Browsing by Author "Correia, Jorge"
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- Food waste biorefinery : stability of an acidogenic fermentation system with carbon dioxide sequestration and electricity generationPublication . Ortigueira, Joana; Pacheco, Marta; Trancoso, Maria Ascensão; Farrancha, Pedro; Correia, Jorge; Silva, Carla M.; Moura, PatríciaABSTRACT: The present study focused on the integration of the non-sterile conversion of food waste (FW) into hydrogen (H2) through dark fermentation with the subsequent electricity generation in a proton-exchange membrane fuel cell (PEMFC), and the assessment of the global warming potential (GWP) of the process. The acidogenic conversion of FW performed in continuous operation for 16 days produced 45.6 ± 0.1 L H2 at an average H2 productivity of 6.1 ± 1.3 L L−1 d−1. Butyric and acetic acid were simultaneously produced at average concentrations of 3.6 ± 0.5 and 1.6 ± 0.3 g L −1, respectively. The carbon dioxide (CO2) from biogas product was sequestered by reaction with sodium hydroxide and the resulting H2-rich stream was fed to a PEMFC, producing 1.7 Wh L−1 H2. The process scale-up was simulated based on the bench-scale conversion yields and was used to assess the GWP. Two of the developed scenarios, which considered the reuse of the fermentation sludge as nitrogen source in the acidogenic fermentation, diminished the GWP emissions by 63.8% and 64.3% when compared to the default condition. In the best-case scenario, an annual average of 0.18 t of CO2 per t of FW separately collected was generated.
- When gold stops glittering: corrosion mechanisms of René Lalique's Art Nouveau jewelleryPublication . Tissot, Isabel; Correia, Jorge; Monteiro, Olinda C.; Barreiros, M. Alexandra; Guerra, M. F.ABSTRACT: Art Nouveau jewellery created by René Lalique is presently corroded. To identify the corrosion processes, Au-Ag-Cu alloys with compositions comparable to those used in the René Lalique’s jewellery were fabricated to be exposed to sulphide-containing environments. Using SEM-EDS, XRD, UV-Vis spectroscopy and ellipsometry, it was for the first time demon-strated that at the surface of tarnished Au alloys forms a corrosion film with a layer-by-layer structure. Considering the complex refractive indices of bulk Cu and Ag oxides and sulphides, a two-step corrosion mechanism was proposed. The formation of Cu-based compounds during the early corrosion stages is followed by the formation of Ag-based compounds. The thinness of the formed film, shown for one of the gold alloys to be of 80 nm, is due to a corrosion kinetics controlled by the presence of Au and by the formation of an Au-S self-assembled monolayer. The corrosion mechanism of gold alloys raises a new conservation challenge concerning the removal of nanometric layers.