Formation of Uniform Colloidal Spheres Based on Lignosulfonate, a Renewable Biomass Resource Recovered from Pulping Spent Liquor

Abstract

Effects of mass ratios on the sodium lignosulfoante (NaLS) and cetyltrimethylammonium bromide (CTAB) mixing system were first investigated by zeta potential and surface tension measurements. Uniform colloidal spheres from the NaLS/CTAB complex were then fabricated via electrostatic and hydrophobic self-assembly and characterized by DLS, TEM, contact angle, elemental analysis, XPS, and FTIR measurements. Results showed the stoichiometric mass ratio (SMR) of the NaLS/CTAB system was 1:2.82, where the hydrophobicity was strongest and preparing colloidal spheres was feasible. Colloidal spheres were formed through gradual aggregation of NaLS/CTAB molecules at SMR, which was induced by continuously adding water into NaLS/CTAB/EtOH solutions. NaLS/CTAB molecules started to form spheres at a critical water content of 58 vol %, and the formation process was completed at a water content of 84 vol % when the initial concentration of NaLS/CTAB in EtOH was 1.0 mg mL–1. The sizes of NaLS/CTAB colloidal spheres could be well controlled by adjusting water-adding rates. This preparation of lignosulfonate-based nanoparticles is very simple, safe, and low-cost, and these obtained nanoparticles have advantages of biodegradability and ultraviolet resistance. This study provides a green and valuable approach to value-added applications of lignosulfonate biomass recovered from pulping spent liquor and is of great significance for both economic and environmental benefits.