Carbonized sunflower stalks with or without storage tissue for highly efficient water purification and desalination

Solar water evaporator derived from biomass is mainly depended on its natural structure. Sunflower stalk is composed of the outermost dermal tissue, vascular tissue, and pith tissue, which are responsible for protecting the internal tissues, transport, and storage substance, respectively. The three evaporator types based on carbonized sunflower stalks were fabricated by remaining, removing part or whole stem pith, and accordingly denoted as carbonized sunflower stalk (CSS), centerless carbonized sunflower stalk (C-CSS) and hollow carbonized sunflower stalk (H-CSS). Their evaporation performances and water transport behaviors were investigated in detail. According to the results of the evaporation rate and energy conversion efficiency, the optimal carbonization temperature is 700 ℃, and the optimal height is 16 cm for CSS, and 6.0 cm for C-CSS and H-CSS. Under one solar irradiation, the CSS exhibits the fastest water evaporation rate (11.62 kg m−2 h−1) and the best energy conversion efficiency (344.69%), which is better than that of previous biomass-based evaporators. Comparing these evaporators with the identical height (6.0 cm), the H-CSS exhibits the fastest water evaporator rate (8.65 kg m−2 h−1) and the best energy conversion efficiency (252.93%), which means an enhancement of 49.13% compared to CSS. We corroborated the enhanced evaporation phenomenon by viewing the water transform phenomenon within these evaporators through infrared thermal imaginer. The proposed water evaporators show the potential application for high concentration brine, seawater, organic water, and acid/alkaline wastewater, respectively. This study provides a full consideration for the design and fabrication biomass-based solar water evaporator.