Nowadays, solar-driven interfacial steam generation (SISG) is a sustainable and green technology for mitigating the water shortage crisis. Nevertheless, SISG is suffering from the enrichment of volatile organic compounds in condensate water and non-volatile organic compounds in feed water in practical applications. Herein, taking inspiration from nature, a dual-functional bifacial-CuCoNi (Bi-CuCoNi) evaporator with a special biomimetic urchin-like microstructure was successfully prepared. The unique design with 2.5-Dimensional bifacial working sides and urchin-like light absorption microstructure provided the Bi-CuCoNi evaporator with remarkable evaporation performance (1.91 kg m-2 h-1 under 1 kW m-2). Significantly, due to the urchin-like microstructure, the adequately exposed catalytic active sites enabled the Bi-CuCoNi/peroxydisulfate (PDS) system to degrade non-volatile organic pollutants (removal rate of 99.3 % in feed water, close to 100 % in condensate water) and the volatile organic pollutants (removal rate of 99.1 % in feed water, 98.2 % in condensate water) simultaneously. Moreover, the Bi-CuCoNi evaporator achieved non-radical pathway degradation at whole-stages. The dual-functional evaporator successfully integrated advanced oxidation processes (AOPs) into SISG, providing a new idea for high-quality freshwater production from polluted wastewater. ENVIRONMENTAL IMPLICATION: Inspired by nature, a dual-functional bifacial CuCoNi evaporator with a special biomimetic urchin-like microstructure formed by CuCoNi oxide nanowires grown on nickel foam by the hydrothermal synthesis method was successfully prepared. The prepared Bi-CuCoNi evaporator can effectively degrade organic pollutants in feed water and condensate water simultaneously during SISG, thus generating high-quality fresh water. Meanwhile, the health risks associated with the accumulation of organic pollutants in water during traditional SISG were reduced via green and sustainable way. The spatial 2.5-Dimensional structural design of Bi-CuCoNi provided new insights for achieving efficient water evaporation and fresh water generation from various polluted wastewater.

Solar-driven interfacial evaporation (SDIE) with excellent photothermal conversion efficiency is emerging as one of the frontier technologies for freshwater production. In this work, novel carbonized conjugate microporous polymers (CCMPs) hollow microspheres-based composite hydrogel membranes (CCMPsHM-CHM) for efficient SDIE are reported. The precursor, CMPs hollow microspheres (CMPsHM), is synthesized by an in situ Sonogashira-Hagihara cross-coupling reaction using a hard template method. The as-synthesized CCMPsHM-CHM exhibit significantly excellent properties, i.e., 3D hierarchical architecture (from micropore to macropore), superior solar light absorption (more than 89%), better thermal insulation (thermal conductivity as low as 0.32-0.42 W m-1K-1 in the wet state), superhydrophilic wettability with a water contact angle (WCA) of 0°, superior solar efficiency (up to 89-91%), a high evaporation rate of 1.48-1.51 kg m-2 h-1 under 1 sun irradiation, and excellent stability which maintains an evaporation rate of more than 80% after 10 cycles and over 83% evaporation efficiency in highly concentrated brine. In this case, the removal rate of metal ions in seawater is more than 99%, which is much lower than the ion concentration standard for drinking water set by the World Health Organization (WHO) and the United States Environmental Protection Agency (USEPA). Taking advantage of its simple and scalable manufacture, our CCMPsHM-CHM may have great potential as advanced membranes for various applications for efficient SDIE in different environments.

