Solar-driven Seawater Desalination Research Articles

Unidirectionally Driving Nanofluidic Transportation via an Asymmetric Textile Pump for Simultaneous Salt-Resistant Solar Desalination and Drenching-Induced Power Generation

Solar-driven seawater desalination provides a promising technology for sustainable water energy harvesting. Although tremendous efforts have been dedicated to developing efficient evaporators, the challenge of preventing salt accumulation while simultaneously realizing high-performance steam-electricity cogeneration remains to be addressed. In this work, inspired by the water and solute transportation in plants via the wicking mechanism, a one-way asymmetric nanofluidic photothermal evaporator fabricated by disproportionately depositing photothermal MXene nanosheets on a hydrophilic cotton textile is reported for simultaneous freshwater and power production. By unidirectionally driving dynamic saline transportation via this photothermal cotton textile pump, this evaporator not only enables self-operating salt rejection for stable steam generation but also affords continuous electric power generation induced by the formation of an asymmetric double electrode layer within MXene nanochannels under the drenching state. Specifically, the solar-driven evaporation rate and voltage generation reach 1.38 kg/m2/h (with a conversion efficiency of 83.1%) and 363 mV under 1 sun irradiation, respectively. Notably, this designed nanofluidic system suffers negligible performance depreciation after 30 h of operation and washing 15 times, which indicates its outstanding stability and reusability. This facile design of the asymmetric nanofluidic photothermal system may provide prospective opportunities for scaling up sustainable freshwater and electric power production.

Porous TiNO solar-driven interfacial evaporator for high-efficiency seawater desalination

Freshwater scarcity, one of the most serious global challenges, has threatened the development of society in many regions. Solar-driven interfacial evaporation localizing solar-to-thermal energy conversion at the vapor–liquid interface provides a new approach for seawater desalination. In this work, we reported a high-efficiency porous TiNO solar absorber for a solar-driven interfacial evaporation system. The solar absorber was prepared by depositing a solar absorbing coating of TiNO on air-laid paper. Hydrophilicity and porosity of the absorber provide sufficient capillary force to absorb water to the evaporation region, thus resulting in rapid replenishment of water and simultaneously avoiding salt precipitation. Based on the TiNO solar absorber, the interfacial evaporation system achieves a high evaporation rate of 1.33 kg m−2 h−1 with an evaporation efficiency of 84.05% under 1 sun illumination and has good durability under long-time solar irradiation. Such a low-cost, high-efficiency solar-driven seawater desalination system holds the potential for rapid deployment in remote areas or isolated islands to collect freshwater.

A Nature-Inspired Monolithic Integrated Cellulose Aerogel-Based Evaporator for Efficient Solar Desalination.

Solar-driven seawater desalination is a prospective approach to tackle the problem of freshwater shortage. Establishing a robust, efficient solar-thermal water evaporator with great salt-resistance through a facile and scalable fabrication technique is still a challenge. In this study, a floatable and robust monolithic integrated cellulose aerogel-based evaporator (MiCAE) with high performance is fabricated by carefully designing and integrating three functional components, namely, a hydrophilic cellulose-PVA aerogel (CPA), hydrophobic silylated cellulose aerogel (SCA), and multiwalled carbon nanotube (MCNT) coating layer (CPA@CNT), through the heterogeneous mixing and freeze-drying aerogel fabrication step in situ. Inspired by woods and mushrooms, the incorporation of SCA with mushroom-shaped CPA possessing wood-like structures in MiCAE can realize heat localization and effectively suppress irreversible heat dissipation. Meanwhile, CPA endows the evaporator with the rapid water transportation and great salt excretion capability because of its low-tortuosity porous structure. Thanks to the synergistic effect of the integrated functional structures, in the highly concentrated brine (17.5 wt %), the MiCAE can still realize the combination of high efficiency and obvious salt-resistance behavior. This work offers a facile, efficient salt-resistance solution for seawater desalination.

