Methods for recycling cotton and polyester fibers from waste textiles
Systems and methods are provided that involve a subcritical water reaction to recycle the cellulose and polyester components of waste cotton and cotton/polyester blend textiles that would otherwise be discarded or disposed of. Specifically, the disclosed methods provide for treatment of the waste textiles to produce advanced materials including cellulose and terephthalic acid (TPA) with a low environmental impact. The cellulose and TPA that are produced are of a high quality allowing for production of regenerated cellulose and regenerated polyethylene terephthalate (PET) suitable for fiber spinning and textile applications.
1. A method of producing one or both of cellulose and terephthalic acid (TPA) from a waste textile material comprising a cotton/polyester blend material, the method comprising:
treating the waste textile material in a subcritical water reactor, wherein one or both of a cellulose that comprises a degree of polymerization ranging from about 150-2500 and a dissolved TPA and ethylene glycol (EG) is produced.
2. The method of claim 1 , wherein the treating is conducted at a temperature of about 105° C. to 190° C., a pressure of about 40 to 300 psi, or both.
3. The method of claim 1 , wherein the treating is conducted at a pH ranging from 10-14.
4. The method of claim 1 , further comprising recovering the TPA.
5. The method of claim 4 , wherein the recovering the TPA is conducted at a pH adjustment of pH 2-pH 4.
6. The method of claim 4 , wherein the recovering comprises precipitating the dissolved TPA and crystallizing the precipitated TPA.
7. The method of claim 1 , further comprising recovering the ethylene glycol.
8. The method of claim 1 , further comprising recovering the cellulose.
9. The method of claim 8 , wherein the recovering comprises one or more steps of wash, disintegration, sour wash, activation process, dissolution dope, or wet spinning.
10. The method of claim 1 , further comprising removing color from the waste textile material before, during, or after treating with the subcritical water reactor.
11. The method of claim 10 , wherein the color removal comprises treatment with one or more of hydrogen peroxide, sodium peroxide, sodium hypochlorite, calcium hypochlorite, dimethyl sulfoxide, lithium hypochlorite, sodium perborate, ozone, oxygen, activated carbon, biochar, sodium carbonate, peracetic acid, potassium permanganate, persulfate, sodium chloride, calcium oxychloride, chloramine, chlorine dioxide, sulfur dioxide, sodium hydrosulfite, or TAED (tetra-acetyl-ethylene-di-amine).
12. The method of claim 1 , wherein the subcritical water reactor treatment comprises one or more of methanol, ethanol, isopropanol, tetra-n-butylphosphonium bromide (TBPB), or benzyltributylammonium chloride (BTBAC), or co-polymers thereof.
13. The method of claim 1 , wherein the ratio of waste textile material to water within the subcritical water reactor is about 1:5-1:95.
14. The method of claim 1 , wherein the cellulose comprises a degree of polymerization ranging from about 150-2000.
15. The method of claim 1 , further comprising adjusting the pH of water within the subcritical water reactor before subcritical water treatment.
16. The method of claim 15 , wherein the pH is adjusted to about 2-4.
17. The method of claim 16 , wherein the pH is adjusted using 0.01-5% (v/v) organic acid.
18. The method of claim 15 , wherein the pH is adjusted to about 10-14.
19. The method of claim 18 , wherein the pH is adjusted using 0.5-20% (w/v) sodium hydroxide or 0.5-20% (w/v) potassium hydroxide.
20. A recycled cellulose produced using the method of claim 1 .