Removal of textile dye, direct red 23, with glutaraldehyde cross-linked magnetic chitosan beads

One of the most important classes of pollutants is dyes, and today there are more than 100,000 commercial dyes. Conventional treatment processes are very expensive, so it is essential to develop low-cost sorbent materials with high adsorption capacities. The aim of this study is to prepare magnetic microsized adsorbents that have high adsorption capacity for removal of direct red 23. Through this objective, glutaraldehyde cross-linked magnetic chitosan beads were formed in order to remove the textile dye direct red 23. Barium ferrite was used to give a magnetic property so that the beads could easily be separated from the water after treatment. The effects of barium ferrite, pH, incubation time, dye concentration, and glutaraldehyde amounts were investigated. The Langmuir and Freundlich adsorption models were applied to describe the equilibrium isotherms. The adsorption capacity had a very large value: 1250 mg/g at pH 4.0, at room temperature. Compared with activated carbon, magnetic cross-linked chitosan exhibits excellent performance in the adsorption of anionic dyes and the magnetic properties of beads enable us to remove the beads from the water after treatment. Pseudo-second-order and intraparticle diffusion kinetic models were applied.