Ind. Eng. Chem. Res. 2010, 49, 9407–9412
9407
Adsorption Behaviors of Optical Brightening Agents and Precipitated Calcium Carbonate onto Pulp Fibers Hongjie Zhang,*,†,‡ Lanfeng Hui,†,‡ and Yonghao Ni‡ Tianjin Key Laboratory of Pulp and Paper, Tianjin UniVersity of Science and Technology, Tianjin, 300457, P. R. China, and Limerick Pulp and Paper Centre, UniVersity of New Brunswick, Fredericton, N.B., E3B 5A3, Canada
High-yield pulps (HYPs) can be used in the production of high-quality fine paper grades. In such applications, optical brightening agents (OBA) and inorganic fillers, such as precipitated calcium carbonate (PCC) may be used to improve the paper properties, including optical properties, such as brightness, whiteness, opacity. In this study, some fundamental parameters regarding OBA and PCC adsorption onto pulp fibers were investigated. Results showed that OBA was preferably adsorbed onto bleached kraft pulp (BKP) fibers than onto HYP fibers when present in a mixed furnish. The OBA adsorption at a low adsorbed amount followed the Langmuir adsorption isotherm for both BKP and HYP; the adsorbed OBA in a monolayer was more for the BKP than for the HYP. The PCC adsorption behaviors on the same two pulp systems, however, are different from those of OBA: the HYP had more PCC adsorption than the BKP. The results on the adsorption of PCC onto the HYP and kraft pulp fibers showed that they also followed the Langmuir kinetics very well. Introduction Recently, the application of high-quality high-yield pulps, such as high-brightness bleached chemithermomechanical pulp (BCTMP) and alkaline peroxide mechanical pulp (APMP) has received great attention in the papermaking industry.1-7 In particular, the substitution of high-brightness aspen HYP for hardwood bleached kraft pulp (HBKP) in the traditional woodfree papers has achieved good results.5 The main advantages of using HYP include a low furnish cost, high bulk, opacity, and stiffness.5-7 Also, HYP has more micropores than hardwood kraft pulp does.8 However, HYP usually has inferior brightness and other optical properties compared with the bleached kraft pulps. Brightness and whiteness have become important quality parameters for pulp and paper products. Thus, dyes and optical brightening agents (OBA) are commonly used in the production of most paper and paperboard products to reach the desired optical properties. Traditionally, the use of OBA is restricted to wood-free paper grades because lignin can compete with OBA to adsorb UV light. Recently, it was reported that OBA can also be used to improve the brightness of HYP in its manufacturing process,9,10 the HYP-containing paper products,11,12 and the brightness stability of such products.13-16 Moreover, inorganic fillers, such as precipitated calcium carbonate (PCC), are commonly used to improve the properties of paper products and to decrease the production costs in the manufacture of printing and writing paper grades. Therefore, it is of practical interest to determine the fundamentals associated with the OBA and PCC adsorptions onto pulp fibers. The mechanism of photoisomerization of stilbene-type OBA is now well understood and occurs by rotation through the stilbene double bond. The trans-isomer is fluorescence-active while the cis-isomer is not.17,18 Under irradiation conditions, the configuration of OBA can be transformed from the transisomer to cis-isomer.18,19 Stana et al.20 have investigated the * To whom correspondence should be addressed. E-mail:
[email protected]. † Tianjin University of Science and Technology. ‡ University of New Brunswick.
