Bianchi, C, Ferreira LM, Loureiro J, Rodrigues A, Duarte P, Baptista AC, Ferreira IM.
2016.
Vanadium Pentoxide Alloyed with Graphite for Thin-Film Thermal Sensors, Mar. Journal of Electronic Materials. 45:1987–1991., Number 3
AbstractThe thermoelectric (TE) properties of vanadium pentoxide (V2O5) alloyed with graphite (G) were studied as a function of its incorporation percentage. Variable weight percentages of graphite powder (0–50{%}) were added to V2O5 powder and their mixtures were evaporated by a thermal evaporation technique to form thin films with a thickness in the range of 30–80 nm. In the infrared wavelength region, the transmittance of the obtained films increased as the G percentage was increased, while in the visible range, it decreased with G up to 10{%}. The TE properties were improved when G was in the range of 10–30{%}, while it decreased for the other percentages: Seebeck coefficient (S) changed from 0.6 mV/K to 0.9 mV/K and was zero with a G of 50{%}; the electrical conductivity varied slightly from 5 ($Ømega$m)−1 to 0.7 ($Ømega$m)−1 while the mobility improved from 0.07 cm2/V s to 1.5 cm2/V s and the respective carrier concentration was reduced, from 1 × 1018 cm−3 to 4 × 1016 cm−3. These films were applied as temperature sensors evaluating the thermovoltage as a function of thermal gradient between two electrodes, in which one was maintained at room temperature.
Silva, CAC, Figueiredo FCA, Rodrigues R, Sairre MI, Gonçalves M, Matos I, Fonseca IM, Mandelli D, Carvalho WA.
2016.
Enhancing the biodiesel manufacturing process by use of glycerin to produce hyacinth fragrance, Jun. Clean Technologies and Environmental Policy. 18:1551–1563., Number 5
AbstractOxidized and sulfonated-activated carbons (AC) were tested in the catalytic conversion of glycerol by acetalization reactions. The solids were treated with concentrated nitric acid and/or fuming sulfuric acid (AC, AC-N, AC-S, and AC-NS). The presence of sulfur and an increase in the acidity of the solids demonstrate the suitability of the oxidation as well as the sulfonation process, especially in the sample treated with concentrated nitric acid and fuming sulfuric acid (AC-NS). The best catalyst for the reaction of glycerol acetalization with phenylacetaldehyde was AC-NS, with a phenylacetaldehyde conversion of 95 {%} after 90 min at 383 K and selectivity of 88 and 12 {%}, respectively, to dioxolane and dioxane. These products can be used as hyacinth fragrance flavoring compounds. Furthermore, a contribution of homogeneous catalysis in these systems was not identified. Thus, we identified a possibility of glycerol conversion, a biodiesel by-product, into value-added products by suitable catalysts produced from activated carbons.
Bernardo, M, Rodrigues S, Lapa N, Matos I, Lemos F, Batista MKS, Carvalho AP, Fonseca I.
2016.
High efficacy on diclofenac removal by activated carbon produced from potato peel waste, Aug. International Journal of Environmental Science and Technology. 13:1989–2000., Number 8
AbstractIn the present study, a novel porous carbon obtained by K2CO3 activation of potato peel waste under optimized conditions was applied for the first time as liquid-phase adsorbent of sodium diclofenac in parallel with a commercial activated carbon. The biomass-activated carbon presented an apparent surface area of 866 m2 g−1 and well-developed microporous structure with a large amount of ultramicropores. The obtained carbon presented leaching and ecotoxicological properties compatible with its safe application to aqueous medium. Kinetic data of laboratory-made and commercial sample were best fitted by the pseudo-second-order model. The commercial carbon presented higher uptake of diclofenac, but the biomass carbon presented the higher adsorption rate which was associated with its higher hydrophilic nature which favoured external mass transfer. Both adsorbents presented adsorption isotherms that were best fitted by Langmuir model. The biomass carbon and the commercial carbon presented adsorption monolayer capacities of 69 and 146 mg g−1, and Langmuir constants of 0.38 and 1.02 L mg−1, respectively. The better performance of the commercial sample was related to its slightly higher micropore volume, but the most remarkable effect was the competition of water molecules in the biomass carbon.
