Tunable porous ferric composite for effective removal of phosphate in water

Abstract

A novel strategy to fabricate ferric sponge-like bulk adsorbent (FSP-f) for effective phosphate adsorption and recovery was proposed by anchoring β-FeOOH into the polyacrylamide gel network via a rapid and facile free-radical polymerization. Additionally, a foaming method was employed during the fabrication to establish interpenetrated porous structure inside the bulk material. The resultant FSP-f was characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD). Batch adsorption experiments were carried out to understand the kinetics and isotherm as well as the influences of solution pH and coexisting anions on the removal of phosphate. Also, the regeneration and reusability experiments were performed. Results showed that FSP-f possessed abundant hierarchical open-pore structures and numerous β-FeOOH were randomly dispersed inside the pores. The porous morphology allowed the active sites to be fully exposed, thus making FSP-f perform the approximate adsorption capacity as PF (Powder form of FSP-f). The optimal solution pH for phosphate adsorption on FSP-f was determined at the weak acidic region and the mechanism of ion exchange, electrostatic interactions, and Lewis acid-base interactions dominated at different pH values. The co-existing ions effects on phosphate adsorption followed the order as HCO3− > SO42− > Cl− > NO3− and FSP-f could still display preferable selectivity in the presence of competing anions at high concentration levels. Three cycles of adsorption-desorption experiments showed that FSP-f exhibited a satisfactory degree of reusability using 0.01 M NaOH as eluant. The results suggest that FSP-f has a great potential for practical application in the removal of phosphate from contaminated aquatic systems.