OBA adsorption process onto cotton fibers based on the streaming potential measurements, calorimetry, and fluorescence, and the results showed that the adsorption mechanism was different at low and high OBA concentrations. The deposition of calcium carbonate particles onto chemical pulp fibers was studied.21 The kinetics of deposition and detachment of colloidal particles is mainly determined by the chemistry and the mechanical/hydrodynamic forces. The chemistry establishes the nature (attractive, repulsive) of the forces between particles and surface, as well as the bond strength, whereas mechanical/hydrodynamic forces determine the transport process in the solution. The Langmuir isotherm is a well developed theory22-24 and has been used in pulp fiber systems to describe the filler and cationic polymer adsorption behavior.25,26 Also the same model has been used to describe the adsorption behavior of dyes at equilibrium,27 and adsorption of polyelectrolytes onto cellulosic fibers.28 The objective of this study is to determine the OBA and PCC adsorption behaviors onto pulp fibers based on the Langmuir isotherm, particularly regarding the differences between kraft pulp and HYP. Such a study is needed because HYP is now often used in the production of high-quality paper grades, which are traditionally made of chemical pulps only, and both OBA and fillers such as PCC are used in the paper industry in the manufacturing process of these high-quality paper products. Experimental Section Materials. A softwood (mainly spruce) bleached kraft pulp (SWBKP), a hardwood (Eucalyptus) bleached kraft pulp (HWBKP) and a commercial aspen BCTMP were obtained from a mill in Eastern Canada. The properties of the pulp samples are listed in Table 1. The BKP samples were refined in a PFI mill (manufactured by HAM-JERN, Hamar, Norway; adjusted for beating performance by Norwegian Pulp and Paper Research Institute) to about 450 mL of CSF freeness. The HYP was used as received without further refining treatment. The carboxylic acid group content of the pulp, determined based on the conductometric titration,29 was 177 mmol/kg for the HYP and
10.1021/ie1003976 2010 American Chemical Society Published on Web 08/30/2010
9408
Ind. Eng. Chem. Res., Vol. 49, No. 19, 2010
Table 1. Characteristics of the Pulp Samples pulps
CSF, mL
brightness, % ISO
CIE whiteness, %
L*
a*
b*
SWBKP HWBKP HYP
470 490 540
87.2 88.4 83.7
73.6 76.2 61.7
97.2 97.4 96.9
-0.72 -0.60 -1.55
4.28 3.84 6.73
40 mmol/kg for the SWBKP. A precipitated calcium carbonate filler sample (Albcar HO) with an average particle size of 1.62 µm was obtained from Specialty Mineral and an optical brightening agent (Tinopal HW) from Ciba. Tinopal HW is a bisulfonated OBA, which is the most commonly used one for the wet-end application and suitable for HYP.12 The OBA charge was based on the liquid product as is. OBA Adsorption. The required amount of pulp samples (SWBKP, HWBKP, and HYP) were disintegrated for 15000 revolutions in a standard disintegrator at a 1.5% pulp consistency, and then diluted to 1% suspension. The required amount of pulp suspension was then transferred to a 500 mL beaker, and CaCl2 solution was added to reach 100 ppm Ca2+ concentration, which was the optimum condition for such a system.11 The pH of the mixture was adjusted to about 6.5, followed by the OBA addition. Stirring was provided with a magnetic bar for 20 min. For the OBA adsorption experiments, we followed the same experimental procedure except that the stirring time was 2 h. The filtration was carried out on a 200 mesh screen just before making the hand sheet to separate the pulp fibers and the filtrate. Subsequently, the pulp fibers were transferred to a standard handsheet machine to make hand sheets, which were then air-dried. The related optical properties were determined on a TechniBrite Micro TB-1C Tester according to the TAPPI methods (T272 om-92 and T452 om-92). The OBA retention on pulp fibers was determined by following a method developed earlier.11 The amount of OBA retained on fibers is equal to the amount added minus the amount found in the filtrate. The amount of OBA in the filtrate was determined by following a UV spectroscopy method.11 OBA Addition Order. The required amounts of SWBKP and HWBKP were first mixed to produce the mixed BKP (the results are shown in Table 2). In trial 1, we added the HYP into the BKP, which was mixed well, subsequently OBA was added to the mixed pulp furnish, a total mixing time of 20 min was provided. In trial 2, we added OBA to the mixed BKP, which was mixed for 10 min; subsequently the HYP was added, and mixed for another 10 min. In trial 3, we reversed the order of adding OBA, so that OBA was first added to the HYP (10 min mixing), followed by the addition of the BKP (mixed for another 10 min). PCC Adsorption. First, the PCC filler was dispersed well with deionized water. Then, the required amount of pulp sample (SWBKP or HYP) was disintegrated for 15 000 revolutions in a standard disintegrator at a 1.5% pulp consistency, and further diluted to 0.2% pulp consistency. A 500 mL portion of the pulp suspension (equivalent to 1 g o.d. pulp) was stirred on a shaker (Brunswick Scientific, Model Innova 2000), followed by the addition of well-dispersed PCC filler. After the specified time
Figure 1. OBA adsorbed on pulp fibers as a function of OBA charge ((pH, 6.5; 1% pulp consistency, 100 ppm Ca2+, 2-h contact time, room temperature).
