• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 31
  • 26
  • 11
  • 3
  • 3
  • 1
  • 1
  • 1
  • Tagged with
  • 94
  • 19
  • 15
  • 12
  • 12
  • 11
  • 10
  • 10
  • 9
  • 9
  • 8
  • 8
  • 8
  • 8
  • 8
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
21

Potencial das cinzas da queima de biomassa energ?tica de capim-elefante (Pennisetum purpureum Schum.) como fonte de nutrientes / Potential of ashes from the burning of energetic biomass from elephant grass (Pennisetu purpureum Schum.) as a source of nutrients

Cruz, Luis Cl?udio Jord?o da 19 February 2014 (has links)
Submitted by Sandra Pereira (srpereira@ufrrj.br) on 2017-04-25T13:08:45Z No. of bitstreams: 1 2014 - Luis Claudio Jord?o da Cruz.pdf: 1154945 bytes, checksum: 76e27a77176ae3119d01bd7db89464dd (MD5) / Made available in DSpace on 2017-04-25T13:08:45Z (GMT). No. of bitstreams: 1 2014 - Luis Claudio Jord?o da Cruz.pdf: 1154945 bytes, checksum: 76e27a77176ae3119d01bd7db89464dd (MD5) Previous issue date: 2014-02-19 / In the humid tropics elephant grass (Pennisetum purpureum Schum.), also known as Napier, of African origin, is known for its high production of biomass, which made him an ideal candidate for use as an energy feedstock for the biofuels industry, since the amount of fertilizer nitrogen mainly be low to avoid high costs inputs from fossil fuels. In the search for sources of biomass for the production of heat or electricity to reduce greenhouse gas (GHG), highlight the use of highly productive C4 grasses such as Miscanthus, Panicum and Saccharum spp. For this reason, many elephant grass accessions were investigated on the ability of high dry matter production without additions of nitrogen fertilizers, where the largest producers of biomass without N genotypes were as Cameroon and Gramafante. Bacteria were isolated fixing N in high numbers from this species genotypes, resulting in the study with 14 genotypes planted in soil with low 15N enrichment with production of more than 30% of its N biological fixation of N. After 10 years study, five elephant grass genotypes were indicated by the high biomass production, where there was also a lot of soil K extraction, which further highlights the use or reuse of the ashes as a nutrient source for minimize the consumption of said input. The objective of this study was to investigate the potential of ash five elephant grass genotypes and ash from industrial furnace to provide nutrients in soils of low fertility, comparing efficiency of use of nutrients by plants in response to different doses of ash and fertilizers minerals. Three experiments in pots used ash from 5 different elephant grass genotypes (Gramafante, Cameroon, BAG 02, CNPGL F06-3 and Roxo) that were conducted with low fertility soil, with brachiaria (Brachiaria decumbens Stapf.) as an indicator plant of plant development. The experiment consisted in pots with treatments with the ashes of elephant grass genotypes, contrasting with mineral fertilizer. The treatments were arranged in a randomized block design (factorial 3x2+1), with five repetitions, harvested six times at intervals of 60 days after the establishment of biomass brachiaria. A low fertility soil in a field experiment with the ashes derived from the ceramics industry of thermal power generation was conducted using elephant grass Cameroon genotype. The soil used in all experiments