Cordeiro, T, Santos AFM, Nunes G, Cunha G, Sotomayor JC, Fonseca IM, Florence Danède, Dias CJ, Cardoso MM, Correia NT, Viciosa TM, Dionísio M.
2016.
Accessing the Physical State and Molecular Mobility of Naproxen Confined to Nanoporous Silica Matrixes. The Journal of Physical Chemistry C. 120:14390-14401., Number 26
AbstractThe pharmaceutical drug naproxen was loaded in three different silica hosts with pore diameters of 2.4 (MCM), 3.2 (MCM), and 5.9 nm (SBA), respectively: napMCM\_2.4 nm, napMCM\_3.2 nm, and napSBA\_5.9 nm. To access the guest physical state in the prepared composites, differential scanning calorimetry (DSC), X-ray diffraction (XRD), and attenuated total reflectance Fourier transform infrared spectroscopy were used. The different techniques provided complementary information on a molecular population that was revealed to be distributed among different environments, namely the pore core, the inner pore wall, and the outer surface. It was found that naproxen is semicrystalline in the higher pore size matrix being able to crystallize inside pores; after melting it undergoes full amorphization. In the case of the lower pore size matrix, naproxen crystallizes outside pores due to an excess of filling while most of the remaining fraction is incorporated inside the pores as amorphous. Crystallinity in these two composites was observed by the emergence of the Bragg peaks in the XRD analysis, whereas for napMCM\_3.2 nm only the amorphous halo was detected. The latter only exhibits the step due to the glass transition by DSC remaining stable as amorphous at least for 12 months. The glass transition in the three composites is abnormally broad, shifting to higher temperatures as the pore size decreases, coherent with the slowing down of molecular mobility as probed by dielectric relaxation spectroscopy. For napSBA\_5.9 nm the dielectric response was deconvoluted in two processes: a hindered surface (S-) process due to molecules interacting with the inner pore wall and a faster α-relaxation associated with the dynamic glass transition due to molecules relaxing in the pore core, which seems a manifestation of true confinement effects. The drug incorporation inside a nanoporous matrix, mainly in 3.2 nm pores, was revealed to be a suitable strategy to stabilize the highly crystallizable drug naproxen in the amorphous/supercooled state and to control its release from the silica matrix, allowing full delivery after 90 min in basic media.
Batista, MKS, Mestre AS, Matos I, Fonseca IM, Carvalho AP.
2016.
Biodiesel production waste as promising biomass precursor of reusable activated carbons for caffeine removal. RSC Adv.. 6:45419-45427.: The Royal Society of Chemistry
AbstractBiodiesel production generates low particle size rapeseed waste (recovered from warehouse air filtration systems) that was herein explored as promising biomass precursor of chemically activated carbons. The influence of several experimental parameters on the porosity development was investigated. No benefit was observed when solution impregnation was made nor a significant dependence of the biomass : K2CO3 ratio was observed and{,} as expected{,} high porosity development was obtained only for treatments at 700 [degree]C. Microporous materials with apparent surface area around 1000 m2 g-1 were obtained comparing favorably with literature data regarding activated carbons from rapeseed processing by-products. A selected lab-made sample and two commercial carbons were tested as adsorbents of caffeine from aqueous solution. Although commercial materials present a quicker adsorption rate{,} regarding adsorption capacity the lab-made sample reaches the same value attained by a benchmark material. The regeneration tests made over the rapeseed derived carbon through heat treatments at 600 [degree]C for 1 hour under N2 flow proved that at least two exhaustion-regeneration cycles can be made since the material retains a caffeine adsorption capacity similar to that of the fresh carbon. Therefore{,} a waste management problem of biodiesel industry - rapeseed residue - can be transformed in a valuable material with promising properties for environmental remediation processes.
do Fraga, AC, Quitete CPB, Ximenes VL, Sousa-Aguiar EF, Fonseca IM, Rego AMB.
