Biomass-based nanomaterials for water purification

The effective utilization of biomass is essential for transitioning to a circular bioeconomy. Biomass-based nanomaterials, especially those derived from lignocellulosic biomass, emerge as pivotal contributors, given the abundance of lignocellulosic biomass as the Earth's most prevalent renewable raw material.1–3 Lignin nanoparticles (LNPs), stand out as a cost-effective and environmentally friendly alternative to non-biobased adsorbents for water treatment. This study highlights the multifunctionality of LNPs, demonstrating their effectiveness in both adsorption and UV-light driven photocatalytic degradation of methylene blue dye (MB) in water, showcasing their potential as a versatile and sustainable solution in water purification processes. LNPs, synthesized through straightforward processes,4 were applied in water remediation. Solvent-antisolvent LNPs (SLNPs) exhibited exceptional adsorption capacities, achieving a 98% removal of MB within 120 minutes, comparable to existing lignin-based adsorbents in the literature. Hydrotropic LNPs (HLNPs) and pristine softwood Kraft lignin (SKL) also displayed fair adsorption capacities (12.2 and 12.7 mg·g⁻¹, respectively) with shorter adsorption times compared to similar adsorbents reported in the literature.5–9 Data fitting with adsorption models suggested that electrostatic interactions, likely involving hydroxyl groups on LNPs and SKL, primarily drove MB adsorption.10,11 Moreover, HLNPs demonstrated excellent photocatalytic activity, achieving a 98% degradation of MB after 6 hours of UV irradiation, while pristine SKL exhibited a noteworthy 69% degradation. Free radical scavenger experiments indicated the involvement of a combination of free radicals in photocatalytic degradation. Recyclability assessments revealed that the particles could be effectively reused for up to three cycles, maintaining their adsorption capacity and photocatalytic activity without significant decline.