Polyester fiber bundle-based solar evaporator manufactured by dyeing for efficient desalination and zero liquid discharge

Abstract

Interfacial solar desalination is a promising technology to address global freshwater scarcity. However, low evaporation rates, complex manufacturing processes, and poor salt resistance have hindered the practical application of solar evaporators. In this study, a three-dimensional (3D) solar evaporator named DB-PFB was developed by dyeing industrial dispersion black (DB) onto polyester fiber bundle (PFB). Vertical channels in the PFB rapidly transport water from the bottom to the top through the wicking effect. This, together with hydrophobic polyester fibers, prevents salt accumulation, ensures stable desalination performance and achieves zero liquid discharge. The 3D DB-PFB can utilize ambient energy and has a stable evaporation rate of about 2.60 kg m–2h−1 for desalination of 20 wt% brine at 1-solar intensity. Continuous evaporation allows the collection of salt crystals and dye wastes in the distillation tank. Long-term indoor and outdoor desalination experiments (about 150 h each) have proven the durability of the DB-PFB. 1 m2 DB-PFB can produce approximately 18 kg of freshwater per day from 20 wt% brine, meeting the daily drinking water needs of six adults. This efficient, easy-to-manufacture, and salt-resistant solar evaporator offers a feasible solution to alleviate global freshwater scarcity.