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Removal of Pb2+ from aqueous solutions using two Brazilian rocks containing zeolites

Shinzato, M. C.; Montanheiro, T. J.; Janasi, Valdecir de Assis; Andrade, S.; Yamamoto, Jorge Kazuo
Fonte: SPRINGER; NEW YORK Publicador: SPRINGER; NEW YORK
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
46.13%
The removal of Pb2+ from aqueous solution by two Brazilian rocks that contain zeolites-amygdaloidal dacite (ZD) and sandstone (ZS)-was examined by batch experiments. ZD contains mordenite and ZS, stilbite. The effects of contact time, concentration of metal in solution and capacity of Na+ to recover the adsorbed metals were evaluated at room temperature (20A degrees C). The sorption equilibrium was reached in the 30 min of agitation time. Both materials removed 100% of Pb2+ from solutions at concentrations up to 50 mg/L, and at concentrations larger than 100 mg/L of Pb2+, the adsorption capacity of sandstone was more efficient than that of amygdaloidal dacite due to the larger quantities and the type of zeolites (stilbite) in the cement of this rock. All adsorbed Pb2+ was easily replaced by Na+ in both samples. The analysis of the adsorption models using nonlinear regression revealed that the Sips and the Freundlich isotherms provided the best fit for the ZS and ZD experimental data, respectively, indicating the heterogeneous adsorption surfaces of these zeolites.; Fundacao de Amparo a Pesquisa do Estado de Sao Paulo; Fundacao de Amparo a Pesquisa do Estado de Sao Paulo [03/06259-4]

Background concentrations and adsorption of selenium in tropical soils; Valores de referência e adsorção de selênio em solos tropicais

Gabos, Mariana Bassetto
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 25/06/2012 EN
Relevância na Pesquisa
36.19%
Selenium (Se) is a trace element essential to the nutrition of animals. On the other hand, in a narrow concentration range, Se can cause toxicity. The presence of Se in food is related to the concentration of the element in soil. Thus, the knowledge of the Se amount and its behavior in soil are very important to the better manage the environment and to prevent toxicological problems and human deficiency. The objectives of this study were: (i) to quantify the natural content of Se in some Brazilian soils and correlates them with soil attributes; (ii) to evaluate the adsorption of selenite and selenate as a function of pH and Se concentration in tropical soils; (iii) to adjust the constant capacitance model to describe the Se adsorption in tropical soil as compared to empiric models. Se concentrations ranged from <0.08 to 1.61 mg kg-1, with a mean of 0.19 mg kg-1. Concentrations of Se in the samples collected in the superficial layers were positively correlated to cationic exchange capacity, as well as to clay, organic matter and oxide contents of the soils. In the subsurface samples, only pH and aluminum oxide content were correlated with Se concentrations. Most samples with the highest Se concentrations were derived from sedimentary parent material. Se(IV) adsorption was high for all soils...

Adsorção sequencial unidimensional: Modelos para automontagem de moléculas; Unidimensional sequential adsorption: Models for self-assembly of molecules.

Melo, Alexandre Martins
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 15/08/2005 PT
Relevância na Pesquisa
36.34%
Neste trabalho estudamos deposição de partículas em redes unidimensionais, com uma abordagem estatística a partir de modelos como absorção sequencial aleatória (RSA) e cooperativa (CSA). O objetivo é a simulação de formação de monocamadas oligoméricas automontadas em substratos, que se justifica devido aos recentes avanços, por um lado, na área experimental, na formação de SAMs (self-assembled monolayers) e produção de nanoestruturas e, por um lado, na área teórica, no desenvolvimento de diversos modelos estocásticos para processos de adsorção sequencial. Introduzimos o modelo clássico de adsorção sequencial aleatória, a nomenclatura utilizada, e estudamos algumas de suas características. Analisamos a fração da rede que permanece vazia após ser atingida a saturação, para oligômeros formados por um número K de unidades. Em seguida, estudamos a cinética de um processo RSA, primeiro para o caso de monômeros, depois para dímeros, e então para oligômeros maiores. A estrutura da camada para o caso de dímeros é examinada a partir da distribuição de tamanhos de grãos (número de K-meros adjacentes), e da função de correlação. Os dados obtidos nas nossas simulações de Monte Carlo são comparados com resultados de modelos estocásticos existentes na literatura. A partir desse ponto...

