Blockchain Papers

Joseph malisaba, Barah Obinna Onyebuchi, Samuel George Onep, Emmanuel Ninsiima

<ns5:p> Background Access to safe drinking water remains a persistent challenge in low-resource settings such as Ishaka Municipality, Uganda, where surface and groundwater sources are frequently contaminated and access to reliable electricity is limited. This study presents the design, modeling, and performance evaluation of a solar-powered hybrid water treatment system integrated with a biosensor-based microbial detection unit, enabling autonomous operation and real-time water quality monitoring for decentralized applications. Methods A total of 384 water samples were collected from springs, wetlands, wells, and tap sources and analyzed for key physicochemical and microbial parameters, including turbidity, pH, and indicator organisms. The proposed system integrates sedimentation, activated carbon filtration, reverse osmosis, and solar thermal disinfection to achieve multi-barrier treatment. Hydraulic and filtration performance were modeled using fluid flow and porous media principles, while microbial inactivation was described using first-order kinetic models. The photovoltaic subsystem was evaluated through detailed loss modeling, incorporating temperature effects, partial shading, and inverter inefficiencies to assess overall system reliability. Results Baseline results indicated significant contamination, with <ns5:italic>Escherichia coli</ns5:italic> concentrations reaching 210 CFU/100 mL and turbidity values up to 146 NTU. The hybrid system achieved over 95% removal of contaminants, complete elimination of <ns5:italic>E. coli</ns5:italic> , and compliance with World Health Organization drinking water standards. Solar thermal disinfection provided a 4–6 log reduction in microbial indicators. The integrated biosensor demonstrated rapid response times (45–90 seconds) and strong correlation with laboratory biochemical oxygen demand measurements (R <ns5:sup>2</ns5:sup> = 0.89–0.94). The photovoltaic subsystem maintained a performance ratio of 0.84–0.88, consistently meeting 100% of operational energy demand under varying environmental conditions. Conclusion These results demonstrate that the proposed system provides an effective, energy-autonomous solution for decentralized water purification with real-time monitoring capability, offering significant potential for improving access to safe drinking water in rural and resource-limited environments. </ns5:p>

Hamed Abdolahimansoorkhani

Oxygen plays a central role in numerous industrial processes. Several technologies have been reported for producing oxygen from air. Among them, oxygen transport membrane (OTM) technology—based on mixed-conducting, gas-tight ceramic membranes—has attracted significant attention due to its high oxygen selectivity, relatively low capital and operating costs, and versatility for both ex-situ and in-situ applications. Mathematical modeling of OTMs offers a powerful tool to investigate internal multi-physics transport phenomena, providing deeper insight into fundamental mechanisms while serving as a cost-effective approach for optimizing membrane stack designs. After a comprehensive introduction, in the first part of this dissertation (chapter 2), a comprehensive hollow fiber membrane model was developed, grounded in an experimental system as the physical basis. The model couples Multiphysics transport processes within the membrane with large-scale thermal–fluid transport in the test assembly and furnace. Systematic parametric studies are performed to investigate fundamental mechanisms and assess membrane performance. The results show that the oxygen partial pressure on the permeate side increases asymptotically from the inlet to the outlet of the hollow fiber membrane. In contrast, the longitudinal distribution of oxygen vacancy concentration decreases along the same direction, while the oxygen flux distribution follows the profile of oxygen vacancy concentration at the permeate surface. High feed-side air pressure and low permeate-side gas pressure are found to enhance oxygen permeation performance. Among the transport resistances, surface exchange resistance at the permeate side dominates, whereas bulk diffusion resistance contributes minimally in substrate-supported thin-film hollow fiber membranes. Overall, the modeling study provides valuable insight into the underlying mechanisms and offers practical guidance for membrane design and operation to improve oxygen production efficiency. To enable practical applications, upscaling from a single hollow fiber membrane to stacks and modules is essential. However, experimental methods for evaluating upscaling strategies are both time-consuming and costly. Mathematical modeling, by contrast, offers a cost-effective and flexible tool for this purpose. In the second part of the dissertation (chapter 3), building upon experimental results from a proof-of-concept hollow fiber membrane stack, a computational fluid dynamics (CFD)-based Multiphysics stack model was developed and validated. Extensive simulations were performed to examine stack behavior under varying operating