Over the course of our lives we are exposed to airborne particulate matter in the workplace, home, and environment that results in the deposition of millions of particles in the lung. These exposures may result in disease if they are significant enough. The potential for harmful exposure depends in part on the dust's biodurability and the bioavailability of harmful constituents derived from the particles. A mixed flow reactor was used to evaluate two applications of geochemical methods to characterize the behavior of inhaled particles in the body. Dissolution rates of a well-characterized sample of powdered talc were measured in solvents that mimic fluids found in the human lung. These studies showed that variation of solvent chemistry, including the addition of organic chelators and proteins at intercellular fluid concentrations, does not markedly affect the measured dissolution rate of talc at 37 degrees Celcius and the data further indicate that the dissolution mechanism for talc in aqueous solutions is independent of pH over a range of pH from 2 to 8. The dissolution rate, determined by measuring the silicon release rate per unit surface area of talc is 1.4 (+/- 1.0) x 10-11 mol Si/(m2 -sec). A geometric shrinking particle model using this dissolution rate predicts an estimated lifetime (upper limit) of approximately 8 years for a 1 micron talc particle under pulmonary conditions. Talc dissolves considerably faster than quartz, but slower than chrysotile and olivine in the body. These data can be used to place constraints on the role of particle dissolution in the disease models associated with airborne respirable particulate matter. Secondly, the bioavailability of As and Cr was determined from a sample of coal fly ash from an eastern U.S. power plant. The time-release profiles of As and Cr were determined for these materials in physiologically-based solvents and incorporated into a toxicokinetic model to predict the exposure potential to As and Cr from occupational exposures to the coal fly ash. Predicted occupational exposure contributions from the ash relative to total environmental exposures were insignificant. The exposure predicted from the geochemical approach was compared with results observed in a cohort occupationally exposed to coal fly ash and found to be within one order of magnitude of the response of the occupational cohort. These results support the application of geochemical techniques to evaluate exposures to complex respirable materials. / Ph. D.

As cinzas resultantes da queima de carvão por usinas termelétricas tem sido uma fonte de contaminação constante devido a seu descarte sobre o solo de forma inadequada. Os elementos tóxicos presentes na cinza de carvão quando lixiviados da cinza para o solo podem ficar biodisponíveis e serem absorvidos por plantas, consumidos por animais ou ainda transportados para diversas matrizes ambientais, tais como, águas subterrâneas e águas superficiais. Ensaio de germinação e desenvolvimento das radículas de Lactuca sativa e ensaio de toxicidade aguda com Daphnia similis foram realizados para avaliar a toxicidade dos percolados de colunas de cinza de carvão e de solo com cinza de carvão. De acordo com os valores obtidos por meio dos ensaios de germinação e desenvolvimento das radículas de L. sativa foram observados efeitos tóxicos à germinação das sementes de L. sativa nos percolados da coluna de cinza de carvão. Os valores médios de CI50(120h) destes percolados variaram de 27,6 a 90,6% e os valores do índice de germinação (IG) variaram de 6,7 a 40,8. Nos ensaios de toxicidade aguda com os organismos teste D. similis também foram observados efeitos tóxicos à mobilidade e/ou sobrevivência dos organismos expostos aos percolados da coluna de cinza de carvão. Os valores obtidos para CE50(48h) nestes percolados variaram de 25,6 a 84,1%. Os percolados das colunas de solo com cinza de carvão não apresentaram toxicidade tanto à L. sativa como à D. similis. Os resultados obtidos por meio destes ensaios ecotoxicológicos para os percolados das colunas de cinza de carvão e de solo com cinza de carvão indicam que o solo das colunas retiveram as substâncias tóxicas lixiviadas da cinza de carvão, ou seja, os solos utilizados nestas colunas atuaram como filtros. / The coal fly ash of power plants has been a constant source of contamination due to the improperly disposed on the soil. The toxic elements leached from coal fly ash when in contact with soil could become bioavailable and be absorbed by plants, consumed by animals or transported to different environmental matrices, such as groundwater and surface water. Seed germination and root elongation tests with Lactuca sativa and acute toxicity tests with Daphnia similis were done to evaluate the toxicity of the leachate from coal fly ash and soil with coal fly ash columns. According to the values obtained for the seed germination and root elongation tests were observed toxic effects to seed germination of L. sativa for the leachates from coal fly ash column. The mean values of IC50(120h) for these leachates ranged from 27.6 to 90.6% and the germination index values (IG) ranged from 6.7 to 40.8. In the acute toxicity tests with test organisms D. similis were also observed toxic effects to mobility and/or survival of organisms exposed to leachates of the coal fly ash column. The values obtained for EC50(48h) for these leachates range from 25.6 to 84.1%. The leachates of soil with coal fly ash columns not presented toxicity to both test organisms, L. sativa and D. similis. The data obtained by these ecotoxicological tests to the leachates of soil coal fly ash and soil with coal fly ash columns indicate that the soil of the columns have retained the toxic substances leached from the coal fly ash, thus the soils used in these columns have acted as filters.

