The field of the invention relates generally to extraction of metal compounds from ores.
Rare earth metals are important to the fields of electronics, chemical industry, metallurgy, machinery, energy, and the like, and are strategic raw materials for developing new technologies.
Bastnaesite is a source of carbonate rare earth element minerals. Besides the cerium group of elements (Ce, La, Pr, Nd), bastnaesite also contains yttrium (Y(CO3)F) and europium. Some bastnaesite contains hydroxyl instead of F, such as hydroxylbastnaesite-(Ce) and hydroxylbastnaesite-(Nd). Cerium is the primary light rare earth element in most natural bastnaesite. Therefore, bastnaesite-(Ce) is a more accurate expression for bastnaesite study in most cases. Typically, it contains 65-75% rare earth oxides. Bastnaesite is usually found in pegmatites, carbonatite and hydrothermal ore bodies in alkaline gangue minerals. Bastnaesite occurs as veins or dissemination in a complex of carbonate-silicate rocks, occurring with and related to alkaline intrusive, for example, in California.
The separation of rare earth metals from crude ore has typically relied on a flotation separation process, based on hydrophobicity differences, and relies on use of a “collector agent” that selectively associates with the target mineral(s). The selection of a collector agent or mixture of agents plays an important role in bastnaesite flotation. The choice of collector is made based on the properties of ores, such as flotation response of rare earth minerals and gangue minerals. Traditional flotation methods involve use of carboxylic acids (e.g., oleic acid, phthalic acid, oxidized paraffin) as the collectors. Unfortunately, when carboxylic acid collectors are used, cost can become an issue, decreasing the profits of the mine. It is therefore of great importance to introduce a simpler, more environmentally friendly and more cost-efficient flotation scheme using other collectors.
The inventors surprisingly developed a robust, cost effective process for separating rare earth metal compounds from crude ores, such as bastnaesite ore, which include rare earth metal compounds (including, for example, cerium, lanthanum, praseodymium, neodymium, and yttrium).
In one aspect, a method is provided for using flotation techniques for separating rare earth metal compounds from bastnaesite ore. The method can include grinding the ore to obtain an aqueous slurry of particles, adding a depressant agent to the slurry and adjusting the pH to a suitable value for the flotation process, adding a collector mixture to the slurry that includes at least one hydroxamic acid, and adding a frother agent to the slurry, followed by subjecting the slurry to froth flotation.
For the purposes of promoting an understanding of the principles of the invention, reference will now be made to certain embodiments and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended, and alterations and modifications in the illustrated invention, and further applications of the principles of the invention as illustrated therein are herein contemplated as would normally occur to one skilled in the art to which the invention relates.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.
For the purpose of interpreting this specification, the following definitions will apply and whenever appropriate, terms used in the singular will also include the plural and vice versa. In the event that any definition set forth below conflicts with the usage of that word in any other document, including any document incorporated herein by reference, the definition set forth below shall always control for purposes of interpreting this specification and its associated claims unless a contrary meaning is clearly intended (for example in the document where the term is originally used).
The use of “or” means “and/or” unless stated otherwise.
The use of “a” or “an” herein means “one or more” unless stated otherwise or where the use of “one or more” is clearly inappropriate.
The use of “comprise,” “comprises,” “comprising,” “include,” “includes,” and “including” are interchangeable and not intended to be limiting. Furthermore, where the description of one or more embodiments uses the term “comprising,” those skilled in the art would understand that, in some specific instances, the embodiment or embodiments can be alternatively described using the language “consisting essentially of” and/or “consisting of.”
As used herein, the term “about” refers to a ±10% variation from the nominal value. It is to be understood that such a variation is always included in any given value provided herein, whether or not specifically referred to.
As used herein, the term “collector oil” refers to hydrocarbon oil, such as, but not limited to, diesel oil, kerosene. The term “collector oil” as used herein includes collector oils such as diesel oil, kerosene, a copper/molybdenum collector (which may be derived from an organosulfur hydrocarbon and heavy hydrocarbon, which is non-selective to all sulfides; e.g., ORFOM® MCO Collector, also known as “MCO”).
As used herein, the term “P80” refers to the 80% passing size obtained by a sieve size analysis of an ore grinding product. P80 is a well-known term in the mining arts. It is used to refer to the “average” particle size of a sample. i.e. about 40 to about 80 microns In some aspects of the invention, the P80 value used may be in a range from about 45 to about 75 microns, or even about 60 microns, or about 74 microns.
The term “alkyl hydroxamic acid” includes C5-C10-alkyl hydroxamic acids.
Froth Flotation
Froth flotation is one of the most important and economical extraction methods in mineral processing industry. Flotation has been widely applied in the extraction of various types of mineral sulfides, phosphates, oxides, and semi-soluble salts. The separation efficiency of flotation is usually characterized by the recovery and the grade of the target mineral, which depend greatly on the flotation parameters, such as particle size, collector's type and dosage, depressant, and temperature.
Flotation separation is an important process for the recovery of rare earth minerals from low grade ore. The process is based on differences in the surface hydrophobicity of different components. The flotation process typically includes grinding the ore to liberate mineral particles, treating the mineral particles with a depressant agent to render undesired particles hydrophilic, and a collector agent to render the desired particles hydrophobic. A frothing agent is then added to enhance flotation of the more hydrophobic particles, whereby they become selectively concentrated in the froth. The froth can then be conveyed away from undesired particles for further processing.
