Self-Regenerating Solar Evaporation System for Simultaneous Salt Collection and Freshwater from Seawater

Abstract

Water scarcity is a serious issue which is increasing gradually due to rapid industrialization and population explosion. Biomass-inspired photothermal materials are of great importance due to their low-cost and enhanced photothermal conversion efficiencies. Herein, a pyrolyzed honokiol biochar (HB) is successfully synthesized to fabricate a self-regenerating solar evaporating system for in situ freshwater, and salt collection from seawater. The pyrolyzed biochar was innovatively printed onto a non-woven fabric (HB@NF) that exhibits excellent solar absorption (96%), and efficient stability in seawater. The self-regenerating structure is constructed in two parts: (1) HB-printed fabric as a photothermal layer for efficient solar-to-vapor conversion efficiencies (93%) under 1 kW m−2. (2) Umbrella-like centralized seawater supply via cigarette filter to achieve the Marangoni effect for in situ water evaporation and salt collection. More importantly, effective thermal management achieved efficient heat accumulation (48.5 °C) under one sun intensity (1 kWm−2), and its validation is also demonstrated in a COMSOL heat transfer simulation. Furthermore, a series of experiments on salt collection over different periods, evaporation stability under different cycles, and rejection of primary metal ions via Inductively Coupled Plasma–Optical Emission Spectrometry (ICP–OES) have been investigated. It is believed that this work will create new avenues regarding in situ freshwater and minerals recovery from seawater.