Simultaneous Adsorption of Cationic and Anionic Dyes by Chitosan/Cellulose Beads for Wastewaters Treatment

There are thousands of commercially available dyes which represent 7 × 105 tons produced annually worldwide. Discharges of these dyes from dyeing industry effluents have the potential to reach aquatic environments, affecting many life forms. Methylene Blue (MB) is the most common dye used in textile industries. Congo Red (CR) is an azo-based dye that can be metabolized in benzidine, a human carcinogen agent. In this study, polymeric beads made of chitosan and cellulose were used to remove simultaneously a cationic dye (MB) and a anionic dye (CR). The sorption capacity of the beads was evaluated using different dye concentrations under individual (MB or CR) and simultaneous (MB and CR) conditions. Dyes’ concentration in solution was determined by HPLC–DAD. The results evidenced that both dyes can be adsorbed individually and simultaneously on the polymeric beads. The sorption process fitted the Langmuir’s isotherm. The qmax values for CR and MB simultaneous adsorption were 1.6 and 0.68 µmol/g, respectively. The chitosan/cellulose beads exhibited a large adsorption capacity for CR on individual and simultaneous experiments. Adsorption mechanism involves electrostatic interactions, hydrogen bonds and dipole-dipole forces between the functional groups of the polymeric beads and the dyes.