A Novel Cationic Lignin-amine Emulsifier with High Performance Reinforced via Phenolation and Mannich Reactions

Abstract

A novel cationic lignin-amine emulsifier with high surface activity was prepared from kraft lignin (KL) via the phenolation of KL to obtain phenolated kraft lignin (PKL) and improve reaction sites. The introduction of dehydroabietyl groups as hydrophobic groups and diethylenetriamino groups as hydrophilic groups in PKL, by Mannich reactions, enhanced the performance of the emulsifier. The results showed that the number of the hydroxyphenyl groups in PKL was 0.27/C9 unit when 1 mol lignin was treated with 10 mol phenol at 60 °C for 6 h under 60 wt% sulfuric acid. The numbers of dehydroabietyl groups and diethylenetriamino groups in PKL were 0.18/C9 and 0.13/C9 unit, respectively. The surface tension of the emulsifier was 30.03 mN·m-1 at a concentration of 0.03 M hydrochloric acid aqueous solution with a pH 2.0, which is close to the commercial surfactant cetyltrimethylammonium bromide (CTAB). The zeta potential of the emulsifier was 45.1 mV, and its emulsifiability was 72 min. In contrast, the surface tension of the emulsifier prepared by non-phenolated lignin at the same condition was 38.67 mN·m-1, where the maximum zeta potential was 40.03 mV and its emulsifiability was 53 min. As expected, the performance of the emulsifier was reinforced by the phenolation reaction.