Simultaneous solar-driven seawater desalination and spontaneous power generation using polyvalent crosslinked polypyrrole/alginate hydrogels

Sustainable green energy technologies have paid much attention to the development of a solar-driven seawater desalination technique due to its ecofriendly and efficient desalination performance. We propose a novel hybrid hydrogel consisting of conducting polymer of polypyrrole (PPy) and polyvalent cations crosslinked alginate (Alg) with strong repulsive force for simultaneous seawater desalination and electricity generation. The strong repulsive force of polyvalent cations crosslinked with Alg selectively rejects salt cations by inducing reverse salinity gradient against the rapid evaporation-induced salt accumulation on the upper surface of the solar evaporator. The proposed PPy–incorporated Alg (PPy/Alg) hydrogel exhibits an evaporation rate of 1.15 kg h−1 m−2 with a conversion efficiency of 54.12% under 1 sun solar irradiation. In addition, this hydrogel has an excellent crystalline antifouling property, and can be easily scaled-up with maintaining solar desalination performance. Depending on the compositions of PPy and Alg, the spontaneous electricity generation is largely affected by the balance between the decreased salinity gradient by the accumulation of salt cations and the increased salinity gradient by the strong repulsive force. The present results would pave a novel way for the development of sustainable electricity generation in combination with solar-driven seawater desalination by a facile methodology and energy-friendly process.

A Flexible Polymer Nanofiber-Gold Nanoparticle Composite Film for Solar-Thermal Seawater Desalination.

Interfacial solar-thermal conversion has broad application prospects in solar driven steam generation, seawater desalination, sewage purification, and other fields. For a wide range of applications, high-efficiency interfacial solar-thermal conversion materials with the feature of being lightweight, flexible, and easy to scale up at the same time are significantly valued. Herein, a strategy for the preparation of solar-thermal poly (4-vinylpyridine) (P4VP) nanofiber-gold nanoparticle (Au NP) composite film (PGCF) is reported. Combining with the flexible and lightweight P4VP nanofibers, these absorbed Au NPs enable better solar-thermal conversion efficiency. Accordingly, the PGCF provides high-performance interfacial solar-driven steam generation, with 77% solar-heat conversion efficiency under the power density of 3.4kW m-2 , which shows stable output (3.4kg m-2 h-1 ) in the application of solar-driven seawater desalination. In addition, PGCF is light in weight, flexible, and suitable for scalable commercial production, enabling PGCF broad application prospects in the field of light-to-heat conversion.

Constructing 3D optical absorption holes by stacking macroporous membrane for highly efficient solar steam generation

Abstract In recent years, solar steam generation technology has received widespread attention in seawater desalination, but existence of some problems, namely difficulty in salt cleaning and high expense, limited it further development. Herein, in this work, a carbon black gauze membrane (CBGM), with low cost and easy to clean properties, was developed by stacking macroporous membrane to construct 3D optical absorption holes, which were favorable to an enhancement of light absorption. The 4-layer CBGM evaporation device displayed an improved solar steam generation performance, which was corresponded to the evaporation rate of 1.60 kg m−2h−1 and the evaporation efficiency of 96.0% under 1 kW m−2, respectively. Likewise, the 4-layer CBGM evaporation device exhibited superior recyclability, long life and excellent desalination performance, as well as was able to effectively produce potable freshwater from seawater. Consequently, the CBGM was regarded as a promising alternative for high-efficiency solar-driven seawater desalination.

Processing nanocellulose foam into high-performance membranes for harvesting energy from nature

Nanocellulose membranes exhibit good stability and high strength. However, the conventional synthetic routes rely on solvent volatilization of a nanocellulose suspension or solution. The complete hydrogen bonding that occurs in this process leads to a dense structure and poor strength in water. Hereby, lignosulfonate and polycation were mixed to form a complex and then attached to cellulose. The freeze-dried nanocellulose foam was hot-pressed to membrane, resulting in simultaneous co-crosslinking and membrane formation. The membrane had a porous structure with a high mechanical performance, excellent stability and a fast shape recovery. This also represents a method for processing functional nanocellulose membranes, as further demonstrated by the hybrid membrane with exceptional solar-driven seawater desalination and water-flow electricity generation properties. This work established facile methods for tackling the structural weakness of the conventional nanocellulose membrane, and opens the door to the application of nanocellulose membrane with a combination of mechanical stability and functionality.

