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Authors
Advisor(s)
Abstract(s)
No presente trabalho pretendeu-se estudar a viabilidade da utilização de um resíduo
agrícola – casca de amendoim – como biossorvente na remoção de metais pesados –
cobre (II), níquel (II) e zinco (II) – em solução aquosa.
A escolha deste biossorvente baseou-se no facto de se saber que se trata de um
material natural que revela aptidão para a fixação de iões metálicos, bastante
abundante e de baixo custo, podendo vir a ser uma potencial alternativa aos materiais
actualmente utilizados.
O trabalho contemplou os seguintes aspectos: caracterização do biossorvente, estudo
da influência da granulometria, ensaios cinéticos num adsorvedor perfeitamente
agitado, estudo da influência do pH nos sistemas mono-componente, planeamento
factorial para o estudo da influência da força iónica e da razão massa
biossorvente/metal, isotérmicas de equilíbrio e ensaios em coluna mono e tricomponente.
Seleccionou-se a granulometria de 1,0-2,0 mm para o trabalho experimental. No
ensaios cinéticos o modelo que melhor se ajustou aos dados experimentais do cobre e
do zinco foi o de pseudo-primeira ordem, sendo o de pseudo-segunda-ordem o mais
adequado para o níquel.
O estudo da influência do pH permitiu concluir que o valor de pH 5 seria adequado
para todos os sistemas.
O planeamento factorial incidiu sobre os sistemas mono-componente, sendo os
factores – força iónica e concentração de adsorvente – o objecto de estudo. A partir
dos resultados obtidos verificou-se que a capacidade de biossorção aumenta com o
aumento da concentração da casca de amendoim e com a força iónica, apresentando
esta uma forte influência.
Os estudos de equilíbrio foram adequadamente descritos pelo modelo de Freundlich,
verificando-se uma maior afinidade da casca de amendoim para o cobre.
Nos ensaios em coluna de leito fixo, para o cobre nos sistemas mono e tricomponente,
verifica-se que o modelo de Yan é o que melhor descreve a curva de
ruptura experimental.
The present work intended to study the viability of using agricultural wastes – peanut hulls – as biossorbent for heavy metals removal – copper (II), nickel (II) and zinc (II) – from aqueous solutions. The choice of this biossorbent was based upon the fact that it is a natural low cost material able to fix metal ions and easily available. So, it might be a potential alternative to commonly used sorbents. This work focused mainly on the following aspects: biossorbent characterization, kinetic studies into a continuous completely stirred tank reactor, study of the influence of pH in the mono-component systems, factorial experimental design to study the influence of the ionic strength and the reason biossorbent mass/metal, equilibrium isotherms and column studies for the mono and tri-component systems. The grain size used in this experimental work was 1.0-2.0 mm. In the kinetic studies the model that best fited the experimental data for copper and zinc was the pseudo-first order model, and the pseudo-second order was the best model for nickel. The pH influence study showed that the pH of 5 was the most favorable for all systems. The factorial experimental design was focused in the mono-component systems, evaluating the factors – ionic strength (F.I.) and the adsorbent concentration (Cads). From the obtained results it can be said that the biossorption capacity increases with the increasing of peanut hull concentration and ionic strength; this last showned a strong influence. The equilibrium studies were better described by the Freundlich model. The peanut hulls showed a higher affinity to copper. In the fixed bed column experiments, for copper in the mono and tri-component system, the Yan’s model is the model that fits better the experimental curve.
The present work intended to study the viability of using agricultural wastes – peanut hulls – as biossorbent for heavy metals removal – copper (II), nickel (II) and zinc (II) – from aqueous solutions. The choice of this biossorbent was based upon the fact that it is a natural low cost material able to fix metal ions and easily available. So, it might be a potential alternative to commonly used sorbents. This work focused mainly on the following aspects: biossorbent characterization, kinetic studies into a continuous completely stirred tank reactor, study of the influence of pH in the mono-component systems, factorial experimental design to study the influence of the ionic strength and the reason biossorbent mass/metal, equilibrium isotherms and column studies for the mono and tri-component systems. The grain size used in this experimental work was 1.0-2.0 mm. In the kinetic studies the model that best fited the experimental data for copper and zinc was the pseudo-first order model, and the pseudo-second order was the best model for nickel. The pH influence study showed that the pH of 5 was the most favorable for all systems. The factorial experimental design was focused in the mono-component systems, evaluating the factors – ionic strength (F.I.) and the adsorbent concentration (Cads). From the obtained results it can be said that the biossorption capacity increases with the increasing of peanut hull concentration and ionic strength; this last showned a strong influence. The equilibrium studies were better described by the Freundlich model. The peanut hulls showed a higher affinity to copper. In the fixed bed column experiments, for copper in the mono and tri-component system, the Yan’s model is the model that fits better the experimental curve.
Description
Mestrado em Engenharia Química
Keywords
Casca de amendoim Iões metálicos Sorção Cinética Equilíbrio Coluna leito fixo
Citation
Publisher
Instituto Politécnico do Porto. Instituto Superior de Engenharia do Porto