Biosorption of zinc ions from aqueous solution by the microalga Scenedesmus obliquus |
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Authors: | Cristina M Monteiro Paula M L Castro F Xavier Malcata |
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Institution: | (1) CBQF/Escola Superior de Biotecnologia, Universidade Cat?lica Portuguesa, Rua Dr. Ant?nio Bernardino de Almeida, 4200-072 Porto, Portugal; |
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Abstract: | Aquatic environments are often exposed to toxic heavy metals, which gain access to the food chain via microalgae and may cause
severe problems at higher trophic levels. However, such a metabolic specificity can be taken advantage of in bioremediation
strategies. The potential of a novel wild strain of Scenedesmus obliquus, previously isolated from a heavy metal-contaminated site in northern Portugal, to remove Zn from aqueous solutions was thus
studied, using several initial concentrations. The removal extent reached its maximum by 1 day: 836.5 mg Zn/g biomass, at
the initial concentration of 75 mg/L, mainly by adsorption onto the cell surface. Comparative studies encompassing a commercially
available strain of the same microalgal species led to a maximum removal extent of only 429.6 mg Zn/g biomass, under identical
conditions. Heat-inactivated cells permitted a maximum removal of 209.6 mg Zn/g biomass, at an initial concentration of 50 mg
Zn/L. The maximum adsorption capacity of Zn, estimated via Langmuir’s isotherm, was 330 mg Zn/g biomass. Finally, Zn removal
was highest at pH 6.0–7.0. It was proven, for the first time, that such a wild microalga can uptake and adsorb Zn very efficiently,
which unfolds a particularly good potential for bioremediation. Its performance is far better than similar (reference) species,
especially near neutrality, and even following heat-treatment. |
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