Enzymatic crosslinking of lignin nanoparticles and nanocellulose in cryogels improves adsorption of pharmaceutical pollutants

• DOI: 10.1016/j.ijbiomac.2024.131168
• Publication Date: 2024-03-27T08:16:03Z
• Authors: Melissa B. Agustin; Maarit H. Lahtinen; Marianna Kemell; Erfan Oliaei; Kirsi S. Mikkonen; Stina Grönqvist; Mari Lehtonen
• Keywords: Laccase; Wastewater treatment; 416 Food Science; Lignin nanoparticles; SDG 3 - Good Health and Well-being; Adsorbents; Pharmaceutical pollutants; Lignin-containing cellulose nanofibrils; SDG 6 - Clean Water and Sanitation; 0210 nano-technology; Biochemistry, cell and molecular biology; 0105 earth and related environmental sciences

Pharmaceuticals, designed for treating diseases, ironically endanger humans and aquatic ecosystems as pollutants. Adsorption-based wastewater treatment could address this problem, however, creating efficient adsorbents remains a challenge. Recent efforts have shifted towards sustainable bio-based adsorbents. Here, cryogels from lignin-containing cellulose nanofibrils (LCNF) and lignin nanoparticles (LNPs) were explored as pharmaceuticals adsorbents. An enzyme-based approach using laccase was used for crosslinking instead of fossil-based chemical modification. The impact of laccase treatment on LNPs alone produced surface-crosslinked water-insoluble LNPs with preserved morphology and a hemicellulose-rich, water-soluble LNP fraction. The water-insoluble LNPs displayed a significant increase in adsorption capacity, up to 140 % and 400 % for neutral and cationic drugs, respectively. The crosslinked cryogel prepared by one-pot incubation of LNPs, LCNF and laccase showed significantly higher adsorption capacities for various pharmaceuticals in a multi-component system than pure LCNF or unmodified cryogels. The crosslinking minimized the leaching of LNPs in water, signifying enhanced binding between LNPs and LCNF. In real wastewater, the laccase-modified cryogel displayed 8-47 % removal for cationic pharmaceuticals. Overall, laccase treatment facilitated the production of bio-based adsorbents by improving the deposition of LNPs to LCNF. Finally, this work introduces a sustainable approach for engineering adsorbents, while aligning with global sustainability goals.