Dispersion performance of hydroxypropyl sulfonated lignin in aluminum oxide suspension

Abstract

• Hydroxypropyl sulfonated kraft lignin was compared with lignosulfonate as a dispersant. • The adsorption of the biopolymers on the aluminum oxide surface was studied. • The dispersion, sedimentation, and particle size of the system were studied. • The results confirmed that both biopolymers behaved very similarly in the suspension. • Hydroxypropyl lignin can replace lignosulfonate due to its attractive production process. In this work, the adsorption and dispersion characteristics of hydroxypropyl sulfonated lignin (HSL) were assessed and compared with those of lignosulfonate (LS). HSL was synthesized in an environmentally friendly manner by reacting kraft lignin (KL) with 3-chloro-2-hydroxypropansulfonic acid (CHPS) under alkaline conditions. This reaction produced HSL with a charge density (-2.48 mmol/g) and molecular weight (42,000 g/mol) that were similar to those of LS. The adsorption behavior of HSL and LS on the aluminum oxide surface was fundamentally analyzed using a quartz crystal microbalance with dissipation monitoring (QCM-D). HSL and LS formed films of similar thickness, though the HSL films exhibited looser and more viscous structures. The dynamic and static dispersion behaviors of HSL and LS in an aluminum oxide suspension were investigated via ζ potential, particle size, and sedimentation analyses. HSL and LS decreased the suspended particle size and improved suspension stability via electrostatic repulsion similarly. The similar properties, adsorption behavior, and stabilizing performances of HSL and LS indicate that HSL may be an effective substitute for commercial LS dispersants. Furthermore, its environmentally friendly synthesis and use of widely available KL as a starting material make HSL production a commercially attractive option.