Contaminate removal using aluminum-doped magnetic nanoparticles

1. A method comprising:

dispersing solid solution aluminum-doped magnetite nanoparticles in a fluid having a contaminate, forming contaminate-adsorbed nanoparticles;

applying a magnetic field to the fluid, which segregates at least a portion of the contaminate-adsorbed nanoparticles;

applying a magnetic field to the fluid, which segregates at least a portion of the contaminate-adsorbed nanoparticles;

removing at least a portion of the segregated contaminate-adsorbed nanoparticles from the fluid; and

regenerating with an aluminum solution at least a portion of the removed contaminate-adsorbed nanoparticles into regenerated solid solution aluminum-doped magnetite nanoparticles;

wherein the solid solution aluminum-doped magnetite nanoparticles prior to regenerating have an initial contaminate removal efficacy; and

wherein the regenerated solid solution aluminum-doped magnetite nanoparticles have a regenerated contaminate removal efficacy that is at least 70% of the initial contaminate removal efficacy.

2. The method of claim 1 , wherein the solid solution aluminum-doped magnetite nanoparticles have a single crystal structure.

3. The method of claim 1 , wherein the solid solution aluminum-doped magnetite nanoparticles are characterized by a maximum contaminate adsorption capacity of greater than 50 mg/g based on the Langmuir model.

4. The method of claim 1 , wherein the contaminate is selected from the group consisting of biochemical oxygen demand (BOD), chemical oxygen demand (COD), total suspended solids (TSS), total dissolved solids (TDS), fat-oil-grease (FOG), total Kjeldahl nitrogen (TKN), suspended solids, dissolved solids, and a combination thereof;

wherein the solid solution aluminum-doped magnetite nanoparticles are synthesized from a mixture of ferric salt, ferrous salt, and aluminum salt with a basic solution including one or both sodium hydroxide and ammonium hydroxide; and

wherein the solid solution aluminum-doped magnetite nanoparticles are characterized by a maximum contaminate adsorption capacity of greater than 50 mg/g based on the Langmuir model.

5. The method of claim 1 , wherein the solid solution aluminum-doped magnetite nanoparticles are synthesized from a mixture of ferric salt, ferrous salt, and aluminum salt with a basic solution including one or both sodium hydroxide and ammonium hydroxide.

6. The method of claim 1 , wherein an isolation efficiency of the contaminate-adsorbed nanoparticles is pH-independent in the range of the fluid pH from 4 to 9.

7. The method of claim 1 , wherein the solid solution aluminum-doped magnetite nanoparticles are characterized by a maximum contaminate adsorption capacity of greater than 81 mg/g based on the Langmuir model.

8. The method of claim 1 , wherein the solid solution aluminum-doped magnetite nanoparticles are characterized by a maximum contaminate adsorption capacity of greater than 102 mg/g based on the Langmuir model.

9. The method of claim 1 , wherein a containment concentration of the fluid after removal of at least a portion of the removed contaminate-adsorbed nanoparticles is from about 40% to about 97% less than a containment concentration of the fluid prior to forming the contaminate-adsorbed nanoparticles.

10. The method of claim 2 , wherein the solid solution aluminum-doped magnetite nanoparticles are produced by the process comprising:

dissolving stoichiometric amounts of ferric salt, ferrous salt, and aluminum salt in a fluid to form a solution; and

increasing the pH of the solution using a basic solution including one or both sodium hydroxide and ammonium hydroxide until precipitation of the solid solution aluminum-doped magnetite nanoparticles.

11. The method of claim 10 , wherein the process of producing the solid solution aluminum-doped magnetite nanoparticles further comprises:

heating the solution prior to increasing the pH of the solution; and

heating the solution during increasing the pH of the solution.

12. The method of claim 10 , wherein the ferric salt, ferrous salt, and aluminum salt comprise Al 2 (SO 4 ) 3 , FeCl 3 , and FeCl 2 ;

wherein increasing the pH of the solution comprises increasing the pH of the solution with the addition of one or both of NaOH and NH 4 OH; and

wherein the solid solution aluminum-doped magnetite nanoparticles comprise 20 to 50% aluminum.

13. A method comprising:

forming contaminate-adsorbed nanoparticles by introducing solid solution aluminum-doped magnetite nanoparticles having a magnetite structure with aluminum fully incorporated in the cubic inverse spinel lattice of the magnetite structure to a fluid with a contaminate selected from the group consisting of biochemical oxygen demand (BOD), chemical oxygen demand (COD), total suspended solids (TSS), total dissolved solids (TDS), fat-oil-grease (FOG), total Kjeldahl nitrogen (TKN), suspended solids, dissolved solids, and a combination thereof;

isolating at least a portion of the contaminate-adsorbed nanoparticles by applying a magnetic field to the fluid;

removing at least a portion of the isolated contaminate-adsorbed nanoparticles from the fluid; and

regenerating with an aluminum solution at least a portion of the removed contaminate-adsorbed nanoparticles into regenerated solid solution aluminum-doped magnetite nanoparticles;

wherein the solid solution aluminum-doped magnetite nanoparticles are characterized by a maximum contaminate adsorption capacity of greater than 50 mg/g based on the Langmuir model;

wherein the solid solution aluminum-doped magnetite nanoparticles prior to regenerating have an initial contaminate removal efficacy; and

wherein the regenerated solid solution aluminum-doped magnetite nanoparticles are configured such that after the same solid solution aluminum-doped magnetite nanoparticles have been regenerated up through 11 cycles of being regenerated, the cycled regenerated solid solution aluminum-doped magnetite nanoparticles have a regenerated contaminate removal efficacy that is at least 70% of the initial contaminate removal efficacy.

14. The method of claim 13 , wherein an isolation efficiency of the contaminate-adsorbed nanoparticles is pH-independent in the range of the fluid pH from 4 to 9.

15. The method of claim 13 , wherein the solid solution aluminum-doped magnetite nanoparticles are synthesized from a mixture of ferric salt, ferrous salt, and aluminum salt with sodium hydroxide; and

wherein the solid solution aluminum-doped magnetite nanoparticles are characterized by a maximum contaminate adsorption capacity of greater than 81 mg/g based on the Langmuir model.

16. The method of claim 13 , wherein the solid solution aluminum-doped magnetite nanoparticles are characterized by a maximum contaminate adsorption capacity of greater than 102 mg/g based on the Langmuir model.

17. The method of claim 13 , wherein a containment concentration of the fluid after removal of at least a portion of the isolated contaminate-adsorbed nanoparticles is from about 40% to about 97% less than a containment concentration of the fluid prior to forming the contaminate-adsorbed nanoparticles.

18. The method of claim 13 , wherein the solid solution aluminum-doped magnetite nanoparticles are produced by the process comprising:

dissolving stoichiometric amounts of ferric salt, ferrous salt, and aluminum salt in a fluid to form a solution; and

increasing the pH of the solution using a basic solution including one or both sodium hydroxide and ammonium hydroxide until precipitation of the solid solution aluminum-doped magnetite nanoparticles.

19. The method of claim 18 , wherein the process of producing the solid solution aluminum-doped magnetite nanoparticles further comprises:

heating the solution prior to increasing the pH of the solution; and

heating the solution during increasing the pH of the solution.

20. The method of claim 18 , wherein the ferric salt, ferrous salt, and aluminum salt comprise Al 2 (SO 4 ) 3 , FeCl 3 , and FeCl 2 ;

wherein increasing the pH of the solution comprises increasing the pH of the solution with the addition of one or both of NaOH and NH 4 OH; and

wherein the solid solution aluminum-doped magnetite nanoparticles comprise 20 to 50% aluminum.