was Serop?dica?s Planosol, Rio de Janeiro. Experiments in pots showed a strong correlation between the amount of nutrients applied and absorption of nutrients by brachiaria at all doses of mineral fertilizers or ashes. The field trial showed no differences in income or absorption of nutrients in the elephant grass genotype Cameroon / Nas regi?es tropicais ?midas o capim-elefante (Pennisetum purpureum Schum.), tamb?m conhecido como Napier, de origem Africana, ? conhecido por sua alta produ??o de biomassa, o que o tornou um candidato ideal para seu uso como mat?ria-prima energ?tica para a ind?stria de biocombust?veis, desde que a dose de fertilizantes nitrogenados, principalmente, seja baixa para evitar altas entradas de gastos com combust?veis f?sseis. Na busca de fontes de biomassa para a produ??o de calor ou energia el?trica com redu??o de gases de efeito estufa (GEE), destacam-se o uso de gram?neas C4 altamente produtivas, como Miscanthus, Panicum e Saccharum spp. Por este motivo, diversos acessos de capim-elefante foram investigados sobre a capacidade de alta produ??o de mat?ria seca sem adi??es de fertilizantes nitrogenados, onde os maiores produtores de biomassa sem N foram gen?tipos como Cameroon e Gramafante. Foram isoladas bact?rias fixadoras de N em n?meros elevados a partir de gen?tipos desta esp?cie, que resultaram no estudo com 14 gen?tipos plantados em solo com baixo enriquecimento 15N com produ??o de mais de 30% do seu N da fixa??o biol?gica de N. Ap?s 10 anos de estudo, cinco gen?tipos de capim-elefante foram indicados pela alta produ??o de biomassa, onde se verificou tamb?m uma grande quantidade de extra??o de K do solo, o que evidencia ainda mais a utiliza??o, ou reutiliza??o, de suas cinzas como fonte de nutriente, para minimizar o consumo do referido insumo. O objetivo deste estudo foi investigar o potencial de cinzas de cinco gen?tipos de capim-elefante e de cinzas provenientes de forno industrial para disponibilizar nutrientes em solos de baixa fertilidade, com compara??o da efici?ncia de uso dos nutrientes pelas plantas em resposta de diferentes doses de cinzas e fertilizantes minerais. Tr?s experimentos em vasos utilizaram cinzas provenientes de 5 diferentes gen?tipos de capim-elefante (Gramafante, Cameroon, BAG 02, CNPGL F06-3 e Roxo) que foram conduzidos com solo de baixa fertilidade, com braqui?ria (Brachiaria decumbens Stapf.) como planta indicadora do desenvolvimento vegetal. O experimento em vasos consistiu com tratamentos com as cinzas dos gen?tipos de capim-elefante, em contraste com fertilizante mineral. Os tratamentos foram dispostos em blocos casualizados (fatorial 3x2+1), com cinco repeti??es, colhido em seis ocasi?es, com intervalos de 60 dias ap?s o estabelecimento da biomassa de braqui?ria. Um experimento de campo em solo de baixa fertilidade com as cinzas derivada da ind?stria cer?mica de gera??o de energia t?rmica foi realizado com uso do gen?tipo de capim-elefante Cameroon. O solo utilizado em todos os experimentos foi Planossolo de Serop?dica, Rio de Janeiro. Os experimentos em vasos mostraram uma forte correla??o entre a quantidade de nutriente aplicado e a absor??o de nutrientes pela braqui?ria em todas as doses de adubos minerais ou das cinzas. O experimento de campo n?o mostrou diferen?as de rendimento ou de absor??o de nutrientes no gen?tipo de capim-elefante Cameroon.
22

