A highly efficient and stable solar energy-driven device using lignocellulosic biomass Juncus effusus for the recovery of ethanol–water mixture

Abstract

Ethanol (EtOH)–water (H₂O) mixture, as an environmentally friendly organic solvent, has been widely used in green textile dyeing technologies to reduce water consumption. However, it is essential to develop a sustainable and energy-saving approach for the recovery of the EtOH–H₂O mixture to mitigate the global energy crisis. Herein, inspired by the transpiration process of a tree, we designed a bilayer structured solar energy-driven recovery device composed of a solar absorption layer and a liquid transport layer using the lignocellulosic biomass Juncus effusus (JE) and carbon nanotubes (CNTs). Benefiting from the structural design and distinct properties of the 3D hierarchically porous JE fibres, the as-prepared device exhibited an excellent light absorbability (>95.90%) and photothermal conversion capability, and was further used to purify the dye-contaminated EtOH–H₂O mixture by steam generation from solar energy. By using this stable recovery device, the evaporation rate towards the EtOH–H₂O mixture was up to 2.43 kg m⁻² h⁻¹ under one-sun illumination, which is approximately 3.6 times that of natural evaporation. Furthermore, we fabricated a large-scale steam evaporator with a total area of 900 cm² for the recovery of the EtOH–H₂O mixture, which was placed in an outdoor environment for one whole day (0:00–24:00) to evaluate the real-world evaporation and recovery performance. The EtOH content of the collected mixture remained almost invariable after evaporation, showing great potential in industrial production. The lignocellulosic JE-based evaporation device may be a promising solar energy-driven system for the highly efficient recovery of the EtOH–H₂O mixture.