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Wastewater purification. a) Images showing the wastewater generated from kitchen, laundry and bathing before and after purification. b) The salinity of wastewater samples before and after purification and the evaporation rates based on the IPNG upon wastewater generated from kitchen, laundry and bathing demonstrating effective removal of salts. c) The total organic content (TOC) in wastewater generated from kitchen, laundry and bathing showing effective removal of organic contaminants.
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Solar‐driven interfacial evaporation provides a promising method for sustainable freshwater production. However, high energy consumption of vapor generation fundamentally restricts practicality of solar‐driven wastewater treatment. Here a facile strategy is reported to control the hydration of polymer network in hydrogels, where densely cross‐linke...
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Citations
... [1][2][3][4][5][6] The efficiency of SISG is primarily characterized by its water evaporation rate. [7,8] Materials, such as wood, [9][10][11] foam, [12,13] and hydrogel, [7,14,15] are commonly employed to design 2D flat solar evaporators. However, with an ideal 100% solar thermal conversion efficiency and complete absence of heat dissipation, the theoretical maximal evaporation rate of 2D flat solar evaporators is only 1.47 kg m −2 h −1 under 1 kW m −2 solar radiation without wind, which fails significantly meet practical demands. ...
The water evaporation rate of 3D solar evaporator heavily relies on the water transport height of the evaporator. In this work, a 3D solar evaporator featuring a soil capillary‐like structure is designed by surface coating native balsa wood using potassium hydroxide activated carbon (KAC). This KAC‐coated wood evaporator can transport water up to 32 cm, surpassing that of native wood by ≈8 times. Moreover, under 1 kW m⁻² solar radiation without wind, the KAC‐coated wood evaporator exhibits a remarkable water evaporation rate of 25.3 kg m⁻² h⁻¹, ranking among the highest compared with other reported evaporators. The exceptional water transport capabilities of the KAC‐coated wood should be attributed to the black and hydrophilic KAC film, which creates a porous network resembling a soil capillary structure to facilitate efficient water transport. In the porous network of coated KAC film, the small internal pores play a pivotal role in achieving rapid capillary condensation, while the larger interstitial channels store condensed water, further promoting water transport up more and micropore capillary condensation. Moreover, this innovative design demonstrates efficacy in retarding phenol from wastewater through absorption onto the coated KAC film, thus presenting a new avenue for high‐efficiency clean water production.
... Water confinement effects in 1D carbon nanotubes (CNTs) have been reported to be a function of CNT internal diameter in regard to the meltingfreezing points (22) likely due to changes in water entropy, enthalpy, and free energy as a function of the degree of confinement (23). In general, confined water molecules exhibit unusual state and structure, in particular the H-bonding network structure that shifts away from the bulk tetrahedral geometry, which has a substantial impact on the water phase transition behaviors such as the enthalpy of vaporization (12,(23)(24)(25)(26). ...
... Fundamentally, water's strong hydrogen-bond network (H-bonding) determines most of its physical, chemical, and biological properties such as viscosity, solvation, wetting, and phase transition thermodynamics (13,(16)(17)(18). Furthermore, water molecules exhibit abnormal physicochemical properties and behaviors under nanoconfinement, where the H-bonding network structure can be substantially altered, which would likely affect the evaporation coefficient and kinetics (11,12,(23)(24)(25)(26). ...
Intrinsic water evaporation demands a high energy input, which limits the efficacy of conventional interfacial solar evaporators. Here, we propose a nanoconfinement strategy altering inherent properties of water for solar-driven water evaporation using a highly uniform composite of vertically aligned Janus carbon nanotubes (CNTs). The water evaporation from the CNT shows the unexpected diameter-dependent evaporation rate, increasing abnormally with decreasing nanochannel diameter. The evaporation rate of CNT 10 @AAO evaporator thermodynamically exceeds the theoretical limit (1.47 kg m ⁻² hour ⁻¹ under one sun). A hybrid experimental, theoretical, and molecular simulation approach provided fundamental evidence of different nanoconfined water properties. The decreased number of H-bonds and lower interaction energy barrier of water molecules within CNT and formed water clusters may be one of the reasons for the less evaporative energy activating rapid nanoconfined water vaporization.
