Method for producing nanomagnetite

Patent metadata

Field	Value
Publication number	US-10843935-B2
Application number	US-201716307425-A
Country	US
Kind code	B2
Filing date	Jun 6, 2017
Priority date	Jun 6, 2016
Publication date	Nov 24, 2020
Grant date	Nov 24, 2020

Abstract

The application relates to a method for preparing magnetite, comprising steps of:
a) reaction at a temperature of 100° to 500° C. of a material containing wüstite with water, in order to obtain a solid comprising magnetite, and then
b) recovery of the magnetite in the form of particles wherein more than 25% by weight are of nanometric size.

First claim

The invention claimed is:

1. A method for preparing magnetite comprising, in sequence, the steps of:
combining a wüstite-containing material with an acidic aqueous treatment solution to form a reaction mixture;
exposing the reaction mixture to a reaction condition comprising
a reaction temperature between 100 and 500° C., the aqueous solution being at least partially in liquid form during the reaction;

maintaining the reaction mixture under the reaction condition for a reaction period of sufficient duration to produce a treated wüstite-containing material in which at least 10% of the wüstite originally present in the wüstite-containing material has been converted to
magnetite particles, and
recovering the magnetite particles, wherein at least 25 wt % of the recovered magnetite particles are nanoparticles.

2. The method according to claim 1 , wherein the reaction temperature is 150 to 350° C.

3. The method according to claim 1 , wherein the acidic aqueous treatment solution has a pH less than 6 when measured at 25° C. and 1 bar.

4. The method according to claim 3 , wherein the acidic aqueous treatment solution has a pH of from 2 to 5.

5. The method according to claim 3 , wherein the acidic aqueous treatment solution has a pH of from 2.5 to 3.

6. The method according to claim 3 , wherein the acidic aqueous treatment solution includes a carboxylic acid able to form a complex with an iron ion.

7. The method according to claim 1 , wherein the reaction pressure is 5 to 700 bar.

8. The method according to claim 1 , wherein the wüstite-containing material is steelworks slag.

9. The method according to claim 8 , wherein the steelworks slag is a decalcified slag.

10. The method according to claim 8 , further comprising:
treating the steelworks slag with an aqueous decalcification solution, wherein the decalcification solution has a pH of 1 to 6, for a treatment period sufficient to remove at least 90% of calcium from the steelworks slag.

11. The method according to claim 9 ,
the acidic aqueous treatment solution has a pH of from 3 to 4;
the reaction pressure is from 100 to 200 bar; and
the reaction temperature is from 200° to 300° C.

12. The method according to claim 1 , wherein the step of recovering the magnetite comprises a magnetic separation operation.

13. The method according to claim 12 , wherein the step of recovering the magnetite further comprises:
separating the treated wüstite-containing material from the acidic aqueous treatment solution;
optionally grinding the treated wüstite-containing material to obtain smaller particles of the treated wüstite-containing material;
adding water or an acidic aqueous first separation solution to the treated wüstite-containing material in order to obtain a first separation mixture,
separating the first separation mixture using a magnetic field to recover a first solid magnetic portion of the first separation mixture,
adding water or an acidic aqueous second separation solution to the first solid magnetic portion in order to obtain a second separation mixture,
separating the second separation mixture using a magnetic field to recover a second solid magnetic portion of the second separation mixture.

14. The method according to claim 1 , wherein the step of recovering the magnetite further comprises a high-gradient magnetic separation operation.

15. The method according to claim 1 , wherein the wüstite-containing material is wüstite.

16. The method according to claim 1 , wherein the reaction temperature is 150 to 250° C.

17. The method according to claim 3 , wherein
the acidic aqueous treatment solution has a pH of from 2 to 4.

18. The method according to claim 6 , wherein
the organic acid is acetic acid.

19. The method according to claim 1 , wherein
the reaction pressure is 10 to 400 bar.

20. The method according to claim 1 , wherein
the reaction pressure is 40 to 200 bar.

Assignees

• Centre Nat Rech Scient
• Univ Aix Marseille

Inventors

• Brunet Fabrice
• Crouzet Camille
• Goffe Bruno

Classifications

• B22F9/12

  starting from gaseous material · CPC title

• H01F1/344

  Ferrites, e.g. having a cubic spinel structure (X2+O)(Y23+O3), e.g. magnetite Fe3O4 · CPC title

• C01P2004/64

  Nanometer sized, i.e. from 1-100 nanometer · CPC title

• B03C1/002

  High gradient magnetic separation (acting directly on the substance being separated B03C1/025; acting on the medium containing the substance being separated B03C1/32) · CPC title

• B82Y25/00

  Nanomagnetism, e.g. magnetoimpedance, anisotropic magnetoresistance, giant magnetoresistance or tunneling magnetoresistance · CPC title