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Item Adsorption of red azo dyes on multi-walled carbon nanotubes and activated carbon : a thermodynamic study.(2017) 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 Aggregation of sodium dodecylbenzene sulfonate : weak molecular interactions modulated by imidazolium cation of short alkyl chain length.(2020) Patino Agudelo, Alvaro Javier; Ferreira, Guilherme Max Dias; Ferreira, Gabriel Max Dias; Coelho, Yara Luiza; Hudson, Eliara Acipreste; Pires, Ana Clarissa dos Santos; Silva, Luis Henrique Mendes daIonic liquids (ILs) can modify cooperative process in aqueous solutions to a large extent, including anionic surfactant aggregation. Here, the micellization of sodium dodecylbenzene sulfonate (SDBS) was evaluated in low concentrations of 1-alkyl-3-methylimidazolium chloride (CnmimCl, n = 0, 2, and 4) aqueous solutions through fluorescence spectroscopy, isothermal titration calorimetry, dynamic light scattering, and conductometry. The thermodynamic stability of SDBS aggregates strongly depended on the IL structure and concentration, following the order C4mim+ > C0mim+ ≈ C2mim+. At 1.0 mmol L−1 of the ILs, the increase of the hydrophobicity of the imidazolium cation decreased the enthalpic favorableness, changing from −3.75 ± 0.07 kJ mol−1, for C0mim+, to −2.69 ± 0.01 kJ mol−1, for C4mim+. On the other hand, the entropic feasibility showed an opposite trend, i.e., the higher hydrophobicity of C4mim+ overcame the kosmotropic effect of IL cations in the bulks. We suggested that the imidazolium cations interact with the SDBS monomers on the micellar surface, mainly through hydrophobic, π-π, and electrostatic interactions for C4mim+ and C2mim+, and through electrostatic interactions and hydrogen bonds for C0mim+.Item 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; Carvalho, Megg Madonyk Cota Elias; 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 AlvesA 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.Item Application of pyridine-modified chitosan derivative for simultaneous adsorption of Cu(II) and oxyanions of Cr(VI) from aqueous solution.(2021) Gonçalves, Fernanda Jorge; Gurgel, Leandro Vinícius Alves; Soares, Liliane Catone; Teodoro, Filipe Simões; Ferreira, Guilherme Max Dias; Coelho, Yara Luiza; Silva, Luis Henrique Mendes da; Prim, Damien; Gil, Laurent FrédéricThe bioadsorbent C1, which is a chitosan derivative prepared in a one-step synthesis, was successfully used to adsorb Cr(VI) and Cu(II) simultaneously. Here, for the first time the simultaneous adsorption of a cation and an anion was modeled using the Corsel model for kinetics and the Real Adsorbed Solution Theory model for equilibrium data. Batch studies of the adsorption of Cu(II) and Cr(VI) in single and binary aqueous solutions were performed as a function of initial solute concentration, contact time, and solution pH. The maximum adsorption capacities of C1 in single and binary aqueous solutions were 1.84 and 1.13 mmol g− 1 for Cu(II) and 3.86 and 0.98 mmol g− 1 for Cr(VI), respectively. The reuse of C1 was investigated, with Cu(II) ions being almost completely desorbed and fully re-adsorbed. For Cr(VI), the desorption was incomplete resulting in a lower re- adsorption. Energy-dispersive X-ray spectroscopy was used for mapping the distributions of Cr(VI) and Cu(II) adsorbed on the C1 surface in single and binary adsorption systems. Isothermal titration calorimetry experiments were performed for Cr(VI) and Cu(II) adsorption in single solutions. The thermodynamic parameters of adsorption showed that the adsorption of both metal ions was enthalpically driven, but entropically unfavorable.Item Batch and continuous adsorption of Cd(II) and Pb(II) on polycarboxylated sugarcane bagasse.(2023) Carvalho, Megg Madonyk Cota Elias; Soares, Liliane Catone; Maia, Luisa Cardoso; Taylor, Jason Guy; Herrera Adarme, Oscar Fernando; Ferreira, Gabriel Max Dias; Azevedo, Eduardo Ribeiro de; Siervo, Abner de; Silva, Luis Henrique Mendes da; Gurgel, Leandro Vinícius AlvesA bioadsorbent composed of polycarboxylated sugarcane bagasse (PSB) was prepared in a one-step reaction by the esterification of sugarcane bagasse hydroxyl groups with butane-1,2,3,4-tetracarboxylic dianhydride. 