The accelerated increase in freshwater demand, particularly among populations displaced in remote locations where conventional water sources and the infrastructure required to produce potable water may be completely absent, highlights the urgent need in creating additional freshwater supply from untapped alternative sources via energy-efficient solutions. Herein, we present a hydrophilic and self-floating photothermal foam that can generate potable water from seawater and atmospheric moisture via solar-driven evaporation at its interface. Specifically, the foam shows an excellent solar-evaporation rate of 1.89 kg m –2 h –1 with a solar-to-vapor conversion efficiency of 92.7% under 1-Sun illumination. The collected water is shown to be suitable for potable use because when synthetic seawater samples (3.5 wt %) are used, the foam is able to cause at least 99.99% of salinity reduction. The foam can also be repeatedly used in multiple hydration–dehydration cycles, consisting of moisture absorption or water collection, followed by solar-driven evaporation; in each cycle, 1 g of the foam can harvest 250–1770 mg of water. To the best of our knowledge, this is the first report of a material that integrates all the desirable properties for solar evaporation, water collection, and atmospheric-water harvesting. The lightweight and versatility of the foam suggest that the developed foams can be a potent solution for water efficiency, especially for off-grid situations.

This study reports a novel two-step approach to fabricate poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP)/cerium oxide (CeO 2 ) nanocomposite fibrous membranes. The fabrication method is based on the combination of the electrospinning of a polymer/cerium salt solution and the subsequent in situ thermally activated conversion of the salt in CeO 2 nanoparticles, directly in the polymeric fibers. This procedure leads to a homogeneous filler dispersion not only in the bulk of the polymeric fibers but also on their surface, thus conferring to the system remarkable properties, such as radical scavenging and photocatalytic activity. These properties are further improved by the decoration of the CeO 2 with gold nanoparticles, formed upon the dipping of the solid PVDF-HFP/CeO 2 fibers in a gold precursor solution and their subsequent thermal treatment, thanks to the modification of the Ce 3+ /Ce 4+ ratio and the absorption spectrum shifted toward visible wavelengths. Specifically, the presence of Au on the surface of the PVDF-HFP/CeO 2 fibrous membranes dramatically enhances the radical scavenging activity, which reaches up to 90% of scavenged radicals in 24 h. In addition, the photocatalytic degradation activity is remarkably improved, making possible to photodegrade organic dyes under visible light. Such performances, in combination with the straightforward fabrication method, the high surface area, the light weight, and flexibility, offered by the polymeric fibers make the presented system a valuable alternative to the existing ceria-based systems, e.g., ceramic supported, opening up an innovative route to fabricate multifunctional membranes for water purification or bioapplications due to the CeO 2 antioxidant properties.

Herein, expanded graphite is successfully combined with waterborne polyurethane to develop porous foams with underwater oleophobic properties for the separation of surfactant-free, oil-in-water mixtures and emulsions. To obtain foams with different pore sizes and therefore with different performances in the oil−water filtration process, two solvent-free fabrication processes are adopted. In the first one, the expanded graphite granules are mixed with the waterborne polyurethane (PUEGr), and in the second method, calcium carbonate is introduced to the two-component mixture (PUEGr_t). In both cases, the obtained foams exhibit hydrophilicity and oleophilicity in air and oleophobicity underwater, and they have porous interconnected networks, while their pore size distribution differs significantly. The foams can be used as 3D filters, able to separate, through gravity, surfactant-free, oil-in-water mixtures (10% w/w oil in water) with high oil rejection efficiencies and flow rates that depend on the type of foam. In particular, in the gravitydriven filtration process using 100 mL of the feed liquid, the PUEGr foams have an oil rejection efficiency of 96.85% and flow rate of 9988 L m −2 h −1 , while for the PUEGr_t foams the efficiency is higher (99.99%) and the flow rate is lower (8547 L m −2 h −1 ) due to their smaller pore size. Although the PUEGr_t foams have slower separation performance, they are more efficient for the separation of surfactant-free emulsions (1% w/w oil in water) reaching an oil rejection efficiency of 98.28%, higher than the 95.66% of the PUEGr foams of the same thickness. The foams can be used for several filtration cycles, as well as in harsh conditions without deteriorating their performance. The nature of raw materials, the simple solvent-free preparation method, the effective gravity-driven filtration even in harsh conditions, and their reusability suggest that the herein engineered foams have great potential for practical applications in oil−water separation through highly energy-efficient filtration.

An innovative approach for the fabrication of hybrid photocatalysts on a solid porous polymeric system for the heterogeneous photocatalytic degradation of organic pollutants is herein presented. Specifically, gold/zinc oxide (Au/ZnO)-based porous nanocomposites are formed in situ by a two-step process. In the first step, branched ZnO nanostructures fixed on poly(methyl methacrylate) (PMMA) fibers are obtained upon the thermal conversion of zinc acetate-loaded PMMA electrospun mats. Subsequently, Au nanoparticles (NPs) are directly formed on the surface of the ZnO through an adsorption dipping process and thermal treatment. The effect of different concentrations of the Au ion solutions to the formation of Au/ZnO hybrids is investigated, proving that for 1 wt % of Au NPs with respect to the composite there is an effective metal–semiconductor interfacial interaction. As a result, a significant improvement of the photocatalytic performance of the ZnO/PMMA electrospun nanocomposite for the degradation of methylene blue (MB) and bisphenol A (BPA) under UV light is observed. Therefore, the proposed method can be used to prepare flexible fibrous composites characterized by a high surface area, flexibility, and light weight. These can be used for heterogeneous photocatalytic applications in water treatment, without the need of post treatment steps for their removal from the treated water which may restrict their wide applicability and cause secondary pollution.

A novel approach for the valorization of orange peel waste for the removal of aqueous organic pollutants is presented herein. The orange peel is combined with silk fibroin in order to obtain alcogels, which are successfully converted into highly porous biocomposite foams upon supercritical CO2 drying. The biocomposite shows a Brunauer–Emmett–Teller specific surface area of 174.45 m2 g−1 and can absorb three times its weight in water. The resulting adsorbents can adsorb methylene blue from water with a maximum adsorption capacity of 113.8 ± 12.5 mg g−1, with the orange peel activity well preserved in the polymeric matrix. The spectroscopic studies performed show that the methylene blue molecules are adsorbed in the form of monomers on the surface of the biocomposite foams, forming a monolayer as suggested by the Langmuir isotherm model. Although the agrowaste powders are already confirmed to be promising biosorbents for the removal of pollutants from water, the difficulties caused by their recovery after the water treatment may limit their manageability and applicability. With this study, such limitations can be overcome thanks to the incorporation of the powder in a solid porous system, without significantly compromising the dye adsorption capacity of the incorporated orange peel.

Polyethylene terephthalate (PET) is a thermoplastic material that is widely used in many application fields, such as packaging, construction and household products. Due to the relevant contribution of PET to global yearly solid waste, the recycling of such material has become an important issue. Disposed PET does not maintain the mechanical properties of virgin material, as exposure to water and other substances can cause multiple chain scissions, with subsequent degradation of the viscoelastic properties. For this reason, chain extension is needed to improve the final properties of the recycled product. Chain extension is generally performed through reactive extrusion. As the latter involves structural modification and flow of PET molecules, rheology is a relevant asset for understanding the process and tailoring the mechanical properties of the final products. This paper briefly reviews relevant rheological studies associated with the recycling of polyethylene terephthalate through the reactive extrusion process.

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