Ferric Tannate-Decorated Polyester Fiber Pillar with Vertical Channels for Zero Liquid Discharge Solar Desalination

Interfacial solar-driven desalination technology holds great promise for solving global freshwater scarcity. However, it is still a great challenge to develop a solar evaporator that can handle high concentration of brine with excellent evaporation rates. Herein, a three-dimensional (3D) solar evaporator (FeTa-PFP) is developed by coating a polyester fiber pillar (PFP) with ferric tannate (FeTa) using a simple solution immersion method. Black FeTa improves the sunlight absorption of PFP to 93%. PFP with vertical water-transporting channels promotes solution transport and salt ion diffusion backflow, preventing salt accumulation and ensuring consistent desalination performance. The FeTa-PFP solar evaporator with a 3D structure harvests ambient energy and achieves an excellent evaporation rate of 2.45 kg m –2 h –1 for desalination of 20 wt % brine at 1-solar intensity. Continuous evaporation allows salt crystals to accumulate in the distillation tank for zero liquid discharge. One m 2 of FeTa-PFP can produce about 21 kg of freshwater per day from 20 wt % brine. This straightforward, efficient, and salt-resistant solar evaporator presents a promising solution for mitigating global freshwater shortages.