conditions, and different design strategies were evaluated to optimize stack performance. The oxygen permeation process is thermally activated. Increasing the argon sweep gas flow rate lowers the oxygen partial pressure around the shell sides of the hollow fibers and enhances the permeation flux. Along the lumen side, oxygen partial pressure rises from the inlet to the outlet, with flux significantly higher in the upstream region than downstream. A distinct gradient of oxygen vacancy concentrations is observed across upstream fiber sections, from shell to lumen surfaces, but this gradient diminishes downstream. For a fixed stack length, adding more hollow fibers increases the overall permeation rate but reduces flux. Oxygen partial pressure decreases radially from the periphery to the center of the stack, leading to lower average flux in inner layers. An appropriate packing density is therefore required to achieve compact design while limiting pressure losses. For a given total fiber length, an optimal fiber number exists that maximizes average permeation performance. Diffusive oxygen flux dominates near fiber walls, while convective flux becomes increasingly important toward the fiber center. A higher sweep gas flow rate reduces the region where diffusion dominates. To maintain the elevated temperatures required for membrane operation, a high-temperature furnace is typically used. However, this results in low heating power efficiency and makes rapid temperature changes difficult due to the large volume of the furnace. Recently, a novel strategy has been employed in which external electrical power is directly applied to a hollow fiber membrane, enabling compact self-heating. To better understand the fundamental mechanisms, a mathematical model is developed in the third part of the dissertation (chapter 4) for a self-heated hollow fiber oxygen separation membrane, assisted by vacuum conditions applied at the lumen-side outlet. Comprehensive simulations are conducted to study the effects of self-heating on Multiphysics transport processes and oxygen permeation performance. Additional simulations are performed to investigate the influence of electrical field orientations applied to the hollow fiber membrane and the vacuum levels at the lumen-side outlet. The associated fundamental mechanisms are discussed and elaborated. A higher applied voltage increases the average membrane temperature. The longitudinal temperature profile is non-uniform, with a maximum in the mid-region and steep decreases toward both ends. Oxygen permeation flux rises with applied potential and is further enhanced by higher vacuum levels (lower permeate-side oxygen partial pressure). The flux distribution shows a domed shape along the fiber length, approaching zero near the ends. At low potentials, the effect of vacuum level is negligible but becomes significant at higher potentials. On the feed side, oxygen concentration decreases from the bulk to the surface, while on the permeate side it decreases from the surface toward the lumen outlet. Both gradients intensify with increasing voltage and/or vacuum level. Across the membrane bulk, oxygen vacancy concentration increases from feed to permeate surfaces, with steeper gradients under higher potentials and stronger vacuum. The orientation of the applied potential strongly influences performance. Alignment with the permeation direction, with positive and negative electrodes connected to permeate and feed surfaces respectively, greatly enhances flux. The opposite configuration suppresses it, while a perpendicular potential has little effect on radial ion transport. Building on these advances, Chapter 5 integrates the modeling and heating strategies into a Joule-heated hollow fiber ion transport membrane reactor for methane oxidative coupling (OCM). Results demonstrate that methane plays a dual role: it is both the feedstock for conversion and a promoter of oxygen transport by lowering surface oxygen partial pressure and sustaining higher vacancy-driven flux. The coupled transport–reaction model reveals that gradual, membrane-mediated oxygen delivery significantly improves C₂ selectivity compared with conventional co-feed reactors. Methane–vacancy interactions, heterogeneous surface reactions, gas-phase chemistry, and localized Joule heating jointly shape flux, product selectivity, and thermal profiles. This chapter demonstrates the dual functionality of MIEC membranes as both oxygen separators and catalytic reactors, providing a path toward intensified, energy-efficient chemical production. Finally, Chapter 6 synthesizes the insights, highlighting how Multiphysics modeling bridges the gap between laboratory observations and industrial-scale application. By clarifying oxygen transport mechanisms, optimizing stack designs, enabling compact Joule-heating strategies, and extending membranes into reactive processes, this dissertation contributes both fundamental knowledge and practical guidance. The results position MIEC hollow fiber membranes not only as efficient oxygen separators but also as versatile platforms for low-carbon energy, 𝐶𝑂₂ management, and sustainable chemical synthesis.

