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 cotton or cotton/polyester blend material, the method comprising:
treating the waste textile material in a subcritical water reactor at a temperature of about 105° C. to 190° C., a pressure of about 40 to 300 psi, or both for about 0 to 90 minutes, 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 waste textile material comprises cotton/polyester blend material and the treating in the subcritical water reactor comprises a pH ranging from about 10-14.
3. The method of claim 2 , further comprising recovering the TPA.
4. The method of claim 2 , further comprising recovering the cellulose.
5. The method of claim 4 , further comprising subjecting the recovered cellulose to a disintegration process.
6. The method of claim 1 , wherein the waste textile material comprises cotton/polyester blend material and the treating in the subcritical water reactor comprises a first treating at a pH ranging from about 10-14, wherein the dissolved TPA and EG are produced, and a second treating of the cellulose that is produced in the first treating at a pH ranging from about 2-4, wherein the cellulose that is produced in the second treating in the subcritical water reactor comprises a degree of polymerization ranging from about 150-2000.
7. The method of claim 6 , further comprising subjecting the cellulose produced after the second treating to one or more steps of wash, disintegration, sour wash, activation process, dissolution dope, or wet spinning.
8. The method of claim 1 , wherein the waste textile material comprises cotton material, the treating in the subcritical water reactor comprises a pH ranging from about 2-4, and further comprising recovering the cellulose that is produced.
9. The method of claim 8 , further comprising subjecting the recovered cellulose to a mechanical disintegration process.
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 , further comprising adjusting the pH of water within the subcritical water reactor before subcritical water treatment.
15. The method of claim 14 , wherein the pH is adjusted to about 2-4.
16. The method of claim 14 , wherein the pH is adjusted to about 10-14.
17. The method of claim 14 , wherein the pH is adjusted using 0.01-5% (v/v) organic acid, 0.5-20% (w/v) sodium hydroxide, or 0.5-20% (w/v) potassium hydroxide.
18. A recycled cellulose produced using the method of claim 1 .