A novel slide-like cotton-based evaporator with gradient evaporation strategy for seawater resource acquirement

Solar-driven Interfacial Evaporation (SDIE) is a promising green technology with great potential for seawater desalination. In this study, a novel slide-like cotton-based solar evaporator is designed using Carbon Nanotubes (CNTs) and Musou Black (MB) in an inclined mode, achieving a fast capillary force-induced gravity-assisted water transport. The evaporator achieved a stable desalination of the concentrated brine (10.0 wt% NaCl solution) at the evaporation rate of 1.44 kg m-2h−1 under one simulated sunlight (1 KW m−2). Adequate water supply facilitated a superior self-cleaning property without salt aggregation at the evaporation surface and its periphery. In the 10-day long-term evaporation (3.5 wt% NaCl solution), a stable water evaporation rate (1.77 kg m-2h−1) and a light-to-heat conversion efficiency (95.47 %) were obtained without salt aggregation. The evaporation rate could even reach 1.88 kg m-2h−1 in a closed evaporation system outdoors under the practical light. Then, the gradient evaporation strategy was applied by combination of the slide-like solar evaporators consecutively in three stages, in-between which two collection tanks for the concentrated seawater were present. As the concentrated seawater can be used to extract Li, Mg, etc., and the mineral salts of the sea can be used for nutrients, bathing products, etc., the gradient evaporation strategy has realized the simultaneous derivation of the condensed pure water, the concentrated seawater with different concentrations, and the mineral salts at the last stage as industrial raw materials. This study provides new insights into the design of high-efficiency solar evaporators that can comprehensively realize the utilization of seawater resources.