Reduced graphene oxide/carbon nitride composite sponge for interfacial solar water evaporation and wastewater treatment

Hierarchical Ti3C2Tx MXene@Honeycomb nanocomposite with high energy efficiency for solar water desalination

The utilization of solar-driven interfacial evaporation holds immense promise in enhancing energy efficiency and establishing sustainable methods for seawater desalination and water purification. While designing the materials to achieve high evaporation efficiency, the tuning of materials with porosity and surface chemistry is very crucial. Novel sustainable materials are of great importance for solar water desalination applications since clean water production is utmost important in the current era. There exists a lack of exploration in modifying the surface wettability states of solar evaporators to expedite the vapor generation rates. In this study, we showcase a hydrophilic Ti3C2Tx MXene-coated carbonized honeycomb (CHC) (Ti3C2Tx MXene@CHC) nanocomposite-based hexagonal-shaped evaporator surface. This is the first-time report on the effective utilization of hierarchical CHC for the preparation of solar absorber comprising of Ti3C2Tx MXene@CHC nanocomposite, particularly for the solar water desalination. The Ti3C2Tx MXene@CHC nanocomposite evaporator achieves an impressive water evaporation rate of 1.6 kg m-2 h-1 with 90% efficiency under 1 sun illumination. The augmented thickness of the water layer in the hydrophilic surface of the Ti3C2Tx MXene@CHC nanocomposite helps in facilitating the rapid escape of water molecules. The relatively elongated contact lines in the hydrophobic region simultaneously ensure substantial water evaporation, significantly enhancing the water desalination process. The Ti3C2Tx MXene@CHC nanocomposite exceeds stringent quality benchmarks, signaling its potential for solar water desalination.

Facile fabrication of 3D Janus foams of electrospun cellulose nanofibers/rGO for high efficiency solar interface evaporation

Solar-powered interfacial evaporation is one of the most efficient state-of-the-art technologies for producing clean water via desalination. Herein, we report a novel bio-based nanofibrous foam for high efficiency solar interface evaporation. To this end, a hybrid membrane of cellulose nanofibers/graphene oxide (GO) is first fabricated by electrospinning coupled with in situ layer-by-layer self-assembly technique. After that, the membrane is subjected to a foaming process in an aqueous NaBH4, which effectively transforms the 2D membrane into a 3D foam. This structure can improve the photothermal conversion efficiency and also facilitate the water transport at the gas-water interface. In the meantime, the GO is converted to the reduced GO (rGO) with a higher light absorption efficiency. Finally, one side of the foam is hydrophobically modified via spray-coating with a fluorocarbon resin (FR) to obtain the Janus type 3D foam, namely FR@EC/rGO. The resultant 3D foam combines the functions of solar energy absorption in the upper layer and water pumping capability in the lower layer. It exhibits an extraordinary solar vapor conversion efficiency of 94.2 % and a fast evaporation rate of 1.83 kg m-2 h-1, showing high potential in future seawater desalination.

Interfacial Solar Evaporation: From Fundamental Research to Applications

In the last decade, interfacial solar steam generation (ISSG), powered by natural sunlight garnered significant attention due to its great potential for low-cost and environmentally friendly clean water production in alignment with the global decarbonization efforts. This review aims to share the knowledge and engage with a broader readership about the current progress of ISSG technology and the facing challenges to promote further advancements toward practical applications. The first part of this review assesses the current strategies for enhancing the energy efficiency of ISSG systems, including optimizing light absorption, reducing energy losses, harvesting additional energy, and lowering evaporation enthalpy. Subsequently, the current challenges faced by ISSG technologies, notably salt accumulation and bio-fouling issues in practical applications, are elucidated and contemporary methods are discussed to overcome these challenges. In the end, potential applications of ISSG, ranging from initial seawater desalination and industrial wastewater purification to power generation, sterilization, soil remediation, and innovative concept of solar sea farm, are introduced, highlighting the promising potential of ISSG technology in contributing to sustainable and environmentally conscious practices. Based on the review and in-depth understanding of these aspects, the future research focuses are proposed to address potential issues in both fundamental research and practical applications.

A Lotus Seedpods-Inspired Interfacial Solar Steam Generator with Outstanding Salt Tolerance and Mechanical Properties for Efficient and Stable Seawater Desalination

Interfacial solar steam generators (ISSGs) can capture solar energy and concentrate the heat at the gas-liquid interface, resulting in efficient water evaporation. However, traditional ISSGs have limitations in long-term seawater desalination processes, such as limited light absorption area, slow water transport speed, severe surface salt accumulation, and weak mechanical performance. Inspired by lotus seedpods, a novel ISSG (rGO-SA-PSF) is developed by treating a 3D warp-knitted spacer fabric with plasma (PSF) and combining it with sodium alginate (SA) and reduces graphene oxide (rGO). The rGO-SA-PSF utilizes a core-suction effect to achieve rapid water pumping and employs aerogel to encapsulate the plasma-treated spacer yarns to create the lotus seedpod-inspired hydrophilic stems, innovatively constructing multiple directional water transport channels. Simultaneously, the large holes of rGO-SA-PSF on the upper layer form lotus seedpod-inspired head concave holes, enabling efficient light capture. Under 1 kW m-2 illumination, rGO-SA-PSF exhibits a rapid evaporation rate of 1.85 kg m-2  h-1 , with an efficiency of 96.4%. Additionally, it shows superior salt tolerance (with no salt accumulation during continuous evaporation for 10 h in 10% brine) and self-desalination performance during long-term seawater desalination processes. This biomimetic ISSG offers a promising solution for efficient and stable seawater desalination and wastewater purification.

The effect of chemical bond and solvent solubility parameter on stability and absorption value of functionalized PU sponge

Seawater pollution from various sources such as industrial effluents, ship washing at sea, and oil spills harm humans and the marine environment. Therefore, finding ways to eliminate this pollution is crucial. This study successfully modified a polyurethane sponge through a simple dip-coating method with functionalized graphene oxide incorporating octadecylamine and oleic acid, resulting in a hydrophobic sponge capable of absorbing crude oil and various organic solvents. Characterization analyses confirmed the synthesis. The absorption capacity of the modified sponges was examined, for example, the PU sponge has absorbed 4 g/g engine oil, while the modified GO-ODA-PU sponge has increased its absorption to 36 g/g. The GO-ODA-PU sponge demonstrated great reusability compared to the GO-OA-PU sponge owing to the strong covalent bond formed between GO and ODA, which is superior to the weak hydrogen bond formed between GO and OA. The absorption capacity of the GO-OA-PU sponge decreased by 30%. The contact angle test showed that GO-ODA-PU and GO-OA-PU sponges had contact angles of 131° and 115°, respectively. Additionally, the GO-ODA-PU sponge performed optimally for semi-polar solvents in the solubility parameter range of 18-19, with its absorption capacity reaching its maximum value. The amount of oil recycling is even possible up to 98%.