Nanotubos de carbono como nanoadsorventes na remoção de corantes sintéticos de soluções aquosos : um estudo experimental e teórico

Machado, Fernando Machado
Fonte: Universidade Federal do Rio Grande do Sul Publicador: Universidade Federal do Rio Grande do Sul
Tipo: Tese de Doutorado Formato: application/pdf
POR
Relevância na Pesquisa
36.24%
Este trabalho teve como objetivo investigar a adsorção de corantes têxteis (Vermelho Reativo 194 e Azul de Prociona MX-R) em nanotubos de carbono (NTC) em meio aquoso. Para tanto, empregou-se nanotubos de carbono de paredes múltiplas (NTCPM) e carvão ativo (CA) em pó, ambos comerciais, na remoção do corante têxtil Vermelho Reativo 194 e nanotubos de carbono de parede simples (NTCPS) e NTCPM na remoção do corante têxtil Azul de Prociona MX-R. Os NTCPS foram sintetizados utilizando a técnica de deposição química de vapor catalisada. Os adsorventes foram caracterizados por espectroscopia no infravermelho e Raman, isotermas de adsorção/dessorção de N2 e microscopia eletrônica de varredura e de transmissão. Os efeitos do pH, tempo de agitação e da temperatura na capacidade de adsorção foram investigados. O tempo de contato para obter equilíbrio a 298 K foi fixado em uma hora para o caso onde foi empregado o corante Vermelho Reativo 194 e três horas para o caso onde foi empregado o Azul de Prociona MX-R. A região de pH ácido (pH 2,0) foi favorável para as adsorções de ambos corantes. A energia de ativação do processo de adsorção foi avaliada nas temperaturas entre 298-323 K para os NTCPM e CA, na adsorção do corante Vermelho Reativo 194. O modelo cinético de ordem fracionária de Avrami foi o que melhor se ajustou aos dados experimentais do corante Vermelho Reativo 194 em comparação com os modelos cinéticos de adsorção de pseudo-primeira ordem e pseudo-segunda ordem. Por outro lado...

Study of biosorption of rare earth metals (La, Nd, Eu, Gd) by Sargassum sp. biomass in batch systems: Physicochemical evaluation of kinetics and adsorption models

Oliveira, R. C.; Garcia, O.
Fonte: Universidade Estadual Paulista Publicador: Universidade Estadual Paulista
Tipo: Conferência ou Objeto de Conferência Formato: 605-608
ENG
Relevância na Pesquisa
46.25%
This work evaluated kinetic and adsorption physicochemical models for the biosorption process of lanthanum, neodymium, europium, and gadolinium by Sargassum sp. in batch systems. The results showed: (a) the pseudo-second order kinetic model was the best approximation for the experimental data with the metal adsorption initial velocity parameter in 0.042-0.055 mmol.g -1.min-1 (La < Nd < Gd < Eu); (b) the Langmuir adsorption model presented adequate correlation with maximum metal uptake at 0.60-0.70 mmol g-1 (Eu < La < Gd < Nd) and the metal-biomass affinity parameter showed distinct values (Gd < Nd < Eu < La: 183.1, 192.5, 678.3, and 837.3 L g-1, respectively); and (c) preliminarily, the kinetics and adsorption evaluation did not reveal a well-defined metal selectivity behavior for the RE biosorption in Sargassum sp., but they indicate a possible partition among RE studied. © (2009) Trans Tech Publications.

Adsorption of heavy metal ions and epoxidation catalysis using a new polyhedral oligomeric silsesquioxane

Soares, Isaac V.; Vieira, Eduardo G.; Filho, Newton L.D.; Bastos, Andréa C.; da Silva, Niléia C.; Garcia, Edemir F.; Lima, Lucélia Julia A.
Fonte: Universidade Estadual Paulista Publicador: Universidade Estadual Paulista
Tipo: Artigo de Revista Científica Formato: 405-414
ENG
Relevância na Pesquisa
36.24%
The objective of this research was the preparation of a silsesquioxane functionalized with eight chloropropyl chains (T8-PrCl) and of a new derivative functionalized with a pendant linear chain (2-amino-1,3,4-thiadiazole - ATD; T8-Pr-ATD). The two nanostructured materials were characterized by 13C and 29Si NMR, FTIR and elemental analysis. The new nanostructured material, octakis[3-(2-amino-1,3,4-thiadiazole)propyl] octasilsesquioxane (T8-Pr-ATD), was tested as a ligand for transition-metal ions with a special attention to adsorption isotherms. The adsorption was performed using a batchwise process and the organofunctionalized surface showed the ability to adsorb the metal ions Cu (II), Co (II), and Ni (II) from water and ethanol. The adsorption isotherms were fitted by Langmuir, Freundlich, Temkin and Dubinin-Radushkevich (D-R) model. The kinetics of adsorption of metals were performed using three models such as pseudo-first order, pseudo-second order and Elovich. The Langmuir and Elovich models were the most appropriate to describe the adsorption and kinetic data, respectively. Furthermore, the T8-Pr-ATD was successfully applied to the analysis of environmental samples (river and sea water). Subsequently, a new nanomaterial was prepared by functionalization of the T8-Pr-ATD with a Mo (II) organometallic complex (T8-Pr-ATD-Mo). Only a few works in the literature have reported this type of substitution...

