Superhydrophilic Polydopamine-Modified Carbon-Fiber Membrane with Rapid Seawater-Transferring Ability for Constructing Efficient Hanging-Model Evaporator

Abstract

Solar-driven seawater desalination has attracted much attention for alleviating global freshwater shortage, but the practical application is often limited by complicated fabrication processes, unsatisfactory seawater-transferring and severe salt accumulation on the photothermal membranes. To solve these problems, hydrophobic industrial-grade carbon fiber membrane (CFM) with good photoabsorption was surface-modified with polydopamine (PDA) to prepare superhydrophilic CFM@PDA for the construction of efficient hanging-model evaporators without salt accumulation. The coating of PDA on CFM is realized by simple self-polymerization of dopamine, and the as-prepared CFM@PDA exhibits high solar absorption efficiency of 96.7%, good photothermal effect and superhydrophilicity. Especially, when CFM@PDA is hanging between two water tanks (one contains seawater and the other is empty) in a flat hanging-model evaporator, it can transport seawater at a high rate (26.35 g/h) which is 3.6 times that (7.28 g/h) of commercial cotton fabric. Under simulated sunlight (1.0 kW m⁻²) irradiation, CFM@PDA shows a high evaporation rate of 1.79 kg m⁻² h⁻¹ with a solar evaporation efficiency of 92.6%. Even if NaCl solution with a high concentration (21.0 wt%) is used for the evaporation, the hanging CFM@PDA can retain a high evaporation rate (~ 1.80 kg m⁻² h⁻¹) without salt accumulation during the long-time test (8 h), which is significantly better than that of the tradition floating model. Therefore, this study not only demonstrates the simple preparation of superhydrophilic CFM@PDA, but also promotes the further practical applications of hanging-model evaporators for continuous salt-free desalination.

Funding

National Key Research and Development Program of China(2022YFB3804900); the National Natural Science Foundation of China(51972056); Program of Shanghai Academic Research Leader(20XD1420200); the Natural Science Foundation of Shanghai(21ZR1402500)