A wood-based evaporator with robust photothermal layer enabling efficient solar evaporation and antibiotic photodegradation

Abstract

Solar-driven interfacial evaporation has become the most promising solution to the problem of freshwater scarcity. However, challenges remain in developing evaporators that effectively generate freshwater while enabling environmental remediation. Herein, by decorating Fe₃O₄ and carbon nanotubes (CNT) on balsa wood, a wood-based evaporator (CCF@BW) with excellent dual-function of solar evaporation and photocatalytic purification was obtained, in which the CNT photothermal layer formed a stable interfacial adhesion with the wood substrate due to the introduction of chitosan as the "glue". Due to the non-covalent interaction between the hydrophilic groups on the evaporator and water molecules, resulting in an increase in the intermediate water ratio, thus reducing the vaporization enthalpy of water in CCF@BW (only 1549 J g⁻¹), which significantly increase the evaporation rate (1.76 kg m⁻² h⁻¹) exceeding theoretical limit under one sun irradiation. Attributed to its unique structural design, CCF@BW remained stable in the 100-hours continuous evaporation test, and could be recycled in high concentration brine. CCF@BW had the ability to obtain clean water from various simulated sewage, and freshwater evaporated from seawater could be used for agricultural irrigation, even the quality fully met WHO and EPA drinking water standards. More notably, the presence of highly conductive CNT led to a high separation efficiency of photogenerated carriers generated by Fe₃O₄, which resulted in an effective photocatalytic degradation of tetracycline, proving its feasibility of cleaning water environment while producing freshwater. This study provides new insights into the design of multifunctional evaporators to realize freshwater production and environmental remediation.