under the conditions, some samples were taken and filtered by the microfilter (about 10 µm pore size) for the turbidity measurement on a HACH 2100AN laboratory turbidimeter. Neither fibers nor fines can pass through the microfilter and therefore will not affect the turbidity reading. The amount of PCC in the filtrate sample was determined based on the PCCturbidity calibration curve. Results and Discussion OBA Addition Order. Previous studies11,12 have shown that the effectiveness of OBA for HYP is lower than that for bleached kraft pulp, which is due to (i) the presence of lignin and (ii) the lower original brightness of HYP. Under a practical paper making condition, where a mixed pulp furnish consisting of BKP and HYP is used, different addition orders of OBA can be carried out. The required amount of OBA may be added into BKP, followed by the addition of HYP or vice versa. Table 2 showed the effect of OBA addition order on the OBA effectiveness, and the results indicated that in all of the three cases, the final optical properties were almost the same, indicating that the OBA addition order has negligible effect on the OBA performance. OBA Adsorption onto Pulp Fibers. The OBA adsorption onto pulp fibers was mainly based on the formation of hydrogen bonding with cellulose fibers.30 In Figure 1, the adsorbed amount of OBA on pulp fibers was plotted against the OBA charge after 2-h stirring. Two pulp systems were studied: HWBKP and HYP, under otherwise the same conditions (in an industrial paper making process, HYP is usually substituted for HWBKP, not SWBKP). It can be seen that the slope for HWBKP (k1) is higher than that for HYP (k2), suggesting that at the same OBA charge, the HWBKP fibers adsorbed much more OBA than the HYP fibers. Therefore, it can be concluded that when OBA is added to a mixed furnish containing both BKP and HYP, OBA will adsorb preferably on BKP fibers. The reason for that is that the BKP fibers are essentially free of lignin, thus more hydroxyl
Table 2. Effect of OBA Addition Ordera trial no.
addition order of OBA
brightness, %ISO
L*
a*
b*
CIE whiteness, %
fluo. comp., % ISO
1 2
adding OBA to Mixed pulps, 20 min adding OBA to BKP, followed by HYP after 10 min (20 min in total) adding OBA to HYP, followed by BKP after 10 min (20 min in total)
88.9 89.1
96.5 96.6
0.31 0.30
2.14 2.16
81.4 81.6
5.2 5.3
88.9
96.6
0.28
2.29
81.1
5.1
3 a
Notes: (1) The pulp composition includes 30% SWBKP, 50% HWBKP, and 20% HYP. (2) The OBA dosage is 0.6% (on the total pulp furnish).
Ind. Eng. Chem. Res., Vol. 49, No. 19, 2010
Figure 2. Adsorption isotherms for OBA in HWBKP and HYP system (the conditions are the same as Figure 1).
groups are available; consequently, there are more adsorption sites for the OBA. Furthermore, shown in Figure 1 is that the linear relationship is only valid at low OBA charges. OBA Adsorption Based on Langmuir Adsorption Isotherm. Similar to the adsorption of fillers onto pulp21 and the adsorption of polyethylenimine onto pulp,28 we followed the Langmuir adsorption isotherm to describe the relationship between the concentration of OBA on the pulp fibers and that in solution, as shown in eq 1: [OBA]pulp )
Q × K × [OBA]soln 1 + K × [OBA]soln
(1)
where [OBA]pulp ) concentration of OBA adsorbed on pulp fibers, g/g, [OBA]soln ) concentration of OBA in solution, g/g, K ) adsorption equilibrium constant, and Q ) maximum amount of OBA adsorbed on fiber surface, g/g. Further, eq 1 can be rewritten as [OBA]pulp ) (Q - [OBA]pulp) × K × [OBA]soln
(2)
[OBA]pulp ) (-K) × [OBA]pulp + (Q × K) [OBA]soln
(3)
and
The Langmuir adsorption isotherm plotting, [OBA]pulp/ [OBA]soln over [OBA]pulp, is given in Figure 2 for the HWBKP and HYP systems. As the OBA charge increased, the weight ratio of OBA adsorbed onto pulp fibers over OBA in solution decreased, and this was true for both the HWBKP and HYP. A comparison of HWBKP and HYP curves in Figure 2 showed that under otherwise same conditions, the OBA retention on BKP was higher than that on HYP. These results were in agreement with those reported earlier.11,15 It can be found in Figure 2 that the experimental data fits well to a linear regression at a low range of OBA adsorption (e.g., less than 1.6% for HWBKP and less than 0.5% for HYP). With the increase of the amount of OBA adsorbed, there are not any linear relationships for both the BKP system and HYP system. Similar results were obtained by Stana et al.,20 who studied a cotton fiber system. It was proposed20 that these changes were caused by the adsorption of a second layer of OBA on cotton fibers. Likewise, as shown in Figure 2, the OBA adsorption behavior followed the Langmuir isotherm in a monolayer only at a relatively low
9409
Figure 3. Effect of OBA adbsorbed on the pulp brightness (the conditions are the same as Figure 1).
