Article pubs.acs.org/IECR
Influence of Alkaline Treatment and Alkaline Peroxide Bleaching of Aspen Chemithermomechanical Pulp on Dissolved and Colloidal Substances Qingxian Miao,*,†,‡ Guizhen Zhong,† Menghua Qin,§ Lihui Chen,† and Liulian Huang† †
College of Material Engineering, Fujian Agriculture and Forestry University, Fuzhou 350002, China Limerick Pulp and Paper Centre and Department of Chemical Engineering, University of New Brunswick, Fredericton, E3B 5A3 Canada § Tai Shan University, Tai’an 271021, China ‡
ABSTRACT: Dissolved and colloidal substances (DCS) will be released during mechanical pulping and following bleaching operations. The accumulation of DCS in paper machine systems can bring various negative impacts on papermaking operations. In present study, the influence of alkaline treatment and alkaline peroxide bleaching of aspen chemithermomechanical pulp on released DCS was evaluated based on general DCS properties, lignin content, and carbohydrate and organic extractives compositions. Results showed that both treatments could promote the DCS release by increasing the concentration and cationic demand of DCS samples. However, alkaline peroxide bleaching caused the decrease in turbidity and average particle size. The total amounts of dissolved lignin, carbohydrates, and organic extractives were also increased. The dissolved lignin-related substances and carbohydrates were the predominant components of DCS. In the extractives, alkaline peroxide bleaching mainly resulted in the release of some lignin-degraded substances and a slight degradation of unsaturated fatty acids and their esters.
1. INTRODUCTION
Most carbohydrates in the DCS samples were dissolved when spruce TMP was treated with alkali and alkaline peroxide, and the alkaline conditions resulted in an increase in hemicelluloses containing acidic monomers, i.e., galacturonic acid.4 The neutral O-acetyl-galactoglucomannans and the anionic arabinogalactans and arabino-(4-O-methylglucurono)xylans were also released during alkaline treatment and alkaline peroxide bleaching of spruce TMP.17,18As to the extractives present in DCS, it is well-known that lipophilic extractives accounted for much of the colloidal fraction of DCS. Some studies indicated that alkaline hydrogen peroxide had little effect on colloidal fraction.4,19 However, the alkaline peroxide bleaching could effectively remove extractives on the fiber surfaces.20 Also, the lignin or lignin-like substances would be released during alkaline treatment and alkaline peroxide bleaching of spruce TMP.6 Aspen is one of the most suitable hardwoods in the production of mechanical pulps in Northern China and Western Canada due to its good bleachability.5 Although a comprehensive study about the effect of alkaline peroxide bleaching on DCS has been performed, so far, the results have been limited to the softwood mechanical pulp, and little knowledge is available on the DCS release in alkaline treatment and alkaline peroxide bleaching of aspen mechanical pulp. Moreover, the different chemical compositions between hardwood and softwood are supposed to induce the difference in DCS. Thus, in present work, an aspen chemithermomechan-
Nowadays, high yield mechanical pulps have been produced at lower cost and extensively used in the production of various paper grades.1−3 As a most common bleaching method used for mechanical pulps, alkaline peroxide bleaching can selectively remove some color-contributing lignin components while preserving high pulp yield.4,5 However, this common bleaching practice can inevitably lead to the release of a considerable amount of dissolved and colloidal substances (DCS),4,6−10 which consequently results in a drop in pulp yield. Since the mechanical pulps usually do not undergo washing operations prior to being sent to the paper machine, the released DCS are carried over to the paper machine system. The accumulation of DCS during the papermaking operations due to the closure of mill water systems for meeting the stricter environmental regulations gives rise to potentially pronounced runnability and quality problems.4,11−15 These problems induced by DCS limited the wide application of high-yield pulps. In an earlier study, Holmbom et al. observed that dissolved lignin and hemicelluloses made up a major part of the DCS originating from spruce thermomechancal pulps (TMP).10 The anionic portion of DCS which can be considered as the potential “anionic trash” is mainly composed of acidic hemicelluloses, lipophilic extractives, and acidic lignin-degraded productions.7,10 In previous investigations, it has also been shown that alkaline treatment and alkaline peroxide bleaching could cause substantial changes in the DCS released from spruce groundwood pulp and TMP, and the alkalinity appeared to be most responsible for the qualitative and quantitative changes in DCS even though hydrogen peroxide had a slight effect.6,7,16−18 © 2014 American Chemical Society
Received: Revised: Accepted: Published: 2544
December 2, 2013 January 19, 2014 January 22, 2014 January 22, 2014 dx.doi.org/10.1021/ie4040785 | Ind. Eng. Chem. Res. 2014, 53, 2544−2548
Industrial & Engineering Chemistry Research
Article
ical pulp (CTMP) was utilized to investigate the influence of alkaline treatment and alkaline peroxide bleaching on the quality and quantity of DCS released from the fibers. The results will contribute to a better understanding of the peroxide bleaching chemistry of hardwood high-yield pulp.