Estudo da lixiviação e da estabilização de elementos tóxicos presentes em cinzas leve de carvão / Study of the leaching and stabilization of toxic elements present in coal fly ash

Felipe Arrelaro Campello 29 November 2018 (has links)
A lixiviação de elementos tóxicos presentes nas cinzas de carvão causa contaminação no meio ambiente e é, por isso, motivo de grande preocupação. Ensaios em batelada e em coluna de leito fixo foram realizados para avaliar a estabilização de As, Cr, Mo e Se em cinzas leve de carvão modificadas com orgânosilano (OS) e surfactante de amônio quaternário (SF). As cinzas leve utilizadas foram coletadas na Usina Termelétrica da Figueira, localizada na cidade de Figueira, Estado do Paraná. Nos ensaios em batelada, em primeiro lugar, avaliou-se a influência da relação massa de cinzas/volume de água na concentração dos elementos lixiviados das cinzas não tratadas. Posteriormente, determinou-se o pH, a condutividade e as capacidades de imobilização dos elementos tóxicos presentes nas cinzas após a modificação. As reduções de concentração usando OS foram de 89%, 77%, 42% e 11% para Cr, Mo, As e Se, respectivamente. Quando SF foi utilizado para o tratamento das cinzas, a redução de concentração nos lixiviados foi superior a 60% para todos os elementos. As cinzas tratadas foram caracterizadas em relação ao ponto de carga zero, morfologia, grupos funcionais, mineralogia e hidrofobicidade. As superfícies das cinzas tratadas com OS e SF apresentaram carga superficial positiva em água. A composição mineralógica e a morfologia das cinzas não foram alteradas após o tratamento, enquanto mudanças nos grupos funcionais foram observadas. Esse resultado corroborou com o observado nos testes de hidrofobicidade onde, as cinzas tratadas com OS e SF na proporção 1:10 foram classificadas como material extremamente hidrofóbico e na proporção 1:100 foram classificadas como material fortemente hidrofóbico, confirmando que foi efetivo o tratamento das cinzas com os agentes imobilizadores. Na segunda etapa do estudo foram realizados três ensaios de lixiviação em colunas contendo cinzas de carvão e solo coletado na região da Usina Termelétrica da Figueira. Nos ensaios foram usadas cinzas não tratadas, cinzas tratadas com OS e cinzas tratadas com SF nas diluições de maior efetividade selecionadas pelos ensaios em batelada. Nas colunas foi aplicado um volume de chuva ácida sintética simulando a precipitação que ocorre na região. Na coluna com cinzas tratadas com OS ocorreu redução considerável na concentração de As e principalmente do Cr. Após o tratamento com SF, as concentrações de As e Cr reduziram aproximadamente 30%. Em ambos os tratamentos, as concentrações de Mo e Se também foram reduzidas. Os resultados evidenciaram que tanto o orgânosilano, quanto o surfactante podem ser utilizados como agentes imobilizadores para a retenção de elementos tóxicos presentes em cinzas de carvão. / The leaching of toxic elements in coal ash causes contamination of the environment and is therefore of great concern. Batch and column tests were performed to evaluate the stabilization of As, Cr, Mo and Se in fly ash modified with organosilane (OS) and quaternary ammonium surfactant (SF). The fly ashes used were collected at the Figueira Thermoelectric Plant, located in the city of Figueira, State of Paraná. In the batch tests, first, the influence of ash / volume ratio on the concentration of the leached elements of the untreated ash was evaluated. Subsequently, the pH, conductivity and immobilization capacities of the toxic elements present in the ashes after the modification were determined. The reductions in the concentrations of toxic elements using OS were 89%, 77%, 42% and 11% for Cr, Mo, As and Se, respectively. When SF was used for ash treatment, the concentration reduction in the leachates was greater than 60% for all elements. The treated ash was characterized in relation to zero charge point, morphology, functional groups, mineralogy and hydrophobicity. OS and SF treated ash surfaces showed a positive surface charge in water. The mineral composition an morphology of the ashes was not altered after treatment, while changes in the functional groups were observed. This result corroborated with that observed in the hydrophobicity tests, where ashes treated with OS and SF in the proportion 1:10 were classified as extremely hydrophobic material and in the proportion 1: 100 were classified as strongly hydrophobic material, confirming that the treatment of the ashes with immobilizing agents were efficient. In the second stage of the study three leaching tests were carried out on columns containing coal ash and soil collected in the Figueira Thermoelectric Power Plant region. In the tests, untreated fly ash, OS treated fly ash and SF treated fly ash were used at the most effective dilutions selected by batch tests. In the columns a synthetic acid rain was applied simulating the precipitation that occurs in the region. In the column with ash treated with OS there was a considerable reduction in the concentration of As and especially of Cr. After treatment with SF, concentrations of As and Cr reduced approximately 30%. In both treatments, the concentrations of Mo and Se were also reduced. The results showed that both the organosilane and the surfactant can be used as immobilizers for the retention of toxic elements present in coal ash.
23

