EQA - Escola de Química e Alimentos
URI permanente desta comunidadehttps://rihomolog.furg.br/handle/1/1610
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16 resultados
Resultados da Pesquisa
- ItemKinetics and mechanism of the food dye FD&C Red 40 adsorption onto chitosan(ACS, 2011) Piccin, Jeferson Steffanello; Dotto, Guilherme Luiz; Vieira, Mery Luiza Garcia; Pinto, Luiz Antonio de AlmeidaThe kinetics and mechanism of the food dye disodium 6-hydroxy-5-((2-methoxy-5-methyl-4-sulfophenyl)azo)-2-naphthalenesulfonate (FD&C Red 40) adsorption onto chitosan were studied. The effects of pH (5.7 to 7.4), chitosan dosage [(250 to 500) mg 3 L 1], deacetylation degree (42 % to 84 %), and particle size [(0.10 to 0.26)mm] were investigated. The adsorption reaction models were used to evaluate the kinetic behavior. Infrared analysis and models based on mass transfer phenomena were used to investigate the adsorption mechanism. The maximum adsorption capacity (300 mg 3 g 1 ) was found at a pH 5.7, chitosan dosage of 250 mg 3 L 1 , deacetylation degree of 84 %, and particle size of 0.10 mm. Pseudosecond-order and Elovich models were the most appropriate to fit the experimental data of adsorption kinetics. The adsorption process was controlled by intraparticle diffusion, film diffusion, or convection according to the experimental conditions. Infrared analysis showed the chemical interaction between chitosan and food dye FD&C Red 40.
- ItemDiffusional mass transfer model for the adsorption of food dyes on chitosan films(Elsevier, 2014) Dotto, Guilherme Luiz; Buriol, Celene; Pinto, Luiz Antonio de AlmeidaThe adsorption kinetics of erythrosine B and indigo carmine on chitosan films was studied by a diffusional mass transfer model. The experimental curves were obtained in batch system under different conditions of stirring rate (80–200 rpm) and initial dye concentration (20–100 mg L−1). For the model development, external mass transfer and intraparticle diffusion steps were considered and the specific simplifications were based on the system characteristics. The proposed diffusional mass transfer model agreed very well with the experimental curves, indicating that the surface diffusion was the rate limiting step. The external mass transfer coefficient (kf) was dependent of the operating conditions and ranged from 1.32 × 10−4 to 2.17 × 10−4 m s−1. The values of surface diffusion coefficient (Ds) increased with the initial dye concentration and were in the range from 0.41 × 10−14 to 22.90 × 10−14 m2 s−1. The Biot number ranged from 17.0 to 478.5, confirming that the intraparticle diffusion due to surface diffusion was the rate limiting step in the adsorption of erythrosine B and indigo carmine on chitosan films.
- ItemApplication of chitosan films for the removal of food dyes from aqueous solutions by adsorption(Elsevier, 2013) Dotto, Guilherme Luiz; Moura, Jaqueline Motta de; Cadaval Junior, Tito Roberto Sant'Anna; Pinto, Luiz Antonio de AlmeidaChitosan films were applied to remove acid red 18 and FD&C blue no. 2 dyes from aqueous solutions. The films were prepared by casting technique and characterized. Batch adsorption equilibrium experiments were carried out at different temperatures (298–328 K). Freundlich, Langmuir and Redlich–Peterson models were fitted to the experimental data. The thermodynamic parameters (ΔG0, ΔH0 and ΔS0) were also estimated. Kinetic study was realized using pseudo-first order, pseudo-second order and Elovich models. The possible films–dyes interactions were investigated by Fourier transform infrared spectroscopy, differential scanning calorimetry and color parameters. The maximum experimental adsorption capacities were 194.6 mg g−1 and 154.8 mg g−1 for the acid red 18 and FD&C blue no. 2, respectively, obtained at 298 K. It was found that the Redlich–Peterson isotherm model presented satisfactory fit with the experimental data (R2 > 0.98 and ARE < 9.00%). The adsorption process was spontaneous, favorable, exothermic, and occurred by electrostatic interactions. The Elovich model was the more appropriate to represent the adsorption kinetic data (R2 > 0.95 and ARE < 5.00%). The chitosan films maintained its structure and were easily separated from the liquid phase after the adsorption process.
