Centro de Ciências Exatas e Tecnológicas
URI permanente desta comunidadehttps://locus.ufv.br/handle/123456789/9791
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Resultados da Pesquisa
Item Synthesis and application of sugarcane bagasse cellulose mixed esters. Part I: Removal of Co2+ and Ni2+ from single spiked aqueous solutions in batch mode using sugarcane bagasse cellulose succinate phthalate(Journal of Colloid and Interface Science, 2019-01-01) Silva, Luis Henrique Mendes da; Elias, Megg Madonyk Cota; Ferreira, Gabriel Max Dias; Almeida, Francine Tatiane Rezende de; Rosa, Nathália Cristina Martins; Silva, Isabela Almeida; Filgueiras, Jefferson Gonçalves; Azevedo, Eduardo Ribeiro de; Melo, Tânia Márcia Sacramento; Gil, Laurent Frédéric; Gurgel, Leandro Vinícius AlvesSugarcane bagasse cellulose mixed ester succinate phthalate (SBSPh) was synthesized by a novel one-pot reaction method. The effects of temperature, time and mole fraction of succinic anhydride (χSA) on the responses weight gain (wg), number of carboxylic acid groups (nT,COOH), and adsorption capacity (q) of Co2+ and Ni2+ were evaluated by a 23 experimental design. The chemical structure of the material was elucidated by Fourier transform infrared, 13C Multiple Cross-Polarization solid-state NMR spectroscopy and 1H NMR relaxometry. The best SBSPh synthesis condition (100 °C, 11 h, χSA of 0.2) yielded a wg of 59.1%, nT,COOH of 3.41 mmol g−1, and values of qCo2+ and qNi2+ of 0.348 and 0.346 mmol g−1, respectively. The Sips model fitted better the equilibrium data, and the maximum adsorption capacities (pH 5.75 and 25 °C) estimated by this model were 0.62 and 0.53 mmol g−1 for Co2+ and Ni2+, respectively. The ΔadsH° values estimated by isothermal titration calorimetry were 8.43 and 7.79 kJ mol−1 for Co2+ and Ni2+, respectively. Desorption and re-adsorption efficiencies were evaluated by a 22 experimental design, which showed that SBSPh adsorbent can be recovered and reused without significant loss of adsorption capacity.Item Synthesis and application of a new carboxylated cellulose derivative. Part I: Removal of Co2+, Cu2+ and Ni2+ from monocomponent spiked aqueous solution(Journal of Colloid and Interface Science, 2016-12) Ferreira, Gabriel Max Dias; Silva, Luis Henrique Mendes da; Teodoro, Filipe Simões; Ramos, Stela Nhandeyara do Carmo; Elias, Megg Madonyk Cota; Mageste, Aparecida Barbosa; Gil, Laurent Frédéric; Gurgel, Leandro Vinícius AlvesA new carboxylated cellulose derivative (CTA) was prepared from the esterification of cellulose with 1,2,4-Benzenetricarboxylic anhydride. CTA was characterized by percent weight gain (pwg), amount of carboxylic acid groups (nCOOH), elemental analysis, FTIR, TGA, solid-state 13C NMR, X-ray diffraction (DRX), specific surface area, pore size distribution, SEM and EDX. The best CTA synthesis condition yielded a pwg and nCOOH of 94.5% and 6.81 mmol g−1, respectively. CTA was used as an adsorbent material to remove Co2+, Cu2+ and Ni2+ from monocomponent spiked aqueous solution. Adsorption studies were developed as a function of the solution pH, contact time and initial adsorbate concentration. Langmuir model better fitted the experimental adsorption data and the maximum adsorption capacities estimated by this model were 0.749, 1.487 and 1.001 mmol g−1 for Co2+, Cu2+ and Ni2+, respectively. The adsorption mechanism was investigated by using isothermal titration calorimetry. The values of ΔadsH° were in the range from 5.36 to 8.09 kJ mol−1, suggesting that the mechanism controlling the phenomenon is physisorption. Desorption and re-adsorption studies were also performed. Desorption and re-adsorption efficiencies were closer to 100%, allowing the recovery of both metal ions and CTA adsorbent.Item Determination of driving forces for bovine serum albumin-Ponceau4R binding using surface plasmon resonance and fluorescence spectroscopy: A comparative study(Food Hydrocolloids, 2017-09) Lelis, Carini Aparecida; Ferreira, Gabriel Max Dias; Ferreira, Guilherme Max Dias; Hespanhol, Maria do Carmo; Pinto, Maximiliano Soares; Silva, Luis Henrique Mendes da; Pires, Ana Clarissa dos SantosPonceau 4R (P4R) and bovine serum albumin (BSA) may interact changing food properties. We compared fluorescence spectroscopy and surface plasmon resonance (SPR) for studying, in vitro, the interactions between BSA and P4R at pH 7.4 and 3.5 in different temperatures. Fluorescence data pointed to the formation of a complex where P4R was bound on site I or II of BSA, with a stoichiometry around one and a binding constant (Kb) ranging from 1.37 × 105 to 20.15 × 106 L mol−1. The complex formation at both pH was enthalpically driven (standard enthalpy change, ΔH°F = −60.69 and −63.06 kJ mol−1, for pH 7.4 and 3.5, respectively). Using SPR, we also found the formation of 1:1 BSA-P4R complexes, but the calculated Kb values were much smaller, on the order of 103 L mol−1. Again, we found that the formation of BSA-P4R complex was driven by enthalpy decreasing; however the standard enthalpy change was less negative than that found by fluorescence (ΔH°SPR = −15.05 and −40.55 kJ mol−1, at pH 7.4 and 3.5, respectively). Our results show that these distinct techniques provided different thermodynamic binding parameters for the BSA-P4R interaction, especially regarding ΔH° values, indicating that BSA-P4R binding was a multisite phenomenon, and that sites far from tryptophan residues were the main responsible by electrostatic interaction. Thus, this work clearly shows the importance of using complementary techniques for a complete thermodynamic characterization of complexes formed between azo-colorants and proteins; which is directly related to physicochemical properties of systems containing both molecules together.Item Determination of driving forces for bovine serum albumin-Ponceau4R binding using surface plasmon resonance and fluorescence spectroscopy: a comparative study(Food Hydrocolloids, 2017-09) Lelis, Carini Aparecida; Ferreira, Gabriel Max Dias; Ferreira, Guilherme Max Dias; Hespanhol, Maria do Carmo; Pinto, Maximiliano Soares; Silva, Luis Henrique Mendes da; Pires, Ana Clarissa dos SantosPonceau 4R (P4R) and bovine serum albumin (BSA) may interact changing food properties. We compared fluorescence spectroscopy and surface plasmon resonance (SPR) for studying, in vitro, the interactions between BSA and P4R at pH 7.4 and 3.5 in different temperatures. Fluorescence data pointed to the formation of a complex where P4R was bound on site I or II of BSA, with a stoichiometry around one and a binding constant (Kb) ranging from 1.37 × 10^5 to 20.15 × 10^6 L mol^−1. The complex formation at both pH was enthalpically driven (standard enthalpy change, ΔH°F = −60.69 and −63.06 kJ mol^−1, for pH 7.4 and 3.5, respectively). Using SPR, we also found the formation of 1:1 BSA-P4R complexes, but the calculated Kb values were much smaller, on the order of 103 L mol^−1. Again, we found that the formation of BSA-P4R complex was driven by enthalpy decreasing; however the standard enthalpy change was less negative than that found by fluorescence (ΔH°SPR = −15.05 and −40.55 kJ mol^−1, at pH 7.4 and 3.5, respectively). Our results show that these distinct techniques provided different thermodynamic binding parameters for the BSA-P4R interaction, especially regarding ΔH° values, indicating that BSA-P4R binding was a multisite phenomenon, and that sites far from tryptophan residues were the main responsible by electrostatic interaction. Thus, this work clearly shows the importance of using complementary techniques for a complete thermodynamic characterization of complexes formed between azo-colorants and proteins; which is directly related to physicochemical properties of systems containing both molecules together.Item Phase diagrams, densities and refractive indexes of poly(ethylene oxide) + organic salts + water aqueous two-phase systems: effect of temperature, anion and molar mass(Fluid Phase Equilibria, 2015-11-25) Rengifo, Andrés Felipe Chamorro; Ferreira, Gabriel Max Dias; Ferreira, Guilherme Max Dias; Silva, Maria C. Hespanhol da; Silva, Luis Henrique Mendes daThe application of aqueous two-phase systems (ATPSs) at the industrial level requires systems formed by non-toxic substances to decrease the negative impact on the environment. Organic salts such as sodium citrate, sodium tartrate and sodium succinate have been utilized in order to fulfill this objective. In this work, ATPSs formed by poly(ethylene oxide), PEO, with molar mass 10,000 or 35,000 g mol^−1, organic salts and water, namely PEO10000 + sodium citrate + water, PEO10000 + sodium tartrate + water, PEO10000 + sodium succinate + water and PEO35000 + sodium citrate + water ATPSs at (283.15, 298.15 and 313.15) K have been studied. Effects of temperature, anion and polymer molar mass on the phase diagrams, as well as, the densities and refractive indexes of both phases of the ATPSs were evaluated. The segregation process was endothermic and entropically driven for all ATPSs. The biphasic region on the phase diagrams increased as the molar mass of PEO increased. In addition, the biphasic region also increased in relation to the anions studied: citrate > tartrate > succinate. The consistency of the tie-line data was ascertained by applying the Othmer–Tobias correlation.Item Physicochemical aspects of chitosan dispersibility in acidic aqueous media: effects of