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Isolation of lignosulfonate with low polydispersity index
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Chinese Chemical Letters 21 (2010) 1479–1481 www.elsevier.com/locate/cclet
Isolation of lignosulfonate with low polydispersity index Xin Ping Ouyang, Pan Zhang, Chun Mei Tan, Yong Hong Deng, Dong Jie Yang, Xue Qing Qiu * School of Chemistry and Chemical Engineering, South China University of Technology, Guangzhou 510640, China Received 30 March 2010
Abstract Lignosulfonate with low polydispersity index of 1.178–1.210 was isolated by gel column chromatography of Sephacryl S-100 eluted with 0.2 mol/L of NaNO3 aqueous solution, whereas nearly monodisperse ligosulfonate fraction with polydispersity of 1.067 can be obtained after chromatographic separation twice. This method provides an available approach to investigate the structure and characteristics of lignosulfonate. # 2010 Xue Qing Qiu. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved. Keywords: Lignosulfonate; Sephacryl; Chromatographic separation
Lignosulfonate, one of the most abundant natural polymers, is usually obtained as a by-product of pulping process. From the points of view of environment and resource, the characterization and utilization of lignsolfonate have been attracted wide attention recently. Lignosulfonate is an anionic surfactant, possessing a certain degree of surface activity, adsorptivity and dispersing effect to suspension system. It may be used in various industrial processes, such as being animal feed pellet binders, dispersants for dyes or pesticides, concrete water-reducer [1], coal water slurry additives [2–4], corrosion and scale inhibitor in the recirculating cooling water system [5], lignin–phenol– formaldehyde resins [6]. Industrial applications of lignosulfonate as a chemical feedstock have, however, been limited for its complicated structural characteristics, scattered molecular weight (Mw) distribution, and quite differences in the properties of lignosulfonate with various Mw [7,8]. Lignosulfonate isolation is the preferred approach to explore the relationship between structure and characteristic, and hence provides a theoretical support for chemical modification and making use of lignosufonate more efficiently. Up to now, a lot of separation methods have been reported, including ultrafiltration [9], solvent extraction [10], long chain amine extraction [11], liquid membrane separation [2,4,12]. However, lignosulfonate fraction after separation method reported is still a mixture with diverse Mw. It is well known that preparative column chromatography is the technique used most commonly for separation of compounds with different Mw [13]. In the present work, the lignosulfonate fraction with low polydispersity was isolated by using preparative column packed with Sephacryl S-100.
* Corresponding author. E-mail address: [email protected] (X.Q. Qiu). 1001-8417/$ – see front matter # 2010 Xue Qing Qiu. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved. doi:10.1016/j.cclet.2010.06.032
[(Fig._1)TD$IG] 1480
X.P. Ouyang et al. / Chinese Chemical Letters 21 (2010) 1479–1481
Fig. 1. Effect of mobile phase on the separation efficiency of lignosulfonate.
20 wt% of lignosulfonate retentate ultrafiltrated with a 2500 Dalton (Da) cutoff membrane was injected into the 1.6 cm I.D. 70 cm long column packed with Sephacryl S-100 gel and eluted with 0.02–0.2 mol/L NaNO3 solution, flowing at 0.2 mL/min. The Mw distribution of the lignosulfonate sample collected was determined by using gel permeation chromatography [14] (GPC, Waters 1515), using UltrahydrogelTM 120 and 250 columns, 0.10 mol/L of NaNO3 as a mobile phase at a flow rate of 0.50 mL/min, and sodium polystyrene sulfonate as a standard. The fractionation results of lignosulfonate eluted with different concentrations of NaNO3 solution and distilled water are shown in Fig. 1. The Mw of lignosulfonate fractions collected with elution time ranging from 220 min to 340 min varies from 14100 Da to 1800 Da, and all the resulting lignosulfonate fractions have the characteristic of low