Jute stick derived self-regenerating sustainable solar evaporators with different salt mitigation mechanisms for highly efficient solar desalination

Abstract

The accumulation of salt crystals on the solar-absorbing surface of the evaporator is one of the main challenges associated with solar desalination. To solve this problem, sustainable evaporators with diverse salt mitigation mechanisms were fabricated using alkali-treated jute stick (PJS), an agricultural waste. The influence of solar irradiation on salt accumulation on the solar-absorbing surface is investigated. JS features a center natural hole surrounded by several microchannels with pits on the microchannel walls, which make it exceptional for constructing solar evaporators with natural hole induced salt ion diffusion backflow mechanism by simply carbonizing the top surface. This mechanism works well under 1 sun illumination for sea water desalination (no salt growth after 8.5 h) with maximum evaporation rate and efficiency of 1.52 kg m⁻² h⁻¹ and 87.01%, respectively. A solar evaporator with direct salt blocking and salt ion diffusion backflow mechanism is also fabricated by coating the top surface of PJS with hydrophobic MWCNTs to impart Janus characteristics to the evaporator. Under 1 sun, it evaporates sea water at a rate of 1.46 kg m⁻² h⁻¹ with 84.39% efficiency and demonstrates excellent regeneration performance while evaporating highly concentrated NaCl water under varying solar irradiance with efficiency above 70%.