Methods of pulp fiber treatment
In some embodiments, a method may include treating pulp. The method may include contacting a wood pulp with a singlet oxygen source. The method may include contacting the wood pulp with an alkaline peroxide source. The singlet oxygen source may include a peracetate oxidant solution and generating a reactive oxygen species. The peracetate oxidant solution may include peracetate anions and a peracid. In some embodiments, the peracetate solution may include a pH from about pH 10 to about pH 12. In some embodiments, the peracetate solution has a molar ratio of peracetate anions to peracid ranging from about 60:1 to about 6000:1. In some embodiments, the peracetate solution has a molar ratio of peracetate to hydrogen peroxide of greater than about 16:1. The peracetate oxidant solution may provide enhanced treatment methods of bleaching, brightening, and delignifying pulp fibers involving the use of peracetate oxidant solutions.
1. A method of bleaching pulp, comprising a bleaching process including a bleaching sequence comprising:
first contacting a pulp with a singlet oxygen source; and
after the first contacting, second contacting the pulp with an alkaline peroxide source;
wherein the singlet oxygen source comprises a peracetate oxidant solution comprising peracetate anions and a peracid, and wherein the peracetate oxidant solution as added to the pulp for the first contacting has a pH from about pH 10 to about pH 12 and a molar ratio of peracetate anions to peracid ranging from about 60:1 to about 6000:1; and
wherein the bleaching process comprises subjecting the pulp in multiple stages to the bleaching sequence.
2. The method of claim 1 , wherein following the bleaching process the resulting bleached pulp comprises a pulp brightness of about 80% ISO or greater.
3. The method of claim 1 , further comprising, prior to the first contacting, subjecting the pulp to oxygen delignification.
4. The method of claim 1 , wherein treated pulp resulting from the second contacting comprises a pulp brightness of about 60% ISO or greater.
5. The method of claim 1 , wherein treated pulp resulting from the second contacting of a final said bleaching sequence comprises a pulp brightness of about 85% ISO or greater.
6. The method of claim 1 , wherein the bleaching sequence is in the absence of contacting the pulp with chlorine dioxide between and during the first contacting and the second contacting.
7. The method of claim 6 , wherein the bleaching sequence includes, between the first contacting and the second contacting, intermediate contacting the pulp with a chelating agent.
8. The method of claim 1 , wherein the bleaching sequence includes, between the first contacting and the second contacting, intermediate contacting the pulp with a chelating agent.
9. The method of claim 1 , comprising in a first said stage subjecting the pulp to a first said bleaching sequence and in a second said stage subjecting the pulp to a second said bleaching sequence, and wherein:
the first said bleaching sequence and the second said treating bleaching sequence are each in the absence of contacting the pulp with chlorine dioxide between and during the first contacting and the second contacting.
10. The method of claim 9 , wherein the first said bleaching sequence comprises, between the first contacting and the second contacting, intermediate contacting the pulp with a chelating agent.
11. The method of claim 9 , wherein the bleached pulp resulting from the second contacting of the second said bleaching sequence comprises a pulp brightness of about 60% ISO or greater.
12. The method of claim 9 , further comprising, after the second contacting of the second said bleaching sequence, contacting the pulp with chlorine dioxide.
13. The method of claim 10 , wherein the bleached pulp resulting from the second contacting of the second said bleaching sequence comprises a pulp brightness of about 80% ISO or greater.
14. The method of claim 13 , wherein the bleaching process is totally chlorine free.
15. The method of claim 9 , further comprising:
monitoring at least one of absorbance spectra of bleaching liquors, kappa number, fiber brightness, or fiber viscosity; and
optimizing a said bleaching sequence based upon the monitored values.
16. The method of claim 9 , wherein the bleaching process is in the absence of contacting the pulp with chlorine dioxide.
17. The method of claim 9 , wherein the peracetate oxidant solution comprises a molar ratio of peracetate to hydrogen peroxide of greater than 16:1.
18. The method of claim 1 , wherein the peracetate oxidant solution comprises a molar ratio of peracetate to hydrogen peroxide of greater than 16:1.
19. A method of bleaching pulp, comprising a bleaching process including a bleaching sequence comprising:
first contacting a pulp with a singlet oxygen source;
after the first contacting, second contacting the pulp with an alkaline peroxide source; and
after the second contacting, contacting the pulp with chlorine dioxide:
wherein the singlet oxygen source comprises a peracetate oxidant solution comprising peracetate anions and a peracid, and wherein the peracetate oxidant solution as added to the pulp for the first contacting has a pH from about pH 10 to about pH 12 and a molar ratio of peracetate anions to peracid ranging from about 60:1 to about 6000:1; and
wherein the bleaching sequence is in the absence of contacting the pulp with chlorine dioxide between and during the first contacting and the second contacting.
20. The method of claim 19 , wherein the bleaching sequence includes, between the first contacting and the second contacting, intermediate contacting the pulp with a chelating agent.
21. The method of claim 19 , wherein the peracetate oxidant solution comprises a molar ratio of peracetate to hydrogen peroxide of greater than 16:1.
22. The method of claim 21 , further comprising, prior to the first contacting, subjecting the pulp to oxygen delignification.
23. A method of bleaching pulp, comprising:
first contacting a pulp with a singlet oxygen source;
after the first contacting, second contacting the pulp with a chelating agent;
after the second contacting, third contacting the pulp with an alkaline peroxide source;
after the third contacting, fourth contacting the pulp with chlorine dioxide; and
after the fourth contacting, fifth contacting the pulp with an alkaline peroxide source;
and wherein:
the singlet oxygen source comprises a peracetate oxidant solution comprising peracetate anions and a peracid, and wherein the peracetate oxidant solution as added to the pulp for the first contacting has a pH from about pH 10 to about pH 12 and a molar ratio of peracetate anions to peracid ranging from about 60:1 to about 6000:1;
the peracetate oxidant solution comprises a molar ratio of peracetate to hydrogen peroxide of greater than 16:1, and
the method is in the absence of contacting the pulp with chlorine dioxide between and during the first contacting, the second contacting and the third contacting.
24. The method of claim 23 , further comprising, prior to the first contacting, subjecting the pulp to oxygen delignification.
25. The method of claim 23 , wherein the bleached pulp resulting from the fifth contacting comprises a brightness of at least 80% ISO.