BIOSORPTION OF Pb2+, Cd2+, & Ni2+ FROM WATERS BY ...

protuberans and Porphyridium cruentum. Additionally, the biomasses examined have
demonstrated the highest affinity towards Pb 2+ which was followed by Cd 2+ and Ni 2+ .
Biosorption experiments were performed to find the optimum amount of the
biomass for a fixed sample volume of 10.0 mL for the metal ion concentration of 250.0
mg/L. Increase in the amount of biosorbent was expected to increase also the metal
sorption since the number of available functional sites would be higher. As mentioned
before, Dunaliella salina has shown a better sorption performance than the other
sorbents and it was found that even 20.0 mg of Dunaliella salina was sufficient to
obtain maximum sorption for Pb 2+ while 100.0 mg was required for Cd 2+ and Ni 2+ .
To recover the metal ions from Oocystis sp. and Scenedesmus protuberans
desorption experiments were performed and it was found that acidic eluents can be used
to release the previously sorbed metal ions from the algae with a desorption percentage
of around 60%. The disadvantage of using acidic eluents and the inevitable damage to
the algae can be compensated by the economical production of the biomasses. Sodium
citrate can also be used for the same purpose with a lower recovery. However, in
contrast to acidic eluents, its use eliminates the risk of damaging the biomass.
The biosorption experiments were performed in the presence of the other metal
ions to evaluate the performance of biosorbents in a competitive environment. Uptake
of Pb 2+ ions was not influenced by the presence of other ions for all the algae studied.
However, the general trend for the other biomasses was a decrease in their sorption
efficiency towards Cd 2+ and Ni 2+ ions with the increase in the concentration of the
competitive ions.
From environmental point of view, it can be said that the algal biomasses are
natural, highly abundant, and easy to produce materials which can be utilized
successfully in the selective removal of toxic metal ions from waters.
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