Abstract
Non-living lichen Evernia prunastri was studied as biosorbent material for zinc and cobalt removal from single and binary metal solutions. Sorption equilibrium of Zn2+ and Co2+ ions was reached within 1 hour. Both cobalt and zinc biosorption was not pH dependent within the range pH 4-6 and negligible at pH 2. The experimental results were fitted to the Langmuir, Freundlich, Redlich-Peterson and Langmuir-Freundlich adsorption isotherms to obtain the characteristic parameters of each model. The Langmuir, Redlich-Peterson and Langmuir-Freundlich isotherms were found to well represent the measured sorption data. According to the evaluation using the Langmuir equation, the maximum sorption capacities of metal ions onto lichen biomass were 112 μmol/g Zn and 97.2 μmol/g Co from single metal solutions. E. prunastri exhibited preferential uptake of zinc from equimolar binary Zn2+ - Co2+ mixtures within the range 50 – 4000 μM. Even thought mutual interference was seen in all Co-Zn binary systems. To evaluate the two-metal sorption system, simple curves had to be replaced by three-dimensional sorption surface. These results can be used to elucidate the behavior of lichens as bioindicators of cobalt and zinc pollution in water and terrestrial ecosystems.
Highlights
Sorption processes represent one of the possible mechanisms of interaction of toxic metals in contaminated aquatic systems
The time-course studies on the biosorption of cobalt and zinc ions were performed by contacting Co and Zn solutions with lichen biomass at pH 4.0 and 20 °C
Biosorption of Co2+ and Zn2+ ions by E. prunastri shown in Fig. 1 is a rapid process
Summary
Sorption processes represent one of the possible mechanisms of interaction of toxic metals in contaminated aquatic systems. When several metals are present, many other parameters affect the sorption process. Simple sorption isotherms are usually constructed as a result of studying equilibrium batch sorption behavior of different biosorbent materials. These curves enable quantitative evaluation of biosorption performance of these materials for only one metal (HAMMAINI et al, 2003; AKSU and DŐNMEZ, 2006). When more than one metal at a time is present in a sorption system, evaluation, interpretation, and representation of biosorption results become much more complicated. A range of equilibrium adsorption isotherms were obtained to quantitatively describe cobalt and zinc uptake
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