Concentrating graphite particles by agglomeration with hydrophobic magnetic particles

Abstract

A process for concentrating graphite particles comprising a) providing a feedstock which contains the graphite particles and an undesired material, b) adding hydrophobic magnetic particles to the feedstock which results in a loaded feedstock containing agglomerates of the magnetic particles and the graphite particles, and c) separating the agglomerates from the loaded feedstock by a magnetic field which results in isolated agglomerates.

Claims

1. A process for concentrating graphite particles comprising a) providing a feedstock which contains the graphite particles and an undesired material, b) adding hydrophobic magnetic particles to the feedstock which results in a loaded feedstock containing agglomerates of the magnetic particles and the graphite particles, and c) separating the agglomerates from the loaded feedstock by a magnetic field which results in isolated agglomerates; wherein the magnetic particles are added to the feedstock in an amount of from 0.1 to 20% by weight, based on the weight of the dry graphite particles and undesired material.

2. The process according to claim 1, which further comprises d) breaking up the isolated agglomerates to obtain the magnetic particles and the graphite particles separately.

3. The process according to claim 1, wherein the feedstock is a dispersion.

4. The process according to claim 1, wherein the feedstock is an aqueous dispersion.

5. The process according to claim 1, wherein the feedstock further contains a collector, which selectively forms a hydrophobic layer on the graphite particles.

6. The process according to claim 5, wherein the collector is a hydrocarbon selected from the group consisting of mineral oils, vegetable oils, biodiesel, BtL (Biomass-to-Liquid) fuels, products of coal liquefaction, products of the GtL (Gas to Liquid, from natural gas) process, long chain alcohols, and mixtures thereof.

7. The process according to claim 1, wherein the feedstock comprises 5 to 99 wt % graphite.

8. The process according to claim 1, wherein the magnetic particles are added to the feedstock in an amount of from 0.5 to 10% by weight, based on the weight of the dry graphite particles and undesired material.

9. The process according to claim 1, wherein the feedstock is based on natural graphite ore, electronic scrap, or battery scrap.

10. The process according to claim 1, wherein the undesired material comprises a hydrophilic metal compound or a hydrophilic semimetal compound.

11. The process according to claim 1, wherein the feedstock is subjected to a magnetic separation to remove a magnetic or magnetizable material.

12. The process according to claim 1, wherein the concentration of the graphite particles in the feedstock is increased by the process by a factor of 1.1 to 100.

13. The process according to claim 1, wherein the hydrophobic magnetic particles are hydrophobized by treatment with a hydrophobizing agent selected from the group consisting of polyorganosiloxanes, alkylsiliconates, alkyltrichlorosilanes, alkyltrimethoxysilanes, alkylphosphonic acids, mono- or dialkylphosphoric esters, fatty acids and mixtures thereof.

14. The process according to claim 1, wherein the graphite particles have an average diameter D.sub.50 of 1 nm to 1 mm.

15. The process according to claim 1, wherein the magnetic particles comprise magnetic metals, ferromagnetic or ferrimagnetic alloys of magnetic metals, magnetic iron oxides, cubic ferrites; or mixtures thereof.

16. The process according to claim 1, wherein the graphite particles comprise graphite which is a hexagonal or rhombohedral crystalline, multi-layer modification of chemical element carbon.

17. An agglomerate produced by the process as defined in claim 1, comprising a graphite particle, a hydrophobic magnetic particle, and a collector.

18. A process for concentrating graphite particles comprising a) providing a feedstock which contains the graphite particles and an undesired material, b) adding hydrophobic magnetic particles to the feedstock which results in a loaded feedstock containing agglomerates of the magnetic particles and the graphite particles, and c) separating the agglomerates from the loaded feedstock by a magnetic field which results in isolated agglomerates; wherein the feedstock further contains a collector, which selectively forms a hydrophobic layer on the graphite particles, wherein the feedstock comprises 0.1 to 10 wt % of the collector, based on dry mass of the feedstock.

19. The process according to claim 18, wherein the magnetic particles are added to the feedstock in an amount of from 0.01 to 100% by weight, based on the weight of the dry graphite particles and undesired material.

Description

EXAMPLES

Example 1

(1) a) Feedstock

(2) A graphite ore from a European deposit containing 20% of graphite and 0.03% of carbon as carbonates and feldspar as calcian Albite, Sanidine, Quartz, Pyrrhotite and Biotite as main crystalline constituents according to a XRD-analysis was milled to a particle size D.sub.50 of 20 μm. 20 g (19.9 g dry mass) of this milled ore were dispersed in 60 g of filtrated river water followed by the addition of 100 mg of Hydrocarbon Collector (a technical mixture of linear, branched and cyclic alkanes (mainly C.sub.9-11), aromatic content below 2%, initial boiling point 160° C.) (0.5 wt % based on dry mass feedstock). Afterwards this dispersion was vigorously mixed in a buffled beaker with an Ultra Turrax® T25 stirrer for 10 min at 10000 rpm (spec. energy input approx. 600 kWh/m.sup.3).

(3) b) Agglomeration

(4) Dried hydrophobic magnetite particles were prepared according to Example 1 of WO 2015/110555 based on magnetite particles with a D.sub.50 4 μm and a polyorganosiloxane (a solid methyl silicone resin, Mp 35-55° C., average composition of approx. [CH.sub.3SiO.sub.1.5].sub.100 having a molecular weight Mw of approx. 6700 g/mol).

(5) The hydrophobic magnetite particles (0.6. g) were suspended in 3.6 g of a 0.1 wt % solution of an ethoxylated alkanol (liquid, cloudpoint about 55° C. as 1% in water according to EN1890) in water.

(6) To the resulting feedstock of step a) the suspension of 0.6 g hydrophobic magnetite particles was added and stirred in a buffled beaker by a 30 mm pitch blade stirrer at 1400 rpm for 15 min (spec. energy input approx. 0.7 kWh/m.sup.3) at room temperature.

(7) c) Magnetic Separation

(8) The resulting dispersion is pumped with a rate of 6 l/h to an Wet High Intensity Magnetic Separator (WHIMS) lab-scale magnetic separator equipped with a 4×2 mm wedged wire matrix at a magnetic field strength of 0.7 T (commercially available from Eriez Magnetics Europe Ltd., UK). After completion of the feed addition the matrix is flushed with water. The combined dispersion and flush water are collected as non-magnetic tailings. Afterwards the magnetic field was switched of and the magnetic fraction containing the magnetite graphite agglomerates are flushed out from the matrix yielding the magnetic concentrate. The results of the analysis are summarized in Table 1. The graphite content has been determined by combustion of the samples in air and determination of the amount of carbon dioxide generated.

(9) It was demonstrated that the graphite content was increased from 20% in the graphite ore to 43.6% in the magnetic concentrate.

(10) TABLE-US-00001 TABLE 1 Non-magnetic tailings Magnetic concentrate Dry mass 11.59 g 8.90 g Graphite content 1.0% 43.6% Graphite recovery 3.1% 96.1%

Example 2

(11) Experimental conditions as in example 1 were used except that 20.1 g feed as dry mass and 500 mg of the Hydrocarbon Collector (2.5 wt % based on dry mass feedstock) were employed. The results of the analysis are summarized in Table 2.

(12) TABLE-US-00002 TABLE 2 Non-magnetic tailings Magnetic concentrate Dry mass 11.88 g 8.84 g Graphite content <0.5% 46.1% Graphite recovery <1.4% >98.6%