Simulação molecular da adsorção de hidrocarbonetos em aluminofosfatos; Molecular simulation of hydrocarbons adsorption in aluminophosphates

Sebastião Mardonio Pereira de Lucena
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 17/08/2006 PT
Relevância na Pesquisa
36.2%
Devido a grande importância dos processos industriais de separação de xilenos por adsorção, técnicas de simulação molecular foram usadas para estudar as causas da orto-seletividade de isômeros C8 em peneiras moleculares aluminofosfatadas. Aplicaram-se campos de força aproximados e otimizados do tipo AA no ensemble grande canônico com algoritmos Monte Carlo (GCMC) convencional e dirigido. Foram calculadas isotermas monocomponentes, calores de adsorção a baixa concentração e realizamos uma detalhada análise estrutural para definir sítios de adsorção e posicionamentos moleculares nos poros das peneiras AlPO4-5, AlPO4-8, AlPO4-11 e VPI-5. Obteve-se acordo quantitativo entre as isotermas experimentais e simuladas para o sistema xilenos/AlPO4-5 e um acordo qualitativo para o sistema xilenos/AlPO4-11. A análise estrutural levou em conta as variações no interior dos poros dos aluminofosfatos que ocorre em duas regiões: uma mais larga, denominada região de grades, e outra mais estreita, que corresponde à região de janelas. A orto-seletividade evidenciada experimentalmente é causada pela forte interação xileno-peneira e pela modulação dos canais. Este conjunto de fatores determina o posicionamento das moléculas dentro dos poros. Para o orto-xileno este microambiente provoca um posicionamento face-a-face na região das grades...

Preparação e caracterização de argila oganofílica para adsorção de BTX; Preparation and characterization of organoclay for adsorption of BTX

Sidmara Bedin
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 14/03/2014 PT
Relevância na Pesquisa
36.2%
Diariamente, uma grande quantidade de fluxos de água sofre contaminação por compostos orgânicos como, por exemplo, o benzeno, tolueno e xileno (BTX), os quais são compostos tóxicos e nocivos ao meio ambiente e aos seres humanos. Sendo assim, o estudo de técnicas de remoção e tratamento desses poluentes vem se tornando tema de muitas pesquisas. A adsorção tem se mostrado uma técnica bastante eficiente, pois atende aos limites da legislação, apresenta baixo consumo energético e custo de processo, ainda mais quando se faz uso de um adsorvente alternativo, como é o caso da argila organofílica. Nesse trabalho foi proposto avaliar a argila esmectítica sódica nacional Fluidgel, na forma natural e organofilizada, como materiais adsorventes alternativos na remoção dos compostos orgânicos BTX de soluções aquosas, em ensaios em sistema batelada e em sistema dinâmico. A argila organofílica foi preparada a partir da argila comercial e do sal quaternário de amônia HDTMA e se verificou a capacidade de troca catiônicas dos adsorventes. Foram realizadas técnicas de caracterização com a finalidade de determinar a área superficial do material, estrutura de poros, estrutura cristalina, morfologia de superfície, composição química...

Adsorption of glyphosate in chilean soils and its relationship with unoccupied phosphate binding sites