This is an in-depth analysis of coal fire burning power plants, their effects on human health and the environment. It also employed case study data from Tampa Electric Company’s Big Bend facility to examine environmental infractions at that facility. Tampa Electric Company’s Big Bend Utility Plant, violated the Clean Air Act, which led to a lawsuit filed by the Department of Justice on behalf of the United States Environmental Protection Agency and the Florida Department of Environmental Protection in 1997. This case study details the lawsuit, and subsequent settlement as well as Tampa Electric Company’s record of compliance since 2000. This study examines the area surrounding the plant, and impacts the facility may cause local residents and the ecosystem in this part of Florida. Several questions are explored in this case study revolving around environmental justice and environmental racism. Did the actions taken by the Department of Justice in 2000 on behalf of the Environmental Protection Agency and the people of the State of Florida through its Department of Environmental Protection fit the corporate crimes that Tampa Electric were accused of in the lawsuit? Has this company been compliant with state and federal law as required by the settlement? Finally, has the Tampa Electric Company maintained their commitment to provide environmental justice for the communities surrounding the Big Bend Utility Plant or would their actions fit a definition for the crime of corporate environmental violence?

L'objectif principal de cette thèse a été d'évaluer le potentiel de valorisation des cendres volantes de charbon issues de centrales thermiques Spreader Stoker (Cendres Volantes Spreader Stoker), dans la fabrication d'éco-ciments sur l'île de La Réunion. Nous avons dans un premier temps effectué une caractérisation physico-chimique des CVSS et vérifié leur réactivité. Deux voies de valorisation ont ensuite été retenues, l'une qui ne présente pas de valeur ajoutée mais qui permet de valoriser un volume important de CVSS par une stabilisation dans des matrices à base de ciment, l'autre qui offre une valeur ajoutée aux CVSS par une incorporation dans la fabrication de ciments composés. Le relargage en lixiviation a été étudié pour la première voie de valorisation retenue, puis, les effets des CVSS dans les matrices à base de ciment, notamment le rôle des imbrûlés contenus dans les cendres, ont été évalués aux états frais, durcissant et durci, suivi d'une petite exploitation numérique des données expérimentales. Enfin, une étude de durabilité sur des bétons à base de ciments de laboratoire a été faite par une approche comparative avec la pouzzolane naturelle, qui est actuellement utilisée pour la fabrication de ciments composés sur l'île de la Réunion. / The main objective of this project was to evaluate the potential of coal fly ash from Spreader Stoker thermal power plants (Spreader Stoker Coal Fly Ash) in the manufacture of eco-cements in Reunion Island. We first performed a physico-chemical characterization SSCFA and verified its reactivity. Two valorisation paths were chosen, one of which did not present any added value but which permit to value a large quantity of SSCFA by stabilization in cement-based matrices, the other which offers added value to SSCFA by incorporating it in the manufacture of composed cements. Leachate release was studied for the first path of valorisation, and then the effects of SSCFA in the cement matrices, especially the unburned particles contained in SSFCA, were evaluated in fresh, hardening and hardened states, followed by a small numerical exploitation of the experimental data. Finally, a sustainability study on concretes based on laboratory cements was made using a comparative approach with natural pozzolana, which is currently used for the manufacture of composite cements in Réunion Island.