Table 1. General Properties of DCS Released from Aspen Chemithermomechanical Pulp (CTMP), Alkali Treated CTMP (ACTMP), and Alkaline Peroxide Bleached CTMP (BCTMP) cationic demand (meq/L)
conc (g/L)
2. MATERIALS AND METHODS 2.1. Materials. The aspen chemithermomechanical pulp (CTMP) sample was taken from the second stage refiner in a CTMP mill which is located in eastern China. The pulp was stored at its initial consistency in a freezer at −24 °C until needed. 2.2. Alkaline/Peroxide Treatments of Aspen CTMP and DCS Sampling. The pulp was treated with sodium hydroxide (ACTMP) and alkaline hydrogen peroxide (BCTMP), respectively, at 10% consistency in polyethylene bags at 70 °C for 120 min. The dosage of chemicals based on dry weight of pulp was as follows: 0.05% MgSO4, 2% Na2SiO3, 3% NaOH, and 0.2% EDTA. When peroxide bleaching was performed, the dosage of H2O2 was 4%. After treatments, the pulps were directly diluted to 2% pulp consistency with distilled water for DCS samples preparation. The DCS samples were prepared according to a previous paper.3 The dissolved substances (DS) were separated from DCS by filtration through a pore size 0.22 μm membrane. 2.3. Analysis of DCS Samples. The concentrations of DCS and DS samples were determined by gravimetric method, in which 50 mL of DCS and DS water samples were dried in an oven at 105 °C to a constant, and the residual solids were the DCS and DS, respectively. The determination of cationic demand was performed using a particle charge detector (Mütek PCD-03, Germany), and the standard cationic polyelectrolyte was 0.001 N polydiallyldimethylammonium. The turbidity was determined using a scattering light turbidity detector (WGZ-800, China). The pH values of all samples were adjusted to 5 prior to the cationic demand and turbidity measurements. A BI-90Plus laser particle size analyzer (Brookhaven, US) was employed to determine the particle size distributions of DCS samples. The DCS samples were adjusted to pH 5 prior to the determination. The DCS samples were first freeze-dried prior to methanolysis (2 M HCl in dry methanol) when the carbohydrates were analyzed followed by silylation and gas chromatography coupled to mass spectrum (GC-MS; QP-2100, SHIMADZU, Japan) analysis.18,21 The extractives determination was performed according to a previous method, as described by Ö rså and Holmbom.22 Since the GC column used in this study was a long column (30 m × 0.25 mm ×0.25 μm), so for determining the fatty alcohols and sterols, the DCS samples were first hydrolyzed by alkali, and then analyzed by GC-MS, as described by Qin et al.23 The lignin content in DCS water samples was determined by UV-adsorption at 280 nm using a UV-2550 spectrophotometer (Shimadzu, Japan).22
turbidity (NTU)
sample
DCS
DS
DCS
DS
DCS
CTMP ACTMP BCTMP
0.787 3.363 3.848
0.653 3.243 3.765
0.50 1.46 1.76
0.39 1.13 1.47
130.4 191.2 116.3
concentration from 0.787 to 3.363 g/L, and the cationic demand from 0.50 to 1.46 meq/L; while the addition of hydrogen peroxide only increased the DCS concentration by 0.484 g/L and the cationic demand by 0.300 meq/L. Both treatments mainly resulted in the release of dissolved substances (Table 1). These dissolved substances possibly derived from dissolved hemicelluloses, dissolved lignins, and pectic acids, which are also the main sources of the cationic demand (Table 1).9,24 Partly oxidized polymers such as ligninderived substances become dominant sources of the cationic demand during peroxide bleaching.6 The uronic acids maybe the major sources accounting for the cationic demand of untreated and alkaline treated pulps .4 The turbidity of the DCS sample, known to be caused mostly by colloidally stable lipophilic extractives droplets,25 increased due to the alkaline treatment, implying that alkaline treatment of aspen CTMP promoted the release of colloidal lipophilic extractives. However, the addition of hydrogen peroxide decreased the turbidity significantly compared to untreated and alkaline treated CTMP, as shown in Table 1. This change might be induced by the oxidative degradation or dissolution of some colloidal substances,8,26 and the changes in the polysaccharides caused by alkaline conditions might be also responsible for the change in the stability of colloidal substances.4 3.2. Distribution of Particle Size. Compared to aspen CTMP whose mean effective diameter was 470.4 nm, the particle in the range of 500−5000 nm increased dramatically after alkaline treatment, as shown in Table 2, which resulted in Table 2. Distribution of Particle Size of DCS Released from Aspen Chemithermomechanical Pulp (CTMP), Alkali Treated CTMP (ACTMP), and Alkaline Peroxide Bleached CTMP (BCTMP) particle diameters (nm) ≤200 CTMP ACTMP BCTMP
