Advanced phosphate removal by La–Zr–Zn ternary oxide: Performance and mechanism

Abstract

Advanced phosphate removal is in great need in order to alleviate the eutrophication problem. In this study, La–Zr–Zn ternary oxide (La–Zr–Zn) was synthesized and characterized by XRD, SEM-EDS, BET, XPS and FTIR. The synthesized La–Zr–Zn had a rough and irregular surface with specific surface area of 52.08 m2/g, and its surface was composed of La, Zr, Zn and O. The adsorbent was then used for adsorption of low-concentration phosphate (≤2 mg/L) in water. The La–Zr–Zn showed a high phosphate removal (>97%) with low residual phosphate levels (0.005–0.045 mg/L) at low dosage of 0.2 g/L. The adsorption process of La–Zr–Zn was in accordance with pseudo second-order kinetic model and Langmuir model. At a pH of 6.80, the phosphate adsorption capacity of La–Zr–Zn reached 71.58 mg/g. Moreover, the adsorbent showed a wide pH usability range (5–9) and selective adsorption toward phosphate. Mechanism analyses indicated that the phosphate removal could be explained by ligand exchange and electrostatic interaction. The results suggested that the La–Zr–Zn adsorbent has a potential application for advanced phosphate removal.