As cinzas resultantes da queima de carvão por usinas termelétricas tem sido uma fonte de contaminação constante devido a seu descarte sobre o solo de forma inadequada. Os elementos tóxicos presentes na cinza de carvão quando lixiviados da cinza para o solo podem ficar biodisponíveis e serem absorvidos por plantas, consumidos por animais ou ainda transportados para diversas matrizes ambientais, tais como, águas subterrâneas e águas superficiais. Ensaio de germinação e desenvolvimento das radículas de Lactuca sativa e ensaio de toxicidade aguda com Daphnia similis foram realizados para avaliar a toxicidade dos percolados de colunas de cinza de carvão e de solo com cinza de carvão. De acordo com os valores obtidos por meio dos ensaios de germinação e desenvolvimento das radículas de L. sativa foram observados efeitos tóxicos à germinação das sementes de L. sativa nos percolados da coluna de cinza de carvão. Os valores médios de CI50(120h) destes percolados variaram de 27,6 a 90,6% e os valores do índice de germinação (IG) variaram de 6,7 a 40,8. Nos ensaios de toxicidade aguda com os organismos teste D. similis também foram observados efeitos tóxicos à mobilidade e/ou sobrevivência dos organismos expostos aos percolados da coluna de cinza de carvão. Os valores obtidos para CE50(48h) nestes percolados variaram de 25,6 a 84,1%. Os percolados das colunas de solo com cinza de carvão não apresentaram toxicidade tanto à L. sativa como à D. similis. Os resultados obtidos por meio destes ensaios ecotoxicológicos para os percolados das colunas de cinza de carvão e de solo com cinza de carvão indicam que o solo das colunas retiveram as substâncias tóxicas lixiviadas da cinza de carvão, ou seja, os solos utilizados nestas colunas atuaram como filtros. / The coal fly ash of power plants has been a constant source of contamination due to the improperly disposed on the soil. The toxic elements leached from coal fly ash when in contact with soil could become bioavailable and be absorbed by plants, consumed by animals or transported to different environmental matrices, such as groundwater and surface water. Seed germination and root elongation tests with Lactuca sativa and acute toxicity tests with Daphnia similis were done to evaluate the toxicity of the leachate from coal fly ash and soil with coal fly ash columns. According to the values obtained for the seed germination and root elongation tests were observed toxic effects to seed germination of L. sativa for the leachates from coal fly ash column. The mean values of IC50(120h) for these leachates ranged from 27.6 to 90.6% and the germination index values (IG) ranged from 6.7 to 40.8. In the acute toxicity tests with test organisms D. similis were also observed toxic effects to mobility and/or survival of organisms exposed to leachates of the coal fly ash column. The values obtained for EC50(48h) for these leachates range from 25.6 to 84.1%. The leachates of soil with coal fly ash columns not presented toxicity to both test organisms, L. sativa and D. similis. The data obtained by these ecotoxicological tests to the leachates of soil coal fly ash and soil with coal fly ash columns indicate that the soil of the columns have retained the toxic substances leached from the coal fly ash, thus the soils used in these columns have acted as filters.

