Relationship between the hydrophilicity of lignin dispersants and their performance towards pesticide particles

The correlation between the hydrophilicity of sodium lignosulfonate (NaLS) and its dispersing performance towards pesticide particles has been investigated. NaLS was classified into three fractions by adsorption chromatography on macroporous resins. A positive correlation has been found between the hydrophilicity and the contents of phenolic hydroxyl and sulfonic acid groups. On the other hand, the NaLS fraction with high carboxyl content is not strong hydrophilic. With decreasing the hydrophilicity of NaLS, its amounts on pesticide particles surface increased and the dispersing performance of pesticide particles was improved. Obviously, NaLS and pesticides with similar hydrophilicity match better according to the similarity-intermiscibility theory. Carboxymethylated alkali lignin (CML) is not as hydrophilic as NaLS. The adsorption and dispersing performance of CML for hydrophobic pesticide particles are better than those of NaLS, demonstrating that lignin formulations with lower hydrophilicity are an alternative to obtain excellent pesticide dispersants.