polydispersity index when NaNO3 was used as the mobile phase. While the elution time exceeds 340 min, the polydispersity index of the separated fraction exhibits a trend towards an increase although the polydispersity index remains low. It is also found that the lignosulfonate fractions with polydispersity index ranging from 1.178 to 1.210 can be obtained when 0.2 mol/ L NaNO3 is used as mobile phase. Theoretically, gel column chromatographic separation is based largely on molecular size and geometry, so it seems that the component of eluent do not have an impact on the separation efficiency. However, the experimental result shows that NaNO3 solution exhibits a good separation effect compared with distilled water used as the mobile phase. It may be because lignosulfonate is a non-linear anionic polyelectrolyte, and hence there is existence of polyelectrolyte effect caused by Coulomb interactions between charged lignosulfonate chains in the aqueous solution. This effect can be weakened by adding inorganic salt [15,16]. The exact reason is not very clear, and a further study seems to be needed. The lignosulfonate fraction collected at 320 min of elution time was chromatographically separated once again under the condition of eluting with 0.2 mol/L of NaNO3 at flow rate of 0.2 mL/min, and the results of the Mw and polydispersity are listed in Table 1. It indicates that the nearly monodispersed lignosulfonate can be obtained by using the two-step chromatographic separation, and the lowest polydispersity index is 1.067. Table 1 Characteristics of Mw and polydispersity of lignosulfonate fractions obtained by two-step chromatographic separation. Elution time (min)
Mw
Mn
Polydispersity
Sample 87 92 97 102 107 112 117 122
4584 5345 5174 4700 4306 3966 3759 3518 3410
3785 4596 4580 4272 3972 3718 3487 3162 2509
1.211 1.163 1.129 1.100 1.084 1.067 1.078 1.112 1.359
[(Fig._2)TD$IG]
X.P. Ouyang et al. / Chinese Chemical Letters 21 (2010) 1479–1481
1481
Fig. 2. Mw distribution profiles of the lignosulfonates before and after separation.
Fig. 2 shows the Mw distributions of the lignosulfonates before and after the separation. It is easy to observe that the range of Mw distribution reduces greatly after the one-step chromatographic separation, whereas the Mw distribution becomes very narrow after the two-step chromatographic separation, indicating that the column chromatography is a good method for fractionation of lignosulfonate. In conclusion, column chromatography is an efficient method to separate the lignosulfonate into fine fractions with low polydispersity index, and the nearly monodisperse lignosulonate can be obtained after two-step chromatographic separation. Acknowledgments This work is financially supported by the National Natural Science Fund of China (No. 20876064), the Guangdong Provincial Natural Science Fund (No. 9151064101000082) and the Guangdong Provincial International Cooperation Fund (No. 2008B05010006). References [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13] [14] [15] [16]
X. Ouyang, X. Qiu, P. Chen, Colloids Surf. A 282–283 (2006) 489. K. Chakrabarty, K.V. Krishna, P. Saha, et al. J. Membr. Sci. 330 (2009) 135. Y. Pang, X. Qiu, D. Yang, et al. Colloids Surf. A 312 (2008) 154. K. Chakrabarty, P. Saha, A.K. Ghoshal, J. Membr. Sci. 340 (2009) 84. X. Ouyang, X. Qiu, H. Lou, et al. Ind. Eng. Chem. Res. 45 (2006) 5716. Y. Park, W.O.S. Doherty, P.J. Halley, Ind. Crops Prod. 27 (2008) 163. D. Yang, X. Qiu, M. Zhou, et al. Energ. Convers. Manage. 48 (2007) 2433. S.A. Gundersen, J. Sjoblom, Colloid. Polym. Sci. 277 (1999) 462. A. Garcia, A. Toledano, L. Serrano, Sep. Purif. Technol. 68 (2009) 193. A.K. Kontturi, K. Kontturi, P. Niinikoski, Acta Chem. Scand. 44 (1990) 883. O. Ringena, B. Saake, R. Lehnen, Holzforschung 59 (2005) 405. K. Chakrabarty, P. Saha, A.K. Ghoshal, J. Membr. Sci. 346 (2010) 37. V.R. Botaro, A.A. Silva Curvelo, J. Chromatogr. A 1216 (2009) 3802. R.C. Sun, J. Tomkinson, Sep. Purif. Technol. 24 (2001) 529. C.L. De Vasconcelos, P.M. Bezerril, D.E.S. Dos Santos, Biomacromolecules 7 (2006) 1245. J. Kim, T.K. Ahn, J.H. Park, Pollimo 20 (1996) 885.