Rare earth elements (REEs) are critical materials in many electronics and green technology products. Though the demand for REEs is growing rapidly, China controls over 90% of the REEs supply and the US currently is not producing any REEs. As most of the REEs occurred together in the mineral ores with low concentrations and they have similar chemical and physical properties, the extraction and purification processes are challenging. Conventional methods for producing REEs require large amounts of toxic chemicals and generate large amounts of hazardous wastes. Therefore, it is important to develop alternative REE sources as well as efficient and environmentally friendly processes to produce REEs domestically. In this dissertation, coal fly ash, a major coal combustion byproduct, was explored as a potential source for REEs. Novel separation and purification methods were developed for producing high purity REEs from class F coal fly ash.<div><br></div><div>First, a sequential separation process was developed to recover and concentrate REEs from class F coal fly ash. The ash was first digested using a NaOH solution and subsequently dissolved in an acid to extract REEs as well as other chemicals. About 74% of REEs, 92 % of SiO2, 74% of Al2O3, 24% of Fe2O3, and 65% of CaO were extracted. Most (>99%) of the extracted REEs and cations (Al+3, Fe+3, Ca+2) were captured in a cation exchange column. Negatively charged Si species were eluted by water. The captured REEs were separated from the other cations in the column. A solution of NaCl was used to elute the cations and most of the REEs, which were strongly adsorbed in the column, were eluted using a solution of diethylenetriaminepentaacetic acid (DTPA). In this separation process, high purity SiO2 (>99%), Al(OH)3 (>99%), and Fe(OH)3 (>95%) were produced. The eluted DTPA-REEs solution was then loaded in a cation exchange column. The REEs accumulated in the column could be further separated into pure REE fractions using a ligand-assisted displacement chromatography method (LAD), instead of the conventional liquid-liquid extraction method.<br></div><div><br></div><div>Detailed rate model simulations were developed for LAD and verified with experimental and literature data. The dynamic column profiles in simulations showed that a prestaurant which has a higher ligand affinity and a lower sorbent affinity than REEs is required to develop an isotachic train in LAD. When a constant-pattern isotachic train is developed, high concentration bands with high purity and high yield can be achieved. Further increase in column length is not needed. Thus, if purity, yield, sorbent, and ligand are fixed, the constant-pattern state gives the highest sorbent productivity and the highest ligand efficiency. It is critical to develop a method to find the general conditions required for developing constant-pattern states. Key dimensionless parameters affecting the constant-pattern states were formulated first based on the h-transformation theory for an ideal system and the shock layer theory for a nonideal system. Strategetic combinations of the key dimensionless groups were developed to express a dimensionless mininum column length as a function of the combined dimensionless groups. Rate model simulations were used to find various minimum column lengths for developing constant-pattern states from transient states. The simulation results were used to generate a correlation curve in a two-dimensional plot or map where the curve divided the map into two regions, the transient region, and the constant-pattern region. The map can be used to find the minimum required conditions for developing a constant-pattern state for a general LAD system at any scale.<br></div><div><br></div><div>A constant-pattern design method for both ideal and non-ideal (with significant mass transfer effects) LAD systems was developed based on the general correlation equation for the map. In addition, an equation for the yield of a target component as a function of the key dimensionless groups was derived based on the constant-pattern mass transfer zone lengths. The column length and operating velocity solved from the two equations ensured the yields and the constant–pattern state for the target components. A selectivity weighted composition factor was developed to allow the design method to specify a minimum target yield for one or multiple components. The design method is robust and scalable because it provides the optimal operating conditions to meet the minimum target yield and purity of one or multiple components for LAD systems at any scale. The design method was verified using simulations and experiments for different target yields, ligand concentrations, and feed compositions for ternary mixtures. The minimum target yields were achieved or exceeded in all cases tested. The results showed that high ligand concentration, long column length, and high effective sorbent selectivity can increase sorbent productivity. The minimum column length required to achieve a constant-pattern state and the productivity of LAD are limited by the lowest selectivity or by a minority component with a low concentration in the feed, even when it does not have the lowest selectivity. If both minor and major REE components in a mixture need to be recovered in the same LAD process, the overall productivity could be significantly limited. Thus, separating major components first and recycling/separating the minor components in a separate LAD process could increase the total productivity significantly. The productivities achieved using this design method are two orders of magnitude higher than the literature results with similar REE yields and purities.<br></div>

