Reduction of adsorbable organically bound halogens (AOX) formation at near-neutral pH chlorine dioxide bleaching of softwood kraft pulp

Starrsjö, Sara; Sevastyanova, Olena; Sandström, Peter; Fiskari, Juha; Boman, Maria; Lindström, Mikael

doi:10.1515/hf-2019-0266

Cited by 4 publications

(2 citation statements)

References 12 publications

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“…[ 6 ] Another approach is to use a relatively small amount of chlorine dioxide in one bleaching stage only, which is referred to as ECF‐light. [ 7 ] This concept combines the efficiency and high selectivity of chlorine dioxide bleaching yet emphasizing more environmentally benign oxygen‐based bleaching chemicals.…”

Section: Introductionmentioning

confidence: 99%

Synergism of enzymes in chemical pulp bleaching from an industrial point of view: A critical review

Immerzeel

Fiskari

2022

Can J Chem Eng

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Enzymes are biological catalysts and are very specific, catalyzing either a single chemical reaction or a limited number of closely related reactions. For example, xylanases are enzymes that catalyze the cleavage of polymeric xylan and thereby break down this hemicellulose. The first xylanase enzyme preparations used in the bleaching process of chemical pulp also contained cellulase, which catalyzes the hydrolysis of cellulose. This obviously had an adverse effect on pulp yield and quality. Unfortunately, this setback gave enzyme-assisted pulp bleaching a negative reputation. At a later stage, enzyme producers managed to engineer enzyme production strains that generated cellulase-free xylanase preparations. However, due to the initial negative experiences with the earlier enzyme mixtures, only a limited number of companies in the pulp industry have seriously considered using these so-called second-generation enzymes in their bleach plants. It is apparent that these improved enzyme preparations would bring about significant benefits in terms of chemical cost savings and effluent quality. In addition to xylanaseaided bleaching, it is possible to improve the effectivity further by adding other enzymes, such as lipase and esterase, to create an enzyme cocktail. This may be particularly beneficial in the bleaching of hardwood pulp, such as white birch, which often encounters complex and troublesome problems with wood extractives. By adding different types of enzymes at more than one position in the fiberline, even further improvements are possible. The main objective of this review is to discuss the advantages of incorporating modern enzyme preparations in the bleaching of chemical pulp.

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Section: Introductionmentioning

confidence: 99%

Synergism of enzymes in chemical pulp bleaching from an industrial point of view: A critical review

Immerzeel

Fiskari

2022

Can J Chem Eng

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“…Researchers have attempted to reduce the production of AOX at the source [ 17 , 18 ]. Hypochlorite was generated owing to the decomposition of chlorine dioxide during the bleaching process [ 19 , 20 ].…”

Section: Introductionmentioning

confidence: 99%

Effects of the Preferential Oxidation of Phenolic Lignin Using Chlorine Dioxide on Pulp Bleaching Efficiency

Liu

Deng

Liang

et al. 2022

IJMS

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Chlorine dioxide is widely used for pulp bleaching because of its high delignification selectivity. However, efficient and clean chlorine dioxide bleaching is limited by the complexity of the lignin structure. Herein, the oxidation reactions of phenolic (vanillyl alcohol) and non-phenolic (veratryl alcohol) lignin model species were modulated using chlorine dioxide. The effects of chlorine dioxide concentration, reaction temperature, and reaction time on the consumption rate of the model species were also investigated. The optimal consumption rate for the phenolic species was obtained at a chlorine dioxide concentration of 30 mmol·L−1, a reaction temperature of 40 °C, and a reaction time of 10 min, resulting in the consumption of 96.3% of vanillyl alcohol. Its consumption remained essentially unchanged compared with that of traditional chlorine dioxide oxidation. However, the consumption rate of veratryl alcohol was significantly reduced from 78.0% to 17.3%. Additionally, the production of chlorobenzene via the chlorine dioxide oxidation of veratryl alcohol was inhibited. The structural changes in lignin before and after different treatments were analyzed. The overall structure of lignin remained stable during the optimization of the chlorine dioxide oxidation treatment. The signal intensities of several phenolic units were reduced. The effects of the selective oxidation of lignin by chlorine dioxide on the pulp properties were analyzed. Pulp viscosity significantly increased owing to the preferential oxidation of phenolic lignin by chlorine dioxide. The pollution load of bleached effluent was considerably reduced at similar pulp brightness levels. This study provides a new approach to chlorine dioxide bleaching. An efficient and clean bleaching process of the pulp was developed.

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Assessment of Q(OP)D(PO) bleachability of softwood kraft pulp

Starrsjö

Boman

Sevastyanova

et al. 2021

Nordic Pulp &Amp; Paper Research Journal

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Bleachability is evaluated as how easily a pulp sample is bleached and it depends on the structure of residual lignin and carbohydrates. Also, the bleachability varies depending on the bleaching sequence. ECF light sequences have been improved significantly in the recent years. However, we still don’t fully understand how ECF light bleach plants are optimally run. This work studies the bleachability of softwood kraft pulp in an ECF light bleaching sequence, (OO)Q(OP)D(PO). Three pulp samples with brown stock kappa number 27, 32 and 35 were bleached and studied for residual lignin, hexenuronic acid and carbohydrate content. It was found that in the bleaching stages that are highly delignifying, it is beneficial with a higher kappa number for the delignifying bleachability. However, in the bleaching stages where the objective is brightness increase, the brightness gain bleachability is improved by a lower kappa number. We also intended to determine which of the three samples had the best suited kappa number for this particular bleaching sequence. According to our results, the bleaching was most effective with kappa number around 32. Although an even higher kappa number resulted in higher yield after cooking, it seemed that this bleaching sequence cannot preserve the yield gain.

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Reduction of adsorbable organically bound halogens (AOX) formation at near-neutral pH chlorine dioxide bleaching of softwood kraft pulp

Cited by 4 publications

References 12 publications

Synergism of enzymes in chemical pulp bleaching from an industrial point of view: A critical review

Synergism of enzymes in chemical pulp bleaching from an industrial point of view: A critical review

Effects of the Preferential Oxidation of Phenolic Lignin Using Chlorine Dioxide on Pulp Bleaching Efficiency

Assessment of Q(OP)D(PO) bleachability of softwood kraft pulp

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