Development of colloidal lignin particles through particle design strategies and screening of their Pickering stabilizing potential

Colloidal lignin particles (CLPs) have increased interest as green and sustainable materials for Pickering stabilizers, with particle design being an important step towards their effective use. In this context, the antisolvent precipitation method was selected to conduct a study aiming at understanding the effect of process variables (initial lignin concentration, antisolvent pH, final ethanol concentration, and antisolvent addition rate) on particle size, zeta potential, color parameters, and contact angle. Moreover, their Pickering stabilizing potential was preliminarily screened. The evaluation using a Fractional Factorial Design revealed that the particle size is significantly influenced by the initial lignin concentration (as it increases, larger particles are obtained) and the final ethanol concentration (as it increases, smaller sizes result). The zeta potential is significantly affected by the antisolvent pH and the initial lignin concentration; the increase in both parameters results in higher negative values. The color is significantly dependent on the used initial lignin concentration (as it increases, particles become lighter and the yellowish accentuates) and the antisolvent pH (as it increases, particles become darker). Both initial lignin concentration and final ethanol concentration increase promote hydrophobicity, whereas increasing the antisolvent pH and its addition rate turns particles more hydrophilic. Through this strategy, it was possible to achieve CLPs with promising Pickering stabilizing potential, putting in evidence the importance of understanding the production process to design effective particles for target applications.