Research Interests:
Research Interests:
Viscoelastic properties of layers of polyampholytes adsorbed on charged surfaces were studied by quartz microgravimetry. By applying the Voigt viscoelastic model the effective mass and thickness of layers after adsorption from solution at... more
Viscoelastic properties of layers of polyampholytes adsorbed on charged surfaces were studied by quartz microgravimetry. By applying the Voigt viscoelastic model the effective mass and thickness of layers after adsorption from solution at different salt concentrations were calculated. The obtained results were compared with the Sauerbrey equation, which applies to the case of thin, rigid adsorbed layers. The estimates of
Research Interests:
Research Interests:
Research Interests:
Research Interests:
Research Interests:
Cellulose nanocrystals, also known as cellulose whiskers, are the crystalline domains of cellulosic sources. These nanoparticles, when isolated, have been evaluated as reinforcement material in polymeric matrixes due to their potential to... more
Cellulose nanocrystals, also known as cellulose whiskers, are the crystalline domains of cellulosic sources. These nanoparticles, when isolated, have been evaluated as reinforcement material in polymeric matrixes due to their potential to improve, among others, the mechanical, optical, and dielectric properties of these matrixes. Recent literature works, involving raw material, isolation process, characterization, and performance of isolated cellulose whiskers, were considered when working out this paper. Tables summarizing the dimensional characteristics with their respective sources, description of isolation processes, hydrolysis conditions, techniques of determination and performance of this material in suspension and in polymeric matrixes are presented. Also contained in this work are challenges to be met in this promising research area, especially with regard to whisker dispersibility, connected with their tendency towards agglomeration, and their compatibility with commercial ...
Polyelectrolyte complexes (PEC) were evaluated in this study as paper dry-strength agent. These complexes were formed between a cationic starch (CS) and an anionic carboxymetylcellulose (CMC) at different ratios of the polymers at pH 7... more
Polyelectrolyte complexes (PEC) were evaluated in this study as paper dry-strength agent. These complexes were formed between a cationic starch (CS) and an anionic carboxymetylcellulose (CMC) at different ratios of the polymers at pH 7 and ionic strength 1000 mM NaCl. Firstly, individual polyelectrolyte solutions were characterized by turbidity and charge density. The polyelectrolyte complexes formed were characterized by turbidity and charge density as well. The results showed that the charge density of cationic polyelectrolyte solution was very lower than the charge density of the anionic polyelectrolyte solution at the same solution concentration, 200 mg/L, 43.5 and 633.8 mEq/g, respectively. When the complexes were formed, the turbidity of the solution complexes was higher than the turbidity of the solution separated, cationic or anionic. The maximum turbidity, 10.5 NTU, was found when the cationic to anionic ratio was very high, 80mg of starch to 5.5 mg of CMC. It is important ...
The relation between the properties of polyampholytes in aqueous solution and their adsorption behaviors on silica and cellulose surfaces was investigated. Four polyampholytes carrying different charge densities but with the same nominal... more
The relation between the properties of polyampholytes in aqueous solution and their adsorption behaviors on silica and cellulose surfaces was investigated. Four polyampholytes carrying different charge densities but with the same nominal ratio of positive to negative segments and two structurally similar polyelectrolytes (a polyacid and a polybase) were investigated by using quartz crystal microgravimetry using silica-coated and cellulose-coated quartz resonators. Time-resolved mass and rigidity (or viscoelasticity) of the adsorbed layer was determined from the shifts in frequency (Deltaf) and energy dissipation (DeltaD) of the respective resonator. Therefore, elucidation of the dynamics and extent of adsorption, as well as the conformational changes of the adsorbed macromolecules, were possible. The charge properties of the solid surface played a crucial role in the adsorption of the studied polyampholytes, which was explained by the capability of the surface to polarize the polyampholyte at the interface. Under the same experimental conditions, the polyampholytes had a higher nominal charge density phase-separated near the interface, producing a soft, dissipative, and loosely bound layer. In the case of cellulose substrates, where adsorption was limited, electrostatic and polarization effects were concluded to be less significant.
