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

3.7. Sorption Isotherm Results
The Langmuir, Freundlich, and Dubinin-Radushkevich isotherm models were
employed for the investigation of the sorption equilibrium between the metal ion
solution and the biomass, in this study. The data obtained from the sorption experiments
are used in the linear fits (3.27-3.38.) of the isotherm models. The constants obtained
from the linear fits are tabulated in the Table 3.9. with their correlation coefficients, R 2 ,
and are used for the evaluation of the nonlinear fits (Figure 3.39.-3.42.) of the isotherm
models. The nonlinear fits are given with the experimental results to understand the
behaviour of the sorption isotherm model with the expermental result.
Dunaliella salina has an ability to biosorb Pb 2+ from the aqueous medium,
almost totally, so it could not be mentioned about which isotherm model is fitted to the
experimental data. The Dubinin-Radushkevich isotherm model fits the experimental
data for the sorption of Cd 2+ ions that can be seen from the nonlinear fit of the model
with the experimental data.The applicability of the Dubinin-Radushkevich isotherm to
the sorption of Ni 2+ ions by Dunaliella salina is supported by the linear (R 2 as 0.9982)
and nonlinear fits of the isotherm model.
The obtained results demonstrates that the Langmuir isotherm model is able to
fit the sorption of Pb 2+ ,Cd 2+ and Ni 2+ by Oocystis sp. with the correlation coefficient,
R 2 , as 0.8148, 0.9958, and 0.9365, respectively. These results can also be confirmed by
the nonlinear fits of the isotherm.
The sorption of Pb 2+ by Porphyridium cruentum follows Dubinin-Radushkevich
isotherm with the correlation coefficient, R 2 , 0.9960, while that of Cd 2+ , and Ni 2+ by
Porphyridium cruentum obeys Langmuir isotherm, with the correlation coefficients,
0.9904 and 0.9836, respectively.
It has been observed that the Dubinin-Radushkevich isotherm is able to fit the
experimental data for the sorption of Pb 2+ by Scenedesmus protuberans. According to
the data obtained from the sorption of Cd 2+ and Ni 2+ by Scenedesmus protuberans, the
Langmuir isotherm correlates with the experimental results.
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