Advancements in Solar Desalination of Seawater by Various Ti3C2 MXene Based Morphologies for Freshwater Generation: A Review

Efficient Solar Desalination of Seawater Using a Novel Carbon Nanotube-Based Composite Aerogel

Solar desalination of seawater is an effective approach to address the scarcity of freshwater resources. For solar steam generation, it is critical to design biodegradable, sustainable, low-cost, and high-evaporation-rate technology. This study aims to develop a novel solar desalination technology by designing and fabricating a nanocomposite material with excellent light absorption and thermal conversion properties. We designed a double-layer aerogel structure, which uses naturally abundant carboxymethyl cellulose (CMC) as the basic skeleton to achieve sustainability and biodegradability, and uses carbon nanotubes as the photothermal material for efficient light absorption to prepare a ferric tannate/carbon nanotube/carboxymethyl cellulose composite aerogel (FT-CNT-CMC aerogel). Experimental results demonstrate that the FT-CNT-CMC aerogel exhibits a high light absorption rate of 96-98% within the spectral range of 250-2400 nm, showcasing remarkable photothermal conversion performance. Under a sun intensity of 1 kW·m-2, the FT-CNT-CMC aerogel achieves a significant evaporation rate of 1.942 kg·m-2·h-1 at room temperature. Moreover, the excellent performance of the FT-CNT-CMC aerogel is validated in practical seawater desalination and organic dye wastewater purification. The FT-CNT-CMC aerogel exhibits a retention rate exceeding 99% for Na+, Mg2+, K+, and Ca2+ ions in simulated seawater, while no characteristic absorption peaks are observed in methylene blue and rhodamine B dye solutions after purification. These findings highlight the promising potential of the FT-CNT-CMC aerogel in the field of novel solar desalination, providing a viable solution to obtain freshwater.

Fibrous MXene Aerogels with Tunable Pore Structures for High-Efficiency Desalination of Contaminated Seawater

The seawater desalination based on solar-driven interfacial evaporation has emerged as a promising technique to alleviate the global crisis on freshwater shortage. However, achieving high desalination performance on actual, oil-contaminated seawater remains a critical challenge, because the transport channels and evaporation interfaces of the current solar evaporators are easily blocked by the oil slicks, resulting in undermined evaporation rate and conversion efficiency. Herein, we propose a facile strategy for fabricating a modularized solar evaporator based on flexible MXene aerogels with arbitrarily tunable, highly ordered cellular/lamellar pore structures for high-efficiency oil interception and desalination. The core design is the creation of 1D fibrous MXenes with sufficiently large aspect ratios, whose superior flexibility and plentiful link forms lay the basis for controllable 3D assembly into more complicated pore structures. The cellular pore structure is responsible for effective contaminants rejection due to the multi-sieving effect achieved by the omnipresent, isotropic wall apertures together with underwater superhydrophobicity, while the lamellar pore structure is favorable for rapid evaporation due to the presence of continuous, large-area evaporation channels. The modularized solar evaporator delivers the best evaporation rate (1.48 kg m-2 h-1) and conversion efficiency (92.08%) among all MXene-based desalination materials on oil-contaminated seawater.

2D/1D MXene/MWCNT Hybrid Membrane-Based Evaporator for Solar Desalination

Solar vapor generation through evaporation using photothermal materials is a promising candidate for seawater desalination. The Ti3C2 MXene membrane has exhibited photothermal behavior in solar water evaporation. However, dense packed two-dimensional (2D) MXene membrane with high reflection loss and insufficient vapor escape channels limited its solar evaporation performance. In this work, one-dimensional (1D) multi-walled carbon nanotubes (MWCNT) were added into 2D Ti3C2 nanosheets as the holder to form a 2D/1D hybrid photothermal membrane. Owing to the 2D/1D hybrid structure, more effective broadband solar absorption, water transportation and vapor escape were achieved.