Estudo da fração areia da lama vermelha para a produção de revestimentos em liga de alumínio por oxidação eletrolítica assistida por plasma
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Data
2019-01-21
Autores
Moraes, Renan Fernandes
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Universidade Estadual Paulista (Unesp)
Resumo
A geração de resíduos de mineração, sempre foi considerada um potencial risco ao meio ambiente, sendo de suma importância encontrar soluções alternativas de aproveitamento e valorização dos mesmos, com o objetivo de minimizar a disponibilidade no meio ambiente e atribuir novas funções para este tipo de material. O Brasil é um grande produtor de bauxita, sendo classificado entre os primeiros produtores desse mineral no mundo, porém o seu processamento gera um resíduo bastante alcalino denominado lama vermelha. Neste trabalho, foram determinadas propriedades físicas e químicas da lama vermelha total e de sua fração areia, obtida por peneiramento. Para isso foram feitas análises por Microscopia Eletrônica de Varredura (MEV), Espectroscopia de Dispersão de Energia (EDS), Fluorescência de Raios-X (FRX) e massa específica pela técnica de picnometria. Através desses resultados pode-se concluir que é possível através de uma técnica simples, segregar diferentes composições químicas elementares desse resíduo, como Si, Fe, Na e Ca. Atrelados à separação granulométrica, os resultados de massa específica mostram que a fração areia é mais densa e destaca-se também que cerca de 96% da massa da lama vermelha aqui estudada encontra-se nessa fração granulométrica. Também foi possível verificar a viabilidade de se utilizar esse resíduo e sua fração areia para produzir revestimentos em ligas de alumínio 1200, através de oxidação eletrolítica assistida por plasma (PEO). Dependendo das condições de deposições, como concentração (5 g/L e 10 g/L) e tempo de deposição(300, 600 e 900 segundos), os revestimentos propiciam características físicas e químicas diferentes, podendo proporcionar diferentes aplicabilidades para essas superfícies. Os resultados das analises por EDS permite concluir que os revestimentos obtidos utilizando-se lama vermelha total com menor concentração apresentam menos elementos químicos incorporados, já em relação aos revestimentos da lama vermelha fração areia há mais elementos incorporados, devido a uniformidade do tamanho das partículas. A análise cristalográfica dos revestimentos mostra que a fase alumina alfa é encontrada com maior presença nos revestimentos obtidos utilizando a fração areia da lama vermelha. Elementos como Ti e Si encontram-se também em algumas formas cristalinas nas deposições. A molhabilidade para os revestimentos obtidos com lama total apresentaram comportamento hidrofóbico, enquanto que com sua fração areia um comportamento hidrofílico. No teste de desgaste mecânico do pino sobre disco constatou-se que todos os revestimentos obtidos apresentaram melhorias na resistência mecânica, porém com melhor desempenho para os obtidos com lama vermelha total.
The generation of mining waste has always been conducted as a potential risk to the environment, and the amount of residual resources is the option of utilization and valorization, with the aim of minimizing the environment and new functions for this type of material. Brazil is a major producer of bauxite, being classified among the first producers of this mineral in the world, but its processing generates a rather alkaline residue called red mud. In this work, the physical and chemical properties of the total red mud and its sand fraction obtained by sieving were determined. For this, analyzes were performed by Scanning Electron Microscopy (SEM), Energy Dispersion Spectroscopy (EDS), X-Ray Fluorescence (FRX) and specific mass by the technique of pycnometry. Through these results it can be concluded that it is possible through a simple technique to segregate different elementary chemical compositions of this residue, such as Si, Fe, Na and Ca. The results show that the sand fraction is denser and that 96% of the mass of the red mud studied here is in this granulometric fraction. In this work, it was also possible to verify the viability of using this residue and its sand fraction to produce coatings in aluminum alloys 1200, through plasma assisted electrolytic oxidation (PEO). Depending on the deposition conditions, such as concentration (5g/ L and 10 g/L) and deposition time (300, 600 and 900 seconds), the coatings provide different physical and chemical characteristics and may provide different applicabilities for these surfaces. The results of the analyzes by ESD allow to conclude that the coatings obtained using total red mud with lower concentration have less incorporated chemical elements, already in relation to the coatings of the red mud sand fraction there are more incorporated elements, due to the uniformity of the particle size. The crystallographic analysis of the coatings shows that the alumina alpha phase is found with greater presence in the coatings obtained using the sand fraction of the red mud. Elements such as Ti and Si are also found in some crystalline forms in the depositions. The wettability for the coatings obtained with total mud presented a hydrophobic behavior, while with its sand fraction a hydrophilic behavior. In the test of mechanical wear of the pin on the disc, all the coatings must be respected in the mechanical resistance, but with better performance for the results with the total red mud.
The generation of mining waste has always been conducted as a potential risk to the environment, and the amount of residual resources is the option of utilization and valorization, with the aim of minimizing the environment and new functions for this type of material. Brazil is a major producer of bauxite, being classified among the first producers of this mineral in the world, but its processing generates a rather alkaline residue called red mud. In this work, the physical and chemical properties of the total red mud and its sand fraction obtained by sieving were determined. For this, analyzes were performed by Scanning Electron Microscopy (SEM), Energy Dispersion Spectroscopy (EDS), X-Ray Fluorescence (FRX) and specific mass by the technique of pycnometry. Through these results it can be concluded that it is possible through a simple technique to segregate different elementary chemical compositions of this residue, such as Si, Fe, Na and Ca. The results show that the sand fraction is denser and that 96% of the mass of the red mud studied here is in this granulometric fraction. In this work, it was also possible to verify the viability of using this residue and its sand fraction to produce coatings in aluminum alloys 1200, through plasma assisted electrolytic oxidation (PEO). Depending on the deposition conditions, such as concentration (5g/ L and 10 g/L) and deposition time (300, 600 and 900 seconds), the coatings provide different physical and chemical characteristics and may provide different applicabilities for these surfaces. The results of the analyzes by ESD allow to conclude that the coatings obtained using total red mud with lower concentration have less incorporated chemical elements, already in relation to the coatings of the red mud sand fraction there are more incorporated elements, due to the uniformity of the particle size. The crystallographic analysis of the coatings shows that the alumina alpha phase is found with greater presence in the coatings obtained using the sand fraction of the red mud. Elements such as Ti and Si are also found in some crystalline forms in the depositions. The wettability for the coatings obtained with total mud presented a hydrophobic behavior, while with its sand fraction a hydrophilic behavior. In the test of mechanical wear of the pin on the disc, all the coatings must be respected in the mechanical resistance, but with better performance for the results with the total red mud.
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Palavras-chave
Lama vermelha, Oxidação eletrolítica assistida por plasma, Liga alumínio 1200, Resíduos sólidos, Red mud, Plasma-assisted electrolytic oxidation, Aluminum alloy 1200, Solid waste