As cinzas de carvão são subprodutos da combustão de carvão mineral gerados em grandes quantidades a partir de usinas termelétricas no mundo todo. Nos últimos anos, pesquisas sobre a utilização das cinzas estão sendo desenvolvidas visando soluções sustentáveis, garantindo, assim, a preservação do meio ambiente e a saúde humana. As cinzas de carvão podem ser aproveitadas como matéria-prima para síntese de zeólita, material este que possui uma vasta gama de aplicações industriais. Em muitas dessas aplicações é requerido o uso de formas peletizadas de zeólitas. Nesse contexto, o objetivo do presente estudo foi desenvolver um método de obtenção de zeólita de cinzas leves de carvão na forma granular e avaliar seu uso como material adsorvente. A primeira etapa deste estudo consistiu na síntese e caracterização de zeólita convencional (ZCL) e de zeólita do tipo NaA com alto grau de pureza (ZA). As cinzas leves de carvão utilizadas na síntese das zeólitas foram coletadas na Usina Termelétrica Jorge Lacerda, localizada no Estado de Santa Catarina, Brasil, o maior complexo termelétrico a carvão da América Latina. O material de partida e as zeólitas sintetizadas em pó foram caracterizados em termos da composição química, composição mineralógica, morfologia, capacidade de troca catiônica, estabilidade térmica, área superficial específica, distribuição de poros e dos grupos funcionais. As fases zeolíticas formadas por tratamento hidrotérmico foram hidroxisodalita e traços de NaX. A zeólita do tipo NaA foi sintetizada por método de duas etapas apresentando grau de pureza de 84%. O valor de capacidade de troca catiônica da zeólita A com alto grau de pureza foi aproximadamente duas vezes maior do que o valor encontrado para a zeólita convencional (1,84 meq g-1 para ZCL e 3,81 meq g-1 para ZA). Na segunda etapa, os produtos zeolíticos sintetizados neste estudo foram peletizados com a aplicação de diferentes métodos. Os grânulos de zeólitas foram formados manualmente na forma de esferas na faixa de tamanho entre 3 mm e 7 mm a partir da mistura das zeólitas em pó com um ou mais agentes aglutinantes e adição de água deionizada. As diferentes metodologias experimentais de peletização das zeólitas sintetizadas foram comparadas e avaliadas por meio da determinação da capacidade de troca catiônica dos produtos obtidos, trabalhabilidade, resistência mecânica e estabilidade em água. O método de peletização no qual as argilas caulinita e bentonita foram usadas como agentes aglutinantes, na proporção de 5% em massa cada, foi considerado o melhor para a zeólita convencional. Para a zeólita A, foi selecionado o método com 10% de bentonita. Os valores de capacidade de troca catiônica dos produtos zeolíticos foram mantidos após o processo de peletização. Posteriormente foi realizado um estudo direcionado à aplicação da zeólita granular no tratamento de água. A amostra de zeólita A com alto grau de pureza peletizada, obtida pelo método otimizado, foi selecionada para ser usada como material adsorvente no processo de adsorção de íons cádmio em solução aquosa em coluna de leito fixo. Os resultados evidenciaram a potencialidade do uso da zeólita A peletizada no tratamento de efluentes. / Coal ashes are by-products of coal combustion generated in large quantities from thermoelectric plants worldwide. In recent years, research on the use of ash has been developed aiming at sustainable solutions, thus guaranteeing the preservation of the environment and human health. Coal ashes can be used as raw material for zeolite synthesis, which has a wide range of industrial applications. In many such applications the use of zeolite pelletized forms is required. In this context, the objective of the present study was to develop a method to obtain zeolite of light ash from coal in the granular form and to evaluate its use as an adsorbent material. The first step of this study was the synthesis and characterization of zeolite conventional (ZFA) and of the zeolite NaA type with a high degree of purity (ZA). The coal fly ashes used in the synthesis of the zeolites were collected in the Thermoelectric Complex Jorge Lacerda, located in the Santa Catarina State, Brazil, the largest coal burning thermoelectric complex of Latin America. The starting material and the zeolites synthesized in powder were characterized in terms of chemical composition, mineralogical composition, morphology, cation exchange