Abdoul Wahab Nouhou Moussa, Adel Zrelli, Boukary Sawadogo, Rachida Chemini

Africa’s growing water stress and energy access challenges necessitate sustainable wastewater treatment solutions. This review critically examines three emerging approaches: solar-based, membrane-based, and hybrid solar-membrane systems, across the African continent. Solar technologies, including solar water disinfection, photocatalysis, and advanced oxidation processes, demonstrate significant potential in sun-rich regions, achieving more than 90% pathogen and contaminant removal in decentralized settings. Membrane bioreactors (MBRs) and advanced filtration systems show robust performance in industrial applications, with 95%–99% pollutant rejection, though their energy demands remain a significant constraint. Hybrid solar-membrane systems synergize these advantages, as evidenced by case studies in Kenya (solar-MBR for aquaculture, 40% energy autonomy) and Namibia (solar-powered desalination, 99.7% salt rejection). Despite technological promise, adoption barriers persist, including high capital costs, technical capacity gaps, and policy fragmentation. This review analyze 32 implementations across 17 African countries, evaluating performance metrics, scalability, and socioeconomic viability. Key findings highlight the cost-effectiveness and sustainability gains from waste-derived membranes (e.g., geopolymers, recycled plastics, oasis waste), nanoparticle-enhanced photocatalysts (TiO 2 /MnO 2 ), and modular system designs tailored to off-grid and resource-limited settings. The review concludes with policy recommendations to accelerate deployment. These include fostering decentralized systems in peri-urban and rural areas, promoting public-private partnerships to finance infrastructure, and supporting localized research to adapt technologies to diverse hydroclimatic and socio-economic conditions. Together, these approaches offer a viable pathway toward achieving SDG 6 and SDG 7 in Africa.

Fuchang Xu, Dehui Weng, Xiang Li, Yang Li · 5 authors

Open AccessCCS ChemistryRESEARCH ARTICLE14 Jul 2022Self-Healing Hydrophilic Porous Photothermal Membranes for Durable and Highly Efficient Solar-Driven Interfacial Water Evaporation Fuchang Xu, Dehui Weng, Xiang Li, Yang Li and Junqi Sun Fuchang Xu State Key Laboratory of Supramolecular Structure and Materials, College of Chemistry, Jilin University, Changchun 130012 , Dehui Weng State Key Laboratory of Supramolecular Structure and Materials, College of Chemistry, Jilin University, Changchun 130012 , Xiang Li State Key Laboratory of Supramolecular Structure and Materials, College of Chemistry, Jilin University, Changchun 130012 , Yang Li *Corresponding author: E-mail Address: [email protected] State Key Laboratory of Supramolecular Structure and Materials, College of Chemistry, Jilin University, Changchun 130012 and Junqi Sun State Key Laboratory of Supramolecular Structure and Materials, College of Chemistry, Jilin University, Changchun 130012 https://doi.org/10.31635/ccschem.021.202101111 SectionsSupplemental MaterialAboutAbstractPDF ToolsAdd to favoritesDownload CitationsTrack Citations ShareFacebookTwitterLinked InEmail It is highly desirable to develop a solar-driven interfacial water evaporator with a self-healing ability and high-efficiency water evaporation performance for water distillation and desalination; however, this process is considerably challenging. Herein, by exploiting the advantages of a self-healing hydrophilic polymer, a self-healing hydrophilic porous photothermal (SHPP) membrane was fabricated by curing a mixture of the polymer, carbon black, and NaCl, followed by removal of the NaCl from water. Since the SHPP membrane could serve as a photothermal layer and water transportation channel simultaneously, a solar-driven interfacial evaporator could be fabricated readily by assembling the SHPP membrane with polyethylene foam. We have shown that the SHPP membrane-based evaporator exhibited a water evaporation rate of 1.68 kg m−2 h−1 and an energy efficiency of 97.3%. These values are superior to those obtained using solar-driven interfacial evaporators with self-healing capability. Notably, by hydrogen bonds reformation between the fracture surfaces, the SHPP membrane could regain its structural integrity after breaking, making the SHPP membrane-based evaporator the first to heal entirely and repeatedly from physical damage to sustain its water evaporation capacity. Therefore, the potential of using SHPP membranes to develop stable, long-lasting, and high-efficiency solar-driven interfacial water evaporators is highlighted. Download figure Download PowerPoint Introduction Fresh water, accounting for only 3% of the total water resources on earth, is vital to human survival and social development. However, with increased population, as well as persistent environmental pollution, the shortage of fresh water