Solar-driven continuous seawater desalination of KBC/SA based porous evaporator with excellent salt resistance and high evaporation rate

Abstract

Solar thermal-driven interfacial evaporation technology holds significant promise for applications in sewage purification and desalination. However, challenges such as intermittent solar illumination and salt accumulation hinder its practical effectiveness. In this study, phase change materials (PCMs) were introduced to enhance the evaporation efficiency of evaporator under weak sunlight conditions. Specifically, stearic acid serves as a PCM, conductive carbon black (KBC) as a photothermal material, while chitosan and microcrystalline cellulose (MCC) are utilized as matrix materials. Stearic acid (SA) was encapsulated in a microgel derived from chitosan (CS) using a vacuum impregnation technique, and KBC/SA was synthesized via a bidirectional regeneration method. Experimental results reveal that the evaporation rate can reach 3.46 kg m⁻² h⁻¹ under a light intensity of 1 kW m⁻². With the light source off, the KBC/SA evaporator still sustains an evaporation rate of 1.53 kg m⁻² h⁻¹. On semi-cloudy days, the latent heat released from SA supplies substantial thermal energy, enabling continuous evaporation and increasing water production by 1.85 kg m⁻² h⁻¹ compared to the conventional evaporators without PCMs. In addition, the evaporation rate of the solar evaporator in 20 % salt solution can reach 2.98 kg·m⁻²·h⁻¹, which is only slightly different from that in pure water solution. This study presents an effective strategy to address the intermittent use of solar energy and mitigate salt accumulation in solar-powered seawater desalination systems that employ interfacial evaporation.