Study of antagonistic effect in the simultaneous removal of two textile dyes onto cellulose extracted from Posidonia oceanica using derivative spectrophotometric method

The sorption of Acid Blue 25 (AB) and Direct Blue 86 (DB) was investigated in single and binary aqueous systems using cellulose extracted from Posidonia oceanica as sorbent by employing a batch experimental set-up. First order derivative spectrophotometric method was successfully applied to the simultaneous analysis of AB and DB concentrations with overlapping spectra in their bicomponent mixtures. The single and multi-component Langmuir and Freundlich isotherm models were applied to describe the experimental equilibrium adsorption data of both the dyes. The data fitted more adequately to mono-component Langmuir isotherm model than mono-component Freundlich isotherm model, while the revisited extended Langmuir isotherm model best predicted the multi-component sorption data, suggesting sorption selectivity toward DB dye. The maximum monolayer dye uptake capacity of extracted cellulose in single dye system was determined as 0.623 mmol g−1 and 0.057 mmol g−1 for AB and DB, respectively. It was observed that the equilibrium uptake amounts of AB and DB dyes in binary mixture onto extracted cellulose decreased considerably with increasing concentrations of the other dye resulting in their antagonistic effect.