has become a key global issue. Therefore, it is imperative to develop effective technologies to generate fresh water from seawater or sewage.1–3 Among all the water treatment technologies, solar-driven evaporation has attracted extensive research attention due to the environment-friendly and renewable characteristics of solar energy.4 Recently, solar-driven interfacial water evaporation, which minimizes thermal dissipation and applies most of the heat to the liquid–vapor phase transition by concentrating heat at the water–air interface, has been developed to improve the water evaporation efficiency.5–17 Generally, most of the reported solar-driven interfacial evaporators comprise three parts18,19 (Scheme 1a1: (1) a photothermal layer with broadband light absorption and high photothermal conversion, (2) a floatable supporting layer with low thermal conductivity, and (3) a hydrophilic water channel either on the outside or in the middle of the supporting layer that ensures a continuous water supply to the photothermal layer. Although many high-efficiency solar-driven interfacial evaporators have been developed, in practical applications, the photothermal layer or water channel can be damaged by scratching or corrosion, thereby deteriorating the water evaporation efficiency (Scheme 1a2). Hence, to satisfy the requirements for practical applications, it is critical to develop solar-driven interfacial evaporators with a stable water evaporation efficiency. In particular, it is crucial to develop solar-driven interfacial evaporators that can maintain their water evaporation performance after damage. Scheme 1 | (a) Schemes of (1) the composition of a typical solar-driven interfacial evaporator and (2) the loss of its water evaporation capacity due to damage to the water transportation channel. (b) Schematics of (1) the composition of the SHPP membrane-based solar-driven interfacial evaporator and (2) its ability to restore the water evaporation ability via self-healing after physical damage. Download figure Download PowerPoint With the progress in supramolecular chemistry and synthetic chemistry, various self-healing polymers capable of healing damage by themselves to restore the mechanical and/or chemical properties have been synthesized successfully.20–23 In addition, by combining self-healing polymers with functional materials, plenty of self-healing functional materials with superhydrophobicity,24–27 antifouling,28–30 electrical conductivity,31–34 sensing,35–41 and other functions42–50 have been fabricated, decreasing maintenance costs and promoting safety, reliability, and service life significantly. The design and fabrication of self-healing materials with photothermal and water transportation capabilities, able to repair their functions upon damage, would be a judicious solution to increase the stability and service life of solar-driven interfacial evaporators. Although our group and a few other researchers have reported the fabrication of self-healing photothermal membranes for solar-driven water evaporation, these membranes can only heal chemical damage.51,52 Furthermore, the water evaporation rates of these self-healing photothermal membranes were not ideal (<1.31 kg m−2 h−1), related to their hydrophobic/superhydrophobic nature that hindered water transportation and evaporation. Previously, our group reported that self-healing superhydrophobic porous materials with a photothermal conversion ability capable of healing physical damage could be obtained using a self-healing hydrophobic polymer and carbon nanotubes as the main materials using NaCl as the template.53 Based on the experience in self-healing porous materials fabrication, along with the widely available knowledge in hydrophilic self-healing polymer synthesis, a rational selection of the material composition was made that led to self-healing hydrophilic photothermal membranes with long-term advantages of high-efficiency evaporation capability for solar-driven interfacial evaporators. As a proof of concept, for the first time, we are reporting a self-healing hydrophilic porous photothermal (SHPP) membrane for highly efficient solar-driven interfacial water evaporation based on a carefully designed and synthesis of a self-healing hydrophilic polymer. The SHPP membrane was fabricated by curing a mixture of self-healing hydrophilic polymer with carbon black (CB) and NaCl, followed by removing the NaCl from water. By tuning the hydrophilicity of the self-healing polymer and the mass ratios of the feed materials, the water content of the SHPP membrane that considerably affects the water evaporation performance could be controlled. From the self-healing perspective, the self-healing polymer permitted the coalescence of the cut SHPP membrane via the reformation of hydrogen bonds between the fracture surfaces, leading to the healing of structural integrity. As the SHPP membrane could