No description available.

published_or_final_version / Chemistry / Doctoral / Doctor of Philosophy

No description available.

Amongst treatment technologies, adsorption is rapidly gaining prominence because it can remove metal pollutants at low concentrations, economical, ease of operation, and the adsorbent can be regenerated for reuse. This study therefore, aimed at developing a simple material for selective removal of cesium from wastewater. An agricultural waste material (pine cone) was used as a cheap solid support for transition metal hexacyanoferrate and applied as biosorbents for cesium removal. The preparation and characterization of biosorbent for cesium removal in the presence of alkali metals is reported. The experimental procedure was carried out in three phases; the first phase described the sample preparation. Toluene-ethanol mixtures of different ratios were investigated as surface treatment method for pine cone and the optimum treatment ratio determined by measuring the improvement in surface properties of the pine cone such as bulk density, iodine number, and surface negative charge. The modification of pine cone with iron hexacyanoferrate was examined in the second phase. The preparation of potassium iron(III) hexacyanoferrate (KFeHCF) supported toluene-ethanol modified pine cone powder was studied in order to consider its application for cesium removal from aqueous solution. The biosorbent was designed to incorporate the hexacyanoferrate ligand which is known to have a high affinity for cesium ions in aqueous solution. Fe(III) was loaded onto the toluene-ethanol treated pine cone powder followed by hexacyanoferrate ligand incorporation on the biosorbent producing the potassium iron hexacyanoferrate supported toluene-ethanol treated pine cone. The modified pine cone was characterized by FTIR, XRD and TGA analysis. The influence of solution pH and adsorbent dose were studied. The application of potassium iron hexacyanoferrate for the selective removal of cesium in the presence of sodium and calcium was investigated in the third phase. Batch adsorption kinetic studies were performed to determine the effect of modification on cesium removal. Coefficient of correlation, r2, and Chi-square, χ2, methods were applied in the determination of the best fit kinetic method. Increasing the ratio of toluene in the extractant mixture increased formation of esters and iodine capacity of the material, but reduced carboxylate ions and surface charge. Maximum cesium vi adsorption was observed for the 2:1 toluene-ethanol treated sample. Structural characterization using FTIR, XRD and TGA confirmed the successful modification of KFeHCF pine cone powder. Cesium adsorption experiments indicate that KFeHCF supported toluene-ethanol modified pine was more efficient for cesium removal than the raw pine cone powder. Kinetic modeling of Cs+ adsorption was done using the pseudo-first, pseudo-second order and diffusion chemisorption kinetic models. The pseudo first order kinetics could not accurately predict the experimental data. The kinetics data fitted the pseudo-second order and diffusion-chemisorption models. The chemisorption diffusion model only accurately describes the experimental data after 5 min of contact whereas the pseudo second order describes the experimental data over the range of contact time. The application of the FeHCF modified pine cone for cesium removal from aqueous solution revealed that the FeHCF modified pine was less affected by the presence of competitive cations than the toluene-ethanol treated sample and the raw pine cone sample.

