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URI permanente para esta coleçãohttps://locus.ufv.br/handle/123456789/11800

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Autor: search.filters.author.Silva, Luis Henrique Mendes daData inicial: 2006Tem arquivos: Sim

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Agora exibindo 1 - 10 de 25
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    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 Alves
    Sugarcane 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.
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    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 Alves
    A 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.
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    Chromium speciation using aqueous biphasic systems: Development and mechanistic aspects
    (Separation and Purification Technology, 2016-01-28) Patrício, Pamela R.; Cunha, Roselaine C.; Vargas, Silvia J. Rodriguez; Coelho, Yara Luiza; Silva, Luis Henrique Mendes da; Silva, Maria C. Hespanhol da
    The two principal oxidation states of chromium diverge significantly in their biological and toxicological properties, and it is very important to distinguish between them. Develop procedures that are efficient, fast, easier and cheaper for chromium speciation is an analytical challenge. Chromium speciation was investigated using aqueous biphasic systems (ABS) formed by polyethylene oxide (PEO1500) or a triblock copolymer (L64), an electrolyte (Li2SO4, Na2SO4, MgSO4, C6H5Na3O7, or C4H4Na2O6) and water, without the presence of any extractant. Cr(III) was favorably partitioned to the electrolyte-rich phase (ERP) of the ABS, whereas the Cr(VI) was preferentially concentrated in the macromolecule-rich phase (MRP) in most analyzed ABS. The fluorescence spectroscopy data revealed that the Cr(III) and Cr(VI) separation process is governed by specific interactions between the ethylene oxide segments in the macromolecules and the Cr(VI) species, which do not occur for Cr(III) species. The extraction percentage (%E) of chromium species from the ERP to the MRP was affected by pH, tie-line length (TLL), electrolyte nature, and macromolecule hydrophobicity. For the ABS comprising of PEO1500 + Na2SO4 + H2O, TLL = 50.89% (m/m), 25 °C and pH 2.0, the %E values for Cr(III) and Cr(VI) were 0.0100 and 99.9%, respectively. The speciation of Cr(III) and Cr(VI) that was achieved in this ABS resulted in an excellent separation factor (SCr(VI),Cr(III)) of 1.00 × 10 8.
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    Aqueous two-phase systems of copolymer L64 + organic salt + water: Enthalpic L64–salt interaction and Othmer–Tobias, NRTL and UNIFAC thermodynamic modeling
    (Chemical Engineering Journal, 2011-06-15) Andrade, Vivianne Molica de; Rodrigues, Guilherme Dias; Carvalho, Raquel Moreira Maduro de; Silva, Luis Henrique Mendes da; Silva, Maria C. Hespanhol da
    Phase diagrams of two-phase systems (ATPS) composed by the triblock copolymer L64 + organic salt (sodium tartrate, sodium succinate, sodium citrate, or ammonium citrate) + water, at different temperatures (278, 288, and 298 K) are presented in this work. Contrary to behavior of ATPS formed by inorganic salts, the study of the temperature influence in the liquid–liquid equilibrium behavior of L64–organic salts ATPS showed an exothermic character for phase separation process. Microcalorimetric measurements showed that this phase separation energy is around −0.2 kJ mol−1 for all organic salts. The module of slope of tie line (STL) tends to increase with an increase in temperature. The cation nature effect showed that the salt Na3C6H5O7 was more effective in promoting phase separation than (NH4)3C6H5O7. The capacity of the different anions tested for inducing ATPS formation with L64 followed the order: C6H5O73− > C4H4O62− > C4H4O42−. Because the salt–L64 interaction energy to be very similar, the cation and anion effects on the phase separation could be attribute to a process driven by entropy. The interaction parameters of the NRTL and UNIFAC models were estimated through the experimental data of all ternary systems. The results of the NRTL (with 64 tie-lines) and UNIFAC (with 27 tie-lines) were considered excellent with global root mean square deviations, respectively, of the 1.04% and 0.87%. The consistencies of the all tie-line experimental compositions were improved by applying the Othmer–Tobias correlation.
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    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 da
    The 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.