3 4 23
200−500 70 35 25
500−2000 7 28 13
2000−5000 20 17 0
>5000 0 16 0
a mean effective diameter of 935.2 nm. While the alkaline peroxide bleaching caused a decrease in particle size (Table 2), the fractions whose size was less than 200 nm increased, and the mean effective diameter was 342.9 nm. A study has indicated that the carbohydrates, lignans, low molecular-mass organic acids, and oligomeric lignin-like substances are in dissolved form while lipophilic extractives are the major constitutes of colloidal particles.27 Qin et al. found that the lipophilic extractives present in poplar were composed of glycerides, steryl esters, free fatty acids, sterols,
3. RESULTS AND DISCUSSION 3.1. Effect of Alkaline/Peroxide Treatment on DCS Properties. As Table 1 shows, both alkaline treatment and alkaline peroxide bleaching can promote the release of DCS, which is supported by the increase in DCS concentration and cationic demand. Alkaline treatment increased the DCS 2545
dx.doi.org/10.1021/ie4040785 | Ind. Eng. Chem. Res. 2014, 53, 2544−2548
Industrial & Engineering Chemistry Research
Article
and free fatty alcohols, among which glycerides, mainly triglycerides, were the predominant component of the lipophilic extractives.23 The increase in the particle size due to alkaline treatment might be induced by the release of lipophilic substances with larger particle size such as the triglycerides. Degradation of some colloidal substances during alkaline peroxide bleaching probably caused the decrease of particle size.8,26 3.3. Determination of Lignin. Lignin or lignin-like substances in wood or pulp have the UV absorption at 280 nm, and this UV absorption is generally utilized for qualitative and quantitative determination of lignin.28 As shown in Figure 1, alkaline treatment of aspen CTMP caused the increase in
Table 3. Concentration of Sugar Units Comprising DCS Carbohydrates Released from Chemithermomechanical Pulp (CTMP), Alkali Treated CTMP (ACTMP), and Alkaline Peroxide Bleached CTMP (BCTMP) conc (mg/L) carbohydrates
CTMP
ACTMP
BCTMP
xylose glucose galactose mannose arabinose total neutral sugars glucuronic acid galacturonic acid total uronic acids total carbohydrates
15.0 14.4 4.3 9.4 6.7 49.8 3.3 13.8 17.1 66.9
45.6 14.8 7.8 14.1 6.7 89.0 18.9 27.3 46.2 135.2
72.9 15.1 9.3 12.2 21.1 130.6 28.7 38.2 66.9 197.5
O-Acetyl-4-O-methylglucurono-xylan is the major polysaccharides comprising the hardwood hemicellulose. It can be found in Table 3 that xylose is the dominant sugar unit present in the carbohydrates of DCS. Both treatments enhanced the xylose concentration. Similar results were obtained when spruce TMP was treated by alkali and alkaline peroxide.6 The release of xylose was mainly caused by the alkaline degradation of xylans, and this might be also due to the cleavage of lignin− carbohydrate bonds, mainly uronic acid ester linkages to lignin.32 Then the solubility of polysaccharides in alkaline conditions would be enhanced because of the cleavage of ester bonds between lignin and O-acetyl-4-O-methylglucuronoxylan.33 Both alkali and alkaline hydrogen peroxide treatments resulted in a great increase in the uronic acids content, as shown in Table 3. It has been shown that uronic acids were more prevalent in waters from bleached spruce TMP than from unbleached spruce TMP.16 Alkaline treatment resulted in an increase of 29.1 mg/L in galacturonic acid content, and alkaline peroxide bleaching further enhanced the release of galacturonic acid (Table 3). Similar results were also observed by Thornton et al. and Pranovich et al., who treated spruce TMP with alkali and alkaline peroxide.6,17 Native pectic substances, some of which are methyl esterified, are primarily comprised of galacturonic acid units.17 Methylated pectic substances can be degraded in alkaline conditions by β-elimination reactions which occur together with demethylation.17,34 Polygalacturonic acids can be decomposed by hydrogen peroxide, which generates low-molar-mass acids and carbon dioxide.35 Polygalacturonic acids released during alkaline peroxide bleaching of TMP have a much lower molar mass than that released during alkaline treatment.36 The release of glucuronic acids during alkaline peroxide bleaching was probably mainly induced by the cleavage of bonds between xylose units and 