A lignin-derived carbon dot-upgraded bacterial cellulose membrane as an all-in-one interfacial evaporator for solar-driven water purification

Abstract

Solar-driven interfacial evaporation has emerged as an efficient approach for wastewater treatment and seawater desalination. New trends demand adaptive technology to develop photothermal membranes with multifunctional features. Herein, we report a robust multi-purpose near-infrared (NIR)-active hydrogel composite (c-BC@N-LCD) from broad-spectrum active nitrogen-doped lignin-derived carbon dots (N-LCDs) covalently cross-linked with a bacterial cellulose (BC) matrix. BC provides adequate porosity and hydrophilicity required for easy water transport while managing heat loss. A commendable evaporation rate (ER) of 2.2 kg m⁻² h⁻¹ under one sun (1 kW m⁻²) is achieved by c-BC@N-LCD. The developed hydrogel system is also found to be efficient for desalination (∼2.1 kg m⁻² h⁻¹) and for remediating various pollutants (heavy metal ions, dyes, and pharmaceuticals) from feed water. The efficacy of the membrane remains unaltered by different grades of water, and hence can be adoptable for economically stressed communities living in water-polluted regions as well as those residing in coastal areas.