capacity, thermal stability, specific surface area, pore distribution and functional groups. The zeolitic phases formed by conventional hydrothermal treatment were hydroxysodalite and traces of NaX. The zeolite of the NaA type was synthesized by a two-step method with a fusion step having a degree of purity of 84%. The value of cation exchange capacity of zeolite A with high purity was approximately two times higher than the value found for the zeolite conventional (1.84 meq g-1 for ZFA and 3.81 meq g-1 for ZA). In the second step, the zeolitic products synthesized in this study were pelletized with the application of different methods. The zeolite granules were formed manually in the form of spheres in the size range between 3 mm and 7 mm from the powder mixture of zeolite with one or more binders and addition of deionized water. The different experimental methodologies of pelletization the synthesized zeolites were compared and evaluated through of the determination of the cation exchange capacity, workability, mechanical strength and water stability. The pelletization method in which clays kaolinite and bentonite were used as binders in the proportion of 5% by weight each was considered the best for the conventional zeolite. For zeolite-A, was selected the method with 10% bentonite. The cation exchange capacity values of the zeolitic products were maintained after the pelletization process. Subsequently, a study was carried out on the application of granular zeolite in water treatment. The zeolite-A sample with high degree of pelletized purity, obtained by the optimized method, was selected to be used as adsorbent material in the adsorption process of cadmium ions in aqueous solution in a fixed bed column. The results evidenced the potential of the use of pelletized zeolite-A in the treatment of effluents.

Cinza leve de carvão, resíduo gerado em usina termelétrica, foi usada para sintetizar zeólita por meio de tratamento hidrotérmico com solução de NaOH. A cinza leve (CL-2) e a zeólita sintética (ZM-2) que foi predominantemente identificada como hidroxi-sodalita foram utilizadas como adsorventes dos corantes aniônicos índigo carmina (IC) e reativo laranja 16 (RL16) de soluções aquosas. Nos processos de adsorção, os efeitos de tempo de contato, concentração inicial de corantes, pH, massa de adsorventes e temperatura foram avaliados. O estudo cinético de adsorção demonstrou que os resultados apresentaram melhor ajuste ao modelo de pseudo-segunda ordem e que adsorção de superfície e difusão intrapartícula participaram no mecanismo de adsorção. Os parâmetros termodinâmicos demonstraram que a adsorção foi espontânea em todos os processos de adsorção. Os processos de adsorção foram de natureza endotérmica para todos os sistemas, com exceção do sistema IC/ZM-2, em que foi exotérmico. Os dados de entropia mostraram a ocorrência do aumento da desordem na interface sólido/solução durante a adsorção em todos os sistemas, exceto novamente no IC/ZM-2, no qual se verificou a diminuição da desordem na interface. As isotermas de adsorção ajustaram-se à equação linear de Langmuir. As capacidades máximas de adsorção foram 1,48 mg/g para o sistema IC/CL-2; 1,13 mg/g para IC/ZM-2; 0,96 mg/g para RL16/CL-2 e 1,14 mg/g para RL16/ZM-2 à temperatura ambiente. O estudo de dessorção realizado com água, com soluções aquosas ácidas e com solução aquosa básica demonstrou ser ineficiente tanto para a recuperação dos corantes quanto para a regeneração dos adsorventes. / Coal fly ash, a waste generated in coal-fired electric power plant, was used to synthesize zeolite by hydrothermal treatment with NaOH solution. The fly ash (CL-2) and this synthesized zeolite (ZM-2) that was characterized as hydroxy-sodalite were used as adsorbents for anionic dyes indigo carmine (IC), and reactive orange 16 (RO16) from aqueous solutions. Effects of contact time, initial dye concentration, pH, adsorbent mass, and temperature were evaluated in the adsorption processes. The kinetics studies indicated that the adsorption followed the pseudo-second order kinetics and that surface adsorption and intraparticle diffusion were involved in the adsorption mechanism. The thermodynamics parameters demonstrated that the adsorption was spontaneous for all adsorption processes. The enthalpy data confirmed the endothermic nature for all adsorption processes except for IC/ZM-2 system which was exothermic. The entropy data showed an increased disorder at the solid/solution interface during the adsorption for all systems except for IC/ZM-2 whose negative entropy value indicated a decreased disorder at the interface. The adsorption isotherms were closely fitted to the Langmuir linear equation. The maximum adsorption capacities were 1.48 mg/g for the IC/CL-2 system; 1.13 mg/g for IC/ZM-2; 0.96 mg/g for RO16/CL-2, and 1.14 mg/g for RO16/ZM-2 at room temperature. The desorption study carried out with water, with acid aqueous solutions, and with an alkali aqueous solution showed to be inefficient both for recovering the dyes and regenerating the adsorbents.