Kogan,Marcelo; Metz,Alejandra; Ortega,Rodrigo
Fonte: Embrapa Informação Tecnológica; Pesquisa Agropecuária Brasileira Publicador: Embrapa Informação Tecnológica; Pesquisa Agropecuária Brasileira
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/04/2003 EN
Relevância na Pesquisa
36.27%
The objective of this work was to investigate glyphosate adsorption by soils and its relationship with unoccupied binding sites for phosphate adsorption. Soil samples of three Chilean soils series - Valdivia (Andisol), Clarillo (Inceptisol) and Chicureo (Vertisol) - were incubated with different herbicide concentrations. Glyphosate remaining in solution was determined by adjusting a HPLC method with a UV detector. Experimental maximum adsorption capacity were 15,000, 14,300 and 4,700 mg g¹ for Valdivia, Clarillo, and Chicureo soils, respectively. Linear, Freundlich, and Langmuir models were used to describe glyphosate adsorption. Isotherms describing glyphosate adsorption differed among soils. Maximum adjusted adsorption capacity with the Langmuir model was 231,884, 17,874 and 5,670 mg g-1 for Valdivia, Clarillo, and Chicureo soils, respectively. Glyphosate adsorption on the Valdivia soil showed a linear behavior at the range of concentrations used and none of the adjusted models became asymptotic. The high glyphosate adsorption capacity of the Valdivia soil was probably a result of its high exchangeable Al, extractable Fe, and alophan and imogolite clay type. Adsorption was very much related to phosphate dynamics in the Valdivia soil...

Adsorption of 1-(2-thiazolylazo)-2-naphthol on amberlite XAD-7 and silica gel: isotherms and kinetic studies

Anaia,Grazielle C.; Freitas,Patricia A. M.; Suárez-Iha,Maria E. V.; Rocha,Fábio R. P.
Fonte: Sociedade Brasileira de Química Publicador: Sociedade Brasileira de Química
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/04/2014 EN
Relevância na Pesquisa
36.2%
The reagent 1-(2-thiazolylazo)-2-naphtol (TAN) has been extensively used in solid-phase extraction without a critical evaluation of the adsorption process. In this work, the adsorption of TAN onto XAD-7 and silica gel has been investigated and the experimental equilibrium data were fitted to the Langmuir, Freundlich and Dubinin-Radushkevich models. These models provided good fits for both adsorbents and their respective parameters K L, K F and K D-R were calculated. For the same TAN concentration range, the minimum time of contact for adsorption and the maximum amount of TAN adsorbed per gram were lower in XAD-7 (35 min and 4.05 × 10-3 g g-1) than in silica gel (210 min and 1.81 × 10-2 g g-1). The evaluation of the mean sorption energy characterized the adsorption as physical and the surfaces for both adsorbents as energetically heterogeneous. The experimental data for both systems showed an excellent adjustment to the pseudo-second order model. Excellent agreements between q max,calc and q max,exp were found in all cases and the kinetic constant value confirmed the different minimum time to reach maximum adsorption of TAN onto XAD-7 and silica gel. By considering the adsorption capacity and the force of the interaction, silica gel can be pointed out as the best support for adsorption of TAN.

Adsorption isotherms and thermochemical data of FD&C Red n° 40 binding by Chitosan

Piccin,J. S.; Dotto,G. L.; Pinto,L. A. A.
Fonte: Brazilian Society of Chemical Engineering Publicador: Brazilian Society of Chemical Engineering
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/06/2011 EN
Relevância na Pesquisa
36.2%
Chitosan 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.

Comparison of adsorption equilibrium and kinetic models for a case study of pharmaceutical active ingredient adsorption from fermentation broths: parameter determination, simulation, sensitivity analysis and optimization

Likozar,B.; Senica,D.; Pavko,A.
Fonte: Brazilian Society of Chemical Engineering Publicador: Brazilian Society of Chemical Engineering
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/09/2012 EN
Relevância na Pesquisa
36.22%
Mathematical models for a batch process were developed to predict concentration distributions for an active ingredient (vancomycin) adsorption on a representative hydrophobic-molecule adsorbent, using differently diluted crude fermentation broth with cells as the feedstock. The kinetic parameters were estimated using the maximization of the coefficient of determination by a heuristic algorithm. The parameters were estimated for each fermentation broth concentration using four concentration distributions at initial vancomycin concentrations of 4.96, 1.17, 2.78, and 5.54 g l−¹. In sequence, the models and their parameters were validated for fermentation broth concentrations of 0, 20, 50, and 100% (v/v) by calculating the coefficient of determination for each concentration distribution at the corresponding initial concentration. The applicability of the validated models for process optimization was investigated by using the models as process simulators to optimize the two process efficiencies.

