Recycling of cellulosic textiles
A method for recycling textiles comprising cellulose with the following steps of: optionally disintegrating the textile, swelling the cellulose, under reducing conditions, wherein at least one reducing agent is present at least during a part of the swelling, and then performing at least one of the following two bleaching steps in any order: i) bleaching the material with oxygen at alkaline conditions with a pH in the range 9-13.5, and ii) bleaching the material with ozone at acid conditions below pH 6. An advantage is that the yield is improved at the same time as excellent decolourization is achieved. If the recycled material is used in viscose manufacture, the risk of clogging nozzles and so on is reduced.
1. A method for recycling textiles comprising cellulose, said method comprising the sequential steps:
a. providing at least one textile material comprising cellulose,
b. treating the material to swell the cellulose, under reducing conditions, wherein at least one reducing agent is present at least during a part of the swelling,
c. performing at least one of the following two bleaching steps in any order
i. bleaching the material with oxygen at alkaline conditions with a pH in the range 9-13.5, and
ii. bleaching the material with ozone at acid conditions below pH 6,
d. recovering the cellulose and using the cellulose for making new textiles or for any other purpose where cellulose is used.
2. The method according to claim 1 , wherein the at least one textile is at least one selected from the group consisting of cotton, lyocell, rayon, and viscose.
3. The method according to claim 1 , wherein the at least one textile is cotton.
4. The method according to claim 1 , wherein the textile is mechanically disintegrated to at least partially disintegrate the cellulose before step b).
5. The method according to claim 1 , wherein the textile is mechanically disintegrated in a shredder before step b).
6. The method according to claim 1 , wherein the pH during step b) is in the range of 9-13.5.
7. The method according to claim 1 , wherein the pH during step b) is in the range of 11-13.3.
8. The method according to claim 1 , wherein NaOH is present during step b) in a concentration from 0.01 to 0.5 mol/1.
9. The method according to claim 1 , wherein the temperature during step b) is in the range 50-100° C.
10. The method according to claim 1 , wherein the at least one reducing additive comprises sodium dithionite, Na 2 S 2 O 4 .
11. The method according to claim 1 , wherein sodium dithionite, Na 2 S 2 O 4 is present during step b) in a concentration from 0.01 to 0.25 mol/I.
12. The method according to 1 , wherein the bleaching in step c)-i) is carried out at a temperature in the interval 60-120° C.
13. The method according to claim 1 , wherein the bleaching in step c)-i) is carried out during 20 minutes-24 hours.
14. The method according to claim 1 , wherein the bleaching in step c)-i) is carried out during 30 min-120 min.
15. The method according to claim 1 , wherein the at least one bleaching step comprises step c) ii), and wherein a wash is carried out before step c) ii).
16. The method according to claim 1 , wherein the at least one bleaching step comprises step c) ii), and wherein the material is dewatered to a water content of less than 66 wt % before step c) ii).
17. The method according to claim 1 , wherein the at least one bleaching step comprises step c) ii), and wherein the pH during step c) ii) is in the interval pH 1.5-5.
18. The method according to claim 1 , wherein cellulose is recovered after step c).