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Hydrolyzed Metal Ions as Pyrite Depressants in Coal Flotation: A Laboratory Study.

Baker AF; Miller KJ
NTIS: PB 200 700 :21 pages
Laboratory flotation of synthetic coal-pyrite mixtures and high- pyritic-sulfur coal indicated that ferric chloride fecl3), aluminum chloride (alcl3), chromium chloride (crcl3), and cupric sulfate (cuso4) are potential pyrite depressants. Pyrite was depressed in the ph range from 4.5 to 7.0 With ferric chloride, from 5.8 to 7.0 With aluminum chloride, from 6.4 to 7.1 With chromium chloride, and from 6.4 to 7.4 With cupric sulfate. Best separation of pyrite from coal was achieved in flotation solutions containing from 2 x 10-5 to 5 x 10-5 mole/liter of each salt. In solutions containing excess salt concentrations, coal was also depressed. These Bureau of Mines tests demonstrated on a laboratory scale that, in solutions containing 4 x 10-5 mole/liter ferric chloride and from 1 x 10-4 to 2 x 10-4 mole/liter sodium hydroxide, the pyritic sulfur content of a Lower Freeport bed coal sample could be reduced from about 2.51 percent to less than 0.60 percent with recoveries of over 83 percent. The depression of pyrite appears to be due to the adsorption of positively charged colloidal metal hydroxide at the pyrite-solution interface. This hypothesis is supported by zeta potential determinations which showed that suspended coal and pyrite particles in solutions containing metal salts are positively charged in the ph range where depression occurs.
Publication Date
Document Type
IH; Report of Investigation;
Fiscal Year
NTIS Accession No.
NTIS Price
Identifying No.
RI 7518
NIOSH Division
Source Name
NTIS: PB 200 700
Page last reviewed: December 10, 2021
Content source: National Institute for Occupational Safety and Health Education and Information Division