Browsing by Author "Aliyeva, Mehriban"
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- Electrolyte effects on the Amino acid solubility in water: solubilities of Glycine, l-Leucine, l-Phenylalanine, and l-Aspartic acid in salt solutions of (Na+, K+, NH4+)/(Cl–, NO3–)Publication . Aliyeva, Mehriban; Brandão, Paula; Gomes, José R.B.; Coutinho, João A.P.; Ferreira, Olga; Pinho, SimãoThe solubilities of glycine, L-leucine, L-phenylalanine, and L-aspartic acid in aqueous solutions of the salts composed by combining Na+, K+, and NH4 + cations and Cl− and NO3 − anions were measured up to 2.0 salt molality at 298.2 K by the analytical gravimetric method. Using these data along with a review of literature information, encompassing all amino acids for which solubility is available in the studied aqueous electrolyte solutions, allowed us to interpret the effect of the functional groups of amino acids on their solubility. The four amino acids studied here showed higher solubility in aqueous solutions of salts with the nitrate anion. Except for L-aspartic acid with a polar side chain, amino acids with apolar side chains presented the highest salting-in effect in aqueous salt solutions with NH4 +. The cations Na+ and K+ did not seem to establish relevant interactions with the amino acids and had little impact on their aqueous solubility.
- Octane improvement of gasoline with porous solidsPublication . Aliyeva, Mehriban; Silva, José A.C.In this work is performed the study of the hexane isomers separation with MOFs in order to improve the octane number of gasoline. The studies were performed with MOFs: MIL-125-Amine, MIL-53(Fe)-Cl, MIL-53(Fe)-Br and Fe-TazBz(DMF). It was observed that higher loadings were obtained for high pressure and low temperature. With MOFs like MIL-53(Fe)-Cl and MIL-53(Fe)-Br the components weren’t separated. In MIL-125-Amine hexane isomers were separated according to their boiling point, but the selectivity was small. The best result was obtained with MOF Fe-TazBz(DMF), because of the higher affinity of n-hex with this MOF, the separation from the other isomers was easier.
- Salt effects on the solubility of aromatic and dicarboxylic amino acids in waterPublication . Aliyeva, Mehriban; Brandão, Paula; Gomes, José R.B.; Coutinho, João A.P.; Held, Christoph; Ferreira, Olga; Pinho, SimãoThe salt effect on the solubility of the amino acids L-aspartic acid, L-glutamic acid, L-tryptophan, and L-tyrosine, seldomly found in the literature, was studied at 298.2 K, in aqueous solutions of KCl and (NH4)2SO4, for salt concentrations up to 2.0 mol⋅kg -1. In this concentration range, both salts are salting-in agents for glutamic acid and aspartic acid, with a stronger effect induced by (NH4)2SO4. Regarding the two aromatic amino acids, a slight increase in the solubility was obtained at low salt concentrations, followed by a stronger salting-out effect, more pronounced by (NH4)2SO4 than by KCl. The relative solubility data obtained in this work were compared to literature data for other amino acids in the same electrolyte solutions to establish a relative solubility ranking connected to their structure. Finally, the solubility data were modeled using the electrolyte Perturbed-Chain Statistical Association Theory (ePC-SAFT). The modeling requires parameters for the amino acids and ions as well as melting properties of the amino acids. All these parameters and properties were obtained from previous works. To quantitatively describe the solubility of amino acids upon salt addition, binary interaction parameters (kij) between any amino acid and anions were determined, while between any amino acid and the cations were fixed to kij = 0.08. The kij parameters between amino acid and the inorganic anions show very similar values for amino acids of the same chemical class (e.g. kij between anion and amino acid with apolar side chains), which may be used to systematically reduce the number of adjustable parameters in future work.
