Chitosan-derived carbon aerogel modified with lignin carbon quantum dots for efficient solar evaporation

Abstract

Solar-powered desalination technology offers outstanding benefits in providing clean, safe water and alleviating global freshwater shortages. However, the low evaporation rate, poor salt resistance and high cost limit the development of solar evaporators. Inspired by plant transpiration, a solar evaporator was fabricated from lignin carbon quantum dots (LCQDs) modified chitosan carbon aerogel (C-LCDCA). The introduced LCQDs and low carbonization temperature (280 °C) ensured hydrophilic properties while maintaining the three-dimensional porous structure, as well as improved light absorption and photothermal conversion properties. The evaporation rate of C-LCDCA under one sun was 1.71 kg m−2h−1. Interestingly, C-LCDCA promoted the local crystallization of salt crystals and realized the collection. The evaporation performance of the evaporator can be adapted to different evaporation situations by making simple layer adjustments. The optimal C-LCDCA evaporator (4-layer integrated) surpassed the limit of the interfacial evaporation system, with evaporation rate and efficiency up to 2.32 kg m−2h−1 and 113.9 % respectively under one sun, and with strong salt-rejecting (no obvious salt crystallization in 20 wt% brine for 8 h) and excellent self-cleaning ability (0.3 g NaCl re-dissolved back to 15 wt% brine in 15 min). With superior evaporation performance, the condensate obtained by the evaporator in simulated seawater evaporation experiments met the World Health Organization’s drinking water standards, and enabled effective treatment of industrial wastewater containing heavy metal ions (Cr3+, Fe3+, Pb2+, and Ni2+), nanoplastics (500 and 50 nm), and dyes (Rhodamine B, Methyl Orange, and Malachite green). These findings provide new ideas for the preparation of efficient, salt-rejecting, self-cleaning, and environmentally friendly solar evaporators and advance the practical application of sustainable water purification technologies.