Chinese Chemical Letters 21 (2010) 1479–1481 www.elsevier.com/locate/cclet
Isolation of lignosulfonate with low polydispersity index Xin Ping Ouyang, Pan Zhang, Chun Mei Tan, Yong Hong Deng, Dong Jie Yang, Xue Qing Qiu * School of Chemistry and Chemical Engineering, South China University of Technology, Guangzhou 510640, China Received 30 March 2010
Abstract Lignosulfonate with low polydispersity index of 1.178–1.210 was isolated by gel column chromatography of Sephacryl S-100 eluted with 0.2 mol/L of NaNO3 aqueous solution, whereas nearly monodisperse ligosulfonate fraction with polydispersity of 1.067 can be obtained after chromatographic separation twice. This method provides an available approach to investigate the structure and characteristics of lignosulfonate. # 2010 Xue Qing Qiu. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved. Keywords: Lignosulfonate; Sephacryl; Chromatographic separation
Lignosulfonate, one of the most abundant natural polymers, is usually obtained as a by-product of pulping process. From the points of view of environment and resource, the characterization and utilization of lignsolfonate have been attracted wide attention recently. Lignosulfonate is an anionic surfactant, possessing a certain degree of surface activity, adsorptivity and dispersing effect to suspension system. It may be used in various industrial processes, such as being animal feed pellet binders, dispersants for dyes or pesticides, concrete water-reducer [1], coal water slurry additives [2–4], corrosion and scale inhibitor in the recirculating cooling water system [5], lignin–phenol– formaldehyde resins [6]. Industrial applications of lignosulfonate as a chemical feedstock have, however, been limited for its complicated structural characteristics, scattered molecular weight (Mw) distribution, and quite differences in the properties of lignosulfonate with various Mw [7,8]. Lignosulfonate isolation is the preferred approach to explore the relationship between structure and characteristic, and hence provides a theoretical support for chemical modification and making use of lignosufonate more efficiently. Up to now, a lot of separation methods have been reported, including ultrafiltration [9], solvent extraction [10], long chain amine extraction [11], liquid membrane separation [2,4,12]. However, lignosulfonate fraction after separation method reported is still a mixture with diverse Mw. It is well known that preparative column chromatography is the technique used most commonly for separation of compounds with different Mw [13]. In the present work, the lignosulfonate fraction with low polydispersity was isolated by using preparative column packed with Sephacryl S-100.
* Corresponding author. E-mail address: [email protected] (X.Q. Qiu). 1001-8417/$ – see front matter # 2010 Xue Qing Qiu. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved. doi:10.1016/j.cclet.2010.06.032
[(Fig._1)TD$IG] 1480
X.P. Ouyang et al. / Chinese Chemical Letters 21 (2010) 1479–1481
Fig. 1. Effect of mobile phase on the separation efficiency of lignosulfonate.
20 wt% of lignosulfonate retentate ultrafiltrated with a 2500 Dalton (Da) cutoff membrane was injected into the 1.6 cm I.D. 70 cm long column packed with Sephacryl S-100 gel and eluted with 0.02–0.2 mol/L NaNO3 solution, flowing at 0.2 mL/min. The Mw distribution of the lignosulfonate sample collected was determined by using gel permeation chromatography [14] (GPC, Waters 1515), using UltrahydrogelTM 120 and 250 columns, 0.10 mol/L of NaNO3 as a mobile phase at a flow rate of 0.50 mL/min, and sodium polystyrene sulfonate as a standard. The fractionation results of lignosulfonate eluted with different concentrations of NaNO3 solution and distilled water are shown in Fig. 1. The Mw of lignosulfonate fractions collected with elution time ranging from 220 min to 340 min varies from 14100 Da to 1800 Da, and all the resulting lignosulfonate fractions have the characteristic of low polydispersity index when NaNO3 was used as the mobile phase. While the elution time