Synthesis of a lignin-based surfactant through amination, sulfonation, and acylation

A simple and effective chemical method based on Mannich reaction, sulfonation, and acylation was adopted to anchor the hydrophilic sulfonic groups and lipophilic long carbon chains onto alkaline lignin. The obtained products were characterized by Fourier transform infrared spectroscopy (FTIR) and elemental analysis, and the surface activity was evaluated by interfacial tension, which was determined by a maximum bubble pressure method. The results demonstrated that the ASAL showed high surface activity in comparison to lignosulfonate and the interfacial tension reached 5.0 (10−3 N · m−1) when the mass fraction of ASAL was 5%, in agreement with the properties of good surfactants.**