Robust light-driven interfacial water evaporator by electrospinning SiO2/MWCNTs-COOH/PAN photothermal fiber membrane

Desalination technology by interfacial water evaporator is meaningful to solve the increasing global freshwater shortage. Herein, we prepared an efficient and lightweight silicon dioxide/carboxylated multi-walled carbon nanotube/polyacrylonitrile (SiO2/MWCNTs-COOH/PAN) fiber membrane by electrospinning. And then an interfacial water evaporator was assembled by attaching it onto a piece of filter paper with insulation polystyrene (PS) foam used as support material, and cotton yarns (CYs) used for water transportation. The advantages of this design can prevent heat from dissipating to the bulk water and ensure good evaporation efficiency. The composite fiber membrane exhibited an excellent evaporation rate of 1.28 kg m−2 h−1 and a superior photothermal conversion efficiency of 82.52% under 1 sun illumination (1000 W m−2). Water absorption capability was also demonstrated by MMT, CA and capillary effect tests, while thermal management capacity was analyzed by infrared thermal imaging camera. Furthermore, the prepared composite fiber membrane remained stable evaporation rate and high efficiency even after standing 20 repeated evaporation cycles. Thus, this interfacial water evaporator prepared by this work has an outstanding photothermal conversion capability and will be a promising candidate used for solar-driven seawater desalination.

Resilient biomass-derived hydrogel with tailored topography for highly efficient and long-term solar evaporation of high-salinity brine

A sponge-like biomass-derived hydrogel is constructed via a facile and scalable strategy, and exhibits promising applications in solar-driven seawater desalination, zero-liquid discharge and solute recovery.

Self-assembled core-shell polydopamine@MXene with synergistic solar absorption capability for highly efficient solar-to-vapor generation

As a renewable and environment-friendly technology for seawater desalination and wastewater purification, solar energy triggered steam generation is attractive to address the long-standing global water scarcity issues. However, practical utilization of solar energy for steam generation is severely restricted by the complex synthesis, low energy conversion efficiency, insufficient solar spectrum absorption and water extraction capability of state-of-the-art technologies. Here, for the first time, we report a facile strategy to realize hydrogen bond induced self-assembly of a polydopamine (PDA)@MXene microsphere photothermal layer for synergistically achieving wide-spectrum and highly efficient solar absorption capability (≈ 96% in a wide solar spectrum range of 250–1,500 nm wavelength). Moreover, such a system renders fast water transport and vapor escaping due to the intrinsically hydrophilic nature of both MXene and PDA, as well as the interspacing between core-shell microspheres. The solar-to-vapor conversion efficiencies under the solar illumination of 1 sun and 4 sun are as high as 85.2% and 93.6%, respectively. Besides, the PDA@MXene photothermal layer renders the system durable mechanical properties, allowing producing clean water from seawater with the salt rejection rate beyond 99%. Furthermore, stable light absorption performance can be achieved and well maintained due to the formation of ternary TiO2/C/MXene complex caused by oxidative degradation of MXene. Therefore, this work proposes an attractive MXene-assisted strategy for fabricating high performance photothermal composites for advanced solar-driven seawater desalination applications.

Flexible and Washable CNT-Embedded PAN Nonwoven Fabrics for Solar-Enabled Evaporation and Desalination of Seawater.

Nanostructured photothermal membranes hold great potential for solar-driven seawater desalination; however, their pragmatic applications are often limited by substantial salt accumulation. To solve this issue, we have designed and prepared flexible and washable carbon-nanotube-embedded polyacrylonitrile nonwoven fabrics by a simple electrospinning route. The wet fabric exhibits a strong photoabsorption in a wide spectral range (350-2500 nm), and it has a photoabsorption efficiency of 90.8%. When coated onto a polystyrene foam, the fabric shows a high seawater evaporation rate of 1.44 kg m-2 h-1 under simulated sunlight irradiation (1.0 kW m-2). With a high concentration of simulated seawater as the model, the accumulation of solid salts can be clearly observed on the surface of the fabric, resulting in a severe decay of the evaporation rate. These salts can be effortlessly washed away from the fabric through a plain handwashing process. The washing process has a negligible influence on the morphology, photoabsorption, and evaporation performance of the fabric, demonstrating good durability. More importantly, a larger fabric can easily be fabricated, and the combination of washable fabrics with various parallel PS foams can facilitate the construction of large-scale outdoor evaporation devices, conferring the great potential for efficient desalination of seawater under natural sunlight.