13C SS NMR measurements showed that 0.3 butane-1,2,3,4-tetracarboxylic acid units were grafted per cellobiose unit. PSB was used in the batch adsorption of Cd(II) and Pb(II) from mono-, bi-, and multicomponent aqueous solutions. For upscaling of the technology aiming at practical applications, evaluation was made of 4 cycles of continuous adsorption of Cd(II) and Pb(II) on PSB in a fixed-bed column. The maximum adsorption capacities for Cd(II) and Pb(II) on PSB in batch and continuous modes were 0.55 and 1.164 mmol g− 1 (62 and 241.2 mg g− 1 ), and 0.58 and 0.71 mmol g− 1 (65 and 153 mg g− 1 ), respectively. The standard adsorption enthalpy change (ΔadsH◦) values for Cd(II) and Pb(II) were 8.6 ± 0.5 and − 0.28 ± 0.03 kJ mol− 1 , respectively. The interactions involved in the adsorption of Cd(II) and Pb(II) on PSB were investigated. Multicomponent studies showed that Pb (II) and Cd(II) acted to suppress the adsorption of each other. In the presence of Cu(II) and Zn(II), the adsorption capacity followed the order: Pb(II) > Cu(II) > Cd(II) > Zn(II). Batch and continuous adsorption-desorption studies showed that PSB could be reused in at least 4 successive cycles, with desorption efficiencies of 88–100 %, which is essential for minimizing waste generation and reducing process costs.Item Batch and continuous adsorption of Cu(II) and Zn(II) ions from aqueous solution on bi‐functionalized sugarcane‐based biosorbent.(2022) Teodoro, Filipe Simões; Soares, Liliane Catone; Filgueiras, Jefferson Gonçalves; Azevedo, Eduardo Ribeiro de; Patino Agudelo, Alvaro Javier; Herrera Adarme, Oscar Fernando; Silva, Luis Henrique Mendes da; Gurgel, Leandro Vinícius AlvesA new one-pot synthesis method optimized by a 23 experimental design was developed to prepare a biosorbent, sugarcane bagasse cellulose succinate pyromellitate (SBSPy), for the removal of Cu(II) and Zn(II) from single-component aqueous solutions, in batch and continuous modes. The bi-functionalization of the biosorbent with ligands of diferent chemical structures increased its selectivity, improving its performance for removing pollutants from contaminated water. The suc- cinate moiety favored Cu(II) adsorption, while the pyromellitate moiety favored Zn(II) adsorption. Sugarcane bagasse (SB) and SBSPy were characterized using several techniques. Analysis by 13C Multi-CP SS NMR and FTIR revealed the best order of addition of each anhydride that maximized the chemical modifcation of SB. The maximum adsorption capacities of SBSPy for Cu(II) and Zn(II), in batch mode, were 1.19 and 0.95 mmol g-1, respectively. Homogeneous surface difusion, intraparticle difusion, and Boyd models were used to determine the steps involved in the adsorption process. Isothermal titration calorimetry was used to assess changes in enthalpy of adsorption as a function of SBSPy surface coverage. Fixed- bed column adsorption of Cu(II) and Zn(II) was performed in three cycles, showing that SBSPy has potential to be used in water treatment. Breakthrough curves were well ftted by the Thomas and Bohart-Adams models.Item Lactoferrin denaturation induced by anionic surfactants : the role of the ferric ion in the protein stabilization.(2018) Ferreira, Gabriel Max Dias; Ferreira, Guilherme Max Dias; Patino Agudelo, Alvaro Javier; Hudson, Eliara Acipreste; Pires, Ana Clarissa dos Santos; Silva, Luis Henrique Mendes daHere, investigation was made of the interaction between lactoferrin (Lf) and the anionic surfactants sodium dodecyl sulfate (SDS), sodium dodecylbenzene sulfonate (SDBS), and sodium decyl sulfate (DSS), using isothermal titration calorimetry, Nano differential scanning calorimetry (NanoDSC), and fluorescence spectroscopy. The Lf-surfactant interaction was enthalpically favorable (the integral enthalpy change ranged from −5.99 kJ mol−1, for SDS at pH 3.0, to −0.61 kJ mol−1, for DSS at pH 12.0) and promoted denaturation of the protein. The Lf denaturation efficiency followed the order DSS < SDS < SDBS. The adsorption capacity of the protein with respect to surfactant strongly depended on pH and the surfactant structure, reaching a maximum value of 505 SDBS molecules per gram of Lf at pH 3.0. The different