Facile preparation of anatase coated nanofiber mats for multifaceted water treatment

Access to and availability of freshwater is increasingly important as the World's population grows and pollution threatens freshwater resources providing an underlying impetus to explore efficient and environmentally friendly water treatment technologies targeting seawater, industrial wastewater and domestic sewage. By embedding SiO₂ in blow spun polyacrylonitrile (PAN) fibers that after peroxidation form a flexible nonwoven mat (SiO₂@PNMs) and subsequent carbonization of the PAN and hydrolysis of TiO₂ onto the SiO₂ nanoparticles (TiO₂/SiO₂@CNMs), a multifunctional solar evaporator within the fields of photothermal conversion, catalytic degradation, desalination and disinfection is obtained. The sunlight light absorption is above 90 % and due to disruption of inter-water hydrogen bonds and the ability to evaporate through the sides of the nonwoven mat, the evaporation rate of 1.71 kg m^-2h⁻¹ exceeds the theoretically considered maximum at an energy conversion efficiency of 92.1 %. The evaporation rate remains stable through a 40-day cycle and the evaporation rate is unaffected by addition of NaCl in concentrations up to 20 % due to salt diffusion and pumping through the porous nonwoven structure demonstrating. anti-salt, anti-fouling and self-cleaning ability. In addition to the solar-driven water evaporation process, the photocatalytic properties of the anatase TiO₂ crystals combined with the conducting effect of the carbon fibers trap photogenerated electrons and retard electron-hole complexation to maintain the release of reactive oxygen species to decompose organic dyes and inactivate bacteria in the water source. This multifunctional nanofiber mats provide a simple and sustainable avenue for the production of fresh water, and has potential application in desalination of seawater and purification of printing and dyeing wastewater.