2016.
Biomass derived solid acids as effective hydrolysis catalysts. Journal of Molecular Catalysis A: Chemical. 422:248-257.
AbstractThe conversion of cellulose into products with higher added value often includes a depolymerization step to obtain glucose, its fundamental unity. The depolymerization reaction is carried out via hydrolysis of the β-1,4-glycosidic bond. The search for a solid acid catalyst capable of breaking these bonds is gaining increasing prominence in the literature. In this regard, sulfonated carbons have shown promising results. This work evaluated the use of a residue from the extraction of palm oil as raw material for the production of sulfonated carbons. The raw material was carbonized and sulfonated. The obtained solid acids were tested in the hydrolysis of cellobiose, a dimer of glucose often used as a model compound for cellulose. The hydrolysis reaction is the first step in converting renewable carbon sources into chemical products and biofuels. Some aspects were investigated, as the effect of carbonization temperature on the concentration of sulfonic groups, the results showing that the content thereof reached a maximum value at 300°C. Regarding the hydrolysis of cellobiose, it has been identified that there is a relationship between the concentration of sulfonic acid groups and the activity of these catalysts. However, there is a drop in the turnover number as the amount of sulfonic acid sites increases. This was related to a preferred position sulfonation mechanism. Furthermore, sulfonated carbons showed higher activity than the commercial acid resins, indicating that this material may be a good option for the generation of solid acid catalysts.
Mestre, AS, Nabiço A, Figueiredo PL, Pinto ML, Santos SMCS, Fonseca IM.
2016.
Enhanced clofibric acid removal by activated carbons: Water hardness as a key parameter. Chemical Engineering Journal. 286:538-548.
AbstractClofibric acid is the metabolite and active principle of blood lipid regulators, it represents the class of acidic pharmaceuticals, and is one of the most persistent drug residues detected in the aquatic environment worldwide. This interdisciplinary work evaluates the effect of solution pH and water hardness in clofibric acid adsorption onto commercial activated carbons. Kinetic and equilibrium assays revealed that the highest clofibric acid removal efficiencies (>70%) were attained at pH 3, and that at pH 8 water hardness degree plays a fundamental role in the adsorption process. In hard water at pH 8 the removal efficiency values increased by 22 or 46% points depending on the carbon sample. Adsorbents’ textural properties also affect the adsorption process since for the microporous sample (CP) the increase of water hardness has a great influence in kinetic and equilibrium data, while for the micro+mesoporous carbon (VP) the variation of the water hardness promoted less significant changes. At pH 3 the increase of water hardness leads to changes in the adsorption mechanism of clofibric acid onto CP carbon signaled by a transition from an S-type to an L-type curve. At pH 8 the change from deionized water to hard water doubles the maximum adsorption capacity of sample CP (101.7mgg−1 vs 211.9mgg−1, respectively). The adsorption enhancement, with water hardness under alkaline conditions, was reasoned in terms of calcium complexation with clofibrate anion exposed by molecular modeling and conductivity studies. Ca2+ complexation by other acidic organic compounds may also occur, and should be considered, since it can play a fundamental role in improved design of water treatment processes employing activated carbons.
Lyubchik, S, Lygina E, Lyubchyk A, Lyubchik S, Loureiro JM, Fonseca IM, Ribeiro AB, Pinto MM, Figueiredo AMSá.
2016.
The Kinetic Parameters Evaluation for the Adsorption Processes at ``Liquid–Solid'' Interface. Electrokinetics Across Disciplines and Continents: New Strategies for Sustainable Development. (
Ribeiro, Alexandra B., Mateus, Eduardo P., Couto, Nazaré, Eds.).:81–109., Cham: Springer International Publishing
AbstractThe kinetic parameters of the adsorption process at ``liquid–solid'' interface have been evaluated through the sets of time-based experiments of the Cr(III) adsorption under varying temperature, initial metal concentration, and carbon loading for two sets of the commercially available activated carbons and their post-oxidized forms with different texture and surface functionality.