A Path Home

Vaid, Ajinderjeet Kaur January 2006 (has links)
With the shift in perspective from temporary to permanent residence in this country, Sikhs are caught in between two polar ends of homeland and diaspora. This thesis attempts to illuminate a third – a universal permanence free of physical barriers. This account describes a movement towards establishing a Sikh homeland that is manifested in the collective Sikh body of the world rather than in the physical land of Punjab. The turban that is the physical identity of the Sikhs in diaspora has also come to represent the rigidities of the culture, which neglect the omnipresent divinity, and sacredness of every place. In its form and content, this thesis is engaged in “unfolding of the turban” to open it to the new worlds it is now a part of, to create a new beginning as a human body unfolds upon death into its five primal elements on the verge of reviviscence. Sikhs worldwide are aware of their need to convert diaspora back into a homeland, to fight against restrictions that hinder the completion of rituals of life and death. The unraveling of the turban into an undulating path allows for a new perspective on permanence for the Sikhs in foreign lands. Unfolded into a form of the meandering river, the turban also represents the eternally flowing waters. The silent sacredness of the water indistinctly exists in Toronto. Behind the towering city, the Don River often flows quietly, leading a life parallel to that of the River Ganges and the River Sutlej. This once pastoral valley that sustained villages and nature is now discarded, in post-industrial despair. Trapped within these modern city confines, the river still secretly retains the power to transfigure souls, but its powers of reviviscence remain unidentified and unused due to restrictive cremation bylaws. This thesis attempts to create for the Sikhs an essential funeral landscape, whose icons may be read through an anamorphic lens of Sikh culture, while providing for all an opportunity to engage the forgotten river, and its energy.
24