- ItemAdsorption of food dyes onto chitosan: Optimization process and kinetic(Elsevier, 2011) Dotto, Guilherme Luiz; Pinto, Luiz Antonio de AlmeidaAdsorption of food dyes acid blue 9 and food yellow 3 onto chitosan was optimized. Chitosan was obtained from shrimp wastes and characterized.Afull factorial design was used to analyze the effects of pH, stirring rate and contact time in adsorption capacity. In the optimal conditions, adsorption kinetics was studied and the experimental data were fitted with three kinetic models. The produced chitosan showed good characteristics for dye adsorption. The optimal conditions were: pH 3, 150rpm and 60 min for acid blue 9 and pH 3, 50rpm and 60 min for food yellow 3. In these conditions, the adsorption capacities values were 210mgg−1 and 295mgg−1 for acid blue 9 and food yellow 3, respectively. The Elovich kinetic model was the best fit for experimental data and it showed the chemical nature of dyes adsorption onto chitosan.
- ItemEvaluation of mechanical properties and water vapor permeability in Chitosan biofilms using Sorbitol and Glycerol(Wiley-VHC, 2012) Moura, Catarina Motta de; Moura, Jaqueline Motta de; Santos, Jaqueline Pozzada dos; Kosinski, Roberta da Costa; Dotto, Guilherme Luiz; Pinto, Luiz Antonio de AlmeidaChitosan biofilms were prepared with and without plasticizer (glycerol and sorbitol). The physical and mechanical properties of chitosan biofilms with and without plasticizer were evaluated. Chitosan was obtained from shrimp wastes and characterized. The film forming solution (FFS) was obtained through chitosan dissolution and drying. The solution had its pH adjusted to 6.0 and oven dried (40 8C, 24 h) with forced air circulation. Chitosan biofilms without plasticizer showed a tensile strength about 36% higher than biofilms produced with plasticizer. On the other hand, biofilms with plasticizer presented superior values of elongation. The permeability of the water vapor and color presented significant difference (p<0.05) between all biofilms. Chitosan/plasticizer biofilms showed higher values of water vapor permeability in relation to chitosan biofilms without plasticizer.
- ItemPreparation of bionanoparticles derived from Spirulina platensis and its application for Cr (VI) removal from aqueous solutions(Elsevier, 2012) Dotto, Guilherme Luiz; Cadaval Junior, Tito Roberto Sant'Anna; Pinto, Luiz Antonio de AlmeidaSpirulina platensis nanoparticles were prepared by mechanical agitation and were applied to removal Cr (VI) from aqueous solutions. Nanoparticles preparation was function of stirring rate and contact time. In the optimal conditions, Cr (VI) removal by nanoparticles as a function of pH and initial ion concentration was carried out. The optimal conditions for preparation were 10,000 rpm and 20 min, and the nanoparticles presented mean diameter of 215.6 nm and polydispersity index of 0.151. The best conditions for Cr (VI) removal were at pH 4 and ion concentration of 250 mg L 1, and the Cr (VI) removal percentage was 99.1%.
- ItemUse of Spirulina platensis micro and nanoparticles for the removal synthetic dyes from aqueous solutions by biosorption(Elsevier, 2012) Dotto, Guilherme Luiz; Cadaval Junior, Tito Roberto Sant'Anna; Pinto, Luiz Antonio de AlmeidaIn this research, micro and nanoparticles of Spirulina platensis dead biomass were obtained, characterized and employed to removal FD&C red no. 40 and acid blue 9 synthetic dyes from aqueous solutions. The effects of particle size (micro and nano) and biosorbent dosage (from 50 to 750 mg) were studied. Pseudofirst order, pseudo-second order and Elovich models were used to evaluate the biosorption kinetics. The biosorption nature was verified using energy dispersive X-ray spectroscopy (EDS). The best results for both dyes were found using 250 mg of nanoparticles, in these conditions, the biosorption capacities were 295 mg g−1 and 1450 mg g−1, and the percentages of dye removal were 15.0 and 72.5% for the FD&C red no. 40 and acid blue 9, respectively. Pseudo-first order model was the more adequate to represent the biosorption of both dyes onto microparticles, and Elovich model was more appropriate to the biosorption onto nanoparticles. The EDS results suggested that the dyes biosorption onto microparticles occurred mainly by physical interactions, and for the nanoparticles, chemisorption was dominant.
- ItemChitosan scaffold as an alternative adsorbent for the removal of hazardous food dyes from aqueous solutions(Elsevier, 2014) Esquerdo, Vanessa Mendonça; Cadaval Junior, Tito Roberto Sant'Anna; Dotto, Guilherme Luiz; Pinto, Luiz Antonio de AlmeidaHypothesis: The dye adsorption with chitosan is considered an eco-friendly alternative technology in relation to the existing water treatment technologies. However, the application of chitosan for dyes removal is limited, due to its low surface area and porosity. Then we prepared a chitosan scaffold with a megaporous structure as an alternative adsorbent to remove food dyes from solutions. Experiments: The chitosan scaffold was characterized by infrared spectroscopy, scanning electron microscopy and structural characteristics. The potential of chitosan scaffold to remove five food dyes from solutions was investigated by equilibrium isotherms and thermodynamic study. The scaffold–dyes interactions were elucidated, and desorption studies were carried out. Findings: The chitosan scaffold presented pore sizes from 50 to 200 lm, porosity of 92.2 ± 1.2% and specific surface area of 1135 ± 2 m2 g 1. The two-step Langmuir model was suitable to represent the equilibrium data. The adsorption was spontaneous, favorable, exothermic and enthalpy-controlled process. Electrostatic interactions occurred between chitosan scaffold and dyes. Desorption was possible with NaOH solution (0.10 mol L 1). The chitosan megaporous scaffold showed good structural characteristics and high adsorption capacities (788–3316 mg g 1).