OBA adsorbed amount. For the HWBKP, the Langmuir isotherm is valid only at the adsorbed OBA amount of less than 1.6%, while for the HYP, it was less than 0.5%. This indicates that more OBA can be adsorbed in monolayer onto BKP pulp fibers than onto HYP fibers, that is, the QBKP value was higher than the QHYP value. There are more adsorption sites on BKP fibers for OBA to form monolayer structure than HYP fibers, which is due to the presence of lignin on HYP fibers.11 Also, the weight ratio of OBA adsorbed on fibers to OBA in solution for the BKP system (see the Y-axis in Figure 2) is much higher than that for the HYP system, indicating that the OBA retention on BKP fibers is much higher than that on HYP fibers. Earlier results15 from fluorescence microscopy support the conclusion that the adsorption of OBA molecules through HYP fibers is not as extensive as that of BKP fibers due to the lower porosity (hindrance of lignin) of HYP fibers. Optical Properties. The effects of OBA on pulp brightness are shown in Figure 3, the UV included brightness means that fluorescent composition due to OBA is included while the UV excluded brightness is the pulp brightness without the fluorescent composition. It can be seen that for both the HWBKP and HYP, the UV Inc. brightness increased significantly as the amount of OBA adsorbed onto pulp increased, and leveled off as the amount of OBA adsorbed further increased. This occurred at 1.6% OBA adsorbed for BKP and at 0.6 to 0.7% for the HYP. At even higher OBA adsorbed (about 2.8% for BKP) the UV Inc. brightness showed a slight decrease, which may be due to the bathochromic shift of the emitted light and the readsorption of the emitted photons by the multilayers of adsorbed OBA molecules.20 Also, it was shown in Figure 3 that the UV Exc. brightness always decreased somewhat for both BKP and HYP, which is due to the fact that OBA itself is slightly colored, consequently causing additional light adsorption at the 457 nm wavelength, which was used for the brightness measurement. On the basis of the above results, we drew the conclusion that OBA adsorption onto pulp fibers followed the Langmuir adsorption isotherm very well at a low range of OBA adsorption; under this condition, the monolayer adsorption mechanism dominates. At the same time, the best brightening efficiency can be achieved for both HWBKP and HYP. For the HWBKP when the amount of OBA adsorbed was more than 1.6%, the multilayer mechanism, shown in Figure 4, became effective. For the HYP the transition from the mono- to multilayer occurred at the amount of adsorbed OBA of about 0.5%. Such differences are explained by the presence of lignin in the HYP, which hindered the OBA adsorption onto pulp fibers, conse-
9410
Ind. Eng. Chem. Res., Vol. 49, No. 19, 2010
At the steady state (t ) ∞), eq 421 can be rearranged to 1 K 1 ) + Γ∞ c∞ Γmax
Figure 4. Proposed model of OBA adsorption on pulp (if more OBA adsorbed).
