Fe(II) and Fe(III) adsorption by chitosan-tripolyphosphate beads: kinetic and equilibrium studies

The purpose of this research was to analyze the adsorption behavior of Fe(II) and Fe(III) ions in aqueous solution onto beads of naturally derived chitosan cross-linked with tripolyphosphate in a batch system. Effects of solution pH, contact time and amount of adsorbent were regarded in the kinetic and equilibrium studies. The optimum conditions of adsorption for Fe(II) and Fe(III) were obtained as pH 5 and 3, amount of adsorbent 2 and 1.9 g and contact time 70 and 60 min, respectively. The kinetic and equilibrium experimental data were integrated into different models using the non-linear regression method. As a result, the pseudo-second-order and the Redlich–Peterson isotherm were the best evaluated models. The adsorption capacity, based on Langmuir, was 11.65 mg g⁻¹ for Fe(II) and 13.72 mg g⁻¹ for Fe(III). The beads of chitosan cross-linked with tripolyphosphate may be used as an effective bioadsorbent for the removal of Fe(II) and Fe(III) from an aqueous solution. This study confirms that the chitosan isolated from shrimp waste can be used to remove certain heavy metals in wastewater, without adversely affecting the ecosystem.