Research Interests:
Low phosphorus use efficiency (PUE) is one of the major reasons of poor production worldwide. Among the various approaches used to enhance PUE, polymer coated fertilizers are relatively a new concept. Its main advantages are that they... more
Low phosphorus use efficiency (PUE) is one of the major reasons of poor production worldwide. Among the various approaches used to enhance PUE, polymer coated fertilizers are relatively a new concept. Its main advantages are that they dissolve slowly and release nutrients to plants gradually during the growing season. Keeping this in view, a study was performed in the laboratory to evaluate polymers coated monoammonium phosphate (MAP) to enhance PUE. Commercial MAP and MAP coated with biodegradable polymers with Krafit black liquor (BL) and cellulose acetate (CA) in the concentration (0.5, 1.0, 2.0 wt % coating). The effectiveness of these coatings was assessed by the electrical conductivity (EC) and phosphorus release (PR) in a kinetic experiment. The kinetic study was carried out in a controlled environment (± 25 °C), following the release pattern of P from 1.5 g of fertilizer in 50 mL of H2O, with and without the coatings. The objective of this work was to study different lignin-...
Research Interests: Plant Biology and May
O bagaço de malte é o principal resíduo da indústria cervejeira. Frente a isso, surge a necessidade de avaliar diferentes formas de reaproveitamento deste material. O presente estudo teve como objetivos principais caracterizar a biomassa... more
O bagaço de malte é o principal resíduo da indústria cervejeira. Frente a isso, surge a necessidade de avaliar diferentes formas de reaproveitamento deste material. O presente estudo teve como objetivos principais caracterizar a biomassa e avaliar as possibilidades para seu reaproveitamento como matéria-prima para produtos de valor agregado. Foram obtidos teores de 29,92% de hemiceluloses, 21,16% de proteínas, 20,80% de lignina total, 15,99% de celulose, 8,33% de extrativos e 3,76% de cinzas no material. A composição química encontrada possibilita diversas aplicações deste resíduo como matéria-prima para obtenção de produtos de maior valor agregado. Estas aplicações estão relacionadas aos altos teores de fibras lignocelulósicas e de proteínas, sendo as principais: produção de etanol de segunda geração, de carvão hidrotérmico, de ácido lático, de HMF e de produtos para nutrição humana.
Research Interests:
Nesse trabalho simulou-se, no programa computacional Aspen Plus, a atividade catalítica da zircônia sulfatada no processo de transesterificação da triacetina e avaliou-se a viabilidade econômica das plantas geradas. Nas simulações... more
Nesse trabalho simulou-se, no programa computacional Aspen Plus, a atividade catalítica da zircônia sulfatada no processo de transesterificação da triacetina e avaliou-se a viabilidade econômica das plantas geradas. Nas simulações realizadas, comparou-se o desempenho dos reatores CSTR e PFR a 150°C e 12 bar com o desempenho dos mesmos em condições de operação mais brandas, em torno de 60°C e 1 bar. Nesse último caso, analisou-se o efeito da implantação de uma corrente de reciclo em cada reator. O preço mínimo de venda (PMV) do acetato de metila foi o parâmetro usado para determinar a planta mais viável. Os resultados mostraram que a configuração com o PFR a 150°C e 12 bar foi a que apresentou o menor PMV, 0,98 USD kg-1, e, portanto, foi a mais economicamente viável. A redução nas condições de operação do PFR gerou os maiores PMVs, já para o CSTR, a redução gerou o segundo menor PMV.
Devido aos períodos de crise hídrica nas diferentes Regiões do Brasil é necessário utilizar novas fontes de captação, sendo indispensáveis ensaios de tratabilidade. Foi estudada a viabilidade do uso do Delineamento Composto Central (DCC)... more
Devido aos períodos de crise hídrica nas diferentes Regiões do Brasil é necessário utilizar novas fontes de captação, sendo indispensáveis ensaios de tratabilidade. Foi estudada a viabilidade do uso do Delineamento Composto Central (DCC) nos ensaios de tratabilidade de água como substituição à análise clássica do diagrama de coagulação, por fatorial completo. Os parâmetros de interesse foram a dose de sulfato de alumínio (5 e 60 mg.L-1) e o pH inicial (6 e 8). A variável resposta foi a eficiência de remoção de turbidez. Foi possível maximizar a resposta no ponto de pH inicial de 7,23 e dosagem de 49,9 mg L-1 e encontrar regiões de remoção superior a 80% comuns a ambos os métodos, indicando que o DCC pode ser uma ferramenta viável para análise se comparada com o método convencional, tendo como vantagem a redução da quantidade de ensaios e, consequentemente, o tempo de operação.
