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Pressure leaching alumina from raw kaolinitic clay using hydrochloric acid.

Authors
Sawyer-DL Jr.; Turner-TL
Source
Reno, NV: U.S. Department of the Interior, Bureau of Mines, RI 8978, 1985 Jan; :1-18
Link
NIOSHTIC No.
10004659
Abstract
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.
Keywords
Leaching; Hydrochloric-acid; Performance-evaluation; Filtration; Aluminum-dioxide; Clay-minerals; Solvent-extraction; Kaolinite
Publication Date
19850101
Document Type
IH; Report of Investigations
Fiscal Year
1985
NTIS Accession No.
PB86-126729
NTIS Price
A02
Identifying No.
RI-8978
Source Name
Reno, NV: U.S. Department of the Interior, Bureau of Mines, RI 8978
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