4-O-methylglucuronic acids due to the attack of hydroxyl radical under alkaline conditions.37,38 On the other hand, the cleavage of uronic acid ester linkages between glucuronic acid and lignin might also contribute to the release of glucuronic acid.32 3.5. Determination of Extractives. The term extractives cover a lot of different compounds which can be extracted from biomass by polar or nonpolar solvents. Most of the extractives are located in the parenchyma cells. In the mechanical refining process, the thin wall tissue is breakdown by mechanical friction force resulting in the release of extractives. During following bleaching operations, these extractives will further release into
Figure 1. Concentration of lignin in DCS and DS samples released from aspen chemithermomechanical pulp (CTMP), alkali treated CTMP (ACTMP), and alkaline peroxide bleached CTMP (BCTMP).
lignin content of DCS sample from 0.144 to 0.235 g/L. Some ester bonds in lignin-carbohydrate complex or ether linkages at Cα present in the side chains of guaiacyl-propane units, which are most sensitive to the alkali, would cleave during the alkaline treatment.6 In particular, the cleavage of ether bonds could occur even at room temperature in 0.05 M NaOH.29 These bonds cleavage might be responsible for the release of lignin during alkaline treatment. The release of more lignin whose content reached 0.356 g/L was observed during alkaline peroxide bleaching (Figure 1). Similar results were obtained by Pranovich et al.6 It can also be found from Figure 1 that most lignin in DCS was present as dissolved fractions. The results above indicated that both alkaline treatment and alkaline peroxide bleaching could promote the lignin release. The wood swelling and chemical degradation reactions may be responsible for the above results.6 Furthermore, peroxide bleaching mainly caused the oxidization of lignin with the formation of carboxylic groups, such as the muconic acid structure, which induced the increase in cationic demand of DCS samples, and the molar mass of lignin also decreased notably due to the bleaching reactions.30,31 3.4. Determination of Carbohydrates. The composition of carbohydrates of DCS samples was determined by acid methanolysis followed by GC-MS analysis. The major carbohydrates in the DCS water are likely to be derived from hemicelluloses which are susceptible to an alkaline medium. As shown in Table 3, the total amounts of carbohydrates increased as the function of alkali and alkaline hydrogen peroxide. After treatments, the predominant polysaccharides are neutral, and this result is different from the Thornton study in which the Norway spruce TMP was bleached with alkaline peroxide.18 This difference might be related to the different carbohydrate compositions and contents between hardwood and softwood. 2546
dx.doi.org/10.1021/ie4040785 | Ind. Eng. Chem. Res. 2014, 53, 2544−2548
Industrial & Engineering Chemistry Research
Article
4. CONCLUSION Both alkaline treatment and alkaline peroxide bleaching of aspen CTMP could promote the release of DCS. The concentration and the cationic demand of DCS was respectively increased by 2.576 g/L and 0.96 meq/L after alkaline treatment, and by 3.061 g/L and 1.26 meq/L after alkaline peroxide bleaching. The increase in cationic demand was mainly caused by the release of lignin, glucuronic acid, and galacturonic acid. Alkaline peroxide bleaching led to the decrease in turbidity from 130.4 to 116.3 NTU and particle size from 470.4 to 342.9 nm, but the alkaline treatment had the opposite effect. More lignin was released after alkaline treatment and alkaline peroxide bleaching, and most of the lignins were present as dissolved fractions. Alkaline treatment increased the carbohydrates amount from 66.9 to 135.2 mg/L, and the addition of hydrogen peroxide had a greater effect on the release of carbohydrates. Xylose was the predominant sugar unit in DCS carbohydrates. More release of uronic acids contributed to the great increase in cationic demand. Compared to lignin and carbohydrates, the organic extractives amount was much less, and the main components of organic extractives were lignindegraded substances and fatty acids. However, the amounts of extractives were still increased from 3.06 to 25.92 and 36.55 mg/L by alkali and alkaline peroxide treatments. It was likely that the alkalinity was responsible for the much greater release of organic extractives, and the addition of hydrogen peroxide had a slight influence on the fatty acids and their esters.
