Biosorption of textile metal-complexed dye from aqueous medium using Posidonia oceanica (L.) leaf sheaths: Mathematical modelling

The leaf sheath fibres of the Mediterranean seagrass Posidonia oceanica (L.) were used as low cost, available and renewable biological adsorbent for the removal of a metal complex textile dye from aqueous solutions. Batch experiments were carried out for sorption kinetics and isotherms. Operating variables studied were exposure time, pH and biomass dosage. Maximum color removal was observed at pH 2. Biosorption capacity was enhanced by increasing biomass quantity up to 10 g/L. Experimental sorption kinetic data were fitted to Lagergren irreversible first-order, reversible first-order, pseudo-second-order and Elovich models and rate constants were estimated. The related data were found to follow the pseudo-second-order and Elovich equations, thereby predicting a chemisorption process. Besides, equilibrium data were well represented by both Redlich-Peterson and Langmuir isotherm models, suggesting a monolayer coverage of dye molecules onto the marine biomass surface and adsorption active sites of quite similar affinities toward the experimental textile pollutant.