Core/shell hybrid fiber with aminated PAN and Fe2O3 as a high-capacity adsorbent for phosphate ions

APANF@Fe2O3, a phosphate adsorbent, was synthesized in two steps: the immobilization of an amine group onto polyacrylonitrile fiber (PANF) and the adsorption of an iron ion on aminated PANF (APANF). The amination degree of the PANF was adjusted considering its mechanical properties. The Fe2O3 on the surface of the APANF played a role as a phosphate-grasping layer via a ligand-exchange reaction. The APANF@Fe2O3 showed a considerable PO43- adsorption amount of ca. 6 mmol/g at a low pH region (ca. 2-7) and 3 mmol/g at a high pH region (ca. 8-12). The adsorption data were interpreted with various kinetic and isotherm models. The Langmuir model was more suitable than the Freundlich and Redlich-Peterson models to fit the experimental data of the phosphate adsorption on the APANF@Fe2O3 and the pseudo-second-order model was better matched than the pseudo-first-order and Elovich's models. The results of this study demonstrate that the surface of the fibrous adsorbent was homogenous and the phosphate adsorption behavior of the APANF@Fe2O3 followed a simultaneous chemisorption process into the Fe2O3 layer.