One-step fabrication of chitosan-Fe(OH)3 beads for efficient adsorption of anionic dyes

In this study, we reported the one-step synthesis of chitosan-Fe(OH)3 beads without the use of acid solvent, which could be used as effective adsorbents for anionic dyes removal. The preparation process was easy and green. The as-prepared beads were characterized for structural and morphological analysis in detail using several techniques, such as Scanning Electron Microscope, Fourier Transform Infrared Spectroscopy, X-Ray Diffraction, X-ray photoelectron spectroscopy and Thermogravimetric analysis. The content of Fe(OH)3 in chitosan-Fe(OH)3 beads was 54.64 wt%. The removal efficiencies toward anionic dyes: congo red (CR) and methyl orange (MO) by chitosan-Fe(OH)3 beads were higher than pure chitosan beads. Moreover, the incorporation of Fe(OH)3 into chitosan beads could overcome the obstacle that powdery Fe(OH)3 particles are difficult to be separated from the adsorption solutions. The maximum adsorption capacities from Langmuir model for CR and MO by chitosan-Fe(OH)3 beads were 445.32 and 314.45 mg/g, respectively. The thermodynamic data indicated that the adsorption processes were spontaneous and endothermic. In addition, chitosan-Fe(OH)3 beads also showed good reusability and the removal efficiencies for both dyes retained above 95% after five cycles. From this work, it suggests that chitosan-Fe(OH)3 beads have great potential as low-cost and effective adsorbents for the removal of anionic dyes.