efficiencies of the surfactants in denaturing Lf were attributed to the balance of hydrophobic and electrostatic interactions, which also depended on pH and the surfactant structure, highlighting the SDBS-tryptophan residue specific interaction, where SDBS acted as a quencher of fluorescence. Interestingly, the NanoDSC and fluorescence measurements showed that the ferric ion bound to Lf increased its stability against denaturation induced by the surfactants. The results have important implications for understanding the influence of surfactants on structural changes in metalloproteins.Item Modeling adsorption of copper(II), cobalt(II) and nickel(II) metal ions from aqueous solution onto a new carboxylated sugarcane bagasse. Part II : Optimization of monocomponent fixed-bed column adsorption.(2018) Xavier, Amália Luísa Pedrosa; Herrera Adarme, Oscar Fernando; Furtado, Laís Milagres; Ferreira, Gabriel Max Dias; Silva, Luis Henrique Mendes da; Gil, Laurent Frédéric; Gurgel, Leandro Vinícius AlvesIn the second part of this series of studies, the monocomponent adsorption of Cu2+, Co2+ and Ni2+ onto STA adsorbent in a fixed-bed column was investigated and optimized using a 22 central composite design. The process variables studied were: initial metal ion concentration and spatial time, and the optimized responses were: adsorption capacity of the bed (Qmax), efficiency of the adsorption process (EAP), and effective use of the bed (H). The higher Qmax for Cu2+, Co2+ and Ni2+ were 1.060, 0.800 and 1.029 mmol/g, respectively. The breakthrough curves were modeled by the original Thomas and Bohart- Adams models. The changes in enthalpy (DadsH ) of adsorption of the metal ions onto STA were determined by isothermal titration calorimetry (ITC). The values of DadsH were in the range of 3.0–6.8 kJ/mol, suggesting that the adsorption process involved physisorption. Desorption (Edes) and readsorption (Ere-ads) of metal ions from the STA adsorbent were also investigated in batch mode, and the optimum conditions were applied for three cycles of adsorption/desorption in a fixed bed column. For these cycles, the lowest values of Edes and Ere-ads were 95 and 92.3%, respectively, showing that STA is a promising candidate for real applications on a large scale.Item New insights into the partitioning of phenothiazine dyes in aqueous two-phase systems.(2020) Coelho, Yara Luiza; Patino Agudelo, Alvaro Javier; Ferreira, Guilherme Max Dias; Ferreira, Gabriel Max Dias; Castro, Alan Stampini Benhame de; Hudson, Eliara Acipreste; Pires, Ana Clarissa dos Santos; Silva, Luis Henrique Mendes daAqueous two-phase systems (ATPSs) have proven to be efficient and environmentally safe methods for extracting chemical species. However, the driving forces behind the partition of solutes in these systems are still little understood. A complete thermodynamic partitioning of phenothiazine dyes was investigated in poly(ethylene oxide) (PEO) + salt + water ATPSs. Standard transfer parameters (Gibbs free energy change (ΔtrGo ), enthalpy change (ΔtrHo ) and entropy change (TΔtrSo )) were evaluated, and their dependence on the dye structure, electrolyte nature and tie line length (TLL). All phenothiazine dyes are concentrated predominantly in the polymer enriched phase, with ΔtrGo values ranging from −4.1 up to −13.4 kJ mol−1. Due to the dye-PEO attractive interactions that occur mainly via benzene condensed ring present in the structures of phenothiazine dyes, the partitioning of these dyes was enthalpically driven, with −11.4 ≥ ΔtrHo ≥ −52 kJ mol−1 and −4.93 ≥ TΔtrSo ≥ −38 kJ mol−1.Item Partitioning of cocaine and its adulterants in aqueous two-phase systems : an alternative drug identification method.