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Abstract(s)
A produção de energia de países industrializados é ainda dependente da conversão térmica de combustíveis fósseis. Assim, surge a necessidade não só da redução de emissões de poluentes gasosos, mas também do reaproveitamento dos resíduos destas indústrias. As cinzas volantes produzidas em centrais termoelétricas são um dos exemplos de resíduos industriais.
Este trabalho procurou estudar a viabilidade de valorização cinzas volantes do carvão como substrato adsorvente de substâncias químicas poluentes existentes em águas residuais e desta forma utilizar um resíduo no tratamento de um outro resíduo.
A composição e propriedades das cinzas volantes foram estudadas com vista a correlacionar estes elementos com a sua utilização enquanto material adsorvente. Entre as análises realizadas encontram-se a termogravimetria, ponto de carga zero, microscopia de varrimento eletrónico, difração raios-X, FTIR, distribuição granulométrica e análises elementares e ao teor de metais.
Para avaliar a da capacidade de adsorção das cinzas foram realizados ensaios de remoção de corantes têxteis: Laranja Mordente 1 (Mo1), Azul de Metileno (MeB), Azul de Metilo (Ac93), Rodamina B (Rhb) e o Azul Mordente 9 (MB9). Adicionalmente, foram testados poluentes emergentes como a Cafeína (CAF), o Paracetamol (PARA) e o Ibuprofeno (IBU). Foram também, otimizadas diferentes condições no modo de realização dos ensaios de adsorção. Aos resultados de adsorção foram aplicados os modelos de Langmuir, Freundlich e de Temkin. Optou-se por analisar somente os dados quantitativos do modelo da isotérmica de Langmuir por serem os que melhor descrevem os dados experimentais.
Os resultados mostraram uma grande variação da capacidade de adsorção em função dos diferentes substratos: com o corante aniónico Mo1 obteve-se uma capacidade máxima de 125 mg/g e com o catiónico Rhb 6,7 mg/g; no caso dos poluentes emergentes obteve-se uma remoção máxima de 3 mg/g no caso do PARA.
As diferenças evidenciadas na capacidade de adsorção são relacionadas com as caraterísticas dos adsorvato mas também com as caraterísticas de química superficial das cinzas. A capacidade de adsorção depende maioritariamente de componentes como SiO2 e Al2O3, (maioritários na cinza) e o desenvolvimento de cargas positivas ou negativas na superfície que interferem fortemente com o fenómeno de adsorção.
Os estudos de lixiviação também realizados neste trabalho concluíram que as cinzas em estudo apresentaram concentrações muito reduzidas de metais pesados pelo que não constituem uma fonte de potencial toxicidade para as águas residuais ou efluentes a tratar.
Energy production in industrialized countries still depends on the thermal conversion of fossil fuels. Thus, it is required not only to reduce pollutant gas emissions, but also to reuse solid waste from these industries. Fly ashes produced in thermal power plants is one example of industrial waste. This work aimed to study the viability of coal fly ash utilization as an adsorbent substrate of chemicals pollutants presents in wastewater and promote the use of this residue in the treatment of another waste. The composition and properties of fly ashes were studied in order to correlate these elements with their performances as adsorbent material. The characterization include thermogravimetry, zero charge point, scanning electron microscopy, X-ray diffraction, FTIR, particle size distribution and elemental and metal content analysis. In order to evaluate the adsorption capacity of the ashes, textile dye removal tests were carried out with Mordant Orange 1 (Mo1), Methylene Blue (MeB), Methyl Blue (Ac93), Rhodamine B (Rhb) and Mordant Blue 9 (MB9). In addition, emerging pollutants such as Caffeine (CAF), Paracetamol (PARA) and Ibuprofen (IBU) were also tested. Different experimental conditions were optimized in the way the adsorption essays were performed. Adsorption results were fitted by Langmuir, Freundlich and Temkin models. Only the Langmuir isotherm model was used to evaluate data because is the best formulation to describe the experimental results. The results showed a large variation in adsorption capacity as function of the different substrates: anionic dye Mo1 gave a maximum capacity of 125 mg/g and cationic Rhb 6,7 mg/g; for emerging pollutants a maximum removal of 3 mg/g was achieved for PARA. The differences found in the adsorption performance were related with adsorbate and the surface chemistry characteristics of ashes. Adsorption capacity depends mainly on constituents such as SiO2 and Al2O3 (mainly present in ashes) and the existence of positive or negative surface charges that strongly interfere with the adsorption phenomenon. The leaching studies also performed led to the conclusion that this studied ashes had very low concentrations in heavy metals and therefore do not constitute a toxic source to the wastewater or effluent treated.
Energy production in industrialized countries still depends on the thermal conversion of fossil fuels. Thus, it is required not only to reduce pollutant gas emissions, but also to reuse solid waste from these industries. Fly ashes produced in thermal power plants is one example of industrial waste. This work aimed to study the viability of coal fly ash utilization as an adsorbent substrate of chemicals pollutants presents in wastewater and promote the use of this residue in the treatment of another waste. The composition and properties of fly ashes were studied in order to correlate these elements with their performances as adsorbent material. The characterization include thermogravimetry, zero charge point, scanning electron microscopy, X-ray diffraction, FTIR, particle size distribution and elemental and metal content analysis. In order to evaluate the adsorption capacity of the ashes, textile dye removal tests were carried out with Mordant Orange 1 (Mo1), Methylene Blue (MeB), Methyl Blue (Ac93), Rhodamine B (Rhb) and Mordant Blue 9 (MB9). In addition, emerging pollutants such as Caffeine (CAF), Paracetamol (PARA) and Ibuprofen (IBU) were also tested. Different experimental conditions were optimized in the way the adsorption essays were performed. Adsorption results were fitted by Langmuir, Freundlich and Temkin models. Only the Langmuir isotherm model was used to evaluate data because is the best formulation to describe the experimental results. The results showed a large variation in adsorption capacity as function of the different substrates: anionic dye Mo1 gave a maximum capacity of 125 mg/g and cationic Rhb 6,7 mg/g; for emerging pollutants a maximum removal of 3 mg/g was achieved for PARA. The differences found in the adsorption performance were related with adsorbate and the surface chemistry characteristics of ashes. Adsorption capacity depends mainly on constituents such as SiO2 and Al2O3 (mainly present in ashes) and the existence of positive or negative surface charges that strongly interfere with the adsorption phenomenon. The leaching studies also performed led to the conclusion that this studied ashes had very low concentrations in heavy metals and therefore do not constitute a toxic source to the wastewater or effluent treated.
Description
Trabalho final de mestrado para obtenção do grau de mestre em Engenharia Química e Biológica
Keywords
Energia Energy Carvão Coal Termoelétrica Thermoelectric Emissões Emissions Resíduos industriais Industrial waste Cinzas Ashes Efluentes Effluents Corantes Dyes Poluentes emergentes Emerging pollutants Valorização Recovery Adsorção Adsorption
Citation
ROSA, Teresa Sofia Cadete - Valorização de cinzas volantes do carvão para remoção de poluentes em meio líquido. Lisboa: Instituto Superior de Engenharia de Lisboa, 2019. Dissertação de mestrado.
Publisher
Instituto Superior de Engenharia de Lisboa