Biosorption Studies of Methylene Blue by Mediterranean Algae Carolina and Its Chemically Modified Forms. Linear and Nonlinear Models' Prediction Based on Statistical Error Calculation

Biosorption experiments were carried out for the removal of the cationic dye Methylene Blue from its aqueous solution by the brown algae Carolina which is widely distributed in the Mediterranean Sea at Lebanese coast. Langmuir, Freundlich, Redlich-Peterson, Temkin, Elovich, and Dubinin-Radushkevich isotherm models were also investigated. The results showed that the experimental adsorption data were well represented by the Langmuir model for the linear regression analysis and both Langmuir and Redlich-Peterson isotherm models for the non-linear regression analysis. The maximum adsorption capacity qmax based on Langmuir is 55 mg/g at 19 oc. This confirms the monolayer coverage of Methylene Blue dye onto energetically homogenous Carolina surface. Negative values of Gibbs free energy revealed that adsorption process is spontaneous. Carolina algae was chemically modified by treatment with NaOH, CaCl2 or formaldehyde. The biosorption of Methylene Blue was enhanced with the process of cross linking using formaldehyde with qmax of 64 mg/g. The results of isothermal study using modified algae also showed that the experimental adsorption data is well fitted into Langmuir model.