Recycling waste plastic bottles into spherical interfacial solar evaporators for efficient seawater desalination

Waste plastic bottles are upcycled into spherical photothermal aerogels for solar evaporation. • Reduced evaporation enthalpy and enlarged surface area boost evaporation performance. • A high evaporation rate of 2.81 kg·m⁻²·h⁻¹ is achieved under 1 sun. Interfacial solar evaporators (ISEs) have garnered significant attention in seawater desalination due to their high energy utilization efficiency. However, the rational design of ISE with excellent evaporation performance for seawater desalination remains a formidable challenge. In this study, waste plastic bottles (WPB) were recycled and converted into plastic powder through acid-induced crystallization. Subsequently, polypyrrole (PPy)-modified WPB-based spherical photothermal aerogels (PPy-WPB-SPA) were fabricated through crosslinking sodium alginate and calcium chloride, followed by freeze-drying. The PPy-WPB-SPA exhibits an impressive sunlight absorption efficiency of 97%. Benefiting from its unique spherical structure and the ability to reduce the evaporation enthalpy of water, PPy-WPB-SPA achieves a high evaporation rate of 2.81 kg m⁻² h⁻¹ under one-sun illumination (1000 W m⁻²). Salt tolerance tests demonstrate that PPy-WPB-SPA can maintain stable evaporation performance in 3.5 wt% saltwater, with a retained evaporation rate of 2.56 kg m⁻² h⁻¹. Outdoor experiments reveal that one square meter of PPy-WPB-SPA can desalinate approximately 15 kg of 3.5 wt% saltwater under natural daylight. This work not only realizes the high-value upcycling of WPB but also provides a promising strategy to alleviate the global freshwater scarcity crisis. Download: Download high-res image (170KB) Download: Download full-size image