Water filtration using softwood membranes provides a nature-based solution for nanoplastic removal

Nanoplastic (NP) contamination in water intended for human consumption will require efficient, environmentally friendly, and cost-effective NP-removal methods. This study evaluates the use of native wood membranes to filter NPs from freshwater using a pressure-driven process. The performance of the filter was assessed for different wood species, membrane thicknesses and filtration cycles, by measuring NP retention efficiency and NP deposition in the wood membranes. Retention efficiency varied widely between species. After a single filtration cycle, spruce, a common softwood species, reduced NP concentrations by approximately 90%, while poplar, a hardwood, only reduced NP concentrations by ~20%. These differences are linked to microstructural differences between soft- and hardwood tissues. Increased membrane thickness and repeated filtration further enhanced NP retention in all conditions. This work demonstrates that native softwood membranes (i.e., without chemical modification) can be used in low-pressure filtration systems to remove NPs.