(2020) Ferreira, Gabriel Max Dias; Ferreira, Guilherme Max Dias; Maldaner, Adriano Otávio; Silva, Luis Henrique Mendes da; Hespanhol, Maria do CarmoThe partitioning behaviors of cocaine freebase (CoF), cocaine hydrochloride (CoH), and a range of adulterants (procaine (PRO), phenacetin (PHE), caffeine (CAF), benzocaine (BEN), and lidocaine (LID)) in aqueous two-phase systems (ATPS) were evaluated, with the aim of developing a selective and efficient alternative technique for the identification of cocaine in samples confiscated by the police. The partition coefficients (KS) of all the solutes were obtained in ATPS formed using a macromolecule (PEO1500 or L35 copolymer), a salt (Na2SO4 or Li2SO4), and water. The KS values were consistently higher than 1 and increased with increase of the tie-line length. For the PEO1500 + Li2SO4 + water ATPS at pH 6.0, the KS values increased in the order: KLID < KPRO < KCAF < KCoF < KCoH < KPHE < KBEN. The greatest effect on the partitioning was shown by the polymer hydrophobicity, followed by the nature of the electrolyte and the pH of the ATPS. The ratio between two KS values for two different ATPS types was used as a strategic parameter for distinguishing between the two forms of cocaine, as well as between cocaine and the adulterants. The K12/K6 ratio, where K6 and K12 are the KS values for the PEO1500 + Li2SO4 + water ATPS at pH 6.0 and 12.0, respectively, enabled CoH to be distinguished from all the other solutes studied. In addition, the effect of the hydrophobicity of the polymer on the KS values was fundamental for distinguishing CoF from the other solutes.Item A simple and inexpensive thermal optic nanosensor formed by triblock copolymer and polydiacetylene mixture.(2018) Ferreira, Gabriel Max Dias; Ferreira, Guilherme Max Dias; Hespanhol, Maria do Carmo; Rezende, Jaqueline de Paula; Pires, Ana Clarissa dos Santos; Ortega, Paulo Fernando Ribeiro; Silva, Luis Henrique Mendes daPolydiacetylene (PDA) vesicles have been applied as optical sensors in different areas, although there are difficulties in controlling their responses. In this study, we prepared nanoblends of PDA with triblock copolymers (TC) as a better sensor system for detecting temperature change. The influences of diacetylene (DA) monomer, and the TC chemical structure and concentration on the colorimetric response (CR) were examined. The TC/PDA nanoblend was remarkably more sensitive to temperature change, than classical vesicles. A higher L64 concentration of 12.0% (w/w) reduced the chromatic transition temperature (Ttr) to as low as 24 °C. When using different TCs, the Ttr values can be ordered as L35 < F68< L64 < F127Item Solvophobic effect of 1-alkyl-3-methylimidazolium chloride on the thermodynamic of complexation between β-cyclodextrin and dodecylpyridinium cation.(2019) Patino Agudelo, Alvaro Javier; Coelho, Yara Luiza; Ferreira, Guilherme Max Dias; Ferreira, Gabriel Max Dias; Hudson, Eliara Acipreste; Pires, Ana Clarissa dos Santos; Silva, Luis Henrique Mendes daPreferential solvation participate in various supramolecular self-assembly processes, whose thermodynamic properties can be modulated by the addition of ionic liquids (ILs). However, the effects of these liquids on the thermodynamics of the host-guest complexation process remain unexplored. In this study, the thermodynamic properties of the complexation between 1-dodecylpyridinium cations (C12Py+) and β-cyclodextrin (βCD) species in aqueous solutions with different concentrations of 1-alkyl-3-methylimidazolium halides (CnmimX) were investigated by isothermal titration calorimetry. In water, C12Py+ and βCD form a 1:1 inclusion complex, which is enthalpically ( −9.2 ± 0.1 kJ mol−1) and entropically ( 16.1 ± 0.2 kJ mol−1) favorable. However, in IL aqueous solutions, all the βCD―C12Py+ thermodynamic parameters of the complexation change and this IL effect is dependent on the carbon chain length of Cnmim+ cations. ILs with shorter alkyl chains (Cnmim+, n ≤ 4) decreases the system entropy, while ILs with longer alkyl chains (Cnmim+, n ≥ 6) reduce the enthalpy values. These effects are attributed to i) preferential solvation of surfactant tails by ILs; ii) ability of the ILs to modify the 3D water structure and iii) inclusion of IL molecules into the inner cavities of βCD.Item 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; Carvalho, Megg Madonyk Cota Elias; Mageste, Aparecida Barbosa; Ferreira, Gabriel Max Dias; Silva, Luis Henrique Mendes da; 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 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.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.