hardenable modifications, calcium sulfate hemihydrate (a- and P-form) and anhydrite, which are manufactured by dehydrating the dihydrate, are important. The properties and formation conditions of the different calcium sulfate modifications are given in Table 5.3-11. 

Of the two naturally occurring strontium containing minerals, strontianite (SrGOj) and celestite (SrSO, the latter occurs much more frequently in sedimentary deposits of sufficient quantities to make its recovery practical. Strontianite would be the more useful of the two common minerals, because strontium is used most often in the carbonate form. Gelestite occurs principally as nodules, lenses, beds and materials filling crevices in sedimentary rocks such as carbonates, gypsums, days and evaporites. The economic importance of celestite is con-... 

Thus the statistical pattern is governed by the political development in Eastern Europe. During the cold war East European countries had no excess to the major producers of synthetic zeolites thus they developed technologies to use their abundant natural deposits for catalytic applications. The disintegration of the Soviet Union, accompanied by a political and economic crisis, led to a decrease of research activity in this field. The slight recovery of this trend in recent time is associated with an increased number of English papers written by East Europeans (lift of the iron curtain). One may extrapolate that in the future natural zeolites will become less important for catalytic applications. 

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