Preparation and Characterization of a Humate Surfactant with Hydroxymethylation and Esterification Modification of Lignite

In this paper, a humate surfactant based on humic substances which were derived from lignite by modification of hydroxymethylation and esterification methods respectively was prepared. Determined by surface tension method, the cmc (critical micelle concentration) of the humate surfactant is 1.534 g/L and the corresponding surface tension is 48.8 mN/m. The optimum conditions of the modified processes are as follows: hydroxymethylation modification at pH 10.5, reaction temperature 90 degrees C, reaction time of 60 min, dosage of stock (formaldehyde/lignite/g g(-1)) 10:10, and the amount of reacted paraformaldehyde was 6.23 mmol/g lignite. The esterification modification was carried but at 70 degrees C, reaction time 10 h, dosage of 6.0 mmol n-decanoyl chloride/g lignite. The conversion rate of n-decanoyl chloride was 95%.