Kraft Lignin−Poly(DADMAC) Precipitate Formation

The precipitation of kraft lignin with poly(diallyldimethylammonium chloride), poly(DADMAC), was characterized as a function of pH. At a mass mixing ratio of poly(DADMAC) to lignin of 0.53 at pH 12.6, approximately 80% of the added lignin was removed, whereas the precipitate contained less than 35% of the added poly(DADMAC). Lignin precipitated with as much as 75% of the charges not associated with poly(DADMAC). Lower pH solutions required less poly(DADMAC) for lignin precipitation. Colloidal complex formation was measured as a function of time by dynamic light scattering, and the results could be fitted by a diffusion-controlled aggregation model.