Systematic investigation of the adsorption potential of lignin- and cellulose-based nanomaterials towards pharmaceuticals

Pharmaceuticals are emerging water pollutants that pose a global threat to the sustainability and safety of aquatic resources. To mitigate their potential hazardous impacts, one of the keys is to address the removal of pharmaceutical residues from wastewaters. In this study, adsorption utilizing nanostructured wood-based adsorbents is viewed as a simple and versatile wastewater treatment method that can be adapted to remove pharmaceutical pollutants. To realize this potential, there is a need to understand the interaction of wood-based nanomaterials towards various types of pharmaceuticals. Thus, this study characterized and investigated the adsorption potential of the two common wood-based nanomaterials, the nanocelluloses and lignin nanoparticles (LNPs), towards various types of pharmaceuticals. The unmodified and cationized LNPs from hardwood and softwood lignin and nanocelluloses (TEMPO-oxidized cellulose nanofibrils (TCNF), cellulose and lignocellulose nanofibrils) were characterized for their morphology, zeta potential and surface charge density at different pHs. The adsorption capacity was determined from a multi-analyte adsorption system consisting of seven pharmaceuticals with different chemical characteristics (aromatic, non-aromatic, anionic, cationic, and neutral). Overall, the LNPs, with their polyaromatic structure, adsorbed a wider range of pharmaceuticals than the nanocelluloses. Among the nanocelluloses, the TCNF exhibited the highest adsorption capacity for cationic pharmaceuticals. Based on these findings, LNPs and TCNF are promising materials that can be combined to construct novel nanostructured adsorbents for pharmaceutical pollutants in water. The interaction of different pharmaceuticals with LNPs and nanocelluloses as revealed in this study can also be beneficial in other applications, such as drug encapsulation and release.