Landfill Mining: Prospecting metal in Gärstad landfill

Tanha, Ariana, Zarate, Daniel January 2012 (has links)
All processes in society produce waste. In nature, the waste is normally used as a resource for another process, but in human societies waste is often discarded. These discarded materials end up in places for depositing waste known as landfills. The increase in population, and humans’ tendency to improve their quality of life, has led to an increase in consumption of material. More material consumption means generating more waste, and more waste means bigger landfills. The increasing size of landfills has brought some other issues, such as increased land use and higher environmental impact. However in these landfills a lot of valuable materials are discarded and the concept of landfill mining (LFM) has been proposed in order to solve these issues and use landfills as a possible source of materials. Landfill mining is not yet a common practice, and the first barrier for this is the uncertainty of the amount and value of materials within landfills. The purpose of this study is to prospect the amount of metals in one specific landfill, in this case Gärstad landfill in Linköping, Sweden.  This is a first step to show the feasibility of landfill mining as an alternative way of extracting materials. The study is limited only to metals because they are one of the most important resources in today’s society. The theoretical background of the study is based on material flow analysis (MFA). Two approaches are used to study the materials in the landfill. The first is top-down which studies the flows of materials and the second is bottom-up which studies the stocks of material in the landfill. Based on these approaches the method was developed. First the system boundaries in time and space were defined. Then the amount of waste in landfill was estimated from the two mentioned approaches. In the end the metal content of the waste was estimated. Some criteria are also defined to compare the accessibility of the metals in the landfill. The results of this study show that there is a considerable amount of metals in the landfill, and that ash deposits resulting from incineration are the most interesting source of metals; with iron, aluminium, copper and zinc being the most abundant. The results are presented by type of waste, area of the landfill and accessibility in order to identify the hotspots. Later it is discussed that the method is cheap and fast but highly depends on previous data and available information. Also the metal content of the landfill is compared with natural ores. In the end the metal content of the landfill is evaluated and estimated to be around 3 billion SEK. It shows that aluminium, titanium and copper have the highest value money wise. As conclusion it was shown material flow analysis is a valid way to prospect landfills. But further cost-benefit analysis must be carried out to determine if landfill mining is justifiable. Also some recommendations are proposed to Tekniska Verken in order to facilitate future studies. The first is to develop a systematic way for landfilling different kind of waste and document them. Second is to include metals which have economic potential in the regular sampling from landfill. / Många processer i samhället generar avfall. I naturen används avfallet normalt som en resurs i en annan process, men i människliga samhällen kastas avfallet oftast bort. Bortkastat material hamnar förr eller senare oftast i deponier. Befolkningsökningen och människans tendens till att försöka förbättra sin livskvalitet har lett till en ökad materialkonsumtion. Högre konsumtion genererar mer avfall, och mer avfall kräver större deponier. Växande avfallsanläggningar leder i sin tur till ökad markanvändning och högre miljöpåverkan. I dessa anläggningar finns det emellertid stora mängder värdefullt material deponerat, och från dessa läcker både tungmetaller och metan ut, vilket är skadligt för miljön. Landfill Mining (LFM) har föreslagits som en lösning på dessa problem och avfallsanläggningarna används då även som en möjlig källa till material. Landfill mining är idag inte vanligt förekommande och det huvudsakliga hindret är de många osäkerheterna kring ett sådant projekt, till exempel; hur mycket material finns i deponierna och hur mycket är det värt? Syftet med den här studien är att uppskatta metallinnehållet i en specifik avfallsanläggning, i det här fallet Gärstad avfallsanläggning i Linköping. Detta är ett första steg i att utröna genomförbarheten av LFM som en alternativ resursbas. Studien är begränsad till metaller eftersom dessa håller på att ta slut i jordskorpan och det vore därför intressant att finna nya materialkällor till dessa. Den teoretiska bakgrunden till den här studien är baserad på materialflödesanalys (MFA). Två metoder har använts för att prospektera Gärstad. Dels top-down, som studerar flödet av material, dels bottom-up, som studerar materialförrådet i avfallsanläggningen. Avfallens totalmängd var uppskattad genom att beräkna flödet in och ut från anläggningen. Sedan använde vi tidigare gjorda provtagningar av avfallets metallmängder för att uppskatta metallinnehållet. Slutligen analyserades metallernas tillgänglighet baserad på typ av avfall, och om deponi delområdet var sluttäckt. Resultatet visar att det finns mycket metaller deponerat i Gärstad. Askan från avfallsförbränningen visade sig vara den avfallstyp med rikast metallinnehåll. Järn, aluminium, koppar och zink är de vanligaste förkommande metallerna. Metallkoncentrationen av avfallsanläggningen kan jämföras med naturliga malmer. Värdet av metallerna i Gärstad uppgår till cirka 3 miljarder. Dock är endast 30 % av metallerna tillgängliga med dagens teknik. De största värdena finns enligt följd i aluminium, titan och koppar. För att identifiera hotspots, redovisas resultatet enligt avfallstyp, lokalisering och tillgänglighet. MFA är ett fungerande prospekteringsverktyg för deponier. Metod är billig och snabb men beroende av att det finns tillgänglig data. Innan deponin transformeras till en gruva bör emellertid först en kostnad och nyttoanalys genomföras för att undersöka genomförbarheten vidare. Rekommendationer för att underlätta framtida utgrävningar är att utveckla ett systematiskt sätt att deponera olika typer av avfall och att dokumentera dem. De metaller som har ekonomisk potential bör dessutom inkluderas vid den normala provtagningen av deponerat avfall.
25