Collectors
The collector agent plays an important role in bastnaesite flotation. The choice of collector is made based on the properties of ores, such as flotation response of rare earth minerals and gangue minerals. Traditional flotation methods involve use of carboxylic acids (e.g., oleic acid, phthalic acid, oxidized paraffin) as the collectors. Unfortunately, when carboxylic acid collectors are used, cost can become an issue, decreasing the profits of the mine. It is therefore of great importance to introduce a simpler, more environmentally friendly and more cost-efficient flotation scheme using other collectors.
Alternatives for collectors include hydroxamic acids, which are a feature of the present disclosure. A collector mixture can further include a collector oil, which can be, for example, kerosene, diesel oil, and proprietary oils such as the copper/molybdenum collector derived from an organosulfur hydrocarbon and heavy hydrocarbons (e.g., ORFOM® MCO Collector, which according to the supplier is non-selective to all sulfides).
Depressants and Conditioners
A successful flotation practice requires more than the collectors. Depressants and conditioners are of great significance in flotation process, especially for rare earth minerals, which are often found associated with gangue minerals (impurities) either of high floatability or high similarity in flotation behavior. The selection of depressant and conditioner is mostly affected by gangue minerals, although the target rare earth minerals and collector agents also matter. A combination of all the reagents contributes to the separation of bastnaesite from gangue minerals.
The choice of collectors, depressant and conditioners impacts how environmentally friendliest and more cost-efficiency flotation scheme. The inventors have surprisingly discovered floatation conditions that result in an improved froth floatation process that is environmentally friendly and cost-effective.
In one aspect, the invention encompasses a method for flotation separation of rare earth metal compounds from bastnaesite ore comprising:
In some embodiments, the method of the invention encompasses reaction conditions that involves the use of one or more collectors, one or more depressants, one or more frothers, and one or more pH conditioners chosen from the Table 1 (in the amounts and at the pH listed below):
In further embodiments, the invention encompasses a method:
wherein said collector comprises salicylhydroxamic acid and collector oil and optionally one or more collectors chosen from alkyl hydroxamic acid and benzohydroxamic acid;
wherein said depressants comprises potassium silicate or sodium silicate and optionally one or more depressants chosen from sodium sulfate, potassium sulfate and carboxymethyl cellulose (CMC) or dextrin or starch;
wherein said frother is methyl isobutyl carbinol or a propylene glycol;
wherein the pH of step (c) occurs at a pH between 8-10; and
wherein said amounts of collectors, depressants and frothers, and pH conditioners is as listed preceding table (Table 1).
In some embodiments the method of the invention involves one or more collectors, one or more depressants and one or more frothers, and pH conditioners, chosen from Table 2 (in the amounts and at the temperature and pH listed below):
In some embodiments the method of the invention involves one or more collectors, one or more depressants and one or more frothers, and pH conditioners, chosen from Table 3 (in the amounts and at the temperature and pH listed below):
In some embodiments the method of the invention involves one or more collectors, one or more depressants and one or more frothers, and pH conditioners, chosen from Table 4 (in the amounts and at the temperature and pH listed below):
In some embodiments the method of the invention involves one or more collectors, one or more depressants and one or more frothers, and pH conditioners, chosen from Table 5 table (in the amounts and at the temperature and pH listed below):
In some embodiments the method of the invention involves one or more collectors, one or more depressants and one or more frothers, and pH conditioners, chosen from Table 6 (in the amounts and at the temperature and pH listed below):
In some embodiments the method of the invention involves one or more collectors, one or more depressants and one or more frothers, and pH conditioners, chosen from Table 7 (in the amounts and at the temperature and pH listed below):
In some embodiments the method of the invention involves one or more collectors, one or more depressants and one or more frothers, and pH conditioners, chosen from Table 8 (in the amounts and at the temperature and pH listed below):
In some embodiments, the flotation method of the invention may involve the use of one or more of the following hydroxamic acid collectors listed in Table 9:
In further embodiments, the invention encompasses a method:
wherein said collector comprises salicylhydroxamic acid and collector oil and optionally one or more collectors chosen from alkyl hydroxamic acid and benzohydroxamic acid;
wherein said depressants comprises potassium silicate or sodium silicate and optionally one or more depressants chosen from sodium sulfate, potassium sulfate and carboxymethyl cellulose (CMC) or dextrin or starch;
wherein said frother is methyl isobutyl carbinol or a propylene glycol;
wherein the pH of step (c) occurs at a pH between 8-10; and
wherein said amounts of collectors, depressants and frothers, and pH conditioners is as listed any of the preceding tables (i.e., Tables 1-8).
In some aspects, the invention may also pertain to any of the following embodiments:
Any patents and publication cited above are included to more fully describe and disclose the invention and the state of the art to which the invention pertains. All publications mentioned herein are incorporated by reference to the extent that they support the present invention.
This application claims the benefit of U.S. Provisional Appl. No. 63/036,410, filed Jun. 8, 2020. The content of the foregoing application is relied upon and is incorporated by reference herein in its entirety.
This invention was made with government support under Grant No. N00014-15-C-0165 awarded by NAVY/ONR. The government has certain rights in this invention.
Number | Date | Country | |
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63036410 | Jun 2020 | US |