An all-in-one aPAN/MXene@Ag–Ag2S nanofibrous aerogel for efficient oil/water separation, solar interfacial evaporation and photocatalytic degradation of high-concentration dyes

Abstract

Even though membrane separation materials have worked very well for purifying dyestuff wastewater, the short residence time and high pollutant flow rates in the membrane, which can lead to incomplete or insufficient photodegradation, make it currently difficult to separate and photodegrade large-scale or highly concentrated dyestuff wastewater in one step. Herein, we propose an ‘all-in-one’ 3D nanofibrous aerogel architecture (aPAN/MXene@Ag–Ag₂S), which can achieve efficient purification of high-concentration dyeing effluents under natural sunlight via two methods: filtration or solar interfacial evaporation. Ag–Ag₂S nanoparticles with two different structures are reduced on Ti₃C₂T_x nanosheets through a UV light-induced in situ reaction, and they function as effective photocatalysts with excellent photothermal ability for solar interfacial evaporation. The special combination of Ag–Ag₂S, MXene, and aPAN nanofibers in the aPAN/MXene@Ag–Ag₂S aerogels achieved 95% separation and 99.99% photocatalytic degradation efficiencies for oil/water emulsions with methylene blue at a high concentration of 1000 mg L⁻¹, which far exceeds those of recently reported MXene-based catalysts. In particular, wastewater from industrial dyeing could be treated to clean water under natural sunlight. In addition, the evaporation rates of the aPAN/MXene@Ag–Ag₂S aerogel for seawater and textile dye wastewater respectively reach 2.69 kg m⁻² h⁻¹ and 2.44 kg m⁻² h⁻¹ and almost 100% degradation efficiency is achieved. Both the filtered fresh water and the evaporated water produced by solar evaporation meet the requirements of the Discharge Standard of Pollutants for Municipal Wastewater Treatment Plant or the World Health Organization (WHO) and the US Environmental Protection Agency (EPA) standards for drinking water, respectively.