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The solvent extraction performance of N,N’-dimethyl-N,N’-dibutylmalonamide towa...
Paiva, A. P.; Carvalho, G. I.; Costa, M. Clara; Costa, Ana M. Rosa da; Nogueira, C. A.The solvent extraction performance of N,N’-dimethyl-N,N’-dibutylmalonamide (DMDBMA) in 1,2-dichloroethane (1,2-DCE) towards platinum(IV) and palladium(II) in hydrochloric acid media was systematically evaluated. Pt(IV) extraction (%E) increases with the HCl concentration in the aqueous phases, being always higher than 72%, whereas Pd(II) extraction decreases from 65% at 1 M HCl to 22% at 8 M HCl. Several stripp...
Recovery of platinum and palladium from chloride solutions by a thiodiglycolami...
Paiva, A. P.; Carvalho, G. I.; Costa, M. Clara; Costa, Ana M. Rosa da; Nogueira, C. A.The liquid-liquid extraction of platinum(IV) and palladium(II) from hydrochloric acid media was carried out using N,N’-dimethyl-N,N’-dicyclohexylthiodiglycolamide (DMDCHTDGA) in 1,2-dichloroethane (1,2-DCE). Pt(IV) is efficiently extracted from 5 M HCl onwards (%E = 97%), whereas Pd(II) is quantitatively recovered from 1 to 8 M HCl solutions. Both Pt(IV) and Pd(II) can be successfully stripped from the loaded o...
Recovery of precious metals from exhausted automotive catalysts by leaching and...
Nogueira, C. A.; Carvalho, G. I.; Costa, Maria Clara; Costa, Ana M. Rosa da; Paiva, A. P.Platinum group metals (PGM’s) are precious and rare metals used in many existing and emerging technologies such as electronics, catalysts, energy and medical appliances, among others. PGM’s applications and demand are growing rapidly, and their supply is short and considered critical. Recycling of residues containing PGM’s is therefore mandatory, in order to allow the continuity of supplying. The main market sh...
Liquid-Liquid Extraction of Platinum from Chloride Media by N,N'-Dimethyl-N,N'-...
Costa, M. Clara; Assunção, Ana; Costa, Ana M. Rosa da; Nogueira, C. A.; Paiva, A. P.Liquid-liquid extraction of platinum(IV) from chloride media was carried out using N,N'-dimethyl-N,N'-dicyclohexyltetradecylmalonamide (DMDCHTDMA) in 1,2-dichloroethane. Platinum can be effectively extracted by DMDCHTDMA without addition of tin(II) chloride, since extraction percentages (%E) of 88% and 99% have been achieved from 6 M and 8 M HCl, respectively. Moreover, platinum can be successfully stripped thr...
Pullulan-based nanoparticles as carriers for transmucosal protein delivery
Dionísio, Marita; Cordeiro, Clara; Remuñán-López, Carmen; Seijo, Begoña; Costa, Ana M. Rosa da; Grenha, AnaPolymeric nanoparticles have revealed very effective in transmucosal delivery of proteins. Polysaccharides are among the most used materials for the production of these carriers, owing to their structural flexibility and propensity to evidence biocompatibility and biodegradability. In parallel, there is a preference for the use of mild methods for their production, in order to prevent protein degradation, ensur...
Chitosan/carrageenan nanoparticles: effect of cross-linking with tripolyphosphate
Rodrigues, Susana; Costa, Ana M. Rosa da; Grenha, AnaChitosan/carrageenan/tripolyphosphate nanoparticles were prepared by polyelectrolyte complexation/ionic gelation, the latter compound acting as cross-linker. The incorporation of the three components in the nanoparticle matrix was assessed by analytical techniques (FTIR, XPS and TOF-SIMS). Using chitosan/carrageenan nanoparticles as control, the effect of the cross-linker in the particles properties was studie...
Equilibrium constants and protonation site for N-methylbenzenesulfonamides
Moreira, José A.; Costa, Ana M. Rosa da; García-Río, Luís; Pessêgo, MárciaThe protonation equilibria of four substituted N-methylbenzenesulfonamides, X-MBS: X = 4-MeO (3a), 4-Me (3b), 4-Cl (3c) and 4-NO2 (3d), in aqueous sulfuric acid were studied at 25 °C by UV–vis spectroscopy. As expected, the values for the acidity constants are highly dependent on the electron-donor character of the substituent (the pKBH+ values are −3.5 ± 0.2, −4.2 ± 0.2, −5.2 ± 0.3 and −6.0 ± 0.3 for 3a, 3b, 3...
Importance of phenols structure on their activity as antinitrosating agents: a ...
Moreira, José A.; Pessêgo, Márcia; Costa, Ana M. Rosa daObjective : Nitrosative deamination of DNA bases induced by reaction with reactive nitrogen species (RNS) has been pointed out as a probable cause of mutagenesis. (Poly)phenols, present in many food items from the Mediterranean diet, are believed to possess antinitrosating properties due to their RNS scavenging ability, which seems to be related to their structure. It has been suggested that phenolic compounds ...
Planar non-volatile memory based on metal nanoparticles
Kiazadeh, A.; Gomes, Henrique L.; Costa, Ana M. Rosa da; Rocha, P. R. F.; Chen, Q.; Moreira, José A.; De Leeuw, Dago M.; Meskers, S. C. J.Resistive switching properties of silver nanoparticles hosted in an insulating polymer matrix (poly(N-vinyl-2-pyrrolidone) are reported. Planar devices structures using interdigitated gold electrodes were fabricated. These devices have on/off resistance ratio as high as 103 , retention times reaching to months and good endurance cycles. Temperature-dependent measurements show that the charge transport is weakly...
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