Solar stills are used in distant and arid areas to convert brackish or salty water into potable water fit for human use in a simple, affordable, and effective manner. Even when PCM materials are used, typical solar systems still have minimal production per day. In this study, experimental tests were carried out in order to increase the performance of a single-slope solar still combined with PCM material (paraffin wax) and a solar-powered electric heater. Two identical single-slope solar stills were designed, fabricated, and tested under the same climatic conditions during the summer and spring seasons of 2021 in Al-Arish, Egypt. The first is a conventional solar still (CVSS), and the other is also a conventional still but with PCM and an electric heater (CVSSWPCM). Several parameters were measured during the experiments, including sun intensity, meteorological aspects, cumulative freshwater production, average glass, and water temperatures and PCM temperature. The improved solar still was evaluated at different operating temperatures and was compared to the conventional traditional one. There were four cases studied: one case without a heater (paraffin wax only) and three other cases with a heater operating at 58 °C, 60 °C, and 65 °C, respectively. The experimental results revealed that activating the heater inside the paraffin wax increased daily production (i) in the spring by 2.38, 2.66, and 3.1 times and (ii) and in the summer by 2.2, 2.39, and 2.67 times at the three above-mentioned temperatures respectively (when compared to the traditional still). In addition, the maximum rate of daily freshwater production was achieved at paraffin wax temperature of 65 °C in both spring and summer (Case 5). Finally, the economic evaluation of the modified solar still was carried out according to cost per litre. The modified solar still with a heater operating at 65 °C has a higher exergoeconomic value than the traditional one. The maximum CO2 mitigation in cases 1 and 5 was approximately 28 tons and 160 tons, respectively.

Freshwater production is critical in terms of solving the global water shortage. Aiming at improving freshwater production capability and ensuring its quality, an interfacial charge-modulated MoS2/Ti3C2Tx-modified carbon fiber (CF/MoS2/Ti3C2Tx) penetrating electrode is designed. To maximize the desalination and degradation efficiencies of CF/MoS2/Ti3C2Tx, a photocatalytic component is introduced into the membrane capacitive deionization (PMCDI) device. High desalination capability is derived from the lamellar architecture structure of MoS2/Ti3C2Tx. Meanwhile, excellent degradation performance is due to the formation of two photoelctrocatalytic activity centers, directionally generating singlet oxygen (1O2) and hydroxyl radical (•OH). The intercalated Cl- (desalination) as the electron transfer bridge optimizes the charge distribution of MoS2/Ti3C2Tx, reinforcing the photoelectrocatalytic activity (degradation). The formation of the electron-deficient (desalination) and electron-rich (regeneration) regions at the terminated O atom of Ti3C2Tx accelerate the generations of •OH and 1O2, respectively. In perspective, a mutual promotion process of desalination and degradation is achieved for high-efficiency production of high-quality freshwater.

Atmospheric water harvesting (AWH) is regarded as one of the promising strategies for freshwater production desirable to provide sustainable water for landlocked and arid regions. Hygroscopic materials have attracted widespread attention because of their water harvesting performance. However, the introduction of many inorganic salts often leads to aggregation and leakage issues in practical use. Here, polyzwitterionic hydrogels are developed as an effective AWH material platform. Via anti-polyelectrolyte effects, the hygroscopic salt coordinated with polymer chains could capture moisture and enhance the swelling property, leading to a strong moisture sorption capacity. The hydrogel shows superior AWH performance (0.62 g g-1 , 120 minutes for equilibrium at 30 % relative humidity) and produces 5.87 L kg-1 freshwater per day. It is anticipated that the polyzwitterionic hydrogels with unique salt-responsive properties could provide new insights into the design and synthesis of next-generation AWH materials.

Solar water evaporation is universally considered as an effective method to alleviate the freshwater shortage worldwide. A series of three-dimensional, salt-resistant evaporators have been brought out to improve the evaporation performance. However, little attention was paid to the collection of salt from seawater and high salinity brine. In this work, a carbon black polyvinyl alcohol (PVA) sponge was prepared to harvest light using a physical adsorption method to load carbon black on the PVA sponge. The experimental results showed that optimal light absorption (97.8%) and evaporation rate (1.60 kg m-2 h-1) were achieved when the carbon black PVA sponge was produced at a carbon black concentration of 1 g L-1. Moreover, we stacked PVA sponges beneath the carbon black PVA sponge to construct a non-photothermal evaporation area. It was seen that the evaporator with an eight-layer PVA sponge had an excellent evaporation rate as high as 2.35 kg m-2 h-1. In addition, the salt-collecting paper, all-black printed by a laser printer, was inserted between the stacked PVA sponges for salt collection, and the eight-layer PVA sponge evaporator with the salt-collecting paper at the fourth floor was tested in a 2 h desalination experiment. The outcome indicated that a square meter of this evaporator can produce about 7.03 L of freshwater and 206 g of salt per day from 10 wt % NaCl solution. As a result, the solar evaporator developed in this work is capable of collecting salt and maintaining a high evaporation rate, which is of great competence in the fields of freshwater production and salt collection.

