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Research Project
Associated Laboratory for Green Chemistry - Clean Technologies and Processes
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Publications
Study of the degradation of Nafion modified membranes
Publication . Teixeira, Fatima; Teixeira, António P. S.; Rangel, C. M.
ABSTRACT: The development of new proton exchange membranes for PEM technology in fuel cells and electrolysers with increased durability is paramount to system´s lifetime and scalability. In this work, new modified Nafion membranes are proposed with increased resilience to chemical degradation by H2O2 /Fe2+, mimicking ex-situ radical attack to membrane structure.
Valorisation of spent tire rubber as carbon adsorbents for Pb(II) and W(VI) in the framework of a Circular Economy
Publication . Bernardo, Maria; Lapa, Nuno; Pinto, Filomena; Nogueira, Miguel; Matos, Inês; Ventura, Márcia; Ferraria, Ana Maria; Rego, Ana Maria Botelho do; Fonseca, Isabel Maria
ABSTRACT: Spent tire rubber-derived chars and their corresponding H3PO4 and CO2-activated chars were used as adsorbents in the recovery of Pb(II) ion and (W(VI)) oxyanion from synthetic solutions. The developed chars (both raw and activated) were thoroughly characterized to have insight about their textural and surface chemistry properties. H3PO4-activated chars presented lower surface areas than the raw chars and an acidic surface chemistry which affected the performance of these samples as they showed the lowest removals of the metallic ions. On the other hand, CO2-activated chars presented increased surface areas and increased mineral content compared to the raw chars, having presented higher uptake capacities for both Pb(II) (103-116 mg/g) and W(VI) (27-31 mg/g) ions. Cation exchange with Ca, Mg and Zn ions was appointed as a mechanism for Pb removal, as well as surface precipitation in the form of hydrocerussite (Pb-3(CO3)(2)(OH)(2)). W(VI) adsorption might have been ruled by strong electrostatic attractions between the negatively charged tungstate species and the highly positively charged carbons' surface.The results shown in this work allow concluding that the valorisation of spent tire rubber through pyrolysis and the subsequent activation of the obtained chars is an alternative and a feasible option to generate adsorbent materials with a high uptake capacity of critical metallic elements.
Chemical stability of new nafion membranes doped with bisphosphonic acids under Fenton oxidative conditions
Publication . Teixeira, Fatima; Teixeira, António P. S.; Rangel, C. M.
ABSTRACT: The development of new proton exchange membranes for PEM technology in fuel cells and electrolysers with increased durability is paramount to system's lifetime and scalability. In this work, new modified Nafion membranes doped with bisphosphonic acids are proposed with increased resilience to chemical degradation by H2O2/Fe2+, mimicking ex-situ radical attack to membrane structure. Relevant properties were evaluated throughout Fenton's test using fluoride ion release and gravimetry determinations, and by ATR-FTIR spectros-copy and SEM before and after the chemical degradation. The new membranes showed a very good chemical stability after oxidative degradation under Fenton's test conditions at 80 degrees C, with more durability than Nafion 115 commercial membrane. After chemical degradation, the proton conduction of the membranes was assessed through EIS which reveals a decrease in the proton conductivity of all membranes, with the new modified membranes showing a smaller decrease of their proton conduction properties than Nafion 115 membrane. Fluoride ion release, weight loss measurements and ATR-FTIR spectros-copy data analysis suggest degradation of the side chain of the ionomer.
New triazine-phosphonate dopants for proton exchange membranes (PEM) [Poster]
Publication . Teixeira, Fatima; Teixeira, António P. S.; Rangel, C. M.
ABSTRACT: The establishment of a new paradigm for energy is underway demanding new energy sources for the increasing needs of society with none or lower environmental impact. To reach the ambitious and well defined targets for decarbonized energy systems it is needed new clean technologies. Some of them rely
on well-established or emerging electrochemical devices, including batteries, fuel cells and CO2 and water
electrolysers, whose applications and performances depend on key components such as their separators/ion-exchange membranes.1,2 The most studied and already commercialized membranes go by the brand name of Nafion, which showed great chemical stability, but their high proton conduction depends on their water content, markedly limiting their operating temperature range. Our previous studies have demonstrated that the incorporation of aryl or heterocyclic phosphonic acid dopants into Nafion, by casting, results in an enhancement of the proton conductivity1-4 and stability5 of the Nafion doped membranes.
Innovative approach in sustainable agriculture: Harnessing microalgae potential via subcritical water extraction
Publication . Ferreira, Alice; Vladic, Jelena; Corrêa, D. O.; Butzke, Valéria Louzada Leal; Martins, Pedro L.; Ribeiro, Belina; Santos, Cláudia Marques dos; Acién, F. Gabriel; Gouveia, Luisa
ABSTRACT: Microalgae can contribute to sustainable agriculture and wastewater treatment. This study investigated Tetradesmus obliquus, grown in piggery wastewater (To-PWW), as a biostimulant/biofertilizer compared to biomass grown in synthetic medium (To-B). Subcritical water extraction was tested for disruption/hydrolysis of wet biomass, at three temperatures (120, 170, and 220 °C) and two biomass loads (1:10 and 1:80 (g dry biomass/mL water)). Extracts were evaluated for germination, and root formation/expansion. Residues were quantified for nutrient composition to assess their biofertilizer potential and tested for their affinity to oil compounds for bioremediation. The best germination was achieved by To-B extracts at 170 °C (1:10: 148 % at 0.2 g/L, 1:80: 145 % at 0.5 g/L). Only To-PWW extracts at 0.2 g/L had a significant germination effect (120 °C: 120–123 % for both loads; 170 °C: 115 % for 1:80). To-PWW extract at 120 °C and 1:10 significantly affected cucumber and mung bean root formation (224 and 268 %, respectively). Most extracts significantly enhanced root expansion, with all To-B extracts at 1:10 showing the best results (139–181 %). The residues contained essential nutrients (NPK), indicating their biofertilizer potential, helping decrease synthetic fertilizers demands. To-B residues had high affinity to toluene and diesel but lower to used cooking and car oils. To-PWW showed very low affinity to all oil compounds. Finally, all residues were only able to form stable emulsions with the used car oil. This study fully exploits the use of microalgal biomass in sustainable agriculture, producing biostimulant extracts, and residues for biofertilizer and bioremediation, from a low-cost wastewater source.
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Funding agency
Fundação para a Ciência e a Tecnologia
Funding programme
6817 - DCRRNI ID
Funding Award Number
UIDP/50006/2020