Surface functionalized poly(vinyl alcohol)–hydrous zirconium oxide composite beads for efficient and selective sequestration of phosphate from wastewater

Abstract

The utilization of hydrous zirconium oxide (HZO) to sequester phosphate with good affinity and selectivity poses a significant challenge due to agglomeration and difficult separation. We envision that the simultaneous formation of HZO and host framework is an emerging strategy to improve the accessibility of HZO for phosphate capture. In this study, we reported a facile protocol for the synthesis of HZO encapsulated in crosslinked poly(vinyl alcohol) hydrogel beads (HZO-PVA) based on the simultaneous generation of HZO and cross-linking of PVA chains as a host. The resultant HZO-PVA can be further functionalized with triethylenetetramine (TETA@HZO-PVA) for effective and selective sequestration of phosphate. Specifically, batch experiments showed that TETA@HZO-PVA had better sequestration capacity towards phosphate than HZO-PVA, which was intimately related to the functionality of TETA that created a high density of surface binding sites. Additionally, TETA@HZO-PVA exhibited a great selectivity for phosphate even in the presence of competing anions and dissolved organic matter. Moreover, regeneration tests showed that TETA@HZO-PVA exhibited high reusability during five cycles of adsorption–desorption processes. Combined with characterization techniques and experiments, we identified that electrostatic attraction, ligand exchange, and Lewis acid–base interactions are the dominant mechanisms responsible for phosphate sequestration. Further, fixed-bed column experiments showed excellent phosphorus sequestration performance in real wastewater, making TETA@HZO-PVA a promising material for phosphorus sequestration in practical application.