... They possess a high water content. Additionally, their adjustable physicochemical properties and diverse structures enrich and simplify the functionalization process compared to other substrate materials [44][45][46]. By strategically designing the hydrogel's pore size, distribution, and hydrophilic or hydrophobic characteristics, it is possible to effectively regulate the state of water molecules within the hydrogel, reducing or eliminating the hydrogen bonding between large water clusters. ...
... Part three: preparation and functional analysis of hydrogel substrates in ISDE systems. Reprinted with permission from ref [13,46,52,65] ...
... Consequently, ISDE systems based on multi-network hydrogels, which enhance the multifunctionality of hydrogels through the combined benefits of var-ious networks, have emerged as a focal point of research. The hydrogel created by Yu et al. [46], integrating a polystyrene sulfonate (PSS) network with a densely cross-linked polyvinyl alcohol (PVA) network, effectively manages both water and thermal energy simultaneously (Figure 5b). Notably, the ionic polymer PSS engages in electrostatic interactions with water molecules, activating over 50% of the water into an intermediate water state, thus drastically reducing the energy required for evaporation at solar interfaces. ...
Hydrogel-based interfacial solar-driven evaporation (ISDE) gives full play to the highly adjustable physical and chemical properties of hydrogel, which endows ISDE systems with excellent evaporation performance, anti-pollution properties, and mechanical behavior, making it more promising for applications in seawater desalination and wastewater treatment. This review systematically introduces the latest advances in hydrogel-based ISDE systems from three aspects: the required properties, the preparation methods, and the role played in application scenarios of hydrogels used in ISDE. Additionally, we also discuss the remaining challenges and potential opportunities in hydrogel-based ISDE systems. By summarizing the latest research progress, we hope that researchers in related fields have some insight into the unique advantages of hydrogels in the ISDE field and contribute our efforts so that ISDE technology reaches the finishing line of practical application on the hydrogel track.
... Reproduced with permission. [135] Copyright 2020, Wiley-VCH. The polyvinyl alcohol network restricts the water amount to localize heat near the evaporable water, and polystyrene sulfonate network provides water-polymer interactions to activate water molecules. ...
... The high crosslinked polyvinyl alcohol can restrict the water saturation in the hydrogel to suppress energy loss and enhance the solar vapor generation rate (3.9 kg m −2 h −1 ) with energy utilization efficiency of 92% under one sun irradiation. [135] Apart from hydrophilic polymers, the stacked atomic thick 2D MoN 1.2 and rGO nanosheets with heterointerfaces can form heterogeneous interactions with surrounding water molecules to cause an imbalanced water state, which easily broke the hydrogen bonds, remarkably lowered evaporation enthalpy and boosted solar evaporation rate to 2.6 kg m −2 h −1 (Figure 24c). [192] Some other Janus structured materials can have an effect on evaporation enthalpy. ...
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.
... These intelligent hydrogels exhibit diverse responses to external conditions like temperature [11], pH value [12], salinity [13], electric elds [14], magnetic elds [15], and chemical environments [16]. Smart hydrogels have plenty of applications in industries, agriculture, and biomedical elds, such as wastewater treatment [17], drug release[18], contact lenses [19], tissue engineering [20], and wound healing [21,22]. ...