the food acid counter-anion(Food Biophysics, 2016-12) Amorim, Matheus Lopes; Ferreira, Gabriel Max Dias; Soares, Lucas de Souza; Soares, Wanessa Aparecida dos Santos; Ramos, Afonso Mota; Coimbra, Jane Sélia dos Reis; Silva, Luís Henrique Mendes da; Oliveira, Eduardo Basílio deDifferences in formation of colloidal dispersions of chitosan in aqueous solutions of citric acid or lactic acid (25, 50 or 100 mM) were quantitatively studied. Protonation enthalpies, electrical conductivity and ζ-potential measurements were additionally undertaken, aiming at better understanding these differences at a molecular level. In dispersion kinetics assays, experimental data were well fitted (R2 > 0.9; MAPE < 4 %) by a first-order kinetics model with two terms - one accounting for the fast, direct dispersion of biopolymers chains and another accounting for the slow dispersion of chains from lumps. In all cases, maximal dispersibility was reached after about 20−30 min of stirring. For both acids, the higher the acid concentration in the medium, the higher was the chitosan dispersibility. At a given acid concentration, chitosan showed higher dispersibility in lactic acid than in citric acid solutions. Protonation of chitosan -NH2 groups was strongly exothermic, with ΔH values three times higher for citric acid (triprotic) than lactic acid (monoprotic) (ΔH = −120 kJ∙mol- 1 and ΔH = −40 kJ∙mol- 1, respectively), indicating that chitosan -NH2 protonation itself was not dependent on the type of acid. However, the electrical conductivity of suspensions of powdered chitosan in water evolved differently as these systems were titrated with citric or acid lactic. With citric acid, electrical conductivity remained virtually constant for acid concentration < of 15 mM, and then increased linearly as the acid concentration increased until 75 mM. Instead, with lactic acid, electrical conductivity progressively increased with increasing of acid concentration from 0 to 75 mM. The ζ-potential of chitosan dispersed particles was +28.5 mV and +52.1 mV in dispersions containing 10 mM of citric and lactic acids, respectively. The conjoint analysis of data from physicochemical analyses suggested that, contrarily to lactate anions, citrate anions bind more strongly on the electrical double layer of protonated, positively charged chains of chitosan, diminishing the inter-chains electrostatic repulsion, thus leading to a lower dispersibility of this polysaccharide in aqueous solutions of citric acid, compared to equimolar solutions of lactic acid.Item Adsorption of red azo dyes on multi-walled carbon nanotubes and activated carbon: A thermodynamic study(Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2017-09-20) Ferreira, Guilherme Max Dias; Ferreira, Gabriel Max Dias; Hespanhol, Maria C.; Rezende, Jaqueline de Paula; Pires, Ana Clarissa dos Santos; Gurgel, Leandro Vinícius Alves; Silva, Luis Henrique Mendes daCarbonaceous materials have been extensively studied as highly efficient adsorbents for the removal of dyes from wastewater. However, investigations of thermodynamic aspects of the interactions between these materials and dyes remain scarce. This paper describes the thermodynamics of the interactions between the Ponceau 4R (PR), Congo Red (CR), and Allura Red (AR) dyes and multi-walled carbon nanotubes (MWCNTs). The interactions between the dyes and activated carbon (AC) were also evaluated for comparison. The investigation used a combination of adsorption isotherms and isothermal titration nanocalorimetry (ITC) measurements, and a thermodynamic approach provided full characterization of the adsorption process. For both MWCNT and AC, the amount of adsorbed dye (ΓD) increased in the order ΓD (PR) < ΓD (AR) < ΓD (CR), and the adsorption capacity normalized by the adsorbent specific area was up to 5.6 times higher for MWCNT. The maximum amount adsorbed (ΓD,max) reached values of up to 2.00 μmol m−2 for CR adsorption on MWCNT. For both adsorbents, the process of dye adsorption was enthalpically driven and entropically unfavorable. All the thermodynamic parameters depended on the surface coverage and the structures of both dye and adsorbent. The adsorption enthalpy change (ΔadsH) and entropy change (TΔadsSref) values were higher than −137.0 kJ mol−1 and −114.2 kJ mol−1, respectively. In addition to the structural differences between MWCNT and AC, the ITC data suggested that the adsorption sites are heterogeneous and that the dyes preferentially adsorb on the more hydrophilic sites on the adsorbent surfaces.Item Trimellitated sugarcane bagasse: A versatile adsorbent for removal of cationic dyes from aqueous solution. Part I: Batch adsorption in a monocomponent system(Journal