Small-Angle X-ray Scattering and Rheological Characterization of Aqueous Lignosulfonate Solutions

Abstract

Lignosulfonate is a colloidal polyelectrolyte widely used as a dispersant in various industrial applications and produced during chemical pulping of wood chips. Here we present a systematic small-angle X-ray scattering (SAXS) and rheological study of fractionated lignosulfonate (mass weighted molar mass M w 18 000 g/mol) dissolved in water and 0.2 M NaCl. The concentration range varied from semidilute to concentrated regime. SAXS intensity of all solutions followed the Porod law at all concentrations, which is a clear indication of a compact shape of the lignosulfonate particle. In water, below 10 mass % lignosulfonate, the average interparticle distance obtained from SAXS patterns relates to concentration via a power law with exponent -0.28. Deviation of the power law exponent from ideal -0.33 and a linear decrease in volume fraction normalized Porod constant as a function of concentration are taken as indications of self-association of lignosulfonate. In saline solutions at high lignosulfonate mass fractions the average distance between lignosulfonate particles was longer and the average particle size was larger than those in aqueous solutions. The intrinsic viscosity in saline solution also was larger than that in aqueous solution. Lignosulfonate solutions showed Newtonian viscosity, except at very high concentrations. The variation of the relative zero-shear viscosity eta(0),r) with concentration was interpreted with the Krieger-Dougherty equation. An oblate spheroid shape with an axial ratio of 3.5 describes the average shape of the lignosulfonate particles in saline solutions based on SAXS intensities, the size distribution obtained using gel permeation chromatography, and rheological characterization. The largest dimension of the particles was about 8 nm. SAXS and rheology studies as a function of temperature reveal indications of temperature-dependent self-association.

Catalytic Conversion of Inulin and Fructose into 5‐Hydroxymethylfurfural by Lignosulfonic Acid in Ionic Liquids

“…It is an abundant renewable resource and a waste byproduct from the paper industry ( Figure 1). [12] The development of high-value applications of LS or lignin is one of the most important directions of modern biorefinery. [13] Recent research demonstrated that they can be used as proton-transfer materials for fuel cells [14] or electrochemistry materials due to their sulfonic acid functionality.…”

Surface Location of Individual Residues of SlpA Provides Insight into the Lactobacillus brevis S-Layer

“…The intensity curves were measured with a HI-STAR area detector at a sample-to-detector distance of 50 cm. The magnitudes of the scattering vector k [k ϭ (4 sin)/, where 2 is the scattering angle and is the incident wavelength] were 0.02 to 0.42 Å Ϫ1 (34). The samples were centrifuged into pellets.…”

New Developments in the Commercial Utilization of Lignosulfonates

“…Due to its heterogeneous nature, there is no well-defined critical micelle concentration. The viscosity of dense lignosulfonate solutions is high [5] and an interfacial lignosulfonate film is rigid and provides good film stability in emulsified systems, even in highly concentrated emulsions and in foams. One way to demonstrate this is to look at the compressibility of lignosulfonate films (Figure 14.3).…”

“…A schematic drawing of the suggested branched structure is given in Figure 14.1. That lignosulfonates indeed are compact and rigid molecules was further elaborated by Vainio et al [5], who suggested that lignosulfonates are reminiscent of hyperbranched polymers that behave in a similar way to particles in solution. Similar conjectures have been published earlier [6,7].…”