A Path Home

Vaid, Ajinderjeet Kaur January 2006 (has links)
With the shift in perspective from temporary to permanent residence in this country, Sikhs are caught in between two polar ends of homeland and diaspora. This thesis attempts to illuminate a third – a universal permanence free of physical barriers. This account describes a movement towards establishing a Sikh homeland that is manifested in the collective Sikh body of the world rather than in the physical land of Punjab. The turban that is the physical identity of the Sikhs in diaspora has also come to represent the rigidities of the culture, which neglect the omnipresent divinity, and sacredness of every place. In its form and content, this thesis is engaged in “unfolding of the turban” to open it to the new worlds it is now a part of, to create a new beginning as a human body unfolds upon death into its five primal elements on the verge of reviviscence. Sikhs worldwide are aware of their need to convert diaspora back into a homeland, to fight against restrictions that hinder the completion of rituals of life and death. The unraveling of the turban into an undulating path allows for a new perspective on permanence for the Sikhs in foreign lands. Unfolded into a form of the meandering river, the turban also represents the eternally flowing waters. The silent sacredness of the water indistinctly exists in Toronto. Behind the towering city, the Don River often flows quietly, leading a life parallel to that of the River Ganges and the River Sutlej. This once pastoral valley that sustained villages and nature is now discarded, in post-industrial despair. Trapped within these modern city confines, the river still secretly retains the power to transfigure souls, but its powers of reviviscence remain unidentified and unused due to restrictive cremation bylaws. This thesis attempts to create for the Sikhs an essential funeral landscape, whose icons may be read through an anamorphic lens of Sikh culture, while providing for all an opportunity to engage the forgotten river, and its energy.
26

Effects of wood ash on freshwater organisms and aquatic forest ecosystems /

Aronsson, K. Andreas. January 2007 (has links)
Diss. (sammanfattning) Sundsvall : Mittuniversitetet, 2007. / Härtill 4 uppsatser.
27

Interactions between calcium and heavy metals in Norway spruce : accumulation and binding of metals in wood and bark /

Österås, Ann Helén, January 2004 (has links)
Diss. (sammanfattning) Stockholm : Univ., 2004. / Härtill 5 uppsatser.
28

Performance and sustainability of short-rotation energy crops treated with municipal and industrial residues /

Dimitriou, Ioannis, January 2005 (has links) (PDF)
Diss. (sammanfattning). Uppsala : Sveriges lantbruksuniv. / Härtill 5 uppsatser.
29

Avaliação técnica da utilização de cinzas de combustão do carvão mineral provenientes de termelétrica em argamassas de revestimento / Technical evaluation of the use of ash from the combustion of coal from thermal power plant in coating mortar.

