Lignin dispersion composition and its use in stabilizing emulsions

1. A lignin dispersion composition comprising spherical lignin particles dispersed in an aqueous medium, wherein the spherical lignin particles have a substantially uniform size characterized by a median particle size of 500 nm and a maximum deviation from said median particle size of ±50 nm.

2. The composition of claim 1 , wherein the composition does not contain a surfactant.

3. The composition of claim 1 , wherein the aqueous medium is at least 95 vol % water.

4. The composition of claim 1 , wherein the aqueous medium contains a water- miscible organic solvent in an amount of up to 1 vol %.

5. A method of producing a lignin dispersion, the method comprising:

(i) dissolving lignin in an organic solvent substantially devoid of water yet miscible with water to result in a solution of the lignin in the organic solvent; and

(ii) producing the lignin dispersion by dialyzing said solution of the lignin with water until substantially all of the organic solvent is replaced with water with simultaneous formation of spherical lignin particles dispersed in the water, wherein the spherical lignin particles have a substantially uniform size characterized by a median particle size of 500 nm and a maximum deviation from said median particle size of ±50 nm.

6. The method of claim 5 , wherein the organic solvent comprises a ketone, alcohol, or nitrile.

7. The method of claim 5 , wherein the organic solvent comprises acetone or acetonitrile.

8. The method of claim 5 , wherein the spherical lignin particles have a size exclusively within a range of 200 nm to 2 microns.

9. The method of claim 5 , further comprising: (iii) centrifuging the lignin dispersion produced in step (ii) to separate flocculated matter from the lignin dispersion, and (iv) retrieving the supernatant in which the lignin dispersion is present.

10. A method for stabilizing an emulsion containing at least two immiscible liquids, the method comprising intimately mixing the emulsion with a lignin dispersion composition comprising spherical lignin particles dispersed in an aqueous medium, wherein the spherical lignin particles have a substantially uniform size characterized by a median particle size of 500 nm and a maximum deviation from said median particle size of ±50 nm.

11. The method of claim 10 , wherein the at least two immiscible liquids comprise an oil, hydrocarbon, or halohydrocarbon liquid droplets suspended in a liquid aqueous or alcohol matrix.

12. The method of claim 10 , wherein the spherical lignin particles have a size exclusively within a range of 200 nm to 2 microns.

13. The method of claim 10 , wherein the spherical lignin particles unravel to form a sheet of 5-20 nm thickness at the liquid-liquid interface of the at least two immiscible liquids.

14. A method for producing a hierarchical assembly of porous microparticles, the method comprising:

(i) intimately mixing an emulsion containing at least two immiscible liquids with an amphiphilic block copolymer and a lignin dispersion composition comprising spherical lignin particles having a substantially uniform size characterized by a median particle size of 500 nm and a maximum deviation from said median particle size of ±50 nm dispersed in an aqueous medium, to result in formation of a lignin sheet of 5-20 nm thickness at liquid-liquid interfaces between the at least two immiscible liquids, and forming a double emulsion containing the at least two immiscible liquids;

(ii) spreading the double emulsion onto a surface to produce a film of the double emulsion; and

(iii) evaporating the immiscible liquids from the film to produce a solid film of the hierarchical assembly of porous microparticles.

15. The method of claim 14 , wherein the amphiphilic block copolymer comprises at least one hydrophilic polyalkylene oxide block and at least one lipophilic polyvinylhydrocarbon block.

16. The method of claim 14 , wherein the spherical lignin particles have a size exclusively within a range of 200 nm to 2 microns.

17. The method of claim 14 , wherein the hierarchical assembly of porous microparticles is crosslinked with a crosslinker to render the hierarchical assembly rigid.

18. The method of claim 17 , wherein the crosslinker is boric acid or formaldehyde.