Facile preparation of a novel basalt fiber fabric-based photothermal material for high salinity wastewater treatment and solar interface evaporation

Solar-driven interfacial evaporation (SIE) is a sustainable, efficient, and environmentally friendly desalination technology. It has great potential for solving the shortage of clean water and environmental pollution that humanity faces. Nevertheless, low strength, inadequate efficiency, and complicated preparation process of photothermal materials continue to be primary barriers to achieving the widespread application of SIE technology. Therefore, in the present work, a low-cost and eco-friendly photothermal material was prepared successfully by using multiwalled carbon nanotubes (MWCNTs), sodium alginate (SA) hydrogel, and basalt fiber (BF) fabric for obtaining purified/drinking water from seawater/brackish water. The results indicated that newly developed MWCNTs-SA/BF fabric had better wettability, evaporation performance, and purification capability. The evaporation rate of MWCNTs-SA/BF evaporator using simulated high salinity seawater could reach 1.48 kg/m2 h and 2.5 kg/m2 h, under 1 and 2 suns illumination, respectively, and solar energy utilization efficiency is 91.6% under 1 sun irradiation. Additionally, cyclic evaporation test results show that fabrics are highly durable for long-term solar evaporation. Furthermore, an excellent water purification performance of MWCNTS-SA/BF fabrics was also demonstrated by evaluating the purity of water samples and determining the changes in the four major ions (Na+, K+, Ca2+, and Mg2+) in seawater before and after evaporation experiments. This work provides a simple, practical, and economical approach to preparing a novel BF-based evaporator that utilizes abundant solar energy potential for large-scale desalination and wastewater treatment.