simultaneously serve as the photothermal layer and water transportation channel, a highly efficient solar-driven interfacial evaporator can be readily fabricated by assembling the SHPP membrane with a polyethylene (PE) foam (Scheme 1b1). By floating such a designed evaporator on the water surface, the evaporation rates of lake water and seawater reached 1.67 and 1.61 kg m−2 h−1, respectively. When the water evaporation capacity of the evaporator was lost by cutting the SHPP membrane, it was able to self-heal at room temperature, and the water evaporation performance of the evaporator was fully restored (Scheme 1b2). Moreover, the SHPP membrane was capable of healing damage caused at the exact location repeatedly without losing the water evaporation performance. The simple structure of the SHPP membrane-based evaporator benefits its integration into conventional solar distillation devices. In this study, we fabricated a prototype distillation device comprising an SHPP membrane-based evaporator to demonstrate the applicability of the SHPP membrane for sewage purification and seawater desalination. Experimental Methods Materials PE glycol (PEG; Mw = 1000) and polyvinyl alcohol (PVA; Mw = 85,000–124,000, 87–89% hydrolyzed) were purchased from Sigma-Aldrich (Shanghai, China). Polytetramethylene ether glycol (PTMG; Mw = 1000) was purchased from Aladdin (Shanghai, China). Dicyclohexylmethane 4,4-diisocyanate (DMDI; purity < 90%) was purchased from TCI Development Co., Ltd. (Shanghai, China). Dibutyltin dilaurate (DBTDL; purity < 97.5%) was purchased from J&K Scientific Ltd. (Beijing, China). Tetrahydrofuran (THF) was purchased from Innochem Science & Technology Co., Ltd. (Beijing, China). CB was purchased from Alfa Aesar Chemical Co., Ltd. (Shanghai, China). Anhydrous ethanol and NaCl were purchased from Beijing Chemical Reagents Company (Beijing, China). All of the chemicals were used without further purification. Synthesis of PUx A series of PUx with different molar ratios of PEG and PTMG were synthesized by the step-growth polymerization of PEG, PTMG, and DMDI. Taking PU50 as an example, PEG (5.00 g, 5 mmol) and PTMG (5.00 g, 5 mmol) were added into a 250 mL three-neck round-bottom flask equipped with mechanical agitation, nitrogen inlet, and condensation reflux. The reaction was allowed to proceed under vacuum for 2 h at 100 °C; then the system was cooled to 60 °C and filled with nitrogen gas. Subsequently, THF (100 mL), DMDI (3.15 g, 12 mmol), and DBTDL (0.05 g, 0.08 mmol) were added into the three-neck round-bottom flask. After 48 h of stirring at 60 °C under nitrogen, the reaction solution was purified by dialysis using a dialysis membrane [molecular weight cutoff (MWCO), 8000–14,000 Da] with anhydrous ethanol. Finally, PU50 was obtained after ethanol evaporation. PU0, PU10, PU20, PU30, and PU40 were synthesized separately in accordance with the method described above. Fabrication of PUx/CBm/NaCln membranes CB and NaCl with different mass ratios were mixed for 30 min using a ball mill machine. Next, CB and NaCl blends were added to 15 mL THF solutions of PUx (the concentration of PUx depended on the composition of PUx/CBm/NaCln), followed by mechanical stirring at 500 rpm for 1 h to ensure that CB and NaCl were well dispersed in the PUx solutions. The resulting solution mixtures were poured into Teflon molds and cured at room temperature. After complete removal of THF, the exteriors of the solidified composite blocks were rubbed with sandpaper and immersed in water baths renewed every 6 h over 2 days to remove the NaCl completely with the resultant PUx/CBm/NaCln porous membranes. The water-soaked PUx/CBm/NaCln porous membranes were wiped with filter papers and then dried at room temperature. Characterization The Mw and PDI of PUx were characterized on a Shimadzu gel-permeation chromatography (GPC; Shimadzu, Japan) system. THF was used as the moving phase, and the flow rate was 1.0 mL min−1. Fourier transform infrared (FT-IR) spectra were taken on a Bruker VERTEX 80 V FT-IR spectrometer (Bruker, Germany). The differential scanning calorimetry (DSC) curves of PUx were obtained on a TA instrument Q200 (TA, USA) at the heating/cooling rate of 10 °C min−1 in a N2 atmosphere. Simulated solar light was provided by a PL-XQ500W xenon lamp (Beijing Springs Technology Co., Ltd., Beijing, China), and the light intensity was kept at 1000 W m−2. Temperature values and IR images of the samples were captured using a HIKVISION H10 thermal imager (HIKVISION, Hangzhou, China). The distance between the sample and the thermal imager was fixed at 20 cm. The accuracy in temperature of the thermal imager is ±2 °C. The reflection and transmission spectra of the samples were characterized by a UV-3600 spectrophotometer (Shimadzu, Kyoto, Japan). The optical images and videos were captured using a Canon PowerShot SX40 HS camera (Canon, China). The scanning electron