Investigation of adsorption of the dyestuff astrazon red violet 3rn (basic violet 16) on montmorillonite clay

Fil,B. A.; Yilmaz,M. T.; Bayar,S.; Elkoca,M. T.
Fonte: Brazilian Society of Chemical Engineering Publicador: Brazilian Society of Chemical Engineering
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/03/2014 EN
Relevância na Pesquisa
36.28%
In this study, color removal by absorption from synthetically prepared wastewater was investigated using montmorillonite clay by adsorption. As dyestuff Astrazon Red Violet 3RN (Basic Violet 16) was used. Experimental parameters selected were pH, temperature, agitation speed, initial dyestuff concentration, adsorbent dosage and ionic strength. It was established that adsorption rate increased with increasing pH, temperature, dye concentration and agitation speed, but decreased with increased ionic strength and adsorbent dosage. Adsorption equilibrium data obtained by a series of experiments carried out in a water bath were employed with common isotherm equations such as Langmuir, Freundlich, Temkin, Elovich and Dubinin-Radushkevich. It was found that the Langmuir equation appears to fit the equilibrium data better than the other models. Furthermore, the fit of the kinetic data to common kinetic models such as the pseudo-first-order, second-order, Elovich and intraparticle diffusion models was tested to elucidate the adsorption mechanism. Kinetic data conformed to the pseudo-second-order model, indicating chemisorptions. In addition, the thermodynamic parameters activation energy, Ea, enthalpy ΔH*, entropy, ΔS*, and free energy change...

Adsorption of glyphosate in Chilean soils and its relationship with unoccupied phosphate binding sites.

KOGAN, M.; METZ, A.; ORTEGA, R.
Fonte: Pesquisa Agropecuária Brasileira, Brasília, v.38, nº 4, p.513-519, abr. 2003. Publicador: Pesquisa Agropecuária Brasileira, Brasília, v.38, nº 4, p.513-519, abr. 2003.
Tipo: Artigo em periódico indexado (ALICE)
EN
Relevância na Pesquisa
36.27%
The objective of this work was to investigate glyphosate adsorption by soils and its relationship with unoccupied binding sites for phosphate adsorption. Soil samples of three Chilean soils series - Valdivia (Andisol), Clarillo (Inceptisol) and Chicureo (Vertisol) - were incubated with different herbicide concentrations. Glyphosate remaining in solution was determined by adjusting a HPLC method with a UV detector. Experimental maximum adsorption capacity were 15,000, 14,300 and 4,700 mg g-1 for Valdivia, Clarillo, and Chicureo soils, respectively. Linear, Freundlich, and Langmuir models were used to describe glyphosate adsorption. Isotherms describing glyphosate adsorption differed among soils. Maximum adjusted adsorption capacity with the Langmuir model was 231,884, 17,874 and 5,670 mg g-1 for Valdivia, Clarillo, and Chicureo soils, respectively. Glyphosate adsorption on the Valdivia soil showed a linear behavior at the range of concentrations used and none of the adjusted models became asymptotic. The high glyphosate adsorption capacity of the Valdivia soil was probably a result of its high exchangeable Al, extractable Fe, and alophan and imogolite clay type. Adsorption was very much related to phosphate dynamics in the Valdivia soil...

ADSORPTION ISOTHERMS AND THERMOCHEMICAL DATA OF FD&C RED N° 40 BINDING BY CHITOSAN

Pinto, Luiz Antonio Almeida; Picci, Jeferson Steffanello; Dotto, Guilherme Luiz
Fonte: Abeq Publicador: Abeq
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
36.2%
Chitosan 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.

ADSORPTION OF POLYAMINE CHELATED COPPER IONS ONTO GANGUE MINERALS AND HIGH CAPACITY ADSORBENTS

Cushing, Alexander
Fonte: Quens University Publicador: Quens University
Tipo: Tese de Doutorado
EN; EN
Relevância na Pesquisa
36.24%
The effluent quality from mining & processing operations is monitored to ensure that maximum allowable limits are not exceeded. Recently, copper concentration levels in the effluent discharge flows of a copper and nickel mining company in Ontario have indicated increasing trends. A chemical particular to the problem is use of diethylenetriamine (DETA) in the process. Adsorption tests were conducted to investigate the ability of various adsorbents to remove and retain copper complexed with DETA and triethylenetetramine (TETA) in solutions. The tests were divided into two sections: gangue adsorbents (silica and pyrrhotite) and high capacity adsorbents (natural bentonite, peat, zeolite Y and zeolite ZSM-5). Pyrrhotite as a sulphide gangue had a greater adsorption capacity than silica for the concentration range studied. At 1 ppm initial concentration, over 80% of copper chelate was removed by minus 400 mesh pyrrhotite compared to 72% of the same size silica. Freundlich and Langmuir isotherm models of adsorption are applicable. However, the Langmuir adsorption isotherm was found to more closely represent the experimental data with a maximum adsorption capacity of 129.9 μg/g for copper complexed with DETA on pyrrhotite. For the high capacity adsorbents...

