ALUMINUM AND BAUXITE 



37 



FiGUBE 7. — United States production and imports and world 

 production of bauxite, 1928-71 (1971 world production 

 is inferred), compiled from U.S. Bureau of Mines Minerals 

 Yearbooks and statistical data. 



Since that war, production has remained between 

 1 and a little more than 2 million tons a year. 



The Arkansas district has produced more bauxite 

 than all other districts in the United States com- 

 bined. About 64 million tons was produced in Arkan- 

 sas from 1896 through 1971. Production in all 

 Southeastern States from 1889 through 1971 

 amounted to only 3.6 million tons, dry basis. 



BYPRODUCTS 



A few metals and other byproducts are recovered 

 in making aluminum. Gallium is recovered from 

 Arkansas bauxite by one company and from bauxite 

 in Hungary. Pig iron is produced from bauxite proc- 

 essed by the Pedersen method in Norway. Vanadium 

 has been recovered from bauxite in France. Vana- 

 dium and chromium were produced from bauxite in 

 Germany during World War II. Red mud, the waste 

 product from the Bayer process, has been used as 

 a soil conditioner to neutralize acid soils in Arkan- 

 sas and as a red pigment in foreign countries. Phos- 

 phate and Portland cement are coproducts of alu- 

 mina recovered from nepheline syenite in the 

 U.S.S.R. Some bauxite resources in the United 

 States and large bauxite deposits elsewhere in the 

 world contain substantial amounts of titanium. Al- 

 though there has been considerable research on 

 recovery of titanium from bauxites, its extraction 

 has not yet proved to be profitable. 



ENVIRONMENTAL CONSIDERATIONS 



Like the other mineral and metal industries, the 

 aluminum industry faces serious environmental 



problems. Those related to mining are primarily the 

 reclamation of strip-mined land and the contamina- 

 tion of streams by sediment. Those related to recov- 

 ery and use include (1) disposal of red-mud waste 

 from alumina plants, (2) control of atmospheric 

 contamination by dust and fumes containing fluor- 

 ides, and surface-water contamination from electro- 

 lytic plants, (3) the control of sulfur in fuel for the 

 generation of electricity, and (4) disposal and re- 

 cycling of used metal. The industry is making sig- 

 nificant progress on environmental problems, though 

 improvements are still to be made. The reclamation 

 of recently mined lands is efficient. In most plants, 

 scrubbers are in operation to clean up gaseous efflu- 

 ents, monitoring systems are installed to check their 

 continued efficiency, and water is treated to control 

 toxicants. However, the big problem of disposal or 

 profitable use of red mud remains without a satis- 

 factory solution, and much improvement in the re- 

 cycling of waste metal is needed. In 1970, approxi- 

 mately 3 billion aluminum beer- and soft-drink cans 

 were made from 57,000 tons of aluminum. In that 

 year, approximately 10 percent of the cans were 

 recycled, and there was a modest increase the fol- 

 lowing year. Even if this marks the beginning of a 

 trend, the problem of beer- and soft-drink-can litter 

 control and disposal or reuse remains a monumental 

 one. 



GEOLOGIC ENVIRONMENT OF BAUXITE 



Aluminum, surpassed in abundance only by oxy- 

 gen and silicon in the crust of the earth, is a major 

 constituent in many types of rocks. It occurs in 

 nature only in combination with other elements — 

 mostly with silicate minerals, the remainder with 

 other compounds. Aluminum combined with oxygen 

 and hydrogen makes up the minerals in bauxite 

 deposits, and this is the form most commonly mined 

 for metal. The principal minerals in bauxite are 

 gibbsite, A1(0H)3; boehmite, AIO(OH) ; and dia- 

 spore, which has the same composition as boehmite 

 but is denser and harder. Gibbsitic bauxites are 

 designated the trihydrate type; boehmite- and 

 diaspore-bsaring bauxites are the monohydrate type. 

 Trihydrate bauxites that have a low silica content 

 (or low reactive-silica content) are tne cheapest to 

 process by the Bayer method. The extraction of 

 alumina from monohydrate and mixed monohydrate- 

 trihydrate bauxites is more costly because higher 

 temperatures and pressures and additional amounts 

 of caustic soda are required. Lower metallurgical 

 costs make it possible to utilize trihydrate bauxite 

 of lower grade than the other types. 