microscopy (SEM) images were obtained using a JEOL JSM 6700F field emission scanning electron microscope (JEOL, Japan). The optical microscopy images were obtained using an Olympus DP72 optical microscope (Olympus, China). The porosity (ρ) of the PUx/CBm/NaCln porous membrane was calculated by the following equation: ρ = ( M wet − M dry ) / ( M wet − M sub ) (1)where Mdry is the dry mass of the membrane, Mwet is the mass of the prewetted membrane measured in air, and Msub is the mass of the membranes soaked in water. The solar thermal conversion efficiency (η) of the PUx/CBm/NaCln porous membrane was calculated by the following equation: η = H e × ( ν Total − ν Dark ) / Q s , (2)where He is the heat of water evaporation (2260 kJ kg−1), Qs is the incidence light power, νTotal is the evaporation rate of the PUx/CBm/NaCln porous membrane at stable state under one sun irradiation, and νDark is the evaporation rate of the PUx/CBm/NaCln porous membrane in dark environment. To test its water transport capacity, a piece of PUx/CBm/NaCln porous membrane (0.1 cm × 1 cm × 5 cm) was partially immersed in a beaker containing 50 mL of deionized (DI) water, and a piece of filter paper was used to absorb water from the upper end of the membrane continuously. The filter paper was replaced after it was saturated with water. The water flux (F) of the PUx/CBm/NaCln membrane was calculated by the following equation: F = M water / ( S * t ) , (3)where Mwater is the mass change of the DI water in the beaker, S is the cross-sectional area of the membrane, and t is the test time. Results and Discussion The self-healing hydrophilic polymer that was key for fabricating the SHPP membrane with a stable, highly efficient solar-driven interface water evaporation capability was synthesized by the step-growth polymerization of PEG, PTMG, and DMDI, as shown in Figure 1a. The resulting polymers were denoted as PUx, where x referred to the molar percentage of PEG in the total monomers. A peak characteristic of –N=C=O at 2268 cm−1 was not observable in the FT-IR spectra of PUx ( Supporting Information Figure S1). Meanwhile, peaks corresponding to the C=O stretching vibration, as well as N–H stretching and bending vibrations, were observed around 1720 and 1533 cm−1, respectively, confirming the successful synthesis of PUx. GPC was employed to estimate the weight-average molecular weight (Mw) and polydispersity index (PDI) of PUx. Supporting Information Table S1 lists the results. Although the molar ratios of PEG and PTMG were different, all of the PUx exhibited similar Mw and PDI. In this study, hydrophobic PTMG and hydrophilic PEG were used rationally by adjusting the molar ratio of the two monomers due to the regulation of hydrophilicity of PUx. With an increase in the PEG content, the water uptake of PUx increased, indicating that the hydrophilicity of PUx increases with an increase in the molar ratio of PEG ( Supporting Information Figure S2). Figure 1 | (a) Synthetic route of PUx. (b) Photographs of the PU20 film after being cut and being healed at room temperature for 6 h. (c) Microscopy images of the cut PU20 membrane before and after healing for 6 h at room temperature. (d) Stress–strain curves of the pristine PU20 film and the cut PU20 film after healing for different times at room temperatures. The stretching speed was 50 mm min−1. Download figure Download PowerPoint Taking PU20 as a representative, the self-healing ability of PUx was examined. A piece of the PU20 film (0.6 cm × 3.5 cm) was cut in half with a knife, and the two parts were subsequently reattached closely (Figure 1b). After placing the PU20 film under ambient conditions for 6 h, the separated PU20 film was conglutinated together, restoring its structural integrity. In addition, an optical microscopy image confirmed that the cut was healed completely (Figure 1c). The self-healing ability of PU20 was attributed to its abundant reversible hydrogen bonds and low glass transition temperature (−51.3 °C, Supporting Information Figure S3). When the fracture surfaces were brought into close contact, the polymer chains migrated gradually into the voids, and the hydrogen bonds reformed with one another, leading to healing of the cut.54 Tensile tests were employed to characterize the healing ability of PU20 further. As the healing time increased, the fracture stress of the healed PU20 film increased gradually and recovered to 4.26 MPa after 6 h of healing at room temperature (Figure 1d). Accordingly, the healing efficiency of PU20, defined as the proportion of the restored fracture stress to the original stress, was calculated to be 98.4%, indicating a satisfactory self-healing ability. In addition, the self-healing abilities of PUx with different PEG contents were examined. Supporting Information Table S2 lists the results. With an increase in the PEG content, the healing efficiency of PUx increased due to