O despejo inadequado de efluentes em lagos e rios, associado ao incremento da matéria orgânica dissolvida, tem sido apontado como uma das principais causas do aumento da concentração de íons ferro e manganês presentes na água. Neste... more
O despejo inadequado de efluentes em lagos e rios, associado ao incremento da matéria orgânica dissolvida, tem sido apontado como uma das principais causas do aumento da concentração de íons ferro e manganês presentes na água. Neste trabalho, estudou-se o uso de peróxido de hidrogênio como agente oxidante, em pH próximo ao neutro, na tentativa de remover os íons na forma de precipitados. Foram realizados ensaios em testes de jarros em diferentes concentrações do oxidante, entre valores de 0.63 a 3.8ppm, associado a uma dosagem de 20ppm de PAC, coagulante usualmente utilizados em Estações de Tratamento de Água. Nestas condições, observou-se a remoção de 90% de íons ferro e 36% de íons manganês, sendo que o consumo de peroxido foi de até 40%. Não foi observado efeito significativo sobre os resultados para as diferentes dosagens de oxidante.
A água a ser utilizada em processos industriais demanda um tratamento e qualidade diferenciados. O objetivo desse estudo foi investigar o uso de três materiais celulósicos para abrandamento da água, sendo duas celuloses microcristalinas... more
A água a ser utilizada em processos industriais demanda um tratamento e qualidade diferenciados. O objetivo desse estudo foi investigar o uso de três materiais celulósicos para abrandamento da água, sendo duas celuloses microcristalinas com granulometrias diferentes (CMC101 e CMC500) e a polpa Kraft de Eucalyptus branqueada. Realizou-se um estudo cinético para a obtenção de parâmetros otimizados, e determinaram-se isotermas de adsorção, utilizando diferentes concentrações de cálcio e assumindo três diferentes níveis de pH. A partir dos resultados, pode-se observar que o modelo cinético de pseudo-segunda ordem apresentou o melhor coeficiente de correlação e o modelo de isoterma Freundilch apresentou melhor ajuste aos dados experimentais, sendo a maior adsorção no nível de pH 7,0 para os três materiais, em que as amostras de CMC adsorveram mais significativamente que a polpa. Conclui-se então que o objetivo foi alcançado
Research Interests:
Research Interests:
Cellulose nanocrystals, also known as cellulose whiskers, are the crystalline domains of cellulosic sources. These nanoparticles, when isolated, have been evaluated as reinforcement material in polymeric matrixes due to their potential to... more
Cellulose nanocrystals, also known as cellulose whiskers, are the crystalline domains of cellulosic sources. These nanoparticles, when isolated, have been evaluated as reinforcement material in polymeric matrixes due to their potential to improve, among others, the mechanical, optical, and dielectric properties of these matrixes. Recent literature works, involving raw material, isolation process, characterization, and performance of isolated cellulose whiskers, were considered when working out this paper. Tables summarizing the dimensional characteristics with their respective sources, description of isolation processes, hydrolysis conditions, techniques of determination and performance of this material in suspension and in polymeric matrixes are presented. Also contained in this work are challenges to be met in this promising research area, especially with regard to whisker dispersibility, connected with their tendency towards agglomeration, and their compatibility with commercial ...
Structures consisting of cationic polyelectrolyte and anionic cellulose nanocrystals at different charge ratios, q+/q-, were manufactured for use in improving handmade paper strength properties. Eucalyptus bleached pulp with low fines... more
Structures consisting of cationic polyelectrolyte and anionic cellulose nanocrystals at different charge ratios, q+/q-, were manufactured for use in improving handmade paper strength properties. Eucalyptus bleached pulp with low fines content was used in the paper manufacturing. Cationic starch sample was used as the polyelectrolyte to be associated with nanocrystals isolated from cotton fibers. All study was done on the basis of charge densities of both materials, cationic starch and cellulose nanocrystals. Reference test was conducted for comparison purpose. Results of tensile index of cationic polyelectrolyte (9.8 N.m.g-1) and cellulose nanocrystals (9.1 N.m.g-1) separately applied were higher than the reference test (8.2 N.m.g-1). The association of cationic polyelectrolyte and the anionic cellulose nanocrystals at different charge ratios, +q/q-, resulted in suspensions with different charge balancing when compared to the suspensions with the original constituents only. This ena...
