Control of pyrite surface chemistry in physical coal cleaning. Final report
In Part I, Surface Chemistry of Coal Pyrite the mechanisms responsible for the inefficient rejection of coal pyrite were investigated using a number of experimental techniques. The test results demonstrate that the hydrophobicity of coal pyrite is related to the surface products formed during oxidation in aqueous solutions. During oxidation, a sulfur-rich surface layer is produced in near neutral pH solutions. This surface layer is composed mainly of sulfur species in the form of an iron-polysulfide along with a smaller amount of iron oxide/hydroxides. The floatability coal pyrite increases dramatically in the presence of frothers and hydrocarbon collectors. These reagents are believed to absorb on the weakly hydrophobic pyrite surfaces as a result of hydrophobic interaction forces. In Part III, Developing the Best Possible Rejection Schemes, a number of pyrite depressants were evaluated in column and conventional flotation tests. These included manganese (Mn) metal, chelating agents quinone and diethylenetriamine (DETA), and several commercially-available organic depressants. Of these, the additives which serve as reducing agents were found to be most effective. Reducing agents were used to prevent pyrite oxidation and/or remove oxidation products present on previously oxidized surfaces. These data show that Mn is a significantly stronger depressant for pyrite than quinone or DETA. Important factors in determining the pyrite depression effect of Mn include the slurry solid content during conditioning, the addition of acid (HCl), and the amount of Mn. The acid helps remove the oxide layer from the surface of Mn and promotes the depression of pyrite by Mn.
- Research Organization:
- Virginia Center for Coal and Minerals Processing, Blacksburg, VA (United States)
- Sponsoring Organization:
- USDOE, Washington, DC (United States)
- DOE Contract Number:
- FG22-89PC89789
- OSTI ID:
- 10164748
- Report Number(s):
- DOE/PC/89789-T14; ON: DE93016773
- Resource Relation:
- Other Information: PBD: 19 May 1993
- Country of Publication:
- United States
- Language:
- English
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