the process water with some changes in chemical composition. It has been reported that alkaline peroxide bleaching was effective in removing extractives on the surface of pulp fibers.39 In this study, the extractives were extracted by methyl tertiary butyl ether (MTBE) from DCS water samples. As shown in Table 4, The MTBE extractives were mainly composed of Table 4. Concentration of Methyl Tertiary Butyl Ether (MTBE) Extractives in DCS Samples from Aspen Chemithermomechanical Pulp (CTMP), Alkali Treated CTMP (ACTMP), and Alkaline Peroxide Bleached CTMP (BCTMP) conc (mg/L) extractives
CTMP
ACTMP
BCTMP
benzoic acid benzenedicarboxylic acid cinnamic acid total azelaic acid, C9:2 tetradecanoic acid, C14:0 pentadecanoic acid, C15:0 palmitoleic acid, C16:1 hexadecanoic acid, C16:0 heptadecanoic acid, C17:0 9,12-octadecadienoic acid, C18:2 oleic acid, C18:1 octadecanoic acid, C18:0 tetracosanoic acid, C24:0 total 1-monolinoleoylgylcerol β-sitosterol total total amounts
0.54 0.38
4.82 0.32 0.18 5.32 0.30 0.26 0.30 0.24 5.60 2.28 3.18 5.32 1.72 0.72 19.92 0.20 0.48 0.68 25.92
15.44 0.18 0.58 16.2 0.32 0.28 0.32 0.22 5.68 2.26 2.86 5.30 1.75 0.74 19.73 0.18 0.44 0.62 36.55
0.92 0.12 0.04 0.04 0.38 0.44 0.24 0.32 0.32 0.24 2.14
3.06
■
AUTHOR INFORMATION
Corresponding Author
*E-mail:
[email protected]. Notes
The authors declare no competing financial interest.
■
ACKNOWLEDGMENTS The authors are grateful for the financial support from the State Bureau of Forestry 948 Project (Grant No. 2012-4-01), the National Natural Science Foundation of China (Grant No. 31100444), and Fujian Province University & Industry Cooperation of Major Science and Technology Project (2011H6003).
lignin-degraded substances, fatty acids, and a minor amount of monolinoleoylgylcerol and sitosterol. The total amount of extractives increased respectively from 3.06 to 25.92 and 36.55 mg/L after alkaline treatment and alkaline peroxide bleaching. However, the addition of hydrogen peroxide resulted in the increase of lignin-degraded substances and the slight decrease of fatty acids and esters-degraded substances. In comparison with untreated pulp sample, the increase in benzoic acids and cinnamic acid after alkali and alkaline peroxide treatments were probably due to the degradation of lignins, but might be also induced by hydrogen peroxide oxidation of glycolic acids.4 Besides the lignin-degraded substances, the fatty acids ranked the second in the MTBE extractives, whose content reached 19.9 and 19.73 mg/L respectively after alkaline treatment and alkaline peroxide bleaching. The increase in saturated fatty acids amount indicated that some fatty acids esters were hydrolyzed.8 It can also be observed that the amount of unsaturated fatty acids decreased slightly after alkaline peroxide bleaching compared to alkaline treatment only. This difference could be probably explained by the slight oxidative degradation caused by alkaline hydrogen peroxide.4,8 The partial degradation of triglycerides and steryl esters due to the alkaline conditions caused the release of monogylcerol and sterol, and the dissolved fatty acids soap might promote their dissolution.40 However, the hydrogen peroxide in itself were hardly able to degrade triglycerides and steryl esters.4
■
REFERENCES
(1) Zhang, H.; He, Z.; Ni, Y. Characteristics of dissolved and colloidal substances in high yield pulp and their impact on filler retention. Appita J. 2007, 60, 390−395. (2) Nylund, J.; Sundberg, A.; Sundberg, K. Dissolved and colloidal substances from a mechanical pulp suspension-Interactions influencing the sterical stability. Colloids Surf., A 2007, 301, 335−340. (3) Miao, Q.; Qin, M.; Chen, L. Study on the treatment of dissolved and colloidal substances present in aspen BCTMP with laccase and laccase/violuric acid. 16th International Symposium on Wood, Fiber and Pulping Chemistry Proceedings, Tianjin, 2011. (4) Thornton, J., Eckerman, C., Ekman, R. Effects of peroxide bleaching of spruce TMP on dissolved and colloidal organic substances. In 6th International Symposium of Wood and Pulping Chemistry Proceedings; APPITA: Melbourne, 1991; Vol. 1, pp 571− 577. (5) Pan, G. An insight into the behavior of aspen CTMP in peroxide bleaching. Pulp Pap. Canada 2001, 102, 41−45. (6) Pranovich, A. V.; Sundberg, K. E.; Holmbom, B. R. Chemical changes in thermomechanical pulp at alkaline conditions. J. Wood Chem. Technol. 2003, 23, 89−112.