- ItemBiossorção de corantes alimentícios utilizando nanopartículas de Spirulina platensis(2012) Dotto, Guilherme Luiz; Pinto, Luiz Antonio de AlmeidaNeste trabalho foi verificado o potencial de aplicação de nanopartículas de S. platensis para a remoção de três corantes alimentícios de soluções aquosas pelo processo de biossorção. Primeiramente, as nanopartículas foram preparadas, caracterizadas e tiveram seu potencial de biossorção comparado com micropartículas de S. platensis. Em seguida, a biossorção dos corantes pelas nanopartículas foi avaliada em diversas condições experimentais mediante estudos sequenciais de isotermas de equilíbrio, termodinâmica, otimização estatística e cinética. Por fim, foram elucidados o mecanismo de transferência de massa do processo e as interações entre as nanopartículas e os corantes. Os resultados mostraram que as nanopartículas podem ser preparadas pela técnica de agitação mecânica utilizando taxa de agitação de 10000 rpm por 20 min. Nestas condições foram obtidas nanopartículas, estáveis, monodispersas com diâmetro médio de 215,6 nm e forma elipsoidal-esférica. As nanopartículas de S. platensis apresentaram potencial superior em relação às micropartículas para a biossorção dos três corantes. O estudo das isotermas mostrou que a biossorção foi favorecida em meio ácido e temperatura de 25 °C, sendo o modelo de Sips o mais adequado para representar os dados experimentais. A biossorção dos três corantes pelas nanopartículas foi um processo espontâneo, favorável e exotérmico. As condições ótimas para a biossorção foram pH 2, 400 rpm e 100 min para os corantes amarelo tartrazina e azul brilhante, e pH 2, 225 rpm e 100 min para o corante vermelho n° 40. Nestas condições, as capacidades de biossorção foram, respectivamente, 228,2, 1653,0 e 400,3 mg g-1 , para os corantes amarelo tartrazina, azul brilhante e vermelho n° 40. O modelo cinético de Avrami foi o mais adequado para representar a biossorção dos três corantes pelas nanopartículas. A transferência de massa externa e a difusão intrapartícula atuaram simultaneamente na biossorção dos três corantes pelas nanopartículas, sendo que, o principal mecanismo difusivo intrapartícula foi a difusão superficial. A biossorção dos três corantes pelas nanopartículas de S. platensis, em condições ácidas, ocorreu principalmente por quimiosorção. Os grupamentos amina e hidroxila das nanopartículas foram responsáveis pela interação com os corantes. Os resultados apresentados nesta pesquisa mostram que as nanopartículas de S. platensis são um potencial nanobioadsorvente que pode ser utilizado no pós-tratamento de efluentes contendo corantes alimentícios.
- ItemADSORPTION ISOTHERMS AND THERMOCHEMICAL DATA OF FD&C RED N° 40 BINDING BY CHITOSAN(Abeq, 2011) Pinto, Luiz Antonio de Almeida; Picci, Jeferson Steffanello; Dotto, Guilherme LuizChitosan is a natural polymer that has been employed in dye adsorption. In this work, adsorption and thermodynamic data for the interaction of FD&C Red n° 40 food dye with chitosan in aqueous solutions were investigated. The equilibrium adsorption isotherms were determined by the batch method, from 298 to 338 K. Adsorption data were adjusted to five isotherm models: Langmuir, Freundlich, Redlich-Peterson, Temkin and Dubinin-Radushkevich, in order to determine which presented the best adjustment to the experimental data. Error analysis showed that the Langmuir isotherm model was the most appropriate for fitting the experimental data, with a maximum monolayer adsorption of 3065.8 μmol g-1 at 308 K. Negative enthalpy (-112.7 kJ mol-1), entropy (-0.338 kJ mol-1 K-1) and Gibbs free energy (-15.6 to 1.0 kJ mol-1) values demonstrated that the adsorption process is exothermic, spontaneous, favorable, and that randomness of the system decreases during the adsorption process.