Tratamento de efluentes contaminados com crómio por biossorção na alga Sargassum muticum
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2013
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Neste trabalho pretendeu avaliar-se a viabilidade da utilização da macroalga castanha, Sargassum muticum, no tratamento de efluentes contendo crómio hexavalente e trivalente pelo processo de biossorção.
A escolha do biossorvente usado baseou-se nos seguintes parâmetros: uso de um material natural, custo e abundância na costa portuguesa.
Numa primeira fase submeteu-se o biossorvente a um pré-tratamento (protonação), de modo a melhorar o seu desempenho no processo de biossorção. Procedeu-se também à caraterização do biossorvente, tendo sido identificados, por espectroscopia de infravermelho, os principais grupos funcionais presentes na superfície da alga – grupos hidroxilo, carboxilo, amina e sulfónicos. Realizaram-se ainda análises SEM/EDS à alga protonada verificando-se uma alteração na composição química da parede da alga.
Numa segunda fase estudou-se a cinética de redução do Cr (VI) a Cr (III). Realizaram-se diversos ensaios onde, para diferentes condições experimentais, se avaliou a influência de parâmetros como o pH, a temperatura, a massa de alga utilizada e a concentração inicial de metal. Tendo em conta, igualmente, ensaios realizados numa fase preliminar deduziu-se que as condições operacionais ótimas para aplicação da alga protonada como biossorvente seriam: pH = 2,5, temperatura = 20ºC e concentração de biossorvente = 2,0 g/L.
Numa terceira fase estudou-se o processo de biossorção do Cr (III). A concentração inicial de metal e o pH foram os parâmetros que mais influenciaram a capacidade de biossorção. O pH óptimo encontrado para a adsorção de Cr (III) foi 4.
A alga Sargassum muticum revelou um elevado potencial para a remoção de crómio de soluções aquosas, em particular do Cr (VI). Esta tecnologia pode então ser aplicada com sucesso na redução/remoção de crómio dando, ao mesmo tempo, um valor económico à indesejada espécie presente na nossa costa.
This work evaluated the viability of the brown macroalgae Sargassum muticum, in the treatment of effluents containing hexavalent and trivalent chromium. This biosorbent was selected based on the following parameters: use of a natural material, cost and abundance on the Portuguese coast. In a first step, the Sargassum muticum algae underwent a pre-treatment (protonation) in order to improve its performance in the biosorption process. Afterwards, it was characterized by spectroscopy of infrared (FTIR) and the main functional groups present in the surface of the seaweed were identified – hydroxyl, carboxyl, amino and sulphonic groups. SEM/EDS analyses were also carried out in protonated algae having been observed changes in their wall composition. In a second step it was studied reduction kinetics of Cr (VI) to Cr (III). Several tests were carried out under different experimental conditions as, pH, temperature, mass of algae and initial concentration of Cr (VI). Having regard also tests carried out in a preliminary phase it was deduced that the optimal conditions for application of protonated seaweed as biosorbent were, pH = 2,5, temperature = 20ºC and biosorbent concentration = 2,0 g/L. In a third step it was studied the biosorption of Cr (III). The initial metal concentration and the pH were the parameters that revealed the highest influence in algae biosorption capacity. The pH found as the optimum for the adsorption of Cr (III) was 4. As a final remark, it is possible to state that the algae Sargassum muticum has a high potential for removing chromium from aqueous solutions, particularly Cr (VI). Therefore, this technology can be successfully applied in the reduction/removal of chromium and at the same time give economical value to unwanted species present in our coast.
This work evaluated the viability of the brown macroalgae Sargassum muticum, in the treatment of effluents containing hexavalent and trivalent chromium. This biosorbent was selected based on the following parameters: use of a natural material, cost and abundance on the Portuguese coast. In a first step, the Sargassum muticum algae underwent a pre-treatment (protonation) in order to improve its performance in the biosorption process. Afterwards, it was characterized by spectroscopy of infrared (FTIR) and the main functional groups present in the surface of the seaweed were identified – hydroxyl, carboxyl, amino and sulphonic groups. SEM/EDS analyses were also carried out in protonated algae having been observed changes in their wall composition. In a second step it was studied reduction kinetics of Cr (VI) to Cr (III). Several tests were carried out under different experimental conditions as, pH, temperature, mass of algae and initial concentration of Cr (VI). Having regard also tests carried out in a preliminary phase it was deduced that the optimal conditions for application of protonated seaweed as biosorbent were, pH = 2,5, temperature = 20ºC and biosorbent concentration = 2,0 g/L. In a third step it was studied the biosorption of Cr (III). The initial metal concentration and the pH were the parameters that revealed the highest influence in algae biosorption capacity. The pH found as the optimum for the adsorption of Cr (III) was 4. As a final remark, it is possible to state that the algae Sargassum muticum has a high potential for removing chromium from aqueous solutions, particularly Cr (VI). Therefore, this technology can be successfully applied in the reduction/removal of chromium and at the same time give economical value to unwanted species present in our coast.
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Dissertação de Mestrado em Engenharia do Ambiente
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Tratamento de efluentes , Crómio , Algas castanhas , Biossorção , Sargassum muticum