Multifunctional lignin biocomposite for broad-spectrum water purification

Abstract

Removal of heavy metal ions, PFAS, and synthetic dyes from anthropogenic wastewater using versatile sustainable materials is of prime importance for a clean environment and human health. This study presents a sustainably engineered lignin-based biocomposite reinforced with chitosan, designed for multifunctionality, enhanced material performance, and produced via a ‘green’ and simple one-pot synthesis in aqueous medium. The synthesized granular material, i.e. a zwitterionic lignin-chitosan composite (ZLC), was used for the removal of a wide range of chemically diverse contaminants. ZLC showed 80–90% removal of heavy metals such as Cr(VI), Cu(II), and four different cationic and anionic dyes. It was also tested against an array of five PFAS molecules, such as perfluorinated sulfonic and carboxylic acids, showing up to 86% removal for perfluorooctane sulfonic acid (PFOS). All adsorption processes followed the pseudo-second order and Langmuir models. The material also showed antifouling behavior, demonstrating robustness for real-time application. Lastly, ZLC was tested against effluent water matrices, i.e., wastewater streams from mining areas located in Sweden. The multifunctional adsorption performance of the environment-friendly material, coupled with its ease of production, cost effectiveness, and reusability, indicates that ZLC has a high potential that can garner industrial interest for simplifying multi-step filtration processes.