Adsorption models of hybridization and post-hybridisation behaviour on oligonucleotide microarrays

Burden, C. J.; Pittelkow, Y.; Wilson, S. R.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
46.03%
Analysis of data from an Affymetrix Latin Square spike-in experiment indicates that measured fluorescence intensities of features on an oligonucleotide microarray are related to spike-in RNA target concentrations via a hyperbolic response function, generally identified as a Langmuir adsorption isotherm. Furthermore the asymptotic signal at high spike-in concentrations is almost invariably lower for a mismatch feature than for its partner perfect match feature. We survey a number of theoretical adsorption models of hybridization at the microarray surface and find that in general they are unable to explain the differing saturation responses of perfect and mismatch features. On the other hand, we find that a simple and consistent explanation can be found in a model in which equilibrium hybridization followed by partial dissociation of duplexes during the post-hybridization washing phase.; Comment: 26 pages, 6 figures, some rearrangement of sections and some additions. To appear in J.Phys.(condensed matter)

Cooperative sequential adsorption models on a Cayley tree: analytical results and applications

Mazilu, D. A.; Mazilu, I.; Seredinski, A. M.; Kim, V. O.; Simpson, B. M.; Banks, W. E.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 09/07/2012
Relevância na Pesquisa
45.94%
We present a class of cooperative sequential adsorption models on a Cayley tree with constant and variable attachment rates and their possible applications for ionic self-assembly of thin films and drug encapsulation of nanoparticles. Using the empty interval method, and generalizing results known from reaction-diffusion processes on Cayley trees, we calculate a variety of quantities such as time-dependent surface coverage and time-dependent probabilities of certain particle configurations.

Adsorption Behaviour of [(4-Hydroxy-6-methyl-2-oxo-2H-pyran-3-yl)-(4-methoxy-phenyl)-[1] methyl]-urea on Stainless Steel in Phosphoric Media

Olusola,James O.; Oluseyi,Ajanaku K.; Kehinde,Ogunniran O.; Olayinka,Ajani O.; Oluwatosin,John M.
Fonte: Sociedade Portuguesa de Electroquímica Publicador: Sociedade Portuguesa de Electroquímica
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/01/2009 EN
Relevância na Pesquisa
46.13%
The adsorption of [(4-hydroxy-6-methyl-2-oxo-2H-pyran-3-yl)-(4-methoxy-phenyl)-methyl]-urea on iron in phosphoric media was studied by using electrochemical technique. The adsorption mechanism was investigated using adsorption isotherms. The experimental data fit localized adsorption models. The values for free energy of adsorption, ΔGads0, were also calculated at each surface coverage, θ of the studied compound by applying the mathematical model of Bockris - Swinkels adsorption isotherm. The variation of free energy of adsorption ΔGads0 with surface coverage, was interpreted in terms of deviation from ideal condition assumed in Langmuir model. A possible adsorption model of HPU2 molecules on to the metal surface was suggested.

The influence of pH on the adsorption of lead by Na-clinoptilolite: Kinetic and equilibrium studies

Cozmuta,L Mihaly; Cozmuta,A Mihaly; Peter,A; Nicula,C; Nsimba,E Bakatula; Tutu,H
Fonte: Water SA Publicador: Water SA
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/01/2012 EN
Relevância na Pesquisa
36.29%
The objectives of this study were, firstly, to establish the mechanism by which modified clinoptilolite (in Na form) adsorbs lead ions and, secondly, to assess the extent of influence of pH on the adsorption capacity. To this end, the experimental data have been fitted by adsorption isotherms, thermodynamic and kinetic models. Based on the standard errors obtained during experiments, it was determined that the accuracy of prediction of the isotherm models considered for adsorption decreases in the order: Dubinin-Raduschkevich (4.63%, average normalised standard deviation error); Langmuir (7.90%); and Freundlich (15.98%). For the kinetic models, the accuracy of prediction decreases in the order: intra-particle Weber-Morris (with an average normalised standard deviation error of 5.53%); heterogeneous diffusion (5.67%); pseudo-second order kinetic model (10.47%); diffusion through the particle surface (41.73%); and the pseudo-first kinetic model (47.51%). The mechanism of adsorption of lead ions by Na-clinoptilolite was found to occur in a monolayer and heterogeneous surface. The pH of contact solutions played an important role owing to competition by hydrogen ions. As the pH of the solution decreased, the maximum monolayer adsorption capacity established theoretically...