A STUDY OF KRAFT LIGNIN ACID PRECIPITATION IN AQUEOUS SOLUTIONS USING FOCUSED BEAM REFLECTANCE MEASUREMENT (FBRM (R))

Journal article, 2018

This study has measured the evolution of the particle size distribution during acid precipitation of Kraft lignin in aqueous solutions. Sulphuric acid was added to acidify the solutions, and precipitation occurred. The influence of Na+ concentration was investigated, and temperature, lignin concentration, and agitation speed were kept constant throughout the study. The results show that the onset of precipitation, as defined in this work, is strongly dependent on Na+ concentration and pH. Furthermore, a shift in the onset pH was observed if existing particles were filtered off before acidification; this indicates a metastable regime in particle-free solutions. The kinetics of precipitation were found to depend predominantly on the density of existing particles in the liquid at the start of acidification.