Differences and similarities between kraft and oxygen delignification of softwood fibers: effects on chemical and physical properties

Esteves, Cláudia V.; Sevastyanova, Olena; Östlund, Sören; Brännvall, Elisabet

doi:10.1007/s10570-021-03713-0

Cited by 15 publications

(11 citation statements)

References 44 publications

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“…(2013) decreased the kappa number of eucalyptus pulps by 0.5-1.5 units when alkali leaching was performed at 90 C for 90 min. For spruce pulps, a kappa number reduction of 3-4 units was obtained at 100 C for 30 min (Esteves et al 2021). This together with the present study shows that the residual alkali level has only a minor effect on lignin re-precipitation.…”

Section: Washing Of Pulp Bressupporting

confidence: 78%

Effect of Residual Alkali Level in Softwood Kraft Cooking

Brännvall

Norberg

Karlström

2022

Preprint

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In washing of softwood pulp, pH is reduced to such low levels that re-precipitation of dissolved lignin may result. It was hypothesized that the lower the residual alkali after cooking, the higher the risk of lignin re-precipitation, which in turn would affect the subsequent oxygen delignification stage negatively. To test the hypothesis, kraft cooks were performed to different residual alkali levels, ranging from 5 to 15 g/l and the delignified chips were subjected to different washing strategies and then oxygen delignified. However, the results show that even at low residual alkali, lignin stays in solution and only minor amounts of lignin re-precipitate during washing. The amount was irrespective of the residual alkali level in the cook and amounted to 1-2 kappa number units. No effect of residual alkali level was observed on the performance of the oxygen delignification stage. The residual alkali level affected the lignin concentration in the lumen after cooking. At the low residual alkali level, the lignin concentration in the lumen liquor was equal to the free liquor and as the residual alkali level increased, the lignin concentration in the lumen increased, while the lignin concentration in the free black liquor remained on the same level at all residual alkali levels.

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Section: Washing Of Pulp Bressupporting

confidence: 78%

Effect of Residual Alkali Level in Softwood Kraft Cooking

Brännvall

Norberg

Karlström

2022

Preprint

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“…However, it has been shown that oxygen can improve the mechanical strength of paper (Esteves et al 2020;Snowman et al 1999;Yang et al 2003;Zhang et al 2005) even if fiber deformation occurs. Fiber deformation can be due to an increased fiber vulnerability after cooking and defibration and not to the oxygen delignification (Esteves et. al.…”

Section: Discussionmentioning

confidence: 99%

“…It has previously been shown that fibers with a high internal integrity (higher lignin and less mechanical processes/steps) show a greater resistance to expansion and therefore less swelling development (Stone et al 1971). After the individualization of the fibers by defibration process after kraft cook they may be more susceptible to subsequent treatment (Esteves et. al.…”

Section: Fiber Charge: Effect On Refinability and Mechanical Propertiesmentioning

confidence: 99%

Differences and similarities between kraft and oxygen delignification of softwood fibers: effects on mechanical properties

et al. 2021

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Charged groups in pulp have been shown to enhance the tensile strength of the paper produced from the pulp. Oxygen delignification introduces charged groups and it is of interest to determine how the delignification should be distributed between the cooking and the oxygen stage with respect to mechanical properties. A number of unbleached kraft cooked and oxygen delignified pulps within a wide kappa number range were produced and refined, and the effects of the refining on the morphology and mechanical properties were studied. The WRV correlated with the fiber charge and at a given fiber charge, kraft cooked and oxygen delignified pulps had the same WRV development in refining, although they had significantly different kappa numbers. The tensile strength development during refining depends on the fiber rigidity which is affected by the lignin content, the fiber charge and the chemical and mechanical processes used. Refining increased the curl of the kraft cooked pulps and decreased the curl of oxygen delignified pulps, irrespective of kappa number. A greater increase in tensile strength was seen for the pulps with a higher fiber charge and WRV, probably because of the greater degree of fibrillation achieved in the beating process. Despite the greater fiber deformation in the oxygen delignified pulps, the strength can be increased by a larger amount of charged groups and a greater swelling of the fibers. Graphic abstract

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“…Because the influence of solvents in the C60/C70 solution and hydrosols could be avoided, the dried, coated gold showed a high SERS activity [ 199 , 200 ]. The SERS subtract intensity of most peaks of colloidal Au coatings increased and then slowly decreased depending on the saturation [ 201 , 202 ].…”

Section: Applications Of Cellulosementioning

confidence: 99%

A Review on the Modification of Cellulose and Its Applications

et al. 2022

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The latest advancements in cellulose and its derivatives are the subject of this study. We summarize the characteristics, modifications, applications, and properties of cellulose. Here, we discuss new breakthroughs in modified cellulose that allow for enhanced control. In addition to standard approaches, improvements in different techniques employed for cellulose and its derivatives are the subject of this review. The various strategies for synthetic polymers are also discussed. The recent advancements in polymer production allow for more precise control, and make it possible to make functional celluloses with better physical qualities. For sustainability and environmental preservation, the development of cellulose green processing is the most abundant renewable substance in nature. The discovery of cellulose disintegration opens up new possibilities for sustainable techniques. Based on the review of recent scientific literature, we believe that additional chemical units of cellulose solubility should be used. This evaluation will evaluate the sustainability of biomass and processing the greenness for the long term. It appears not only crucial to dissolution, but also to the greenness of any process.

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Differences and similarities between kraft and oxygen delignification of softwood fibers: effects on chemical and physical properties

Cited by 15 publications

References 44 publications

Effect of Residual Alkali Level in Softwood Kraft Cooking

Effect of Residual Alkali Level in Softwood Kraft Cooking

Differences and similarities between kraft and oxygen delignification of softwood fibers: effects on mechanical properties

A Review on the Modification of Cellulose and Its Applications

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