Solar water evaporators (SWE) have shown growing interest due to their capacity to transform sunlight to thermal energy. In this work, SWE were prepared based on microwave-expanded graphite as light absorber deposited onto an ecological porous substrate obtained by casting a mixture of coconut fibers and recycled polystyrene. The materials were characterized by SEM, FTIR and UV/Vis-NIR spectroscopies, and thermogravimetric analyses. It was observed that the light absorber film presented high and wide light absorption in the solar electromagnetic spectrum and increased superficial area when compared to the unexpanded graphite film counterpart. Nanopores between 400 and 900 nm and microcavities in the 200 to 500 μm range were formed at the surface of the SWE after 6 seconds of microwave exposure, which are destroyed at higher exposure times. SWE of laboratory scale diameter were tested for water evaporation at different light intensities, microwave expanding time, and thicknesses to determine their effects on evaporation rate and efficiency. It was observed that SWE rates increased from 1.09 ± 0.006 to 1.73 ± 0.007 kg h −1 m −2 for unexpanded and expanded graphite through 6 seconds, respectively; being the latter the best SWE reaching 91.5% of efficiency at 1200 W m −2 of illumination. This efficiency was stable after reaching the maximum stable efficiency in only 15 minutes. The scaling-up of the process was studied in a SWE of 6.1 cm in diameter using a bigger glass cell in the presence of pure water or simulated seawater (3.5% NaCl), achieving efficiencies of 89.8% and 86.1%, respectively.
Summary
In the present work, porous supports from carbonized agave flower stalk (CAFS) were prepared and tested in solar water evaporation. These supports were characterized by FTIR and UV/Vis spectroscopies, and their morphology and structure were determined by SEM microscopy. The results of these studies showed a wide absorption range in the UV/Vis‐NIR (200‐1100 nm), consisting of structures with micropores and well oriented microchannels whose morphology resembles micro‐packed bed distillation columns. Pure water evaporation efficiency of CAFS was studied as a function of the thickness of the support and its diameter under visible light irradiation at different power density. It was observed that optimal thickness of the support is 4.05 mm with 1.99 kg h−1 m−2 of evaporation rate and 97.5% of efficiency under 1300 W m−2 of illumination, therefore, this support was tested in the simulated seawater evaporation (3.5% NaCl) with multiple evaporation cycles under 1300 W m−2 of light irradiation, achieving 1.91 kg h−1 m−2 of evaporation rate and 93% of efficiency, which demonstrates that this material is comparable to its synthetic counterparts and opens a possible new line of commercial use of agave sub product.
In this study, styrene (St) and methyl methacrylate (MMA) were copolymerized in semicontinuous heterophase using Hitenol-BC10 (HBC10) as polymerizable surfactant and ammonium persulfate as initiator to obtain copolymers of poly(Stco-MMA). The effects of St/MMA weight ratio and surfactant concentration on kinetics, and colloidal properties of latexes were studied. Copolymers and latexes were characterized by scanning electron microscopy, thermogravimetric analysis (TGA), gel permeation chromatography (GPC), Fourier transform infrared (FTIR) spectroscopy, and X-ray diffraction analysis. Fast reaction rates under monomer starved conditions and high conversions (>85%) were observed in all cases, with a weight-average molecular weight in the range of 2.10 Â 10 6 to 0.96 Â 10 6 g mol À1 , decreasing with the HBC10 concentration due to an effect of chain transference to surfactant. Stable latexes with spherical particles with average diameter in the interval of 65-41 nm and Z-potential in the interval of À68.24 to À38.44 mV were obtained. Copolymers were sulfonated using acetyl sulfate as sulfonating agents and subsequently used for filtration membrane fabrication through the phase inversion method. Membranes were tested in simulated seawater filtration (3.5% NaCl) under constant pressure. At a pressure of 20 psia, permeated flux (J) of pure water and salt rejection (R) varied from 13.8 to 20.5 L m À2 h À1 and 37.8%-50.7%, respectively. It was concluded that membrane's performance is dependent on copolymer composition, the crystallinity of copolymers, and the ionic exchange capacity of membranes, being the best membrane composed of 90/10 of St-to-MMA weight ratio and using a monomer-to-surfactant weight ratio of 29.9.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.