Chemistry of inorganic compounds – Boron or compound thereof – Binary compound
Patent
1996-05-31
1998-11-03
Langel, Wayne
Chemistry of inorganic compounds
Boron or compound thereof
Binary compound
423489, 4236585, C01B 908, C01B 3506
Patent
active
058304240
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a method of extracting fluorine from minerals or mineral species.
The term "mineral species" is understood herein to mean any mineral-containing product formed by processing mineral ores, for example, mineral concentrates for pyrometallurgical processes such as smelting.
The present invention is not mineral specific and applies to all fluorine containing minerals or mineral species.
Fluorine is present in rocks in a range of minerals; for instance as discrete mineral grains, such as fluorite (CaF.sub.2) and fluorapatite often with a wide range of compositions. Fluorine can also occur dispersed throughout mineral species as a replacement ion or displacement anion, for example, by substitution for chloride or hydroxyl ions. Fluorine can also occur as complex ions such as (FeF.sub.6).sup.3- or (AlF.sub.6).sup.3- in some mineral assemblages, usually at low concentrations.
There is a need to reduce fluorine levels to less than 100 ppm (0.01 wt. %) in mineral concentrates such as lead, zinc and copper sulfides prior to smelting because at levels above 100 ppm fluorine may interfere with the smelting process and result in a cost penalty.
An object of the present invention is to provide a method of extracting fluorine from minerals or mineral species, such as mineral concentrates, to reduce the fluorine levels to less than 100 ppm.
According to the present invention, there is provided a method of extracting fluorine from a mineral or mineral species comprising contacting the mineral or mineral species with a leachate solution which contains metal or metalloid ions capable of forming soluble fluoro-complexes of high bond strength with fluorine in the mineral or mineral species.
The term "metalloid" is understood to mean elements that exhibit properties that are characteristic properties of metals and properties that are characteristic properties of non-metals.
The present invention is based on the realization that the bond strength of some fluoro-complexes can be several orders of magnitude above the bond strength of fluorine in minerals, for example Ca--F in fluorite, and therefore can provide the chemical driving force for extracting fluorine from minerals. As a consequence, providing there are no kinetic, chemical, thermodynamic or solubility restrictions to the formation of fluoro-complexes, contact between a fluorine-containing mineral or mineral species and a suitable metal-containing or metalloid-containing leachate solution will result in the formation of a soluble fluoro-complex and thereby the removal of fluorine from the mineral or mineral species.
BRIEF DESCRIPTION OF DRAWINGS
FIG. 1 shows the results obtained from multileach trials on fluorine removal from lead and zinc concentrates according to the present invention .
A typical extraction reaction for a metal-containing leachate solution is as follows: ##STR1##
It is preferred that the method further comprises repeating the step of contacting the mineral or mineral species with the leachate solution.
It is preferred that the method further comprises separating the leachate solution from the mineral or mineral species.
It is preferred that the method further comprises removing the fluoride complex ions from the leachate solution by precipitation, absorption, displacement, ion exchange, ion exclusion, solvent extraction, or distillation.
Alternatively, it is preferred that the method further comprises decomposing the soluble fluoro-complexes in the leachate solution to separate the metal or metalloid ions and the fluoride ions.
It is preferred particularly that the method comprises recycling the metal or metalloid ions.
It is preferred particularly that the method comprises decomposing the soluble fluoro-complexes in the leachate solution by adjusting the acidity (pH) and/or oxidation potential (Eh) of the leachate solution.
For example, the soluble fluoro-complexes may be decomposed by adjusting the acidity by contacting the leachate solution with lime, limestone, or other alkaline species to raise the pH above 6.
Al
REFERENCES:
patent: 3928019 (1975-12-01), Marsh
patent: 4444740 (1984-04-01), Snodgrass et al.
patent: 4597953 (1986-07-01), Bush
patent: 5352419 (1994-10-01), Jenkins
Hughes Terence Charles
Jomoto Kimitaka
Clarke Dennis P.
Langel Wayne
The Broken Hill Proprietary Company Limited
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