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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 (LSstat and LSdyn). Results show that the salt content must be larger to eliminate the slow mode in LSdyn 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 Mw 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 cm2 s-1, and the corresponding Mw=1.7×105 g mol-1. [ABSTRACT FROM AUTHOR]

Sodium lignosulfonate (NaLS) was dissolved in saline solutions, and the dissolving process was examined by a combination of static and dynamic light scattering. When NaLS was dissolved in 1.2 mol l-1 NaCl solution for 24 h and filtered through a 0.45 μm syringe filter, only a fast relaxation mode was observed, which was attributed to the co-diffusion of NaLS molecular ions and counterions. When the concentration of NaCl was below 1.2 mol l-1 or the dissolving time was <24 h, an additional slow relaxation mode (SRM) appeared due to hindered motions of electrostatically interacting chains. Without filtering or filtering followed by rising temperature to 38°C, SRM appeared due to aggregation, which occurred at a position similar to that caused by electrostatic interaction. For poly(sodium styrenesulfonate) (NaPSS) and modified bamboo lignin derivate with open polyelectrolyte structures, 0.1 mol l-1 NaCl was enough to inhibit the electrostatic interaction. For NaLS with a closed polyelectrolyte structure, the SRM could not be removed until the concentration of NaCl reached 1.2 mol l-1. Above observations give insights for the first time into the relationship between the SRM caused by electrostatically interacting chains and the diffusion mode due to NaLS aggregation, and the influence of the closed polyelectrolyte structure on the SRM. [ABSTRACT FROM AUTHOR]

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 slow-mode 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 ( Mw) obtained from the SLS had a sharp increase, intensity ratio (I1/I3) of pyrene in FS suddenly decreased, and the adsorption of NaLS on a solid substrate and the corresponding roughness of the surface increased significantly. [ABSTRACT FROM AUTHOR]

The problems related to the determination of the absolute molecular weight ( Mw) of sodium lignosulfonate (NaLS) are the focus of the present work. Four narrow-dispersed NaLS fractions were collected by filtration, ultrafiltration, and gel permeation chromatography (GPC), and their Mw measured by laser light scattering (LLS Mw) was compared with that obtained by GPC (GPC Mw). The LLS Mw values were much larger than GPC Mw, and this Mw difference increased with increasing Mw of NaLS. This finding confirms the known polyelectrolyte and aggregation effects of NaLS. The deviation is also partly due to the conformation differences between the GPC standard (sodium polystyrene sulfonate) and the NaLS molecules. The effects of polyelectrolytes and NaLS aggregates could be inhibited by adding enough NaCl salt in the NaLS solution and filtering the NaLS/NaCl solution through a syringe filter. As a result, the slow mode in dynamic LLS measurement disappeared. By this approach, the absolute LLS Mw values were only slightly larger than that determined by GPC due to the conformation differences between the GPC standard and the NaLS molecules. [ABSTRACT FROM AUTHOR]

The ability of commercial laccase for improvement of the physicochemical properties of sodium lignosulfonate (NaLS) without any mediator has been investigated. Surface tension, adsorption characteristics, rheological behaviors and fluidity of cement pastes were in focus. Gel permeation chromatography (GPC) shows an initial decrease and then an extensive increase of molecular weight (MW) of NaLS after incubation with laccase. Parallel to MW decrement, the content of phenolic groups is increasing, while an MW increment has the opposite effect. The UV-Vis spectra and the zeta potential of NaLS do not indicate further modification of the substitution pattern on the aromatic ring. The surface tension of NaLS and the adsorbed amount of NaLS on MgO particles is elevated after laccase treatment. The electrostatic attraction between MgO particles and NaLS is the main driving force during this adsorption process. The dispersion efficiency of laccase modified NaLS on the MgO slurry and cement paste is improved. [ABSTRACT FROM AUTHOR]

Abstract: The solution behavior of purified sodium lignosulfonate (PSL) at different pH values were investigated by means of acid–base titration, surface tension, viscosity, fluorescence spectrometry, dynamic light scattering (DLS) and environmental scanning electron microscopy (ESEM) experiments. Fluorescence experiments showed that the critical aggregate concentration (CAC) of PSL was 0.05g/L. DLS results indicated that the average dimension of PSL molecule and PSL aggregate was about 8nm and 80nm, respectively. The surface charge of PSL molecules and the aggregation degree of PSL in solution increased with the increasing of pH due to the ionization of sulfonic and phenolic hydroxyl groups. The size of PSL aggregates and reduced viscosity of PSL solution increased as pH values increased because expansion of the PSL cores. A model for the assembly behavior of PSL was first proposed to explain the influence of pH on the molecular configuration and aggregation behaviors of lignosulfonate in aqueous solutions. [ABSTRACT FROM AUTHOR]

Abstract: As a plasticizer and retarder, calcium lignosulfonate (CL) frequently leads to quick set of Portland cement containing anhydrite. For exploring the cause of this problem, the hydration characteristics of the tricalcium aluminate–anhydrite system in the saturated calcium hydroxide solution with and without CL were researched from two aspects: the compositions of liquid phases and the formations of hydration products. Results show that the CL can promote the formation of ettringite, which induces a significant decrease in sulfate ion concentration at the initial time of hydration. The size of ettringite crystals becomes large in the presence of CL, which seems to be related to a decrease in calcium sulfate saturation ratio. It can be deduced that the quick set in the presence of CL is mainly caused by the accelerated reaction between the tricalcium aluminate and the anhydrite at the initial time of hydration. [Copyright &y& Elsevier]

Abstract: Lignosulfonate is an anionic surfactant from pulp processing industries. Alcohols are often used as cosurfactants in the application of surfactant. The improvement of straight-chain alcohols with different alkyl chain lengths as cosurfactant on the physicochemical properties of calcium lignosulfonate (CL) aqueous solution has been investigated. The results indicate that small amounts of straight-chain alcohols with longer alkyl chains are helpful in improving the surface activity of CL, especially when the number of carbon atoms in alcohols is 10 or larger. The adsorption amount of CL solutions with additives of longer chain alcohols on TiO2 particles increases greatly, and the zeta potential of TiO2 particles adsorbing CL rises significantly. It can be concluded that there is a cooperative effect of the longer chain alcohols on lignosulfonate to form a tighter adsorption layer at the interface. The steric hindrance increases with the increasing amount of adsorption, and the static repulsive force increases with the increasing zeta potential. Therefore, the effect of CL on the stability of the TiO2 suspension is enhanced dramatically by addition of longer chain alcohols. This understanding can lead to further development in expanding the functionalities of the lignosulfonate through manipulation of the adsorption capacity of CL on solid particles and enhance the dispersive ability of CL on solid suspensions by adding longer straight-chain alcohols. [Copyright &y& Elsevier]