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    Liquid–liquid equilibrium of aqueous two-phase systems composed of poly(ethylene oxide) 1500 and different electrolytes ((NH4 )2SO4 , ZnSO4 and K2HPO4 ): experimental and correlation
    (Fluid Phase Equilibria, 2011-06-15) Lemos, Leandro Rodrigues de; Patrício, Pamela da Rocha; Rodrigues, Guilherme Dias; Carvalho, Raquel Moreira Maduro de; Silva, Maria C. Hespanhol da; Silva, Luis Henrique Mendes da
    Phase diagrams of aqueous two-phase systems composed of PEO1500 + salt (di-potassium phosphate + potassium hydroxide or ammonium sulfate or zinc sulfate) + water were determined at (283.15, 298.15, and 313.15) K. All systems produce a large two-phase region; however the influence of temperature on the binodal position seems to be very small. By analyzing the effects of ammonium sulfate or zinc sulfate, it was observed that zinc was more effective in promoting phase separation than ammonium. The consistency of the tie-line data was ascertained by applying the Othmer–Tobias correlation. In this paper, aqueous two-phase systems data for nine ternary systems are correlated by using the NRTL model and UNIFAC for the activity coefficient. The results are very satisfactory, with root mean square deviations between experimental and calculated compositions as low as 0.99 and 1.21%, respectively. However the NRTL model better represents the systems in study, when compared with UNIFAC.
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    Thermodynamics and optimization of norbixin transfer processes in aqueous biphasic systems formed by polymers and organic salts
    (Separation and Purification Technology, 2012-09-19) Mageste, Aparecida Barbosa; Senra, Tonimar Domiciano Arrighi; Silva, M. Carmo Hespanhol da; Bonomo, Renata Cristina Ferreira; Silva, Luis Henrique Mendes da
    Partitioning of the natural dye norbixin has been studied in aqueous two-phase system (ATPS) that are formed by mixing aqueous solutions of a polymer (or copolymer) and an organic salt (sodium tartrate or succinate). In this work, the norbixin partition coefficient (KN) was optimized, taking into account the variables of polymer concentration, salt concentration and pH. It was found that KN is highly dependent on the electrolyte nature, system hydrophobicity and TLL values. Testing produced KN values between 8 and 130, indicating the great potential of ATPS as a method for norbixin pre-concentration/purification. Thermodynamic transfer parameters (ΔtrG, ΔtrH, ΔtrS) indicate that the preferential concentration of norbixin in the top phase is favored by enthalpic and entropic contributions.
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    Phase diagram and thermodynamic modeling of PEO + organic salts + H2O and PPO + organic salts + H2O aqueous two-phase systems
    (Fluid Phase Equilibria, 2015-06-15) Patrício, Pamela da Rocha; Mageste, Aparecida Barbosa; Lemos, Leandro Rodrigues de; Carvalho, Raquel Moreira Maduro de; Silva, Luis Henrique Mendes da; Silva, Maria C. Hespanhol da
    The phase diagrams of PEO1500 + sodium tartrate + water, PPO400 + sodium tartrate + water, PEO1500 + sodium succinate + water, PPO400 + sodium succinate + water, PEO1500 + sodium citrate + water, PPO400 + sodium citrate + water and PPO400 + sodium acetate + water aqueous two-phase systems were determined at (283.15, 298.15, and 313.15) K. Both equilibrium phases composition were analyzed by conductimetry and refractive index. In this paper, the influences of polymer hydrophobicity, salt nature and temperature on the phase diagram were analyzed. The phase separation processes was endothermic and the hydrophobic increase make easier the phase splitting, while the electrolyte capacity to induce phase separation follow the order: citrate > tartrate > succinate. The consistency of the tie-line data was ascertained by applying the Othmer–Tobias correlation. The experimental data were correlated with the NRTL model for the activity coefficient, with estimation of new interaction energy parameters. The results, analyzed in terms of root mean square deviations between experimental and calculated compositions, were considered satisfactory.
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    Separation of Cd and Ni from Ni–Cd batteries by an environmentally safe methodology employing aqueous two-phase systems
    (Journal of Power Sources, 2009-09-05) Lacerda, Vânia Gonçalves; Mageste, Aparecida Barbosa; Santos, Igor José Boggione; Silva, Luis Henrique Mendes da; Silva, Maria do Carmo Hespanhol da
    The separation of Cd and Ni from Ni–Cd batteries using an aqueous two-phase system (ATPS) composed of copolymer L35, Li2SO4 and water is investigated. The extraction behavior of these metals from the bottom phase (BP) to the upper phase (UP) of the ATPS is affected by the amount of added extractant (potassium iodide), tie-line length (TLL), mass ratio between the phases of the ATPS, leaching and dilution factor of the battery samples. Maximum extraction of Cd (99.2 ± 3.1)% and Ni (10.6 ± 0.4)% is obtained when the batteries are leached with HCl, under the following conditions: 62.53% (w/w) TLL, concentration of KI equal to 50.00 mmol kg−1, mass ratio of the phases equal to 0.5 and a dilution factor of battery samples of 35. This novel methodology is efficient to separate the metals in question, with the advantage of being environmentally safe, since water is the main constituent of the ATPS, which is prepared with recyclable and biodegradable compounds.
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    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 Alves
    Trimellitated-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.