- Solubilities of amino acids in aqueous solutions of chloride or nitrate salts of divalent (Mg2+ or Ca2+) cationsPublication . Aliyeva, Mehriban; Brandão, Paula; Gomes, José R.B.; Coutinho, João A.P.; Ferreira, Olga; Pinho, SimãoThe solubilities of glycine, L-leucine, L-phenylalanine, and L-aspartic acid were measured in aqueous MgCl2, Mg(NO3)2, CaCl2,, and Ca(NO3)2 solutions with concentrations ranging from 0 to 2 mol/kg at 298.2 K. The isothermal analytical method was used combined with the refractive index measurements for composition analysis guaranteeing good accuracy. All salts induced a salting-in effect with a higher magnitude for those containing the Ca2+ cation. The nitrate anions also showed stronger binding with the amino acids, thus increasing their relative solubility more than the chloride anions. In particular, calcium nitrate induces an increase in the amino acid solubility from 2.4 (glycine) to 4.6 fold (L-aspartic acid) compared to the corresponding value in water. Amino acid solubility data in aqueous MgCl2 and CaCl2 solutions collected from the open literature were combined with that from this work, allowing us to analyze the relations between the amino acid structure and the salting-in magnitude.
- Solubilities of Amino Acids in the Presence of Chaotropic AnionsPublication . Aliyeva, Mehriban; Brandão, Paula; Coutinho, João A.P.; Ferreira, Olga; Pinho, SimãoThis work addresses the effect of chaotropic anions (thiocyanate and tosylate) on the solubility of glycine, L-leucine, L-phenylalanine, and L-aspartic acid in aqueous solutions at 298.2 K. The salts used were NaSCN, KSCN, NH4SCN, and NaC7H7SO3 (sodium tosylate), with salt concentrations ranging from 0 to 2 molal. The pH of the saturated solutions was registered, and solid-phase studies were also performed. All the thiocyanate salts and sodium tosylate induced a salting-in effect, except in the systems composed of glycine in aqueous sodium tosylate solutions at 0.5 and 1 molal. For L-leucine, L-phenylalanine, and L-aspartic acid the salting effect of anions followed the order tosylate− > SCN− > NO3- > Cl−, in good agreement with the behavior predicted by the Hofmeister series. Differently, the relative solubility of glycine in aqueous nitrate solutions was higher than in those containing thiocyanate, followed by the chloride and, closing the rank, the solutions containing the tosylate anion, suggesting that the solubility change in this case is achieved by a different mechanism.
- Thermodynamic description of aqueous solutions of silver nitrate: Experimental and modelingPublication . Arrad, Mouad; Aliyeva, Mehriban; Martins, Mónia A. R.; Thomsen, Kaj; Pinho, SimãoThe water activity of silver nitrate solutions was measured at 298.2 K and 313.2 K using a humidity sensor instrument. Concentrations of silver nitrate up to almost saturation were included. The thermodynamic properties of the system were described by the Pitzer model, the specific interaction theory (SIT), and the Extended UNIQUAC model. The interaction parameters for the models were estimated using experimental freezing points, osmotic coefficients, and solubility for silver nitrate aqueous solutions collected from the open literature, as well as the water activity data measured in this work. Pitzer and SIT parameters were applied by introducing a temperature dependency, enabling these models to cover a more comprehensive temperature range and extrapolate the calculation to higher molalities. Both approaches represent the data satisfactorily up to moderate molalities. The Extended UNIQUAC model, with its built-in temperature dependence, provides the best thermodynamic description of this binary system. It has a very satisfactory solubility diagram and a good description of the osmotic and activity coefficients.
- Water activity and freezing points in aqueous solutions of manganese nitrate: experimental and modelingPublication . Arrad, Mouad; Aliyeva, Mehriban; Vilas-Boas, Sérgio M.; Kaddami, Mohammed; Sippola, Hannu; Taskinen, Pekka; Pinho, SimãoThe water activities of manganese nitrate solutions were measured using a humidity sensor instrument up to almost the saturation molality at 298.15 K; the thermodynamic properties of the system were described by the Pitzer model and specific interaction theory (SIT). The evaluation of the ion interaction parameters for the Pitzer model and SIT were carried out using experimental freezing points and osmotic coefficients of manganese nitrate aqueous solutions, collected from the open literature, and the water activity data measured in this work. A set of Pitzer and SIT parameters were estimated using a temperature dependency, that enables us to cover wider temperature ranges, and consequently calculate system properties to higher molalities. Both approaches represent very satisfactorily, and with similar accuracy, the experimental data and the calculated manganese nitrate molal activity coefficients are comparable to those already published for analogous systems. Additionally, the Pitzer model was also able to calculate the ice curve and the solubility branch of manganese nitrate hexahydrate up to a salt solution 6.5 mol-kg-1.