Figure 5. Adsorption curve of PCC onto HYP fibers (1% pulp consistency, 50 °C, 50 rpm stirring speed).
quently resulting in less OBA adsorption sites in HYP fibers.11 At a high OBA charge, OBA can aggregate, leading to the formation of dimers, trimers, and others,31 The energy conversion due to OBA aggregates may be channeled into heat instead of fluorescence, resulting in further decrease in OBA brightening efficiency. This is because the fluorescence of such OBA aggregates lies at higher wavelengths than 445 nm.31 Also, the bathochromic shift of the emitted light can take place due to the multilayer formation,20 which may have a negative effect on the OBA brightening effect. Adsorption of PCC onto Pulp Fibers. PCC particles can carry a weak positive charge in deionized water.21 The adsorption of PCC onto pulp fibers is due to the electrostatic interaction between PCC particles and negatively charged fibers. The kinetics is shown in Figure 5 for the HYP. Three levels of PCC addition were used: 500, 1000, and 2000 mg/g fibers. The pH of the pulp system was about 8.5. It can be seen that at a short time the deposition increased rapidly and that a plateau was reached at a long time. The deposition at the plateau is less than the amount added, implying that not all of the added PCC can be deposited onto the fibers. Furthermore, the PCC adsorption plateau increased with the PCC concentration in the pulp slurry, suggesting that the deposition process was a dynamic equilibrium between PCC particles deposition and detachment. In an earlier study,21 it was shown that the deposition of PCC onto chemical pulp fibers suspended in water closely follows Langmuir kinetics. We followed a similar analysis for the results in Figure 5, as dθ ) k1(n0 - θ)(1 - θ) - k2θ dt
(5)
where K ) the equilibrium (or steady state) constant (K ) k2/ k1); c∞ ) the concentration of filler in solution, g/g; and Γ∞ ) the amount of filler deposition on the fibers as time goes to infinite, g/g. The Langmuir plot for the aspen HYP was given in Figure 6. From the intercept, we can see that the Γmax value (the maximum deposition of PCC on the HYP pulp fibers) was 955 mg/g. For a comparison, we performed a similar experimental program on a softwood kraft pulp. The results were shown in Figure 7 and the Langmuir plotting was given in Figure 8. It can be found that the Γmax, the maximum deposition of PCC on the softwood kraft pulp, was 538 mg/g. The results presented above demonstrated that for both the aspen HYP and the softwood kraft pulp, the PCC deposition process can be well described by the Langmuir theory. On the other hand, it was noted that the HYP fibers had a faster deposition process and more PCC particles were deposited in comparison with the softwood kraft pulp. These results can be explained by the fact that the aspen HYP contains more negative charges (carboxylic groups and the unique sulfonic groups) than the softwood kraft pulp.32,33 Earlier studies32,33 have shown that aspen HYPs can exhibit better sizing results from rosin and AKD sizing than kraft pulps, and the results were explained by the presence of unique sulfonic groups in the HYP and higher carboxylic group contents than the conventional kraft pulp because of the unique HYP manufacturing process. Likewise,
Figure 6. Langmuir fitting of HYP: Reciprocal amount of PCC deposited into fibers vs reciprocal amount remaining in suspension at the steady state.
(4)
where θ ) the fractional coverage of the fibers by fillers, i.e., θ ) Γ/Γmax; Γ ) the amount of filler deposited on the fibers, g/g; Γmax ) the maximum amount that can deposit, g/g; t ) the time, min; k1 and k2 ) the deposition and detachment rate constants, respectively, 1/min; and n0 ) the initial concentration of filler normalized by the amount required for monolayer coverage.
Figure 7. Adsorption curve of PCC onto softwood kraft pulp (1% pulp consistency, 50 °C, 50 rpm stirring speed).
Ind. Eng. Chem. Res., Vol. 49, No. 19, 2010
9411
of China and Canada (Grant No. 2008DFA91290 of the Ministry of Science and Technology of China), and the Natural Science and Engineering Research Council of Canada (Grant No. CRD 342757-06). Literature Cited
Figure 8. Langmuir fitting of SWBKP: Reciprocal amount of PCC deposited into fibers vs reciprocal amount remaining in suspension at the steady state.