O uso do biodiesel está em expansão no mercado mundial. A presença de metais alcalinos é um dos parâmetros de qualidade que mais se destaca devido aos prejuízos que pode causar ao automóvel. Neste trabalho propôs-se um método alternativo para determinar íon sódio usando um sensor eletroquímico baseado em eletrodo quimicamente modificado (EQM) com filme de octafenilciclotetrasiloxano (OFCTS), o qual possui estrutura molecular sugestiva para uma coordenação com Na+. A caracterização do sensor foi realizada por Espectroscopia de Infravermelho com Transformada de Fourier (FT-IR) e Difração de Raios X (DRX). A interação metal:ligante foi estuda por cálculos teóricos, Espectrofotometria UV-Vis, Espectroscopia de Impedância Eletroquímica (EIE) e Voltametria Cíclica (VC). A imobilização do OFCTS no eletrodo de carbono vítreo foi alcançada por adsorção usando a técnica drop coating. O par redox [Ru(NH 3)5 Cl] 2+/3+foi empregado como íon sonda e a corrente de pico (Ip) foi monitorada por voltametria de pulso diferencial com varredura anódica. Adições sucessivas de Na+ à célula eletroquímica causaram a diminuição da Ip do íon sonda, devido à interação do íon sódio com o ligante imobilizado no eletrodo e consequente repulsão com o íon sonda. Empregando este efeito, a concentração de íons sódio pode ser indiretamente medida. Após a otimização dos principais parâmetros da eletroanálise, a curva analítica foi construída através da relação entre diferença de Ip (δIp) do [Ru(NH 3) 5Cl]2+/3+e a quantidade de íons sódio adicionada, obtendo um coeficiente de correlação (r) de 0,998, LD e LQ iguais a 0,38 mg kg -1 e 1,29 mg kg-1 , respectivamente. As amostras de biodiesel foram preparadas por digestão ácida por via úmida com radiação de micro-ondas. As recuperações foram obtidas e os percentuais para a fortificação foi biodiesel 105% e para água mineral foi 81%. O método alternativo foi aplicado para amostra real e detectou 4,1 mg Kg-1 de sódio em biodiesel. / The use of biodiesel is expanding in the world market. The presence of alkali metals is one of its quality parameters that stand out, due to the damage that they can cause to vehicles. This study aimed to propose an alternative method to determine sodium ions using an electrochemical sensor based on chemically modified electrode (CME) with octaphenylcyclotetrasiloxane (OFCTS), which has suggestive molecular structure for coordination with Na+ ion. The characterization of the sensor was carried out by Fourier Transform Infrared Spectroscopy (FT-IR) and X-Ray Diffraction (XRD). The metal:ligand interaction was studied by theoretical calculations, UV-Visible Spectroscopy, Electrochemical Impedance Spectroscopy (EIS) and Cyclic Voltammetry (CV). Immobilization of OPCTS on glassy carbon electrode was achieved by adsorption through drop coating technique. The [Ru(NH 3) 5Cl]2+/3+e redox couple was used as ion probe, and its peak current (Ip) was monitored by stripping anodic stripping differential pulse voltammetry . Successive additions of Na+ to the electrochemical cell promote the Ip decrease of the ion probe, due to interaction between the sodium ion and the immobilized ligand on the electrode and the subsequent repulsion with the ion probe. Using this effect, the sodium ions concentration could be indirectly measured. After the main parameters optimization of the electroanalysis, the analytical curve was constructed by plotting the Ip difference (δIp) of [Ru(NH 3) 5Cl]2+/3+e against the amount of sodium ions added, obtaining a coefficient of correlation (r 2) of 0.99 and LOD and LOQ equal to 0,38 and 1,29 mg Kg-1, respectively. The biodiesel samples were pretreated by microwave assisted acid digestion. Recoveries were obtained and the percentages for the fortification for biodiesel was 105,5% and for mineral water was 81%. The alternative method was applied for real sample and detected 4 mg Kg -1 of the sodium in biodiesel.

