Continuous and efficient purification of seawater using suspended photothermal nanocomposite fabrics with self-floatation

Abstract

Solar energy is a sustainable clean energy. Evaporating seawater through solar thermal conversion is an ideal solution to the global shortage of fresh water resources. At present, solar evaporating seawater generally suffers from serious heat loss, salt accumulation and high cost. Here, through non-woven technology and spraying process, a flexible non-woven fabric with rough, porous, and fluffy surface is prepared. Polyethylene terephthalate/polypropylene (PET/PP) composite nonwoven fabric is used as the substrate, and polydopamine (PDA) is used as an adhesive and hydrophilic agent to wrap the surface of the fibre. Carbon nanotubes (WCNTS) are used as light-absorbing materials to bond to the surface of the fibre to form an efficient solar evaporator. The rough fabric surface makes the incident light diffusely reflected in the absorption layer multiple times, thereby increasing the light absorption rate (≈94%), while the fluffy and porous micron-scale network structure of the composite non-woven fabric shows a strong capillary effect. Based on these advantages, the air suspension evaporation method is used for evaporation. Under one solar irradiation (1kw m−2), the water evaporation rate reaches 1.42 kgm−2 h−1, and the conversion efficiency is close to 92%. In addition, WCNTS@PDA-PET/PP composite nonwovens can still maintain high solar evaporation efficiency after long-term cycling, indicating that it has long-term durability and good reusability. In addition, the clean water desalinated using WCNTS@PDA-PET/PP composite non-woven fabric meets drinking water standards (defined by WHO) and shows excellent desalination ability. Most importantly, this composite material easy to produce, can be produced on a large scale in industry, and is expected to solve the shortage of clean water resources.