Development of Polymer-Cored Akaganeite Adsorbent for Phosphate Adsorption

Abstract

Environmental issues related to phosphate and resource depletion have recently emerged as serious problems. This study focuses on solving the problems of phosphate removal and recovery using synthesized granular akaganeite (GAK). This study identified that akaganeite, which possesses an FeOOH structure in iron oxyhydroxide, can be synthesized and used as a reusable material. Immobilization with the core–shell method using polyethersulfone was applied as a strategy to recover phosphate anions from a trace of phosphate solution. GAK was successfully analyzed using SEM/TGA/BET to understand its physical properties. XRD and SAD pattern analyses suggested that the GAK powder form was amorphous in nature. The powdered akaganeite had a surface area of 231 mg2/g and a maximum adsorption capacity of 21.27 mg/g. To prevent the dispersion of powder during granulation, polyethersulfone was used as a scaffold since akaganeite particles can be effectively immobilized onto PES polymer scaffolds, as substantiated by the SEM/EDS results. Moreover, a lack of changes in the pore sizes suggested that physical properties remained unchanged. Furthermore, compared to the granular akaganeite, the surface area of powdered akaganeite decreased 4–5-fold. The adsorption kinetic of granular akaganeite fit the pseudo-second-order model. The powdered form displayed high removal efficiency, intimate with phosphate anions, when n > 1.0, instead of lower KF. On the other hand, granular akaganeite showed lower affinity when n < 1.0, but appeared positive for an adsorbate with higher KF. This implies that the granulation of akaganeite with the PES polymer did not change its adsorption property, with the maximum adsorption capacity for granular akaganeite being 3.65 mg/g.