Overcoming salt crystallization with ionic hydrogel for accelerating solar evaporation

A new hydrogel-based solar evaporator was prepared by a convenient one-step cross-linking method. Sodium alginate and PEDOT:PSS composite hydrogels were used as the functional layer to realize photothermal conversion and in situ heating for the generation of the solar steam. The evaporation rate of the evaporator was as high as 1.23 kg/m2h, and the removal rate of various ions in simulated seawater was higher than 99.8%, showing excellent application stability. It was also found that the salt crystallization phenomenon could be effectively overcome in the process of solar desalination. Based on the swelling ability and super hydrophilic three dimensional pores of the ionic hydrogel, the evaporator exhibited stable self-driven water-drawing ability to form a hydration layer in an effort to suppress the supersaturation of the salt solution at the evaporation interface. PEDOT component realized in situ heating of the hydration layer near the evaporation interface for enhancing the utilization of thermal energy. The purpose of this paper is to provide references for the practical desalination application using a new hydrogel-based solar evaporator.