these ionic groups (in a typical paper making process they are fully dissociated) in the HYP are certainly beneficial in retaining fillers, such as PCC. Another factor that contributes to the enhanced PCC deposition on the HYP rather than on the softwood kraft pulp is the presence of more fines in the HYP.1,33 The fines in the HYP have much larger specific surface area and carry more negative charges than the BKP fines;33 therefore, they can retain more PCC, which carries a weak positive charge, than the BKP fines. Although the HYP fines induce an overall negative impact on sizing efficiency,33 for the purpose of retaining PCC fillers, they can have a positive effect in adsorbing these mineral particles. Conclusions When added to a mixed pulp furnish consisting of BKP and HYP, OBA was more likely to be adsorbed onto BKP fibers than HYP fibers, and the amount of adsorbed OBA onto BKP fibers was more than that onto HYP fibers under otherwise the same conditions. For the BKP, at the OBA adsorbed amount of less than 1.6%, the OBA adsorption followed the Langmuir adsorption isotherm very well, indicating that the monolayer adsorption dominates; however when the adsorbed amount of OBA increased further, the multilayer adsorption mechanism became effective. For the HYP, the transition of monolayer to multilayer adsorption occurred at the adsorbed OBA amount of about 0.5%. For both the BKP and HYP, the pulp brightness increased significantly as the amount of OBA adsorbed onto pulp was less than the saturation point of the monolayer adsorption. However, as the amount of adsorbed OBA increased further, the additional brightness increase from OBA was limited, or even a slightly negative effect on the brightness performance was observed. The aspen HYP exhibited more PCC adsorption than the BKP, implying potentially better filler retention in the paper making process when using HYP fibers in the paper making furnish. The adsorption of PCC fillers onto pulp fibers suspended in water closely followed the Langmuir kinetics; the maximum amount of adsorption was 955 mg/g pulp for the HYP and 538 mg/g pulp for the BKP, respectively. These results can be explained by the higher anionic groups content in the HYP (more carboxylic group content and the presence of unique sulfonic groups) than in the BKP. Acknowledgment The authors would like to acknowledge the financial support of the International Scientific and Technological Joint Project
(1) Zhou, Y. Overview of high yield pulps (HYP) in paper and board. In Proceedings of the 90th PAPTAC Annual Meeting; PAPTAC: Montreal, Canada, 2004; p B143-148. (2) Reis, R. The increased use of hardwood high yield pulps for functional advantages in papermaking. In Proceedings of the 2001 Papermakers Conference; Cincinnati, OH, USA, 2001; p 87-108. (3) Xu, E. C.; Zhou, Y. Synergistic effects between chemical mechanical pulps and chemical pulps from hardwoods. Tappi J. 2007, 6, 4–9. (4) Yuan, Z.; Schmidt, J.; Heitner, C.; Zou, X. Coating improves the brightness stability of wood-free coated papers containing high-yield pulp. Tappi J. 2006, 5, 9–13. (5) Hu, K.; Ni, Y.; Zou, X. Substitution of aspen high-yield pulp for hardwood kraft pulp in fine papers and its effect on AKD sizing. Tappi J. 2004, 3 (8), 13–16. (6) Hu, K.; Ni, Y.; Zhou, Y.; Zou, X. Substitution of hardwood kraft with aspen high-yield pulp in light-weight coated wood-free paper. I: Synergy on base stock properties. Tappi J. 2006, 5 (3), 21–26. (7) Hu, K.; Ni, Y.; Zou, X. Substitution of hardwood bleached kraft pulp with aspen high-yield pulp in LWC wood-free papers. Part 2: Impact on coated paper quality. Tappi J. 2007, 6 (1), 26–32. (8) Hui, L.; Liu, Z.; Ni, Y. Characterization of high-yield pulp (HYP) by the solute exclusion technique. Bioresour. Technol. 