Browsing by Author "Elias, Megg Madonyk Cota"

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    Aminated cellulose as a versatile adsorbent for batch removal of As(V) and Cu(II) from mono- and multicomponent aqueous solutions.
    (2020) Pereira, Amanda Raimundi; Soares, Liliane Catone; Teodoro, Filipe Simões; Elias, Megg Madonyk Cota; Ferreira, Gabriel Max Dias; Savedra, Ranylson Marcello Leal; Savedra, Melissa Fabíola Siqueira; Martineau Corcos, Charlotte; Silva, Luis Henrique Mendes da; Prim, Damien; Gurgel, Leandro Vinícius Alves
    A bioadsorbent (CEDA) capable of adsorbing As(V) and Cu(II) simultaneously was prepared by tosylation of microcrystalline cellulose (MC) and nucleophilic substitution of the tosyl group by ethylenediamine. MC, tosyl cellulose, and CEDA were characterized by elemental C, H, N, and S analysis, infrared spectroscopy, and 13C solid-state nuclear magnetic resonance spectroscopy. The adsorption of As(V) and Cu (II) on CEDA was evaluated as a function of solution pH, contact time, and initial solute concentration. The maximum adsorption capacities of CEDA for As(V) and Cu(II) were 1.62 and 1.09 mmol g1 , respectively. The interactions of As(V) and Cu(II) with CEDA were elucidated using thermodynamic parameters, molecular quantum mechanics calculations, and experiments with ion exchange of Cd(II) by Cu(II), and As(V) by SO4 2. Adsorption enthalpies were determined as a function of surface coverage of the CEDA, using isothermal titration calorimetry, with DadsH values of 32.24 ± 0.07 and 93 ± 2 kJ mol1 obtained for As(V) and Cu(II), respectively. The potential to reuse CEDA was evaluated and the interference of other ions in the adsorption of As(V) and Cu(II) was investigated. Multi-component experiments showed that Cd(II), Co(II), Ni(II), and Pb(II) did not interfere in the adsorption of Cu(II), while SO4 2 inhibited As(V) adsorption.
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    Modeling mono- and multi-component adsorption of cobalt(II), copper(II), and nickel(II) metal ions from aqueous solution onto a new carboxylated sugarcane bagasse. Part I: Batch adsorption study.
    (2015) Ramos, Stela Nhandeyara do Carmo; Xavier, Amália Luísa Pedrosa; Teodoro, Filipe Simões; Elias, Megg Madonyk Cota; Gonçalves, Fernanda Jorge; Gil, Laurent Frédéric; Freitas, Rossimiriam Pereira de; Gurgel, Leandro Vinícius Alves
    A new carboxylated-functionalized sugarcane bagasse (STA) was prepared through the esterification of sugarcane bagasse with trimellitic anhydride. The optimized synthesis conditions yield STA with a percent weight gain of 73.9% and the number of carboxylic acid groups accounted for 3.78 mmol/g. STA was characterized by FTIR, elemental analysis, TGA, PZC, and SEM. Adsorption kinetics followed a pseudosecond- order model. The adsorption rate constant showed the following order: k2,Ni 2+ > k2,Cu 2+ > k2,Co 2+. Four mono- and multi-component isotherm models were used to model the adsorption systems. Monocomponent experimental data were fitted to Langmuir and Sips models; whereas, multicomponent data were fitted to modified extended Langmuir and P-factor models. The maximum adsorption capacities (Qmax,mono) obtained from the Langmuir model were 1.140, 1.197, and 1.563 mmol/g for Co2+, Cu2+, and Ni2+, respectively. The competitive studies demonstrated that the multicomponent adsorption capacity (Qmax,multi) was smaller than Qmax,mono, as a result of the interaction between the metal ions. Desorption studies showed that all metal ions could be fully desorbed from STA.
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    Quantification of moisture contents in iron and manganese ores.
    (2013) Costa, Geraldo Magela da; Novack, Kátia Monteiro; Elias, Megg Madonyk Cota; Cunha, Camila Cristina Rodrigues Ferreira da
    The moisture contents of several synthetic and natural goethite-bearing samples were determined by the loss-of-mass method and by the Karl-Fischer titration. It was found that drying at 105°C did not remove all the water from these samples, and that temperatures above 200°C would be required to completely remove the adsorbed water. The multiple peaks observed in the TGA and DSC measurements are not due to the dehydroxylation of goethite, but are due to the release of adsorbed water. The decomposition of goethite into hematite occurs with the release of adsorbed water from room temperature up to the onset of the main dehydroxylation peak. The dehydroxylation occurs in a broad range of temperatures due to the existence of a particle-size distribution, surface hydroxyls and formation of a hematite coating. The determination of all adsorbed water is best performed by adding the powdered sample into the Karl- Fischer reaction vessel.
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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.
    (2016) Teodoro, Filipe Simões; Ramos, Stela Nhandeyara do Carmo; Elias, Megg Madonyk Cota; Mageste, Aparecida Barbosa; Ferreira, Gabriel Max Dias; Silva, Luis Henrique Mendes da; 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 DadsH 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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    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.
    (2018) Teodoro, Filipe Simões; Elias, Megg Madonyk Cota; Ferreira, Gabriel Max Dias; Herrera Adarme, Oscar Fernando; Savedra, Ranylson Marcello Leal; Savedra, Melissa Fabíola Siqueira; Silva, Luis Henrique Mendes da; Gil, Laurent Frédéric; Gurgel, Leandro Vinícius Alves
    In 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.