An Experimental Study of the Effect of Temperature on Effective Charge Numbers and Diffusion Coefficients of Lignosulfonate.

Kontturi, Anna-Kaisa; Kontturi, Kyösti; Niinikoski, Pasi; Murtomäki, Lasse

doi:10.3891/acta.chem.scand.46-0941

Cited by 10 publications

(8 citation statements)

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“…As indicated above, Kontturi et al (1992) found that LS loses its charge at a certain temperature and then it regains charges when the temperature rises further. It was suggested that this phenomenon is caused by the conformational change from a compact sphere to a nonfree unwinding coil and not by the aggregation of LS.…”

Section: Introductionmentioning

confidence: 88%

“…Therefore, the electrostatic repulsion weakens and the hydrophobic interaction strengthens. Conversely, LS tends to loose coordination water when the solution temperature reaches the CT which facilitates the approaching of LS molecules to each other (Kontturi et al 1992). When the solution temperature is above CAT, NaLS molecules with less surface charges tend to aggregate through hydrophobic interaction (state C).…”

Section: Adsorption Behavior Of Nals Above Catmentioning

confidence: 98%

“…Accordingly, the spherical microgels in solution become disk like when spread out in a monolayer or adsorbed onto a surface. Several years later, Kontturi et al (1992) and Kontturi (1988) and Mafé et al (1995) detected that LS in 0.1 mol·l -1 NaCl solution loses its charge when the temperature of the solution reaches 40°C. It was interpreted that the loss of the charge is due to the compact sphere of an LS molecule at this temperature.…”

Section: Introductionmentioning

confidence: 97%

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Aggregation of sodium lignosulfonate above a critical temperature

Qian¹,

Deng²,

Qiu³

et al. 2014

Holzforschung

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Single molecules of sodium lignosulfonate (NaLS) were prepared and their aggregation behavior was studied as a function of temperature. The molecular dispersity of the NaLS solutions were confirmed by dynamic light scattering (DLS), and the aggregation behavior was studied by DLS and static light scattering (SLS), fluorescence spectrometry (FS), and atomic force microscopy (AFM). It was demonstrated that NaLS molecules started to aggregate above a critical temperature and the aggregation behavior was related to their spherical microgel conformation and hydrophobic interaction. During the DLS measurement, when NaLS was dissolved in 1.2 mol·l -1 NaCl aqueous solution and then filtered with 0.45 μm syringe filter, the slowmode diffusion (smD) corresponded to the polyelectrolyte effect and the original aggregates disappeared and the fast-mode diffusion (fmD) corresponded to the monomolecular NaLS (not yet aggregated) in the solution. When the temperature of the NaLS solution was raised to 38°C, the disappeared smD in DLS analysis appeared again, indicating that NaLS molecules started to form new aggregates. Due to the aggregation at 38°C, molecular weight (M w ) obtained from the SLS had a sharp increase, intensity ratio (I 1 /I 3 ) of pyrene in FS suddenly decreased, and the adsorption of NaLS on a solid substrate and the corresponding roughness of the surface increased significantly.

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Section: Introductionmentioning

confidence: 88%

Section: Adsorption Behavior Of Nals Above Catmentioning

confidence: 98%

Section: Introductionmentioning

confidence: 97%

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Aggregation of sodium lignosulfonate above a critical temperature

Qian¹,

Deng²,

Qiu³

et al. 2014

Holzforschung

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show abstract

“…Rezanowich and Goring (1960) and Goring et al (1979) suggested a spherical shape in solution and a disk-like shape at the interface. Because of their spherical structure, LSs tend to lose their charge at about 40°C in 0.1 mol l -1 NaCl (Kontturi et al 1992). Our experiments also proved that LSs have a minimum Zeta potential at about 38°C (Qian et al 2013b).…”

Section: A Modified Microgel Modelmentioning

confidence: 98%

Light scattering characterization of lignosulfonate structure in saline solutions

et al. 2014

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The solution behavior and molecular conformation of sodium lignosulfonates (NaLS) in saline solution has been studied by means of static and dynamic light scattering (LS stat and LS dyn ). Results show that the salt content must be larger to eliminate the slow mode in LS dyn analysis of NaLS than that of the theory, and this discrepancy can only be explained by a modified microgel model. The higher salt amount is needed for the formation of a strong ionic gradient field between surface and the inner part of NaLS, which forces counter ions to penetrate into the inner part of NaLS to screen the small amount of charges. The NaLS single molecular shape can be described by an oblate spheroid based on the absolute molecular weight M w and diffusion coefficients D. The best fitting result is semiaxis a = 1.6 nm and axial ratio r = 3.5, D = 5.73 × 10 -7 cm 2 s -1 , and the corresponding M w = 1.7 × 10 5 g mol -1 .

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“…However, 30 min is too short to effectuate any disaggregation. Kontturi et al (1992) looked at the effective charge number and diffusion coefficients and ruled out LS aggregation. However, the highest concentration in this work was 0.1%, which is too low for aggregate formation.…”

Section: Temp(k)mentioning

confidence: 99%

Evidence for a very slow disaggregation of lignosulfonates

Myrvold¹

2014

Holzforschung

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There is still a challenging question about how lignosulfonates (LS), such as non-sulfonated lignins, aggregate and disaggregate in solution. In the literature, the reported critical aggregation concentration (CAC) of LS varies by orders of magnitude. In the present work, the aggregation of a purified sodium LS (NaLS) from a softwood has been studied by size exclusion chromatography and capillary viscometry. It was found that intermolecular aggregates form at relatively high concentrations. Disaggregation is an extremely slow process for spray dried samples and proceeds for several weeks. The process can be speeded up by increasing the pH and/or temperature. The very slow disaggregation may explain the strongly varying (and sometimes very low) CAC values reported in the literature. An interaction energy of about 8 kJ mol -1 monomer was calculated.

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An Experimental Study of the Effect of Temperature on Effective Charge Numbers and Diffusion Coefficients of Lignosulfonate.

Cited by 10 publications

References 0 publications

Aggregation of sodium lignosulfonate above a critical temperature

Aggregation of sodium lignosulfonate above a critical temperature

Light scattering characterization of lignosulfonate structure in saline solutions

Evidence for a very slow disaggregation of lignosulfonates

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