2009, 100, 6630– 6634. (9) He, Z.; Zhang, H.; Ni, Y.; Zhou, Y. Adding optical brightening agents to high yield pulp at the pulp mill. Pulp and Paper Canada 2009, 110 (3), 18–23. (10) Nguyen, X. T. Process for manufacturing pulp, paper and paperboard products. US Patent application publication, Pub. No. US 2008/ 0066878 A1, 2008. (11) Zhang, H.; Hu, H.; He, Z.; Ni, Y.; Zhou, Y. Retention of optical brightening agents (OBA) and their brightening efficiency on HYPcontaining paper sheets. J. Wood Chem. Technol. 2007, 27 (4), 153–168. (12) Zhang, H.; He, Z.; Ni, Y.; Hu, H.; Zhou, Y. Using optical brightening agents for improving the optical properties of HYP-containing paper sheets. Pulp Pap. Can. 2009, 110 (8), 20–24. (13) Bourgoing, S.; Leclerc, E.; Martin, P.; Robert, S. Use of fluorescent whitening agent to inhibit light-induced colour reversion of unbleached mechanical pulps. J. Pulp Pap. Sci. 2001, 27, 240–244. (14) Zhang, H.; Hu, H.; Xu, Z. Use of fluorescent whitening agents against light-induced colour reversion of aspen BCTMP. Appita J. 2009, 62, 355–359. (15) Zhang, R.; Ni, Y.; Wong, D.; Schmidt, J.; Heitner, C.; Jordan, B. Interactions of optical brightening agents with high yield pulps. J. Wood Chem. Technol. 2009, 29 (4), 141–152. (16) He, Z.; Hui, L.; Liu, Z.; Ni, Y.; Zhou, Y. Impact of high-yield pulp substitution on the brightness stability of uncoated wood-free paper. Tappi J. 2010, 9 (3), 15–20. (17) Wong-Wah-Chung, P.; Mailhot, G.; Bolte, M. 4,4′-Diaminostilbene2,2′-disulfonate (DSD) behavior: under irradiation in water. Decrease of its activity as a fluorescent whitening agent. J. Photochem. Photobiol., A 2001, 138, 275–280. (18) Canonica, S.; Kramer, J. B. Photoisomerization kinetics of stilbenetype fluorescent whitening agents. EnViron. Sci. Technol. 1997, 31, 1754– 1760. (19) Davidson, R. S.; Ismail, G. M.; Lewis, D. M. The photosensitising properties and photostability of stilbene fluorescent whitening agents. J. Soc. Dyers Colour. 1987, 103, 261–264. (20) Stana, K. K.; Pohar, C.; Ribitsch, V. Adsorption of whitening agents on cellulose fiberssMonitored by streaming potential measurements, calorimetry and fluorescence. Colloid Polym. Sci. 1995, 273, 1174–1178. (21) Vanerek, A.; Alince, B.; Van de Ven, T. G. M. Interaction of calcium carbonate fillers with pulp fibers: effect of surface charge and cationic polyelectrolytes. J. Pulp Paper Sci. 2000, 26, 317–322. (22) Hiemenz, P. C.; Rajagopalan, R. Principles of colloids and surface chemistry, 3rd ed.; Marcel Dekker Inc.: New York, 1997; pp 320. (23) Haworth, A. A review of the modeling of sorption from aqueous solution. AdV. Colloid Interface Sci. 1990, 32, 43–78. (24) Ruthven, D. M. Principles of adsorption and adsorption processes; Wiley-Interscience: New York, 1984; p 433.
9412
Ind. Eng. Chem. Res., Vol. 49, No. 19, 2010
(25) Middleton, S. R.; Scallan, A. M. A kinetic model for the adsorption of fillers by pulp fibres. J. Pulp Paper Sci. 1991, 17, J127–J133. (26) Petlicki, J.; Van de Ven, T. G. M. Adsorption of polyethylenimine onto cellulose fibers. Colloids Surf., A 1994, 83, 9–23. (27) Vickerstaff, T. The Physical Chemistry of Dyeing, 2nd ed.; WileyInterscience: New York, 1954; p 301. (28) Kindler, W. A.; Swanson, J. W. Adsorption kinetics in the polyethyleneimine-cellulose fiber system. J. Polym. Sci. 1971, A-2–853. (29) Katz, S.; Beaston, R. P.; Scallan, A. M. The determination of strong and weak acidic groups in sulfite pulps. SVensk Papperstidning 1971, R48– 53. (30) Crouse, B. W.; Snow, G. H. Fluorescent whiteness agents in the paper industry. Tappi J. 1981, 64, 87–89.
(31) Alsins, J.; Bjo¨rling, M.; Furo´, I.; Egle, V. Dimer formation of a stilbene sulphonic acid salt in aqueous solution. J. Phys. Org. Chem. 1999, 171–175. (32) Li, H.; Ni, Y. Sizing behavior of BCTMP at neutral to alkaline pH. Pulp Paper Can. 2001, 102 (6), 45–48. (33) Li, H.; Ni, Y.; Sain, M. Characterization of BCTMP fines and their effect on sizing. Tappi J. 2002, 1 (7), 3–7.
ReceiVed for reView February 22, 2010 ReVised manuscript receiVed August 2, 2010 Accepted August 15, 2010 IE1003976