Cinza leve de carvão, resíduo gerado em usina termelétrica, foi usada para sintetizar zeólita por meio de tratamento hidrotérmico com solução de NaOH. A cinza leve (CL-2) e a zeólita sintética (ZM-2) que foi predominantemente identificada como hidroxi-sodalita foram utilizadas como adsorventes dos corantes aniônicos índigo carmina (IC) e reativo laranja 16 (RL16) de soluções aquosas. Nos processos de adsorção, os efeitos de tempo de contato, concentração inicial de corantes, pH, massa de adsorventes e temperatura foram avaliados. O estudo cinético de adsorção demonstrou que os resultados apresentaram melhor ajuste ao modelo de pseudo-segunda ordem e que adsorção de superfície e difusão intrapartícula participaram no mecanismo de adsorção. Os parâmetros termodinâmicos demonstraram que a adsorção foi espontânea em todos os processos de adsorção. Os processos de adsorção foram de natureza endotérmica para todos os sistemas, com exceção do sistema IC/ZM-2, em que foi exotérmico. Os dados de entropia mostraram a ocorrência do aumento da desordem na interface sólido/solução durante a adsorção em todos os sistemas, exceto novamente no IC/ZM-2, no qual se verificou a diminuição da desordem na interface. As isotermas de adsorção ajustaram-se à equação linear de Langmuir. As capacidades máximas de adsorção foram 1,48 mg/g para o sistema IC/CL-2; 1,13 mg/g para IC/ZM-2; 0,96 mg/g para RL16/CL-2 e 1,14 mg/g para RL16/ZM-2 à temperatura ambiente. O estudo de dessorção realizado com água, com soluções aquosas ácidas e com solução aquosa básica demonstrou ser ineficiente tanto para a recuperação dos corantes quanto para a regeneração dos adsorventes. / Coal fly ash, a waste generated in coal-fired electric power plant, was used to synthesize zeolite by hydrothermal treatment with NaOH solution. The fly ash (CL-2) and this synthesized zeolite (ZM-2) that was characterized as hydroxy-sodalite were used as adsorbents for anionic dyes indigo carmine (IC), and reactive orange 16 (RO16) from aqueous solutions. Effects of contact time, initial dye concentration, pH, adsorbent mass, and temperature were evaluated in the adsorption processes. The kinetics studies indicated that the adsorption followed the pseudo-second order kinetics and that surface adsorption and intraparticle diffusion were involved in the adsorption mechanism. The thermodynamics parameters demonstrated that the adsorption was spontaneous for all adsorption processes. The enthalpy data confirmed the endothermic nature for all adsorption processes except for IC/ZM-2 system which was exothermic. The entropy data showed an increased disorder at the solid/solution interface during the adsorption for all systems except for IC/ZM-2 whose negative entropy value indicated a decreased disorder at the interface. The adsorption isotherms were closely fitted to the Langmuir linear equation. The maximum adsorption capacities were 1.48 mg/g for the IC/CL-2 system; 1.13 mg/g for IC/ZM-2; 0.96 mg/g for RO16/CL-2, and 1.14 mg/g for RO16/ZM-2 at room temperature. The desorption study carried out with water, with acid aqueous solutions, and with an alkali aqueous solution showed to be inefficient both for recovering the dyes and regenerating the adsorbents.

No description available.