GO/CNT-silica Janus nanofibrous membrane for solar-driven interfacial steam generation and desalination

A MAX phase (Ti3AlC2) as a performance enhancer for poly(lactic acid) electrospun membranes in steam generation and solar desalination

Clean water and sanitation issues motivate researchers to develop water evaporators for freshwater generation. The composite membrane evaporator was electrospun herein based on poly(lactic acid) (PLA) and Ti3AlC2 MAX phase as a property enhancer. As a precursor for the MXenes synthesis, the MAX phase has never been explored with PLA for water evaporator potential. Alternative use of the MAX phase can reduce the production cost arising from chemical synthesis. This work explored the potential of the MAX phase as an additive to enhance PLA membrane performance for steam generation and desalination applications. Under the infrared irradiation (∼1.0 kW/m2), the mechanically-improved PLA/MAX phase membrane showed an enhanced water evaporation rate of 1.70 kg/m2 h (93.93 % efficiency), with an approximately 52 % rate increment relative to the PLA membrane. Based on the artificial seawater (3.5 % w/w), the membrane exhibited an evaporation rate of 1.60 kg/m2 h (87.57 % efficiency). The membrane showed self-floating ability at the air-water interface, excellent thermal stability over the entire operating temperatures, and reusability after repeated cycles. Moreover, the generated freshwater contained exceptionally low cations concentrations, as low as those in potable water. The developed composite membrane also had proved its potential for solar desalination in the water generation field.

Solar interfacial evaporation devices for desalination and water treatment: Perspective and future

Water is an essential commodity for society, and alternate resources such as seawater and wastewater are vital for the future. There are various desalination technologies that can provide sufficient and sustainable water sources. Renewable energy-based desalination technologies like solar-based interfacial evaporation are very efficient and sustainable desalination methods. Solar-based interfacial evaporation has been a focus due to its efficient and easy-to-use methods. Still, research is needed for fouling resistance, scalable and low-cost materials, and devices for solar interfacial evaporation. Recent research focuses on the materials for evaporation devices, but various other aspects of device design and fabrication methods are also necessary to improve device performance. In this article, all the evaporator device configurations and strategies for efficient evaporator devices are compiled and summarized. The evaporator devices have been classified into eight main categories: monolayer, bilayer, tree-like design, low-temperature designs, 3D-Origami-based designs, latent heat recovery design, design with storage/batch process, and contactless design. It was found that a good absorber, well-engineered air-water interface, and bottom-layer insulation are necessary for the best systems. The current research focuses on the vapor production output of the devices but not on the water production from devices. So, the focus on device-based water production and the associated cost of the water produced is essential. This article articulates the strategies and various scalable and efficient devices for evaporation-based solar-driven desalination. This article will be helpful for the researchers in improving devices output and coming up with a sustainable desalination and water treatment.

Bioinspired Graphene Aerogels with Hybrid Wettability for Solar-Driven Purification of Complex Wastewater

Salt deposition and pollutant enrichment greatly hamper efficient and sustainable water production for a solar evaporator. Inspired by the desert beetle, a dual-region hydrophobic graphene/hydrophilic titanium dioxide (TiO2) aerogel (GTA) with internal hydrophilic-hydrophobic hybrid wettability structure is prepared via a facile freeze-drying and thermal reduction method. The evaporator shows adjustable wettability, optimized water content, and a low energy loss in the evaporation process. Simultaneously, the hybrid wetting structure in aerogel subjects salt to a dynamic crystallization-dissolution process to prevent salt deposition. The GTA solar evaporator achieves an evaporation rate of 1.52 kg·m-2·h-1 with a 91.02% efficiency under 1 sun irradiation. Furthermore, GTAs achieve a stable evaporation rate in high salinity brine (25 wt % NaCl) under 1 sun irradiation for 100 h, which could compete well with other most advanced photothermal evaporation materials. Moreover, the synergistic effect of graphene and TiO2 endows GTAs with excellent photocatalytic degradation and self-cleaning properties, which can effectively reduce the enrichment of contaminants on the evaporator. Therefore, GTA evaporators can efficiently and stably obtain clean water from seawater and wastewater, which provides a feasible strategy for the purification of complex wastewater.

