A bio-based nanofibre hydrogel filter for sustainable water purification

Removal of suspended solids (SS) is a prerequisite for delivering clean water. However, removal of ultrafine SS during water purification in a cost-effective manner remains a global challenge. Here we develop an injection-driven filter system that integrates a fully bio-based biodegradable nanofibre hydrogel film with a syringe to remove ultrafine SS for portable and sustainable water purification. The hydrogel film features a densely stacked and entangled nanofibre network, enabling it to reject ultrafine SS with a cut-off size of ∼10 nm at a ∼100% rejection efficiency, greatly surpassing commercial filter papers and microporous membranes. During operation, the flux of the injection-driven filter system reaches 90.6 g cm−2 h−1, which is 7.2 times higher than that of commercial polycarbonate ultrafiltration membrane operated under the same conditions. Moreover, this filter system demonstrates good scalability and reusability, with low cost and reduced environmental footprint. The versatility of this filter system is further proven by successful clean water production from various difficult-to-purify water resources, including muddy water, river water, dirty water from melted snow and nanoplastic-contaminated water. Overall, this work provides a facile yet cost-effective tool for sustainable water purification.