2547
dx.doi.org/10.1021/ie4040785 | Ind. Eng. Chem. Res. 2014, 53, 2544−2548
Industrial & Engineering Chemistry Research
Article
(7) Thornton, J.; Ekman, R.; Holmbom, B. R. Release of potential anionic trash in peroxide bleaching of mechanical pulp. Paperi Ja Puu. 1993, 75, 426−431. (8) Ekman, R.; Holmbom, B. The wood extractives in peroxide bleaching of spruce groundwood. Nordic Pulp Paper Res. J. 1989, 4, 188−192. (9) He, Z.; Ni, Y.; Zhang, E. Further understanding on the cationic demand of dissolved substances during peroxide bleaching of a spruce TMP. J. Wood Chem. Technol. 2004, 24, 153−168. (10) Holmbom, B.; Ekman, R. Chemical changes in peroxide of bleaching of mechanical pulps. Das Papier. 1991, 45, 16−22. (11) Lindström, T.; Söremark, C.; Westman, L. The influence on paper strength dissolved and colloidal substances in white water. Svensk Papperstidn. 1977, 80, 341−345. (12) Wearing, J. T.; Barbe, M. C.; Ouchi, M. D. The effect of whitewater contamination on newsprint properties. J. Pulp Pap. Sci. 1985, 11, J113−121. (13) Zhang, X.; Beatson, R. P.; Cai, Y. J.; Saddler, J. N. Accumulation of specific dissolved and colloidal substances during white water recycling affects paper properties. J. Pulp Pap. Sci. 1999, 25, 206−210. (14) Dunham, A. J.; Sherman, L. M.; Alfano, J. C. Effect of dissolved and colloidal substances on drainage properties of mechanical pulp suspensions. J. Pulp Pap. Sci. 2002, 28, 298−304. (15) Li, H.; Ni, Y.; Sain, M. The presence of dissolved and colloidal substances in BCTMP and their effect on sizing. J. Pulp Pap .Sci. 2002, 28, 45−49. (16) Samuelson, O.; Sjoberg, L. Spent liquor from peroxide bleaching of groundwood pulp from spruce. Cellulose Chem. Technol. 1974, 8, 607−613. (17) Thornton, J.; Ekman, R.; Holmbom, B.; Pettersson, C. Effects of alkaline treatment on dissolved carbohydrates in suspension of Norway spruce thermomechanical pulp. J. Wood Chem. Technol. 1994, 14, 177−194. (18) Thornton, J.; Ekman, R.; Holmbom, B.; Ö rså, F. Polysaccharides dissolved from Norway spruce in thermomechanical pulping and peroxide bleaching. J. Wood Chem. Technol. 1994, 14, 159−175. (19) Laamanen, L. Birch kraft pulp extractives in bleaching. Paperi ja Puu 1984, 66, 615−626. (20) Mustranta, A.; Koljonen, K.; Lappalainen, A.; Pere, J.; Tenkanen, M.; Stenius, P.; Buchert, J. Characterization of mechanical pulp fibers with enzymatic, chemical and immunochemical methods. Proc. 6th European Workshop on Lignocellulosics and Pulp; Bordeaux, France, Sept. 3−6, 2000; 15−18. (21) Sundberg, A.; Sundberg, K.; Lillandt, C.; Holmbom, B. Determination of hemicelluloses and pectins in wood and pulp fibers by acid methanolysis and gas chromatography. Nord. Pulp. Pap. Res. J. 1996, 11, 216−219. (22) Ö rså, F.; Holmbom, B. A convenient method for the determination of wood extractives in papermaking process waters and effluents. J. Pulp Pap. Sci. 1994, 20, J361−J365. (23) Qin, M.; Xu, C.; Fu, Y.; Xu, Q.; Hemming, J.; Holmbom, B.; Willför, S. Analysis of lipophilic extractives in populus×euramericana ‘neva’. Cell. Chem.Technol. 