Freshwater production is one of the biggest global challenges today. Though desalination can provide a climate-independent source of clean water, the process requires a high energy consumption. Emerging advancement of photothermal nanomaterials and the urgent demand for a green technology transition have reinvigorated the established solar distillation technology. The current development of photothermal vaporization focuses on material innovation and interfacial heating, which largely emphasizes vapor generation efficiency, without considering pragmatic water collection. Moreover, salt accumulation is another critical issue of seawater solar-driven vaporization. The incorporation of photothermal materials into a photothermal membrane distillation (PMD) solar evaporator design harmoniously resolves these issues through combination of renewable energy and efficient interfacial distillation, to achieve the ultimate goal of practical saline water into freshwater conversion. At this juncture, it is imperative to review the recent opportunities and progresses of the PMD system. Here, the fundamental photothermal processes, strategies for efficient evaporator design, evaluation of various criteria for photothermal material incorporation with desired properties, discussions on desalination, water treatment, and energy generation applications are covered. Guidelines in material and system designs to further advance the PMD system that is highly promising in delivering portable water for both large-scale and decentralized systems are provided.

Solar-driven steam generation has been recognized as a sustainable and low-cost solution to freshwater scarcity using abundant solar energy. To harvest freshwater, various interfacial evaporators with rational designs of photothermal materials and structures have been developed concentrating on increasing the evaporation rate in the past few years. However, pathogenic microorganism accumulation on the evaporators by long-duration contact with natural water resources may lead to the deterioration of water transportation and the reduction of the evaporation rate. Here, we develop cationic photothermal hydrogels (CPHs) based on [2-(methacryloyloxy)ethyl]trimethylammonium chloride (METAC) and photothermal polypyrrole (PPy) with bacteria-inhibiting capability for freshwater production via solar-driven steam generation. A rapid water evaporation rate of 1.592 kg m-2 h-1 under simulated solar irradiation is achieved with CPHs floating on the water surface. Furthermore, we find that CPHs possess nearly 100% antibacterial performance against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus). The significant bacteria-inhibiting capability is mainly attributed to the large number of ammonium groups on the CPH network. Moreover, we show that CPHs exhibit good applicability with stable evaporation in natural lake water over 2 weeks, and the number of bacteria in purified lake water is significantly reduced. The device based on CPHs can achieve ∼0.49 kg m-2 h-1 freshwater production from lake water under natural sunlight. This study provides an attractive strategy for the evaporator to inhibit biological contamination and a potential way for long-term stable freshwater production from natural water resources in practical application.

There is an increasing demand for clean water as the population of the earth is exponentially increasing. Many countries are facing water shortage problems, which are bound to become more prevalent in upcoming years. Therefore, it is necessary to investigate sustainable methods to produce clean water for drinking, irrigation, agriculture and domestic use. Electrodialysis uses electricity and specialized membranes to separate ionic substances from water. This practice can be used for desalination and wastewater treatment. To make the process more sustainable, electrodialysis can be coupled with renewable sources of energy such as solar and wind power. Photo-electrodialysis and photovoltaic-electrodialysis are two methods commonly used to couple solar energy with the electrodialysis process. However, these processes are dependent on the availability of sunlight and wind as weather conditions and the positioning of the sun vary by time. Electrodialysis is more favourable for brackish water desalination instead of seawater desalination as it has a lower energy requirement. Desalinating brackish water (1000-5000 ppm) has an energy requirement in the range of 0.4-4 kWh/m3. This review paper summarizes the fundamental concepts of electrodialysis technology and its integration with renewable energy sources such as photo electrodialysis, photovoltaic assisted electrodialysis, reversible electrodialysis/electrodialysis and wind energy-driven electrodialysis. Some aspects that have been considered are the freshwater capacity, specific energy and costs of the hybrid systems.