This article considers the role of polyampholytes as strength additives for paper and also reviews recent studies that provide insight as to how they work. Practical results will be cited that confirm the ability of these polymers, which... more
This article considers the role of polyampholytes as strength additives for paper and also reviews recent studies that provide insight as to how they work. Practical results will be cited that confirm the ability of these polymers, which have both positive and negative charges, to increase the dry-strength of paper. A case will be made that the superior ability of polyampholytes to increase paper’s strength is related to their behaviors in solution and when adsorbing onto solids surfaces. Theoretical and practical considerations related to polyampholytes are discussed in light of published work.
Research Interests:
During the course of infection, Salmonella must successively survive the harsh acid stress of the stomach and multiply into a mild acidic compartment within macrophages. Inducible amino acid decarboxylases are known to promote adaptation... more
During the course of infection, Salmonella must successively survive the harsh acid stress of the stomach and multiply into a mild acidic compartment within macrophages. Inducible amino acid decarboxylases are known to promote adaptation to acidic environments, as lysine decarboxylation to cadaverine. The idea of Salmonella defenses responses could be employed in systems as polydiacetylene (PDA) to detect this pathogen so important to public health system. Beside that PDA is an important substance because of the unique optical property; that undergoes a colorimetric transitions by various external stimuli. Therefore 10,12-pentacosadyinoic acid (PCDA)/Sphingomyelin(SPH)/Cholesterol(CHO)/Lysine system was tested to determine the colorimetric response induced by Salmonella choleraesuis. PCDA/SPH/CHO/Lysine vesicles showed a colour change even in low S. choleraesuis concentration present in laboratory conditions and in chicken meat. Thus, this work showed a PCDA/SPH/CHO/Lysine vesicle application to simplify routine analyses in food industry, as chicken meat industry.
Research Interests:
The relation between the properties of polyampholytes in aqueous solution and their adsorption behaviors on silica and cellulose surfaces was investigated. Four polyampholytes carrying different charge densities but with the same nominal... more
The relation between the properties of polyampholytes in aqueous solution and their adsorption behaviors on silica and cellulose surfaces was investigated. Four polyampholytes carrying different charge densities but with the same nominal ratio of positive to negative segments and two structurally similar polyelectrolytes (a polyacid and a polybase) were investigated by using quartz crystal microgravimetry using silica-coated and cellulose-coated quartz resonators. Time-resolved mass and rigidity (or viscoelasticity) of the adsorbed layer was determined from the shifts in frequency (Deltaf) and energy dissipation (DeltaD) of the respective resonator. Therefore, elucidation of the dynamics and extent of adsorption, as well as the conformational changes of the adsorbed macromolecules, were possible. The charge properties of the solid surface played a crucial role in the adsorption of the studied polyampholytes, which was explained by the capability of the surface to polarize the polyampholyte at the interface. Under the same experimental conditions, the polyampholytes had a higher nominal charge density phase-separated near the interface, producing a soft, dissipative, and loosely bound layer. In the case of cellulose substrates, where adsorption was limited, electrostatic and polarization effects were concluded to be less significant.
Research Interests:
ABSTRACT
Research Interests:
... The sensors are usually recycled after removal of the film, with limited success, after one of two treatments, either hot acid or ammoniac solutions. ... When applied to remove cellulose films, this solution demanded a long treatment... more
... The sensors are usually recycled after removal of the film, with limited success, after one of two treatments, either hot acid or ammoniac solutions. ... When applied to remove cellulose films, this solution demanded a long treatment time for complete film removal. ...
Research Interests:
Research Interests:
Viscoelastic properties of layers of polyampholytes adsorbed on charged surfaces were studied by quartz microgravimetry. By applying the Voigt viscoelastic model the effective mass and thickness of layers after adsorption from solution at... more
Viscoelastic properties of layers of polyampholytes adsorbed on charged surfaces were studied by quartz microgravimetry. By applying the Voigt viscoelastic model the effective mass and thickness of layers after adsorption from solution at different salt concentrations were calculated. The obtained results were compared with the Sauerbrey equation, which applies to the case of thin, rigid adsorbed layers. The estimates of