Biomass-based bionic solar evaporator for high efficiency and cost effective vapor generation

Solar interfacial evaporation is one of the effective methods to address the freshwater crisis, yet challenges remained in developing solar evaporators that possessed excellent light absorption, photothermal conversion performance, evaporation performance, salt resistance, and cost-effectiveness. Inspired by the echinopsis tubiflora structure, a novel bionic solar evaporator was developed in this study by alkalizing white radish and incorporating carbon dust to efficiently obtain low-cost freshwater. The echinopsis tubiflora -like structure was introduced on the originally smooth walls between pore channels at the evaporation interface, by which the light absorption area was enlarged, multiple reflection and refraction of sunlight were achieved, thereby enhancing the light absorption capability. This evaporator exhibited stable and efficient evaporation performance in seawaters of different salinities as well as in acidic/alkaline wastewater (pH = 2/12). The results showed that the average evaporation rates of this evaporator in deionized water, 3.5 wt% seawater and Huanghai seawater were 2.073, 1.669 and 2.018 kg m −2 h −1 , respectively, with a photothermal conversion efficiency of 98.67% and a light absorption capacity of 94.51%. Furthermore, the average evaporation rates of this evaporator in acidic and alkaline wastewater were 1.795 and 1.722 kg m −2 h −1 , respectively, and the collected condensate was meet neutral water. In a three-day outdoor test, the average evaporation rate of this evaporator under sunshine was 3.012 kg m −2 h −1 . Compared with conventional desalination technologies and other types of solar evaporators, this evaporator was proven to be cost effective, exhibiting a freshwater production cost of 0.35 $ ton −1 . Moreover, this evaporator exhibited excellent salt resistance. Additionally, this evaporator featured a simple fabrication process, high and stable operational performance, and great potential for large-scale production. In summary, this work converted white radish into an efficient solar evaporator through simple chemical treatment and carbon dust loading, by which high-value utilization of biomass was realized and a low freshwater production cost was simultaneously achieved. This work provided a cost effective and efficient new route to alleviate the global freshwater shortage problem.