Influence of Temperature and Lignin Concentration on Formation of Colloidal Lignin Particles in Solvent-Shifting Precipitation

Colloidal lignin particles offer a promising route towards material applications of lignin. While many parameters influencing the formation of these particles in solvent-shifting precipitation have been studied, only a small amount of research on the influence of temperature has been conducted so far, despite it being a major influence parameter in the precipitation of colloidal lignin particles. Temperature influences various other relevant properties, such as viscosity, density, and lignin solubility. This makes investigation of both temperature and lignin concentration in combination interesting. The present work investigates the precipitation at different temperatures and initial lignin concentrations, revealing that an increased mixing temperature results in smaller particle sizes, while the yield is slightly lowered. This effect was strongest at the highest lignin concentration, lowering the hydrodynamic diameter of the particles from 205 to 168 nm. Decreasing the lignin concentration resulted in significantly smaller particles (from 205 to 121 nm at 20 °C mixing temperature) but almost no change in particle yield (between 81.2 and 84.6% at 20 °C mixing temperature). This opens up possibilities for the process control and optimization of lignin precipitation.