Salt isolation from waste brine enabled by interfacial solar evaporation with zero liquid discharge

The discharge of high volumes of waste brine from desalination plants is a serious environmental challenge. While emerging zero liquid discharge (ZLD) technologies hold promise for the treatment of waste brine, the high inherent energy consumption limits their practical applications. In this work, an affordable and easy-to-fabricate solar evaporation-based crystallizer (SEC) was developed to realize ZLD interfacial brine evaporation using only solar light as the energy source. The SEC was rationally designed with jointed solar and non-solar evaporation regions, which mainly served for solar evaporation and salt crystallization, respectively. Over 90 hours of solar evaporation of brine under 1.0 sun radiation, the crystallizer continually delivered a steady and high evaporation rate of ∼1.71 kg m⁻² h⁻¹ until all the water was completely evaporated. Stable salt mass harvest was also achieved during solar evaporation. Thus, this study practically demonstrated a promising and sustainable solution for ZLD brine treatment using interfacial solar evaporation.