of Colloid and Interface Science, 2018-01-06) Fideles, Renata Aparecida; Ferreira, Gabriel Max Dias; Teodoro, Filipe Simões; Adarme, Oscar Fernando Herrera; Silva, Luis Henrique Mendes da; Gil, Laurent Frédéric; Gurgel, Leandro Vinícius AlvesTrimellitated-sugarcane bagasse (STA) was used as an environmentally friendly adsorbent for removal of the basic dyes auramine-O (AO) and safranin-T (ST) from aqueous solutions at pH 4.5 and 7.0. Dye adsorption was evaluated as a function of STA dosage, agitation speed, solution pH, contact time, and initial dye concentration. Pseudo-first- and pseudo-second-order, Elovich, intraparticle diffusion, and Boyd models were used to model adsorption kinetics. Langmuir, Dubinin-Radushkevich, Redlich-Peterson, Sips, Hill-de Boer, and Fowler-Guggenheim models were used to model adsorption isotherms, while a Scatchard plot was used to evaluate the existence of different adsorption sites. Maximum adsorption capacities for removal of AO and ST were 1.005 and 0.638 mmol g−1 at pH 4.5, and 1.734 and 1.230 mmol g−1 at pH 7.0, respectively. Adsorption enthalpy changes obtained by isothermal titration calorimetry (ITC) ranged from −21.07 ± 0.25 to −7.19 ± 0.05 kJ mol−1, indicating that both dyes interacted with STA by physisorption. Dye desorption efficiencies ranged from 41 to 51%, and re-adsorption efficiencies ranged from 66 to 87%, showing that STA can be reused in new adsorption cycles. ITC data combined with isotherm studies allowed clarification of adsorption interactions.Item Synthesis and application of a new carboxylated cellulose derivative. Part III: Removal of auramine-O and safranin-T from mono- and bi-component spiked aqueous solutions(Journal of Colloid and Interface Science, 2017-10-25) Teodoro, Filipe Simões; Elias, Megg Madonyk Cota; Ferreira, Gabriel Max Dias; Adarme, Oscar Fernando Herrera; Savedra, Ranylson Marcello Leal; Siqueira, Melissa Fabíola; Silva, Luis Henrique Mendes da; Gil, Laurent Frédéric; Gurgel, Leandro Vinícius AlvesIn the third part of this series of studies, the adsorption of the basic textile dyes auramine-O (AO) and safranin-T (ST) on a carboxylated cellulose derivative (CTA) were evaluated in mono- and bi-component spiked aqueous solutions. Adsorption studies were developed as a function of solution pH, contact time, and initial dye concentration. Adsorption kinetic data were modeled by monocomponent kinetic models of pseudo-first- (PFO), pseudo-second-order (PSO), intraparticle diffusion, and Boyd, while the competitive kinetic model of Corsel was used to model bicomponent kinetic data. Monocomponent adsorption equilibrium data were modeled by the Langmuir, Sips, Fowler-Guggenhein, Hill de-Boer, and Konda models, while the IAST and RAST models were used to model bicomponent equilibrium data. Monocomponent maximum adsorption capacities for AO and ST at pH 4.5 were 2.841 and 3.691 mmol g−1, and at pH 7.0 were 5.443 and 4.074 mmol g−1, respectively. Bicomponent maximum adsorption capacities for AO and ST at pH 7.0 were 1.230 and 3.728 mmol g−1. Adsorption enthalpy changes (ΔadsH) were obtained using isothermal titration calorimetry. The values of ΔadsH ranged from −18.83 to −5.60 kJ mol−1, suggesting that physisorption controlled the adsorption process. Desorption and re-adsorption of CTA was also evaluated.Item Binding thermodynamics of synthetic dye Allura Red with bovine serum albumin(Food Chemistry, 2017-02-15) Lelis, Carini Aparecida; Hudson, Eliara Acipreste; Ferreira, Guilherme Max Dias; Ferreira, Gabriel Max Dias; Silva, Luis Henrique Mendes da; Silva, Maria do Carmo Hespanhol da; Pinto, Maximiliano Soares; Pires, Ana Clarissa dos SantosThe interaction between Allura Red and bovine serum albumin (BSA) was studied in vitro at pH 7.4. The fluorescence quenching was classified as static quenching due to the formation of AR–BSA complex, with binding constant (K) ranging from 3.26 ± 0.09 to 8.08 ± 0.06 104 L.mol−1, at the warfarin binding site of BSA. This complex formation was driven by increasing entropy. Isothermal titration calorimetric measurements also showed an enthalpic contribution. The Allura Red diffusion coefficient determined by the Taylor-Aris technique corroborated these results because it reduced with increasing BSA concentration. Interfacial tension measurements showed that the AR–BSA complex presented surface activity, since interfacial tension of the water-air interface decreased as the colorant concentration increased. This technique also provided a complexation stoichiometry similar to those obtained by fluorimetric experiments. This work contributes to the knowledge of interactions between BSA and azo colorants under physiological conditions.