2012, 46, 533−539. (24) Sundberg, A.; Pranovich, A. Distribution of anionic groups in TMP suspensions. J. Wood Chem. Technol. 2000, 20, 71−93. (25) Sundberg, A.; Ekman, R.; Holmbom, B.; Sundberg, K.; Thornton, J. Interactions between dissolved and colloidal substances and a cationic fixing agent in mechanical pulp suspensions. Nord. Pulp Pap. Res. J. 1993, 8, 226. (26) Nurmi, M.; Westerholm, M.; Eklund, D. Factors influencing flocculation of dissolved and colloidal substances in a thermomechanical pulp water. J. Pulp Pap. Sci. 2004, 30, 41−44. (27) Thornton, J. Dissolved and colloidal substances in the production of wood-containing paper. Doctoral Thesis; Åbo Akademi University Press: Turku/Åbo, Finland, 1993. (28) Lin, S. Ultraviolet Spectrophotometry. In methods in Lignin Chemistry; Lin, S. Y., Dence, C. W., Eds.; Springer-Verlag: Berlin, 1992; pp 217−232.
(29) Johansson, B.; Miksche, G. Uber die benzyl-arylatherbindung im lignin. II. Versuche an modellen. Acta Chem. Scand. 1972, 26, 289− 308. (30) Bailey, C.; Dence, C. Reactions of alkaline hydrogen peroxide with soft lignin model compounds, spruce milled-groundwood lignin and spruce groundwoood. Tappi J. 1969, 52, 491−500. (31) Pranovich, A.; Holmbom, B.; Sjöholm, R. Characterization of dissolved lignins in the thermomechanical pulp suspensions. In 3th Eur. Workshop Lignocellul. Pulp; Stockholm, Sweden, 1994; pp 219− 222. (32) Obst, J. R. Frequency and alkali resistance of lignin-carbohydrate bonds in wood. Tappi J. 1982, 65, 109−112. (33) Wang, P.; Bolker, H.; Purves, C. Uronic acid ester groups in some softwoods and hardwoods. Tappi J. 1967, 50, 123−124. (34) Renard, C. M. G. C. Degradation of pectins in alkaline conditions: kinetics of demethylation. Carbohydr. Res. 1996, 286, 139− 150. (35) Isbell, H. S.; Frush, H. L.; Orhanovic, Z. Reactions of carbohydrates with hydroperoxide . III. Oxidation of sodium salts of alduronic andglyculosonic acids by sodium peroxide. Carbohydr. Res. 1974, 36, 283−291. (36) Sundberg, K.; Sundberg, A.; Thornton, J.; Holmbom, B. Pectic acids in the production of wood-containing paper. Tappi J. 1998, 81, 131−136. (37) Guay, D.; Cole, B.; Genco, J. Mechanisms of oxidative degradation of carbohydrates during oxygen delignification. I. Reaction of photochemically generated hydroxyl radical with methyl β-Dglucoside[J]. J. Wood Chem. Technol. 2000, 20, 375−394. (38) Guay, D.; Cole, B.; Hausman, M. Mechanisms of oxidative degradation of carbohydrates during oxygen delignification.III.Reaction of photochemically generated hydroxyl radicals with 1, 5anhydrocellobitol and cellulose[J]. J. Pulp Pap. Sci. 2002, 28, 217−221. (39) Kangas, H.; Kleen, M. The effect of bleaching on the surface chemistry of mechanical pulps[J]. J. Pulp Pap. Sci. 2008, 34, 30−37. (40) Qin, M. Resin in Pulp and Its Control; Light Industry Press: Beijing, 1998.
2548
dx.doi.org/10.1021/ie4040785 | Ind. Eng. Chem. Res. 2014, 53, 2544−2548