This study reports for the first time an innovative pH/magnetic dual-responsive hemicellulose-based nanocomposite hydrogel with a nearly 100% bio-based and biodegradable compositions. We synthesized pure Fe 3 O 4 magnetic nanoparticles (Fe 3 O 4 MNPs) using co-precipitation, then engineering xylan hemicellulose (XH), acrylic acid (AA), polyethylene glycol diacrylate (PEGDA), and Fe 3 O 4 MNPs to synthesize the pH/magnetic dual-responsive hydrogel (Fe 3 O 4 @XH-Gel), through free radical graft polymerization on natural XH with in-situ doping Fe 3 O 4 MNPs initiated by the ammonium persulfate/tetramethylethylenediamine (APS/TMEDA) redox system. Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance ( ¹ H-NMR), X-ray diffractometry (XRD), scanning electron microscopy and energy dispersive spectrometer (SEM-EDS), Brunauer-Emmett-Teller (BET), dynamic light scattering (DLS), swelling gravimetric analysis, vibrating sample magnetometer (VSM) were employed to analyze the hydrogel’s chemical structures, surface morphologies, pH-responsive behaviors, and magnetic responsiveness characteristics. The results indicate that the Fe 3 O 4 @XH-Gel nanocomposite hydrogel exhibited excellent dual responsiveness to pH and magnetism. Furthermore, an emphasis was placed on the in-depth analysis of the pH response mechanism and drug release control. Finally, we utilized this cutting-edge hydrogel to investigate the controlled-release behavior of two model drugs, Acetylsalicylic acid and Theophylline , within the simulated gastrointestinal tract. The Fe 3 O 4 @XH-Gel nanocomposite hydrogel demonstrated exceptional controlled release attributes, positioning it as a potential carrier for targeted drug delivery, particularly to the gastrointestinal conditions.
... [7] Hydrogel evaporators have remarkably high evaporation rates due to they can circumvent insufficient solar energy supply by altering the interaction between polymers and water molecules to reduce the vaporization enthalpy of water. [8,9] However, the ultrahigh evaporation rate causes dramatic salt accumulation on the evaporated surface, eventually inducing salt crystallization, reducing the evaporation rate and shortening the lifetime of the evaporator. [10] Avoiding salt crystallization on the hydrogel surface during evaporation is a prerequisite for stable solar desalination. ...
... The peaks at 3518 and 3631 cm −1 correspond to the symmetric and asymmetric stretching of IW with the weak hydrogen, respectively. [9] These results indicate that IW is contained in the 3DP-BHE, reduces the vaporization enthalpy of water and facilitates water evaporation. ...
Solar desalination using hydrogel evaporators is an eco‐friendly, highly efficient means with natural sunlight for sustainable freshwater production. However, it remains challenging to develop a cost‐effective and scalable method to prepare salt‐resistant hydrogel evaporators for stable desalination. Here, inspired by tree transpiration and hierarchical porous structure, a 3D‐printed bionic hydrogel evaporator (3DP‐BHE) is designed for long‐term solar desalination. Commercialized activated carbon (AC) is introduced into biomass starch skeleton as a solar light absorber to build 3DP‐BHE in a cost‐effective fashion ($10.14 m⁻² of total materials cost). The bionic tree leaf layer for 94.01% light absorption and timely vapor diffusion. The bionic tree trunk layer with 3D printed bimodal porous structure for water transfer, thermal isolation, and salt ions convection and diffusion. With the unique bionic structure, the 3DP‐BHE achieves a stable evaporation rate of 2.13 kg m⁻² h⁻¹ at ≈90.5% energy efficiency under one sun (1 kW m⁻²). During the 7‐day desalination of 10 wt.% brine, a steady evaporation rate of 1.98 kg m⁻² h⁻¹ is maintained with a record‐high cost‐effectiveness (195.3 g h⁻¹ $⁻¹) manner. This 3DP‐BHE will open significant opportunities for affordable solar desalination systems on multiple scales, from individual households to off‐grid communities.
... h e refers to the equivalent evaporation enthalpy of the water in the LACH, which can be analyzed by Raman spectra (details in Fig. S19, Supporting Information) and dark evaporation. Assuming the same power input U in , the equivalent vaporization enthalpy of water can be calculated by [43] ...
