Dispersion Mechanisms of Lignosulfonates in Concentrated TiO2 Suspensions and Pastes: The Effects of Molecular Weight Distributions and Ionic Composition

This study investigates how molecular weight, ionic strength, and ionic composition influence the performance of sodium lignosulfonate as a dispersant for titanium dioxide (TiO₂) suspensions. Adsorption behavior was quantified using a quartz crystal microbalance with dissipation monitoring (QCM-D), while dispersion efficiency was assessed in concentrated suspensions via particle analysis (LUMiSizer) and in pastes through rheological measurements. In salt-free conditions, no adsorption occurs; however, the observed low particle size and viscosity can be attributed to depletion stabilization by non-adsorbing lignosulfonates. Both low- and high-molecular-weight fractions exhibit dispersing performance, but high-molecular-weight lignosulfonate provides the greatest stability across electrolyte variations. Increasing ionic strength enhances adsorption, leading to elastic particle network formation and higher viscosity due to reduced Debye length. With divalent ions, this effect is stronger and promoted by divalent cation bridging. These findings underscore the importance of tailoring lignosulfonate molecular weight and dosage to operating conditions, supporting formulation strategies for mineral-rich suspensions and industrial effluents. Future work should address long-term stability, temperature effects, and behavior on hydrophobic surfaces.