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Adsorption of carbon dioxide, methane, and nitrogen on zn(Dcpa) metal-organic framework
Publication . Ribeiro, Rui P. P. L.; Esteves, Isabel A. A. C.; Mota, José P. B.; LAQV@REQUIMTE; DQ - Departamento de Química; MDPI - Multidisciplinary Digital Publishing Institute
Adsorption-based processes using metal-organic frameworks (MOFs) are a promising option for carbon dioxide (CO2 ) capture from flue gases and biogas upgrading to biomethane. Here, the adsorption of CO2, methane (CH4 ), and nitrogen (N2 ) on Zn(dcpa) MOF (dcpa (2,6-dichloro-phenylacetate)) is reported. The characterization of the MOF by powder X-ray diffraction (PXRD), thermogravimetric analysis (TGA), and N2 physisorption at 77 K shows that it is stable up to 650 K, and confirms previous observations suggesting framework flexibility upon exposure to guest molecules. The adsorption equilibrium isotherms of the pure components (CO2, CH4, and N2 ), measured at 273–323 K, and up to 35 bar, are Langmuirian, except for that of CO2 at 273 K, which exhibits a stepwise shape with hysteresis. The latter is accurately interpreted in terms of the osmotic thermodynamic theory, with further refinement by assuming that the free energy difference between the two metastable structures of Zn(dcpa) is a normally distributed variable due to the existence of different crystal sizes and defects in a real sample. The ideal selectivities of the equimolar mixtures of CO2 /N2 and CO2 /CH4 at 1 bar and 303 K are 12.8 and 2.9, respectively, which are large enough for Zn(dcpa) to be usable in pressure swing adsorption.
Calcium alginate beads with entrapped iron oxide magnetic nanoparticles functionalized with methionine—a versatile adsorbent for arsenic removal
Publication . Lilhare, Surbhi; Mathew, Sunitha B.; Singh, Ajaya K.; Carabineiro, Sónia A. C.; LAQV@REQUIMTE; DQ - Departamento de Química; MDPI AG
A novel beads adsorbent, consisting of calcium alginate entrapped on magnetic nanoparti-cles functionalized with methionine (MFMNABs), was developed for effective elimination of arsenic from water. The material was characterized by FT-IR (Fourier Transform Infrared Spectroscopy), SEM (Scanning Electron Microscopic), XRD (X-ray Diffraction) and TEM (Transmission Electron Microscopy). The arsenic removal capacity of the material was studied by altering variables such as pH of the solution, contact time, adsorbent dose and adsorbate concentration. The maximal removal of As(III) was 99.56% under optimal conditions with an equilibrium time of 110 min and pH 7.0–7.5. The adsorption followed a second order kinetics and data best fitted the Langmuir isotherm with a correlation coefficient of R2 = 0.9890 and adsorption capacity (qm ) of 6.6533 mg/g. The thermodynamic study showed entropy change (∆S) and enthalpy change (∆H) to be 34.32 J mol−1 K and 5.25 kJ mol−1, respectively. This study proved that it was feasible to treat an As(III) solution with MFMNABs. The synthesized adsorbent was cost-effective, environmentally friendly and versatile, compared to other adsorbents. The adsorption study was carried by low cost spectrophotometric method using N-bromosuccinimide and rhodamine-B developed in our laboratory.
