Concentrating graphite particles by agglomeration with hydrophobic magnetic particles
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.
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 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.