(2018) Teodoro, Filipe Simões; Carvalho, Megg Madonyk Cota Elias; 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 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 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.(2019) Carvalho, Megg Madonyk Cota Elias; Ferreira, Gabriel Max Dias; Almeida, Francine Tatiane Rezende de; Rosa, Nathália Cristina Martins; Silva, Isabela Almeida; Filgueiras, Jefferson Gonçalves; Azevedo, Eduardo Ribeiro de; Silva, Luis Henrique Mendes da; 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 Thermodynamic and kinetic analyses of curcumin and bovine serum albumin binding.(2018) Hudson, Eliara Acipreste; Paula, Hauster Maximiler Campos de; Ferreira, Guilherme Max Dias; Ferreira, Gabriel Max Dias; Hespanhol, Maria do Carmo; Silva, Luis Henrique Mendes da; Pires, Ana Clarissa dos SantosBovine serum albumin (BSA)/curcumin binding and dye photodegradation stability were evaluated. BSA/curcumin complex showed 1:1 stoichiometry, but the thermodynamic binding parameters depended on the technique used and BSA conformation. The binding constant was of the order of 105 L·mol−1 by fluorescence and microcalorimetric, and 103 and 104 L·mol−1 by surface plasmon resonance (steady-state equilibrium and kinetic experiments, respectively). For native BSA/curcumin, fluorescence indicated an enthalpic and entropic driven process based on the standard enthalpy change (ΔH○F = −8.67 kJ·mol−1), while microcalorimetry showed an entropic driven binding process (ΔH○cal = 29.11 kJ·mol−1). For the unfolded BSA/curcumin complex, it was found thatp ΔH○F = −16.12 kJ·mol−1 and ΔH○cal = −42.63 kJ·mol−1. BSA (mainly native) increased the curcumin photodegradation stability. This work proved the importance of using different techniques to characterize the protein-ligand binding.Item Thermodynamics of multi-walled carbon nanotube biofunctionalization using nisin : the effect of peptide structure.(2019) Ferreira, Guilherme Max Dias; Ferreira, Gabriel Max Dias; Almeida, Germanna Wilk Reis de; Soares, Nilda de Fatima Ferreira; Pires, Ana Clarissa dos Santos; Silva, Luis Henrique Mendes daA detailed adsorption thermodynamic study of two nisin variants (nisA and nisZ) on multi-walled carbon nanotubes (MWCNT) was conducted, and the antimicrobial properties of biofunctionalized MWCNT were evaluated. The MWCNT adsorption capacity for peptides () increased with pH increase, with greater values for nisZ ( up to 250 mg g−1) than for nisA ( up to 180 mg g−1) for all studied conditions. Zeta potential measurements (ζ) showed that the electrostatic repulsion between the MWCNT-peptide complexes determined the dispersion features that were stable at pH 2.0 and 3.0, with ζ reaching 45.0 mV at the lowest pH. Despite the similar ζ values for both peptides, slightly greater stabilization of MWCNT dispersions was exhibited in presence of nisZ at pH 3. At pH 4 and 5, peptide adsorption was not able to promote MWCNT dispersibility. Isothermal titration calorimetry revealed that the adsorption process was driven by enthalpy for both peptides, as the adsorption enthalpy changes () were less negative than −99.7 kJ mol−1. Despite the large dependence of on the pH and values, indicating the important role of electrostatic interactions on the adsorption process, a change in only one amino acid residue in the nisin structure promoted intense changes in the adsorption thermodynamic parameters. We have suggested that the more hydrophobic character of nisZ at the lower pH values caused this peptide to interact with the MWCNT surface through its two domains. Interesting, the antimicrobial properties of both peptides were not damaged, and the functionalized MWCNT showed antibacterial activity against the indicator micro-organism Lactococcus lactis in the agar diffusion and solution assays.Item Trimellitated sugarcane bagasse : a versatile adsorbent for removal of cationic dyes from aqueous solution. Part I : batch adsorption in a monocomponent system.(2018) Fideles, Renata Aparecida; Ferreira, Gabriel Max Dias; Teodoro, Filipe Simões; Herrera Adarme, Oscar Fernando; 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 energy and entropy of adsorption were calculated. These thermodynamic parameters were also used to evaluate the adsorption mechanism at both pH values.