Salt-tolerant, scalable Janus fabric evaporators for desalination and multi-species wastewater purification

Abstract

Solar steam generation is a sustainable technology for efficient seawater desalination and wastewater purification. In this study, SA/PPy/C@CF Janus photothermal fabrics were obtained by loading carbonized corncob powder (C) onto hydrophilic cotton fabric (CF), polymerizing polypyrrole (PPy) in situ, and then spraying hydrophobic stearic acid (SA) on one side. The modification with the C powder gives the fabrics excellent broadband light absorption (∼96.84%), while the adhesion of PPy reduces carbon particle shedding and improves photothermal performance. This is combined with super-hydrophilic air-laid paper and polystyrene (PS) foam insulation to achieve suitable water transport and thermal positioning. The evaporator achieved an evaporation rate and solar energy conversion efficiency of 1.83 kg m⁻² h⁻¹ and 80.16%, respectively, under 1 sun, with similar results obtained when replacing the carbonized corncob with other biomass charcoal. The special Janus structure of the evaporator achieved high efficiency in desalination and prevented salt accumulation when applied to both indoor and outdoor desalination experiments. Additionally, the evaporator has shown excellent purification of dyes, heavy metal wastewater, and a variety of oil-in-water emulsions. This study provides new insights into the design of a multifunctional solar steam generator that is salt-tolerant and scalable, has excellent mechanical properties, and is easy to produce on a large scale.