New silica based adsorbent material from rice straw and its in-flow application to nitrate reduction in waters: Process sustainability and scale-up possibilities

[EN] This paper shows a particular example to move to a sustainable circular economical process from valorization of rice straw ashes by developing a green synthesis for obtaining a useful sub-product. This strategy can palliate negative effects of the agriculture waste practices on the environment and also the obtained silica reduced nitrate content in waters. It is demonstrated that the silica synthesis developed at lab was scalable more than a hundred times with good results. Adsorption studies of nitrate in standards and real well waters at lab scale and scaling-up provided similar results. Adsorption values near to 15 mg/g for nitrate standards and 8.5 mg/g for well water were obtained until achieving the initial nitrate concentration. Experimental breakthrough curves fitted to Thomas model, which gave similar results for adsorption capacities. The adsorption capacity was checked with that obtained by a commercial resin, providing improved results. The method at large scale was compared with industrial traditional methods and green adsorbents.The authors are grateful to EU (EASME LIFE and CIP ECO-Innovation) LIBERNITRATE. LIFE 16 ENV/ES/000419; EU FEDER and the Gobierno de Espana MCIU-AEI (CTQ2017-90082-P) and the Generalitat Valenciana (PROMETEO 2020/078) and EU FEDER-Generalitat Valenciana (ID-FEDER/2018/049) for the financial support received. H. R. Robles-Jimarez expresses his grateful to EU-LIBERNITRATE. L. Sanjuan-Navarro expresses his gratitude for the FPU-grant (MCIU-AEI) .Robles-Jimarez, H.; Sanjuan-Navarro, L.; Jornet-Martínez, N.; Primaz, C.; Teruel-Juanes, R.; Molins-Legua, C.; Ribes-Greus, A.... (2022). New silica based adsorbent material from rice straw and its in-flow application to nitrate reduction in waters: Process sustainability and scale-up possibilities. Science of The Total Environment. 805:1-12. https://doi.org/10.1016/j.scitotenv.2021.15031711280

Triblock SEBS/DVB crosslinked and sulfonated membranes: Fuel cell performance and conductivity

A set of styrene-ethylene-butylene-styrene triblock copolymer (SEBS) membranes with 10 or 25 wt% divinyl-benzene (DVB) as a crosslinking agent were prepared and validated. Physicochemical characterization revealed suitable hydrolytic and thermal stability of photo-crosslinked membranes containing 25 wt% DVB and post-sulfonated. These compositions were evaluated in H/O single cells, and electrical and proton conductivities were furtherly assessed. The membranes with the milder post-sulfonation showed greater proton conductivity than those with excessive sulfonation. In terms of electrical conductivity, a universal power law was applied, and the values obtained were low enough for being used as polyelectrolytes. At the analyzed temperatures, the charge transport process follows a long-range pathway or vehicular model. Finally, fuel cell performance revealed the best behavior for the membrane with 25 wt% DVB, photo-crosslinked during 30 min and mild sulfonated, with a promising power density of 526 mW·cm. Overall, the results obtained highlight the promising fuel cell performance of these cost-effective triblock copolymer-based membranes and indicate that higher sulfonation does not necessarily imply better power density.Ministerio de Economía, Industria y Competitividad, Gobierno de España, Grant/Award Number: ENE2017-86711-C3-1-

Sulfonated poly(vinyl alcohol)/graphene oxide composite membranes for proton exchange membrane fuel cells

Different crosslinked composite membranes of Poly(vinyl Alcohol) PVA with sulfosuccinic acid SSA as crosslinking agent and graphene oxide GO were prepared and characterized as a function of the sulfonating degree and GO percentage of each component. The chemical structure of membranes was confirmed by Fourier transform infrared spectroscopy FTIR. The good dispersion of GO into the polymer matrix was verified by scanning transmission microscopy SEM. The proton conductivity of the membranes in fully hydrated state was also investigated by electrochemical impedance spectroscopy EIS. To measure the potential use of PVA membranes as electrolyte were tested in a single proton exchange membrane fuel cell PEMFC. The results reveal that the addition of graphene oxide GO improves the thermal and mechanical stability of the composite membranes. The proton conductivity of the prepared membranes strongly increases by combination of matrix's sulfonating and introduction of GO nanoparticles. Thus, the sulfonating of the polymer matrix in the 30sPVA/SSA/GO membrane increases the proton conductivity a 42% and a 67% of maximum power density respect its homologue 30PVA/SSA membrane. In addition, 30sPVA/SSA/sGO membrane shows the lowest values of proton conductivity and maximum power density, which is consistent with the obtained water uptake values and confirms the improvement of barrier property of these composite membranes