Sampaio, Kalil Nóbrega Hissa 14 June 2017 (has links)
SAMPAIO, K. N. H. Avaliação técnica da utilização de cinzas de combustão do carvão mineral provenientes de termelétrica em argamassas de revestimento. 2017. 89 f. Dissertação (Mestrado em Engenharia Civil)-Centro de Tecnologia, Programa de Pós-Graduação em Engenharia Civil: Estruturas e Construção Civil, Universidade Federal do Ceará, Fortaleza, 2017. / Submitted by Hohana Sanders (hohanasanders@hotmail.com) on 2017-10-24T14:13:48Z No. of bitstreams: 1 2017_dis_knhsampaio.pdf: 2174900 bytes, checksum: 3f9554b5853871212621dd3af72085ff (MD5) / Approved for entry into archive by Marlene Sousa (mmarlene@ufc.br) on 2017-11-07T18:47:19Z (GMT) No. of bitstreams: 1 2017_dis_knhsampaio.pdf: 2174900 bytes, checksum: 3f9554b5853871212621dd3af72085ff (MD5) / Made available in DSpace on 2017-11-07T18:47:19Z (GMT). No. of bitstreams: 1 2017_dis_knhsampaio.pdf: 2174900 bytes, checksum: 3f9554b5853871212621dd3af72085ff (MD5) Previous issue date: 2017-06-14 / In Brazil, 65% of the power generation projects are thermal plants. In the state of Ceará they are responsible for 61.11% of the energy production, highlighting the thermal plants of Pecém I and Pecém II which together have an installed capacity of 1085MW. However, the thermal plants have a major environmental liability for its waste generation, among which stands out the ashes from the combustion of coal (ACC). In order to give a more suitable destination to this waste, its incorporation into raw materials may generate sustainable materials. This thesis proposes to apply those thermal plants’ ashes in mixed mortar of cement and lime, replacing lime by ACC in contents of 0%, 25%, 50%, 75% and 100%, analyzing the characteristics in fresh state and hardened states, as well as its durability. Regarding the fresh state’s tests, the consistency index was fixed and it was quantified the amount of water necessary for each mixture to reach it. Afterwards, the loss of consistency of each mortar was evaluated after five and ten minutes. Finally, the rheology was investigated by the Squeeze-flow method. Regarding the hardened state’s tests, the tensile strength in flexion, the compressive strength and the tensile strength were evaluated. In the end, the durability was analyzed through the permeability test by the pipe method and the cracking aperture lengths. The results were analyzed by an analysis of variance (ANOVA) and the multiple comparisons of means by the Duncan’s test, using the software Statistica 7.0. They indicate that its replacement is technically feasible, as giving a better performance in its workability, resistance and durability. All of the mortars with ACC have shown an improvement in its characteristics compared to the reference mortar, and the mortars with more than 75% of ACC stood out among in resistance, in consistency, and in durability. Keywords: Coal Ash. Sustainable Materials. / No Brasil, 65% dos empreendimentos de geração de energia são usinas termelétricas. No Ceará as mesmas são responsáveis por 61,11% da produção de energia do estado, destacando-se as usinas termelétricas de Pecém I e Pecém II, que juntas possuem a capacidade instalada de 1085MW. Contudo, as usinas termelétricas possuem um grande passivo ambiental pela sua geração de resíduos, dentre os quais se destacam as cinzas da combustão do carvão mineral (CCCM). Para dar uma destinação adequada a esse resíduo, busca-se incorporá-lo em matérias-primas. O presente trabalho propõe aplicar essas cinzas na confecção de argamassas mistas de cimento e cal, substituindo a cal por CCCM nos teores de 0%, 25%, 50%, 75% e 100%, analisando assim suas características tanto no estado fresco quanto no estado endurecido. Com relação aos ensaios no estado fresco, foi fixado o índice de consistência e a partir do mesmo foi quantificada a quantidade de água necessária para cada mistura atingi-lo, em seguida foi avaliada a perda de consistência da argamassa após cinco e dez minutos. Por fim, foi investigada a reologia pelo método do Squeeze-flow. Com relação aos ensaios no estado endurecido, foram avaliadas as resistências à tração na flexão e à compressão e a resistência de aderência à tração. Finalmente, a durabilidade foi analisada através dos ensaios de permeabilidade pelo método do cachimbo e a taxa de abertura de fissuras. Os resultados foram analisados por uma análise de variância (ANOVA) e o comparativo múltiplo de médias pelo teste de Duncan, utilizando o software Statistica 7.0. Os mesmos indicaram que a substituição é viável tecnicamente conferindo um melhor desempenho na sua trabalhabilidade, resistência mecânica e durabilidade. Todas as argamassas com CCCM mostraram melhoras em suas características quando comparadas ao traço de referência, sendo a argamassa com teores acima de 75% de CCCM as que mais se destacaram em resistência, consistência e durabilidade.
30

