Biosorption of cationic dye onto "Phragmites australis" fibers: Characterization and mechanism

Abstract The problem of industrial wastewater pollution especially the textile industry is becoming more and more crucial and is pushing researchers to try to develop new, low cost and efficient industrial wastewater treatment processes. We present in this work the biosorption of a cationic model dye "Methylene Blue" by the fibers of a Tunisian biomass " Phragmites Australis " in batch system. It was shown that the highest dye removal was found at pH 8. The dye uptake was achieved by increasing the biomass assay up to 0.1 g for an initial dye concentration 10 mg/L. The results showed that the biosorved amount increases when the amount of biomass increases from 60% for 0.1 g of biomass to 72.25% for 0.5 g of biomass. The kinetic rate of pseudo-second order and Brouers-Sotolongo isotherm modeling is the most appropriate to describe the present biosorption phenomenon, thus assuming the fractal character of the process. The thermodynamic study reveals a spontaneous phenomenon of biosorption and confirms the chemisorption shown in desorption tests. The morphology of the different compounds of Phragmites australis fibers was studied by Boehm titration, FTIR, SEM and explained with different mechanisms reactions. The mechanism proposed involved hydrogen-bonding formations, electrostatic interactions and π-π interaction that show the importance of the carboxylic groups in the biosorption process.