Marangoni-driven regional salt deposition in self-cleaning paper based evaporators for stable and high-performance desalination

Sunlight is a mainstream source of energy for obtaining fresh water through a three-dimensional (3D) evaporator in the development of seawater desalination. Controlling salt precipitation during the evaporation process has always been a major obstacle to achieving long-term efficient utilization of the evaporator. Herein, a portable 3D paper-based material combined with traditional Chinese ink and dopamine is proposed as an evaporator (CIP-FP). The introduction of dopamine improves the binding force of ink on filter paper. In the evaporation experiment, it was found that under one solar intensity, the evaporation rate within one hour can reach 3.26 kg m^-2h⁻¹. Simulation tests show that CIP-FP has a more obvious surface temperature gradient distribution compared to IP-FP. At the same time, CIP-FP can still maintain efficient and stable evaporation performance in different concentrations of saltwater, and it can still achieve efficient water evaporation when the saltwater concentration is higher than 15 %. Through long-term uninterrupted testing, it was found that CIP-FP can also maintain high and stable evaporation efficiency. The experiment focuses on the Marangoni thermal effect, and with the promotion of the Marangoni thermal effect, both Marangoni heat flow and solute flow are enhanced in the same direction, thereby alleviating salt precipitation. Combined with its strong hydrophilicity, it coordinates thermal energy with water management to achieve water circulation and self-cleaning effects in evaporation testing, providing a certain method for managing salt precipitation in 3D evaporators.