the reduction in Young's modulus of the resulting polymer via an increase in the PEG segments ( Supporting Information Table S2). With the successful synthesis of PUx, SHPP membranes were fabricated using PUx, CB, and NaCl. CB was used due to its good photothermal conversion ability and low costs,55,56 while NaCl was used as a sacrificial template. The self-healing hydrophilic porous PUx/CBm/NaCln membranes, where m and n represent the mass ratios of CB and NaCl to PUx, respectively, were fabricated by casting a dispersion of PUx, CB, and NaCl in THF into a Teflon (R) mold, followed by solvent evaporation and NaCl removal in water (Figure 2a). Owing to the simple fabrication, a piece of PU20/CB0.5/NaCl5 membrane with dimensions of 11 cm × 11 cm was obtained readily (Figure 2b). The SEM image in Figure 2c reveals that the PU20/CB0.5/NaCl5 membrane exhibits a three-dimensional interconnected hierarchical porous structure, comprising a CB-reinforced PU20 skeleton and macropores with diameters ranging from 9.7 to 109.8 μm. Based on Archimedes' method (eq 1), the porosity of the PU20/CB0.5/NaCl5 membrane was 59.8%. Figure 2 | (a) Schematic of the fabrication processes of the PUx/CBm/NaCln membranes. (b) Photographs of the PU20/CB0.5/NaCl5 membrane. (c) Cross-section SEM image of the PU20/CB0.5/NaCl5 membrane. (d) Photograph showing that the PU20/CB0.5/NaCl5 membrane transported water to a height of 5 cm in 3 min. (e) Photograph of the PU20/CB0.5/NaCl5 membrane-based solar-driven interfacial evaporator. (f) Temperature changes of DI water and the PU20/CB0.5/NaCl5 membrane-based evaporator floating on the DI water under simulated solar light irradiation. (g) Time-sequence IR images of the DI water-filled glass containers without (left) and with (right) the PU20/CB0.5/NaCl5 membrane-based evaporator under simulated solar light irradiation for (1) 1 min and (2) 60 min. (h) The mass changes of the DI water with and without the PU20/CB0.5/NaCl5 membrane-based evaporator under simulated solar light irradiation. Download figure Download PowerPoint The combination of the hydrophilicity of PU20 and the porous structure permitted a 5 cm vertical transport of water by the PU20/CB0.5/NaCl5 membrane due to capillary force (Figure 2d), qualifying it to be a water transportation channel. In addition, the average transmittances and reflections of the PU20/CB0.5/NaCl5 membrane were close to zero in the wavelength range from 200 to 2500 nm ( Supporting Information Figure S4). The intense light absorption of the PU20/CB0.5/NaCl5 membrane was related to the excellent light absorption performance of the CB in a broad wavelength range and the porous structure. This further improved the solar-energy harvesting efficiency via a reduction in light reflection.57 Next, the photothermal ability of the PU20/CB0.5/NaCl5 membrane was investigated by irradiating the membrane with a simulated solar light (1000 W m−2), then an IR camera was used to monitor the temperature of the membrane in air. Under light irradiation, the temperature of the PU20/CB0.5/NaCl5 membrane increased rapidly to 57 °C in 1 min and then reached a steady-state temperature of 70 °C by 5 min ( Supporting Information Figure S5), demonstrating an excellent photothermal ability. As the PU20/CB0.5/NaCl5 membrane simultaneously exhibited excellent water transport and photothermal abilities, we envisioned that a simple efficient solar-driven interfacial water evaporator could be readily by the PU20/CB0.5/NaCl5 membrane a PE foam to serve as a and an layer simultaneously (Figure The water evaporation performance of the PU20/CB0.5/NaCl5 membrane-based evaporator floating on the water was measured by placing the evaporator in a DI water-filled glass on an Simulated light with an intensity of 1000 W m−2 was on the PU20/CB0.5/NaCl5 membrane surface, and the water mass change was Under light irradiation, the PU20/CB0.5/NaCl5 membrane light and the water The temperature of the PU20/CB0.5/NaCl5 membrane rapidly increased to °C in 1 min and reached a steady-state temperature of °C by 5 min (Figure and Since the PU20/CB0.5/NaCl5 membrane transported water from the glass to the of the evaporator (Scheme this membrane-based evaporator exhibited a water evaporation rate of 1.68 kg m−2 h−1 (Figure to 2 provided in the Experimental the solar thermal conversion efficiency of the PU20/CB0.5/NaCl5 membrane-based evaporator was 97.3%. we that such a high solar thermal conversion efficiency for the evaporator was related to the that most of the heat was used to the water at the of the evaporator and that only a of the heat was to the water the glass As after 1 h of simulated light irradiation, the temperature of the water under the evaporator only increased by 5 °C (Figure In the temperature of water in the glass without the PU20/CB0.5/NaCl5 membrane-based evaporator increased by °C after 1 h of simulated light irradiation (Figure