Alkali-triggered wettability reconstruction and hydrophilic/hydrophobic synergistic interface in biomass nanocomposite aerogel for dual-mode oil remediation and water purification

Given the dual challenges of oily/saline wastewater pollution and global freshwater scarcity, the development of a single material platform capable of addressing different water-remediation scenarios remains highly desirable. Herein, a biomass nanocomposite aerogel (BNA) is developed through an alkali-triggered wettability reconstruction strategy, enabling a controllable transition between two operational modes through a simple one-step alkaline treatment. In Mode I , the pristine hydrophobic aerogel (H-BNA) functions as an oil-remediation material, exhibiting superhydrophobic/superoleophilic characteristics for rapid oil–water separation (flux ~ (6.68 ± 0.32) × 10 4 L·m −2 ·h −1 , efficiency ~ 99.58 ± 0.31%), while photothermal/electrothermal assistance and oxygen-limited combustion-assisted regeneration provide complementary capabilities for high-viscosity oil handling and material reuse. Following alkali treatment, AE-BNA exhibits a chemically heterogeneous reconstructed interface, characterized by greater exposure of the hydrophilic biomass framework and localized retention of Si-rich domains. This reconstructed state is associated with improved water replenishment and sustained salt-management behavior during solar evaporation. In Mode II , AE-BNA enables solar-driven desalination and condensate recovery, achieving an evaporation rate of 4.28 ± 0.12 kg·m −2 ·h −1 under one-sun irradiation with an apparent solar-to-vapor conversion efficiency of 107.09%, including environmental heat contribution. The desalinated condensate exhibits substantially reduced concentrations of the measured salinity-related ions and supports short-term plant growth under the tested conditions, while industrial wastewater treatment further demonstrates the extension of the platform to complex water matrices. Magnetic responsiveness, wind resistance, and self-repositioning are presented as auxiliary operational attributes that facilitate material manipulation and deployment. Overall, this work demonstrates that alkali-triggered wettability reconstruction, rather than the accumulation of individual functions, provides the central design principle for a two-mode biomass aerogel platform covering oil remediation and solar-driven water purification.