Removal performance and mechanism of phosphorus by different Fe-based layered double hydroxides.

ABSTRACT

Phosphorus pollution has the potential to cause both aquatic eutrophication and global phosphorus scarcity. Fe-based layered double hydroxides (LDHs) have received much attention due to their high phosphorus adsorption and recovery. The composition of Fe-based LDHs is an important factor in determining their adsorption performance. However, the mechanism by which single component regulation of Fe-based LDHs affects phosphorus adsorption performance remains unknown. In this study, two typical types of Fe-based LDHs were prepared Mg/Fe LDH and Zn/Fe LDH. Results showed that the equilibrium adsorption capacity of Zn/Fe LDH was much greater than that of Mg/Fe LDH, reaching 65.85 mg/g with a phosphorus concentration of 150 mg/L. Calcination facilitated a substantial increase of adsorption capacity for Mg/Fe LDH rather than Zn/Fe LDH. Meanwhile, the phosphorus removal efficiency of Fe-based LDHs both exceeded 90% with an initial pH of 3.0, but it decreased as pH increased, and pH inhibition was relatively weaker for Zn/Fe LDH than Mg/Fe LDH. The common coexisting anions caused a phosphorus adsorption loss, with SO42- possessing the most competition with phosphorus. Combined with FTIR, XRD, XPS, and BET analyses, a superior adsorption performance of Zn/Fe-LDH over Mg/Fe-LDH was probably attributed to a higher surface complexation and larger specific surface area. It was also concluded that Fe-based LDHs are a promising method for removing phosphorus from recirculating aquaculture wastewater.