Owing to the low light absorption capacity of water and water the evaporation rate of water in the glass without the evaporator was only kg m−2 h−1 (Figure with the of the PU20/CB0.5/NaCl5 membrane-based the evaporation rate of water increased Subsequently, the of the composition of the PUx/CBm/NaCln membranes on the performance of the PUx/CBm/NaCln membrane-based evaporators was examined. the membranes with x being were As with an increase in PEG content, the hydrophilicity of PUx the membrane-based evaporators were floating on the water, the membrane water content increased with PEG content of PUx (Figure By an increase in PUx hydrophilicity hindered water flow the membrane, the water flux of the membrane as the PEG content Notably, with an increase in the PEG content, the water evaporation rate of the membrane-based evaporators increased and then water content and water flux of and kg m−2 h−1, the water evaporation rate reached a of 1.68 kg m−2 h−1 (Figure Next, the water evaporation rates of the membrane-based evaporators were (Figure As the NaCl content was increased, the water content and water flux of the membrane This was as increased NaCl content increased the membrane porosity ( Supporting Information Figure with an increase in water content and water a NaCl to PU20 mass ratio of the PU20/CB0.5/NaCl5 membrane-based evaporator exhibited the water evaporation Finally, the of the CB content on the performance of the membrane-based evaporators was (Figure We observed that the PU20/CB0.5/NaCl5 membrane exhibited the water content and water confirming that the PU20/CB0.5/NaCl5 membrane-based evaporator the water evaporation This is at an low CB content, the in the resulting membrane ( Supporting Information Figure thereby leading to a in porosity ( Supporting Information Figure water content, and water flux (Figure the other to its CB led to a in the water content and water flux of the membrane (Figure our that PU20 was the mass ratios of CB to PU20 and NaCl to PU20 were at and respectively, and the PU20/CB0.5/NaCl5 membrane-based evaporator exhibited the water evaporation rate of 1.68 kg m−2 Therefore, in the following study, the PU20/CB0.5/NaCl5 membranes were used to the self-healing solar-driven water evaporator. Figure 3 | Evaporation water and water content of the PUx/CBm/NaCln membrane as a of (a) the molar ratio of PEG, (b) the mass ratio of NaCl, and (c) the mass ratio of (d) changes of the simulated seawater and lake water with PU20/CB0.5/NaCl5 membrane-based evaporators under simulated solar light irradiation. Download figure Download PowerPoint The water evaporation rates of the PU20/CB0.5/NaCl5 membrane-based evaporator floating on lake water and simulated seawater from DI water, were examined. With the of the the evaporation rates of the lake water and simulated seawater were 1.67 and 1.61 kg m−2 h−1, (Figure The corresponding solar thermal conversion were and is a that all solar-driven evaporators seawater desalination. from the good of the PU20/CB0.5/NaCl5 membrane, the seawater evaporation rate of the PU20/CB0.5/NaCl5 membrane-based evaporator was at kg m−2 h−1 after h of seawater evaporation, which was times that of simulated seawater ( Supporting Information Figure Moreover, the seawater evaporation of the evaporator was recovered by 10 mL of seawater the PU20/CB0.5/NaCl5 membrane ( Supporting Information Figure These that the PU20/CB0.5/NaCl5 membranes potential in sewage purification and seawater desalination. the stability of the PU20/CB0.5/NaCl5 membranes was examined. We that the porosity of the PU20/CB0.5/NaCl5 membranes was after in and NaCl solutions for 10 indicating that the membranes exhibited satisfactory Moreover, the porosity of the PU20/CB0.5/NaCl5 membranes was well after placing in the or in water at 50 °C for 10 days ( Supporting Information Figure and Figure indicating that the porous structure in the membranes was highly These that the PU20/CB0.5/NaCl5 membranes good stability and could with the of solar-driven interfacial evaporators. Figure | changes of the PU20/CB0.5/NaCl5 membranes after being

D.N. Georgiou, Essam Sh. Mohammed, Stélios Rozakis

The important energy requirements for the desalination process impose especially in autonomous and decentralized plants supplied by Renewable Energy Sources (RES). In this paper, five alternative energy generation topologies of Reverse Osmosis desalination process are evaluated. The proposed topologies assessed in terms of economic, environmental, technological and societal indices are compared using multi-criteria analysis, namely the Analytic Hierarchy Process (AHP) and the Preference Ranking Organization Method for Enrichment of Evaluations (PROMETHEE). Ranking of topologies resulted in the selection of direct connection and hybrid configuration as optimum solutions. In case economic priorities prevail diesel generation should also be considered.