Recent Development of Carbon-Nanotube-Based Solar Heat Absorption Devices and Their Application

Population growth and the current global weather patterns have heightened the need to optimize solar energy harvesting. Solar-powered water filtration, electricity generation, and water heating have gradually multiplied as viable sources of fresh water and power generation, especially for isolated places without access to water and energy. The unique thermal and optical characteristics of carbon nanotubes (CNTs) enable their use as efficient solar absorbers with enhanced overall photothermal conversion efficiency under varying solar light intensities. Due to their exceptional optical absorption efficiency, low cost, environmental friendliness, and natural carbon availability, CNTs have attracted intense scientific interest in the production of solar thermal systems. In this review study, we evaluated CNT-based water purification, thermoelectric generation, and water heating systems under varying solar levels of illumination, ranging from domestic applications to industrial usage. The use of CNT composites or multilayered structures is also reviewed in relation to solar heat absorber applications. An aerogel containing CNTs was able to ameliorate water filtering performance at low solar intensities. CNTs with a Fresnel lens improved thermoelectric output power at high solar intensity. Solar water heating devices utilizing a nanofluid composed of CNTs proved to be the most effective. In this review, we also aimed to identify the most relevant challenges and promising opportunities in relation to CNT-based solar thermal devices.

Janus Carbon Nanotube@poly(butylene adipate-co-terephthalate) Fabric for Stable and Efficient Solar-Driven Interfacial Evaporation

Solar-driven seawater desalination is considered a promising method for alleviating the water crisis worldwide. In recent years, significant efforts have been undertaken to optimize heat management and minimize salt blockage during solar-driven seawater desalination. However, it remains challenging to achieve an efficient and stable seawater evaporator simply and practically. Here, we designed and prepared a novel three-dimensional (3D) water channel evaporator (3D WCE) equipped with a Janus CNT@PBAT fabric (JCPF). The as-prepared Janus CNT@PBAT fabric has broad-band light absorption (∼97.8%), excellent superhydrophobicity (∼162°), and photothermal properties. After optimizing the structure of the thermal insulator, our designed evaporator could realize the equilibrium between enhanced thermal management and sufficient water supply. As a result, the as-prepared evaporator achieved an excellent evaporation rate of 1.576 kg·m^-2·h^-1 and an energy efficiency of over 92.7% under 1 sun irradiation in 3.5 wt % saline water. Moreover, this evaporator also revealed good salt rejection performance compared to the traditional two-dimensional (2D) water channel evaporator (2D WCE) in high saline water, which could maintain stable evaporation rates under long-term evaporation of 8 h. Our study may develop a simple method for the design and fabrication of a low-cost, effective, and stable solar-driven evaporator for seawater desalination.

Interfacial solar vapor generation for desalination and brine treatment: Evaluating current strategies of solving scaling

Interfacial solar vapor generation, an efficient, sustainable, and low-cost method for producing clean water, has attracted great interest for application in solar desalination and wastewater treatment. Although recent studies indicated significant enhancement of overall performance by developing photothermal materials and constructing different dimensional systems, stable evaporation performance and long-term operation of the evaporator are hindered by severe scaling issues. In this critical review, we present the latest strategies in reducing salt accumulation on the evaporator for solar desalination and brine treatment. We first demonstrate the consequences of salt accumulation, and then discuss various self-cleaning methods based on bio-inspired concepts and other strategies such as physical cleaning, ion rejection and exchange, fast ion diffusion, and controlled crystallization, etc. Importantly, we discuss and address the rational design of the evaporator via establishing a relationship model between its porosity, thickness, and thermal conductivity. Lastly, we evaluate salt-resistance strategies, evaporation performance, and possibilities of real application in different evaporation systems with scaling-resistant abilities.

A graphene assembled porous fiber-based Janus membrane for highly effective solar steam generation

Owing to the shortage of clean water as the global problem, the exploration of photothermal substances with high performance solar steam generation for sustainable water purification is essential and urgent. Herein, we demonstrate the assembly of two-dimensional graphene into one-dimensional rough, loose, and porous fibers and further use the assembled fibers to fabricate Janus membrane evaporator. The specific configuration guarantees an enhanced light harvesting property through multiple reflections, and improves the vapor transport ability through the constructed interlaced network. As a result, the as-obtained evaporator exhibits high solar absorbance, superior photothermal property and energy conversion efficiency, which is much higher than those of other reported Janus membrane evaporators and also better than the fabricated carbon nanotube-, and graphene sheet-based Janus membrane evaporator. The water purification results indicate that the fabricated graphene fiber-based Janus membrane is highly effective in seawater desalination without obvious salt accumulation and heavy metal wastewater purification. This study proposes a neotype graphene assembly for the fabrication of Janus membrane evaporator, which has potential applications in desalination and wastewater decontamination.