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Pressure leaching alumina from raw kaolinitic clay using hydrochloric acid.

Sawyer DL Jr.; Turner TL
Reno, NV: U.S. Department of the Interior, Bureau of Mines, RI 8978, 1985 Jan; :1-18
The Bureau of Mines studied alumina extraction from uncalcined, kaolinitic day at temperatures from 100 deg. to 250 deg. C using 20- or 27-wt-pct-hcl concentrations and with an acid-to-clay ratio of from 0.8 to 1.4 Times stoichiometric. Autogenous digestion pressures ranged from atmospheric pressure to about 900 psia. Extraction of 96 pct of the alumina was obtained by hcl leaching at temperatures and leaching times that varied from 100 deg. C for 120 h to 200 deg. C for 15 min. Hydrochloric acid stoichiometry of the reaction al2o3.2Sio2.2H2o + 6hcl-> 2alcl3 + 2sio2 + 5h2o was studied at different temperatures and leaching times in a 750-ml tetrafluoroethylene-polymer-lined autoclave. A combination of high temperature and 20 wt pct excess hcl promoted rapid and almost quantitative extraction of alumina (99 pct in some tests). Additional Bureau data obtained with 35-ml tantalum bombs and leaching tests with added fluoride are also provided. At high temperatures, the addition of fluoride did not result in a significant improvement over hcl alone and was deleterious to the filtering properties of the digest residue.
Leaching; Hydrochloric-acid; Performance-evaluation; Filtration; Aluminum-dioxide; Clay-minerals; Solvent-extraction; Kaolinite
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IH; Report of Investigations
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Reno, NV: U.S. Department of the Interior, Bureau of Mines, RI 8978
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