exceeds 340 min, the polydispersity index of the separated fraction exhibits a trend towards an increase although the polydispersity index remains low. It is also found that the lignosulfonate fractions with polydispersity index ranging from 1.178 to 1.210 can be obtained when 0.2 mol/ L NaNO3 is used as mobile phase. Theoretically, gel column chromatographic separation is based largely on molecular size and geometry, so it seems that the component of eluent do not have an impact on the separation efficiency. However, the experimental result shows that NaNO3 solution exhibits a good separation effect compared with distilled water used as the mobile phase. It may be because lignosulfonate is a non-linear anionic polyelectrolyte, and hence there is existence of polyelectrolyte effect caused by Coulomb interactions between charged lignosulfonate chains in the aqueous solution. This effect can be weakened by adding inorganic salt [15,16]. The exact reason is not very clear, and a further study seems to be needed. The lignosulfonate fraction collected at 320 min of elution time was chromatographically separated once again under the condition of eluting with 0.2 mol/L of NaNO3 at flow rate of 0.2 mL/min, and the results of the Mw and polydispersity are listed in Table 1. It indicates that the nearly monodispersed lignosulfonate can be obtained by using the two-step chromatographic separation, and the lowest polydispersity index is 1.067. Table 1 Characteristics of Mw and polydispersity of lignosulfonate fractions obtained by two-step chromatographic separation. Elution time (min)
Mw
Mn
Polydispersity
Sample 87 92 97 102 107 112 117 122
4584 5345 5174 4700 4306 3966 3759 3518 3410
3785 4596 4580 4272 3972 3718 3487 3162 2509
1.211 1.163 1.129 1.100 1.084 1.067 1.078 1.112 1.359
[(Fig._2)TD$IG]
X.P. Ouyang et al. / Chinese Chemical Letters 21 (2010) 1479–1481
1481
Fig. 2. Mw distribution profiles of the lignosulfonates before and after separation.
Fig. 2 shows the Mw distributions of the lignosulfonates before and after the separation. It is easy to observe that the range of Mw distribution reduces greatly after the one-step chromatographic separation, whereas the Mw distribution becomes very narrow after the two-step chromatographic separation, indicating that the column chromatography is a good method for fractionation of lignosulfonate. In conclusion, column chromatography is an efficient method to separate the lignosulfonate into fine fractions with low polydispersity index, and the nearly monodisperse lignosulonate can be obtained after two-step chromatographic separation. Acknowledgments This work is financially supported by the National Natural Science Fund of China (No. 20876064), the Guangdong Provincial Natural Science Fund (No. 9151064101000082) and the Guangdong Provincial International Cooperation Fund (No. 2008B05010006). References [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13] [14] [15] [16]
X. Ouyang, X. Qiu, P. Chen, Colloids Surf. A 282–283 (2006) 489. K. Chakrabarty, K.V. Krishna, P. Saha, et al. J. Membr. Sci. 330 (2009) 135. Y. Pang, X. Qiu, D. Yang, et al. Colloids Surf. A 312 (2008) 154. K. Chakrabarty, P. Saha, A.K. Ghoshal, J. Membr. Sci. 340 (2009) 84. X. Ouyang, X. Qiu, H. Lou, et al. Ind. Eng. Chem. Res. 45 (2006) 5716. Y. Park, W.O.S. Doherty, P.J. Halley, Ind. Crops Prod. 27 (2008) 163. D. Yang, X. Qiu, M. Zhou, et al. Energ. Convers. Manage. 48 (2007) 2433. S.A. Gundersen, J. Sjoblom, Colloid. Polym. Sci. 277 (1999) 462. A. Garcia, A. Toledano, L. Serrano, Sep. Purif. Technol. 68 (2009) 193. A.K. Kontturi, K. Kontturi, P. Niinikoski, Acta Chem. Scand. 44 (1990) 883. O. Ringena, B. Saake, R. Lehnen, Holzforschung 59 (2005) 405. K. Chakrabarty, P. Saha, A.K. Ghoshal, J. Membr. Sci. 346 (2010) 37. V.R. Botaro, A.A. Silva Curvelo, J. Chromatogr. A 1216 (2009) 3802. R.C. Sun, J. Tomkinson, Sep. Purif. Technol. 24 (2001) 529. C.L. De Vasconcelos, P.M. Bezerril, D.E.S. Dos Santos, Biomacromolecules 7 (2006) 1245. J. Kim, T.K. Ahn, J.H. Park, Pollimo 20 (1996) 885.