Tailored Lignin Xerogels: Insights into Morphology Control

Lignin, a renewable biopolymer, presents significant potential for sustainable materials development, particularly in the synthesis of porous adsorbents for water treatment. This study introduces a tailored approach for synthesizing lignin-based xerogels (LBX) via a sol-gel process combined with polymerization-induced phase separation (PIPS), enabling a controlled pore morphology and hierarchy. Data on lignin structure and molecular weight are used to effectively predict the outcome of the sol-gel process prior to the incorporation of polyethylene glycol (PEG) as an additive polymer. By systematically varying the molecular weight and concentration of PEG, the influence of these factors on phase separation dynamics, drying behavior, and the structure of the resulting porous bodies is revealed. The synthesized xerogels exhibited tunable pore structures, with average pore sizes ranging from 10 to 90 μm, porosities between 19 and 73 vol %, specific surface areas (SSAs) from 0.7 to 13.2 m²/g, and permeability values spanning 1.3 to 5.6 darcys. This study highlights a tunable strategy for lignin valorization, offering insights into the development of biobased porous materials with potential relevance to heavy metal adsorption.