Biosorption of some heavy metals by Cystoseira barbata (Phaeophyceae), Caulerpa racemosa (Chlorophyceae), Gracilaria verrucosa (Florideophyceae) and Spirulina platensis (Cyanophyceae)

The biosorption of five different metal aqueous solutions of Cu (II), Cd (II), Zn (II), Pb (II) and Co (II) by five different algae, Cystoseira barbata (Phaeophyceae), Caulerpa racemosa (Chlorophyceae), Gracilaria verrucosa (Florideophyceae) and Spirulina platensis (Cyanophyceae), was investigated. In this study, the effects of biosorption conditions such as, modification, solution pH, contact time, initial metal concentration, mixed metal aqueous solution as well as, desorption by different chemicals were studied. According to the results of the expirement, the sorption capacity of C. barbata for Cd (II) and Co (II) and C. racemosa for Cu (II), Cd (II) and Co (II) was increased through modification. The biosorption capacity was depended on the solution?s pH and heavy metal adsorption was more in acidic medium (except Pb (II) in S. platensis). The contact time was changed depending on the type of the algae and heavy metals. In this study, Freundlich and Langmuir isotherm models showed that, the selected metal biomass adsorption types (physical and chemical) changed depending on algae groups.Competition of metal ions was investigated for different concentrations of metal solutions. It has been observed that the sorption rate of heavy metal ions was changed in mixed metal solutions, in general, with an increase in concentration, the rate of adsorption decreased. The adsorbed metal could be desorbed effectively using 0,1 M HCl and 0,1 M HNO3 by more than % 70 (except Pb (II) and Co (II) ions in S. platensis).Algae have ion exchange features since they are comprised of polysaccharides, proteins and fatty acids. The connection of heavy metal ions through functional groups in the cell walls of algae varies depending on the species of algae and the type of the heavy metal. Consequently, the Fourier transform infrared spectroscopy (FTIR) analysis used for the characterization of algae showed, metals were generally bound to the functional groups of algae through -NH, - OH and - CH.In this study, the selected algae removed the selected heavy metals in aquatic environment with a high rate. Consequently, Cystoseira barbata, Caulerpa racemosa, Gracilaria verrucosa and Spirulina platensis can be used in the removal of Cu (II), Cd (II), Zn (II), Pb (II) and Co (II).