Síntese de zeólitas a partir de cinzas de carvão e aplicação como adsorventes

Zen, Barbara Potrich January 2016 (has links)
Cinzas oriundas da combustão de carvão são resíduos produzidos no processo de geração de energia em termoelétricas. Esses resíduos industriais podem ser aproveitados como matéria prima para síntese de zeólitas, as quais são materiais aluminossilicatos porosos com importantes aplicações, como adsorventes no tratamento de efluentes líquidos. Nesse contexto, o objetivo deste trabalho foi sintetizar zeólitas a partir de três diferentes cinzas de carvão e utilizá-las na remoção de corante violeta cristal em soluções aquosas via processo de adsorção. Para isso, foram sintetizadas zeólitas denominadas ZP, ZF e ZFD a partir de três diferentes cinzas de carvão, sendo elas, respectivamente: cinzas de carvão de combustão em leito pulverizado, de combustão em planta piloto de leito fluidizado e de combustão em planta piloto de leito fluidizado utilizando processo de dessulfuração interna. A síntese foi feita pelo método hidrotérmico, utilizando NaOH 3 mol L-1 como agente mineralizante, relação líquido/sólido (L/S) igual a 6 e tempo de reação de 24 h a 100 °C. Os materiais obtidos foram submetidos à caracterização física, química e morfológica, nas quais foi observada a formação de três diferentes fases zeolíticas (zeólitas P, X e sodalita) nas amostras ZF e ZFD, e uma única fase (zeólita P) na amostra ZP. Os valores de área superficial BET encontrados foram de 17, 35 e 40 m2 g-1 para as zeólitas ZP, ZFD e ZF, respectivamente, com tamanho de poros na faixa de 3 a 4 nm para os três materiais. Os valores de capacidade de troca catiônica (CTC) ficaram entre 2,07 e 2,85 meq NH4 + g-1. Posteriormente foram realizados ensaios de adsorção do corante em que foi avaliada a influência do pH, tempo de contato e concentração de sólido adsorvente. Ainda, foram construídas isotermas de adsorção para esses sistemas e os modelos de isotermas de Langmuir, Freundlich e BET modificado foram ajustados aos dados experimentais. Os resultados mostraram que a maior eficiência foi obtida pela zeólita ZF, alcançando máxima remoção de corante de 85 % nos estudos do efeito do tempo de contato, e as melhores condições experimentais obtidas foram de 60 min e 15 g L-1 de concentração de sólido adsorvente. O modelo de isotermas que melhor se ajustou aos dados experimentais foi BET modificado, com R2 = 0,9894. A síntese de zeólita a partir de cinzas de carvão mostrou potencial na produção de um adsorvente alternativo para remoção do corante violeta cristal de águas contaminadas, contribuindo também para a diminuição do impacto ambiental das atividades de combustão de carvão. / Ashes from coal combustion are waste produced in the process of power generation in thermoelectric. These industrial wastes can be used as raw material for zeolite synthesis, which are porous aluminosilicate with important applications, such as adsorbents in the treatment of liquid effluents. The objective of this study was to synthesize zeolites from three different coal ash and apply it in crystal violet dye adsorption processes in aqueous solution. Thereunto, zeolites called ZP, ZF e ZFD were synthesized from the three different coal ashes, as so, respectively: coal ashes from powdered bed combustion, from combustion in a fluidized bed pilot plant and from combustion in a fluidized bed pilot plant with internal desulphurization. The synthesis was carried by hydrothermal method, using NaOH 3 mol L-1 as the mineralizing agent, the liquid/solid ratio (L/S) equal to 6 and 24 hours reaction time at 100 ° C. The materials were subjected to physical, chemical and morphological characterization and it was observed the formation of three different zeolite phases (zeolites P, X and sodalite) in the sample ZF and ZFD, and a single phase (zeolite P) in ZP sample. The BET surface area values were 17, 35 and 40 m2 g-1 to ZP, ZFD and ZF zeolites, respectively, with pore size in the range of 3 to 4 nm for all three materials. The values of cation exchange capacity (CEC) were between 2.07 and 2.85 meq NH4 + g-1. Subsequently, adsorption tests were carried out in which it was evaluated the influence of pH, contact time and adsorbent solid concentration. Still, adsorption isotherms were built for these systems and isotherm models of Langmuir, Freundlich and modified BET were fitted to experimental data. The results showed that the highest efficiency was obtained by zeolite ZF, achieving maximum dye removal of 85 % in the studies of contact time effects, and the best experimental conditions were 60 min and adsorbent solid concentration of 15 g L-1. The BET isotherm model was found to be the best fit to experimental data, with R2 = 0.9894. The zeolite synthesis from coal ash has shown potential in the production of an alternative adsorbent to remove the crystal violet dye from contaminated water, also contributing to reducing the environmental impact of coal combustion activities.

Page generated in 0.0304 seconds