Solar desalination, which relies on localized heating for interfacial water evaporation, is regarded as a promising and sustainable approach for freshwater production. Significant progress has been achieved in developing high-performance solar-driven interfacial vapor generators (SIVGs), however, their performance in high-concentration brine remains unsatisfactory. Herein, a novel SIVG is proposed as a candidate with advanced ionization engineering design for solar desalination, which exhibits enhanced desalination performance. The design of ionization engineering can promote salt-blocking effects through electrostatic attraction between salt ions in seawater and polymer chains of hydrogel-based evaporator, and high-continuity porous structures, which also contributes to a high evaporation performance by increasing the production of activated water molecules. Furthermore, the introduction of CuO nanoparticles with excellent localized surface plasmon resonance effect enables the light-absorbing copper-based hydrogel (LACH) to achieve an impressive sunlight absorptance rate of 95 %. The evaporation rate and energy efficiency of LACH reach a remarkable 3.93 kg·m−2·h−1 and 93.5 % in simulated brine (3.5 wt% NaCl solution) under one-sun illumination. The salt-resistant LACH-related SIVG is one of ideal candidates for sustainable freshwater harvesting over extended periods. This study is expected to offer valuable insights for advancing the research and development of next-generation solar desalination devices.
... [1][2][3] Global ecosystems and social development are also increasingly demanding freshwater resources; meanwhile, the demand for freshwater in remote areas has been in crisis. [4][5][6][7] The scarcity of water resources has prompted the development of efficient, large-scale means of obtaining freshwater. 8,9 Among all means of obtaining freshwater, desalination is a viable solution to the problem of freshwater scarcity due to the Earth's nearly inexhaustible seawater resources. ...
... 14 Chitosan and polystyrenesulfonate are demonstrated to have a positive effect on improving the IW content of PVA-based evaporators, and an extremely high SSG rate of 3.6 kg m −2 h −1 can be obtained based on the molecular modification strategy. 15,16 However, up to now, limited by the large molecular weight and disordered molecular network of the polymer, there is still a lack of in-depth and systematic elucidation of the water evaporation mechanism including the water cluster activation process, the structure and characteristics of water clusters, and the relationship between IW and water clusters. 17,18 In fact, crystalline materials, such as semiconductors, with highly ordered atomic arrangement structures can also generate IW, and they are more conducive to exploring the water evaporation mechanism. ...
... The Co 3 O 4 evaporation layers in Co 3 O 4 -M have a thickness of ∼5 μm, and show good wettability since the water contact angles quickly decrease from ∼50°to 0°within 10 s (Figure S6andFigure S7). The slightly higher water contact angle and saturated water content of the Co 3 O 4 -O membrane can be attributed to the stronger water binding energy of Co 3+ to water molecules (Figure S8).15,29 Based on the solar radiation spectrum (AM 1.5 G), the solar absorptions of Co 3 O 4 -C, Co 3 O 4 -T, and Co 3 O 4 -O membranes are 83.15%, ...
... Generally, the water in the hydrogel electrolytes can be existed in the following three states: free water, intermediate water and bound water. [20] The Raman peak at 3240 cm −1 is assigned to the bound water, which is closely associated with the ions (Zn 2+ and SO 4 2 − ) through hydration and the zwitterionic groups via electrostatically induced hydration. While the peaks of 3365 and 3458 cm −1 are related to the intermediate water that interacts weakly with the ions or polyacrylamide molecules. ...
To date, the exploration of zwitterionic application is confined to the function of electrolyte's additives to improve the properties of the electrolytes. However, reports on the unique properties of zwitterions, namely the anti‐polyelectrolyte effect (APE), as the regulators of the electrochemical stability windows (ESWs) of the zwitterionic electrolytes are scarce. Herein, a zwitterionic electrolyte system is designed and study the relationship between the APE and the ESWs of the zwitterionic electrolytes. The hydrogen/oxygen evolution in the zwitterionic electrolytes is significantly inhibited under the action of the APE. On this basis, the ESWs of zwitterionic electrolytes can be expanded, ultimately achieving an effective improvement in the energy density of zinc‐ion hybrid capacitors (ZHCs). The sulfonic‐based zwitterionic hydrogel electrolytes prepared based on this strategy achieve a wide ESW of 2.58 V and high ionic conductivity of 29.3 mS cm⁻¹. Meanwhile, the corresponding ZHCs possess a high working voltage of 2.1 V (1.6 V for the traditional ZHCs), a high capacity of 188.9 mAh g⁻¹ and a high energy density of 110 Wh kg⁻¹. The way utilizing the APE of zwitterions to expand the ESWs opens up a new avenue to improve the energy density of energy storage devices.
