Effects of Cationic Cetyltrimethylammonium Bromide on the Aggregation Behavior of Sodium Lignosulfonate (NaLS) in Concentrated Solutions and Preparation of Uniform Lignosulfonate-Based Colloidal Spheres

The effects of cetyltrimethylammonium bromide (CTAB) on the aggregation behavior of sodium lignosulfonate (NaLS) in concentrated solutions were investigated by rheology, conductivity, ζ-potential, surface tension, contact angle, and elemental analysis measurements. Results showed that the presence of CTAB led to increased aggregate effects and enhanced association networks due to intermolecular bridging caused by the formation of mixed aggregates containing NaLS hydrophobes and CTAB molecules at CTAB/NaLS mixing ratios (w/w) below stoichiometric mass ratio (SMR). However, further addition of CTAB resulted in the progressive disruption of network structures due to electrostatic repulsions between aggregates. There were electrostatic and hydrophobic interactions between NaLS and CTAB. The NaLS/CTAB mixing system could form regular colloidal spheres via electrostatic and hydrophobic self-assembly in an EtOH/water mixture. As the addition of CTAB increased, the ζ-potential of NaLS/CTAB colloidal spheres was decreased, and the particle size was increased. This work provides a novel approach to the value-added utilization of lignosulfonate biomass resources.