Bio‐based sensors for smart food packaging—current applications and future trends
Publication . Rodrigues, Carolina; Souza, Victor Gomes Lauriano; Coelhoso, Isabel; Fernando, Ana Luísa; MEtRICS - Centro de Engenharia Mecânica e Sustentabilidade de Recursos; DCTB - Departamento de Ciências e Tecnologia da Biomassa (ex-GDEH); LAQV@REQUIMTE; DQ - Departamento de Química; MDPI - Multidisciplinary Digital Publishing Institute
Intelligent food packaging is emerging as a novel technology, capable of monitoring the quality and safety of food during its shelf‐life time. This technology makes use of indicators and sensors that are applied in the packaging and that detect changes in physiological variations of the foodstuffs (due to microbial and chemical degradation). These indicators usually provide information, e.g., on the degree of freshness of the product packed, through a color change, which is easily identified, either by the food distributor and the consumer. However, most of the indicators that are currently used are non‐renewable and non‐biodegradable synthetic materials. Because there is an imperative need to improve food packaging sustainability, choice of sensors should also reflect this requirement. Therefore, this work aims to revise the latest information on bio‐based sensors, based on compounds obtained from natural extracts, that can, in association with biopolymers, act as intelligent or smart food packaging. Its application into several perishable foods is summarized. It is clear that bioactive extracts, e.g., anthocyanins, obtained from a variety of sources, including by‐products of the food industry, present a substantial potential to act as bio‐sensors. Yet, there are still some limitations that need to be surpassed before this technology reaches a mature commercial stage.
The Solubility of Gases in Ionic Liquids:
Publication . Carrera, Gonçalo V. S. M.; Inês, João; Bernardes, Carlos E. S.; Klimenko, Kyrylo; Shimizu, Karina; Lopes, José N. Canongia; LAQV@REQUIMTE; DQ - Departamento de Química; Wiley
This work comprises the study of solubilities of gases in ionicliquids (ILs) using a chemoinformatic approach. It is based onthe codification, of the atomic inter-component interactions,cation/gas and anion/gas, which are used to obtain a pattern ofactivation in a Kohonen Neural Network (MOLMAP descriptors). A robust predictive model has been obtained with the Random Forest algorithm and used the maximum proximity as aconfidence measure of a given chemical system compared to the training set. The encoding method has been validated with molecular dynamics. This encoding approach is a valuable estimator of attractive/repulsive interactions of a generical chemical system IL+gas. This method has been used as a fast/visual form of identification of the reasons behind the differences observed between the solubility of CO2and O2in 1-butyl-3-methylimidazolium hexafluorophosphate (BMIM PF6) at identical temperature and pressure (TP) conditions, The effect of variable cation and anion effect has been evaluated.
Effect of the metal deposition order on structural, electronic and catalytic properties of tio2-supported bimetallic au-ag catalysts in 1-octanol selective oxidation
Publication . Kotolevich, Yulia; Pakrieva, Ekaterina; Kolobova, Ekaterina; Farías, Mario H.; Bogdanchikova, Nina; Cortés Corberán, Vicente; Pichugina, Daria; Nikitina, Nadezhda; Carabineiro, Sónia A. C.; Pestryakov, Alexey; LAQV@REQUIMTE; DQ - Departamento de Química; MDPI - Multidisciplinary Digital Publishing Institute
Au and Ag were deposited on TiO2 modified with Ce, La, Fe or Mg in order to obtain bimetallic catalysts to be used for liquid-phase oxidation of 1-octanol. The effects of the deposition order of gold and silver, and the nature of the support modifying additives and redox pretreatments on the catalytic properties of the bimetallic Au-Ag catalysts were studied. Catalysts were characterized by low-temperature nitrogen adsorption–desorption, energy dispersive spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, high-resolution transmission electron microscopy and ultraviolet-visible diffuse reflectance spectroscopy. It was found that pretreatments with hydrogen and oxygen at 300◦C significantly decreased the activity of AuAg catalysts (silver was deposited first) and had little effect on the catalytic properties of AgAu samples (gold was deposited first). The density functional theory method demonstrated that the adsorption energy of 1-octanol increased for all positively charged AuxAgyq (x + y = 10, with a charge of q = 0 or +1) clusters compared with the neutral counterparts. Lanthanum oxide was a very effective promoter for both monometallic and bimetallic gold and silver catalysts in the studied process.
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Fundação para a Ciência e a Tecnologia
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6817 - DCRRNI ID
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157968