O uso do biodiesel está em expansão no mercado mundial. A presença de metais alcalinos é um dos parâmetros de qualidade que mais se destaca devido aos prejuízos que pode causar ao automóvel. Neste trabalho propôs-se um método alternativo para determinar íon sódio usando um sensor eletroquímico baseado em eletrodo quimicamente modificado (EQM) com filme de octafenilciclotetrasiloxano (OFCTS), o qual possui estrutura molecular sugestiva para uma coordenação com Na+. A caracterização do sensor foi realizada por Espectroscopia de Infravermelho com Transformada de Fourier (FT-IR) e Difração de Raios X (DRX). A interação metal:ligante foi estuda por cálculos teóricos, Espectrofotometria UV-Vis, Espectroscopia de Impedância Eletroquímica (EIE) e Voltametria Cíclica (VC). A imobilização do OFCTS no eletrodo de carbono vítreo foi alcançada por adsorção usando a técnica drop coating. O par redox [Ru(NH 3)5 Cl] 2+/3+foi empregado como íon sonda e a corrente de pico (Ip) foi monitorada por voltametria de pulso diferencial com varredura anódica. Adições sucessivas de Na+ à célula eletroquímica causaram a diminuição da Ip do íon sonda, devido à interação do íon sódio com o ligante imobilizado no eletrodo e consequente repulsão com o íon sonda. Empregando este efeito, a concentração de íons sódio pode ser indiretamente medida. Após a otimização dos principais parâmetros da eletroanálise, a curva analítica foi construída através da relação entre diferença de Ip (δIp) do [Ru(NH 3) 5Cl]2+/3+e a quantidade de íons sódio adicionada, obtendo um coeficiente de correlação (r) de 0,998, LD e LQ iguais a 0,38 mg kg -1 e 1,29 mg kg-1 , respectivamente. As amostras de biodiesel foram preparadas por digestão ácida por via úmida com radiação de micro-ondas. As recuperações foram obtidas e os percentuais para a fortificação foi biodiesel 105% e para água mineral foi 81%. O método alternativo foi aplicado para amostra real e detectou 4,1 mg Kg-1 de sódio em biodiesel. / The use of biodiesel is expanding in the world market. The presence of alkali metals is one of its quality parameters that stand out, due to the damage that they can cause to vehicles. This study aimed to propose an alternative method to determine sodium ions using an electrochemical sensor based on chemically modified electrode (CME) with octaphenylcyclotetrasiloxane (OFCTS), which has suggestive molecular structure for coordination with Na+ ion. The characterization of the sensor was carried out by Fourier Transform Infrared Spectroscopy (FT-IR) and X-Ray Diffraction (XRD). The metal:ligand interaction was studied by theoretical calculations, UV-Visible Spectroscopy, Electrochemical Impedance Spectroscopy (EIS) and Cyclic Voltammetry (CV). Immobilization of OPCTS on glassy carbon electrode was achieved by adsorption through drop coating technique. The [Ru(NH 3) 5Cl]2+/3+e redox couple was used as ion probe, and its peak current (Ip) was monitored by stripping anodic stripping differential pulse voltammetry . Successive additions of Na+ to the electrochemical cell promote the Ip decrease of the ion probe, due to interaction between the sodium ion and the immobilized ligand on the electrode and the subsequent repulsion with the ion probe. Using this effect, the sodium ions concentration could be indirectly measured. After the main parameters optimization of the electroanalysis, the analytical curve was constructed by plotting the Ip difference (δIp) of [Ru(NH 3) 5Cl]2+/3+e against the amount of sodium ions added, obtaining a coefficient of correlation (r 2) of 0.99 and LOD and LOQ equal to 0,38 and 1,29 mg Kg-1, respectively. The biodiesel samples were pretreated by microwave assisted acid digestion. Recoveries were obtained and the percentages for the fortification for biodiesel was 105,5% and for mineral water was 81%. The alternative method was applied for real sample and detected 4 mg Kg -1 of the sodium in biodiesel.

Thesis (Ph. D.)--Institute of Paper Chemistry, 1976. / Includes bibliographical references (p. 129-133).

129 leaves : ill., tables ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, Dept. of Physics, 1978

Thesis (M.S.)--Michigan State University. Dept. of Biochemistry and Molecular Biology, 2008. / Title from PDF t.p. (viewed on July 29, 2009) Includes bibliographical references (p. 78-81). Also issued in print.

Made available in DSpace on 2014-10-09T12:31:45Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:00:43Z (GMT). No. of bitstreams: 1 02280.pdf: 1066409 bytes, checksum: 1d4a4d3302c305f5a5e115b366279083 (MD5) / Dissertacao (Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP