BIOSORPTION OF METHYLENE BLUE ONTO FOUMANAT TEA WASTE: EQUILIBRIUM AND THERMODYNAMIC STUDIES

The sorption of methylene blue (MB) from an aqueous solution by Foumanat tea waste was studied in a batch system. Three widely used isotherms (Langmuir, Freundlich and Temkin) were examined for MB sorption at different temperatures. The four Langmuir linear equations were discussed, and the Langmuir parameters were obtained from them. Langmuir-1 is the most popular linear form and it has the highest coefficient of determination, compared with the other Langmuir linear equation. The maximum saturated monolayer sorption capacity of tea waste for MB was 244 mg/g at 303 K. Various thermodynamic parameters, such as Delta G degrees, Delta H degrees, Delta S degrees and E-a, were calculated. The findings of this investigation suggested that physical sorption plays a role in controlling sorption. We investigated the adsorption mechanism by FTIR and SEM techniques. FTIR data indicated that MB binding occurred mostly at -OH and C=O groups of tea waste.