Interfacial solar evaporation toward efficient recovery of clean water and concentration of nutrients from urine with polypyrrole-based photothermal conversion films

Urine consists of a mixture of water (90∼95%) and nutrients, which makes it a potential source of clean water and nutrients. Interfacial solar evaporation technology is a highly competitive method for wastewater purification and resource recovery. Herein, a series of polypyrrole-based photothermal conversion films were prepared using ferric chloride, where pyrrole was the raw materials, cotton cloth (CC) and paulownia wood (PW) as the substrates. Indoor solar water and urine evaporation experiments demonstrated that CCF-MH (CC photothermal conversion film-monolithic hydrophobic) was the best solution for the outdoor solar urine evaporation experiment under an imitation tree structure (without PVC) evaporation system. The outdoor solar urine evaporation experiment found that CCF-MHLS (CCFMH-large-scale) could recover 1.1 kg·m⁻² of condensed freshwater (meeting WHO standards for drinkable water) at 7.5 h under a low light intensity. This paper provides a new platform for low-cost, high-efficient, and large-scale water recovery and nutrients concentration from urine.