Effect of Cooling Mode on the Performance of a Solar Driven Natural Vacuum Desalination System

A solar driven sea water desalination system operating under natural vacuum has been developed, constructed and tested. The system utilizes the natural forces of gravity and atmospheric pressure to create vacuum under which water can be evaporated at temperatures lower than those in conventional techniques and allowing the use of low -grade heat sources. The proposed desalination system consists of a condenser and a solar flat plate collector acting as an evaporator. An extensive experimental study has been carried out to investigate the effect of condenser cooling mode on the system performance. The external surface of the condenser has been cooled by using three cooling modes; namely, free convection air cooling, forced convection air cooling, and forced convection water cooling. The effect of cooling modes on the system performance has been studied under actual weather conditions. The system performance has been characterized by its fresh water productivity and the performance ratio. The results showed that forced cooling mode causes a lower pressure inside the system than free cooling mode, and water cooling is more effective than air cooling. The average pressure inside the system is about 0.122, 0.106, and 0.09 bars absolute respectively for free air cooling, forced air cooling and water cooling. The cumulative productivity is maximum in the case of external water cooled reaching a value of 6.6 l/m2.day. In case of forced and free air convection, the daily system productivity 5.3 and 2.7 l/m2.day respectively. The average performance ratio was about 70 % which is twice the value for a conventional solar still reported in the literature.

Multifunctional molybdenum oxide for solar-driven water evaporation and charged dyes adsorption

Abstract Significant efforts have been made to seek technologies to resolve water shortages. Among these efforts, seawater desalination and wastewater purification are considered mainstream strategies. Photothermal materials and adsorbents are the main components of solar-driven seawater desalination and wastewater purification, respectively. Herein, we propose MoO3-x (0

Recyclable CNT-coupled cotton fabrics for low-cost and efficient desalination of seawater under sunlight

Photothermal membranes have shown tremendous potential for solar-driven seawater desalination, but their practical applications are hindered by the relatively high cost and solid salt separation. To overcome these limitations, we have developed low-cost and washable photothermal fabrics by dyeing traditional cotton fabrics with carbon nanotube (CNT)-based ink. CNT dyed cotton (cotton-CNT) fabrics exhibit strong optical absorption in 250–2500 nm with a total solar absorption efficiency of 95.7%. Using a polystyrene (PS) foam as the thermal insulator, cotton-CNT fabrics exhibit a high seawater evaporation rate of 1.59 Kg m−2 h−1 under simulated sunlight (1.0 KW m−2). More importantly, the fabric can be cleaned and recycled by removing the salts formed after evaporation, through a simple hand-washing process. These cotton-CNT fabrics may provide a new platform for low-cost, high-efficient and large-area seawater desalination under sunlight irradiation.

The production of ammonia from cyanamid

Photothermal membranes have shown tremendous potential for solar-driven seawater desalination, but their practical applications are hindered by the relatively high cost and solid salt separation. To overcome these limitations, we have developed low-cost and washable photothermal fabrics by dyeing traditional cotton fabrics with carbon nanotube (CNT)-based ink. CNT dyed cotton (cotton-CNT) fabrics exhibit strong optical absorption in 250–2500 nm with a total solar absorption efficiency of 95.7%. Using a polystyrene (PS) foam as the thermal insulator, cotton-CNT fabrics exhibit a high seawater evaporation rate of 1.59 Kg m−2 h−1 under simulated sunlight (1.0 KW m−2). More importantly, the fabric can be cleaned and recycled by removing the salts formed after evaporation, through a simple hand-washing process. These cotton-CNT fabrics may provide a new platform for low-cost, high-efficient and large-area seawater desalination under sunlight irradiation.