Bio-inspired salt-fouling resistant graphene evaporators for solar desalination of hypersaline brines

Abstract

Solar seawater desalination may provide an economical and environmentally friendly means to address the global freshwater crisis. However, salt crystals can precipitate and accumulate on evaporator surfaces during solar seawater desalination, leading to significant deterioration of the performance. Current anti-salt fouling strategies generally suffer from low evaporation rates particularly during the desalination of hypersaline brines. In this paper, we propose bio-inspired graphene evaporators with well-aligned tubular channels to achieve effective solar desalination of hypersaline brines with simultaneously enhanced evaporation rate and long-term anti-salt fouling performance. The unique hierarchical large and small channels inside the evaporators not only increase evaporating surface area, but also provide low-tortuosity pathways for fast salt ion diffusion from the evaporation surfaces to bulk brine. Consequently, the proposed device achieves a high evaporation rate of 2.60 kg m−2 h−1 during a 24-h continuous evaporation test in a hypersaline brine (20 wt% NaCl solution) under one-sun irradiation, among the best values reported in previous studies. Meanwhile, salt precipitation is observed to preferentially occur at the edges of the top surface, leaving the main evaporation area clean during the desalination process. The bio-inspired graphene evaporators with well-aligned tubular channels exhibit great potential for practical solar seawater desalination applications.