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Biosorption of selected heavy metals by the biomass of the green alga Spirogyra sp.

Matei George M. (Jomo Kenyatta University of Agriculture and Technology, Department of Chemistry, Nairobi, Kenya)
Kiptoo Jackson K. (Jomo Kenyatta University of Agriculture and Technology, Department of Chemistry, Nairobi, Kenya)
Oyaro Nathan K. (Maasai Mara University, School of Science, Department of Chemistry, Narok, Kenya)
Onditi Anam O. (Jomo Kenyatta University of Agriculture and Technology, Department of Chemistry, Nairobi, Kenya)

In this paper, the influence of contact time, initial pH and metal ion concentrations on the adsorption properties of a freshwater green alga (Spirogyra sp.) biomass was studied. Several model solutions of selected heavy metals (Cd, Cu, Cr, Pb) were put into contact with the green algae-based sorbent for different time periods. After the treatment, the concentrations of heavy metals in model solutions were determined using flame atomic absorption spectrometry (FAAS) and inductively-coupled plasma-optical emission spectrometry (ICP-OES). Fourier transform infrared spectroscopy (FTIR) was used to reveal which functional groups were responsible for the green algae biosorption properties. Adsorption capacities were found to be 22.52, 38.19, 35.59 and 94.34 mg/g for Cd, Cr, Cu and Pb, respectively, at contact times of 15-50 minutes and initial metal ion concentrations of 500-700 μg/g. The optimum pH for biosorption of Cd, Cr, Cu and Pb were 5.5, 5.8, 5.9 and 5.0, respectively. The biosorption process followed second order kinetics and fittedthe Langmuir isotherm model. Biomonitoring studies suggested the possible use of this freshwater green algaas a bioindicator, with mean concentration factors for the selected elements in the range of 367-7154.

Keywords: Green algae, biosorption, biomonitoring, toxic metals, FAAS, ICP-OES, FTIR