Remarkable phosphate removal and recovery from wastewater by magnetically recyclable La₂O₂CO₃/γ-Fe₂O₃ nanocomposites

Owing to the twin problems of eutrophication and global phosphorus (P) scarcity, the removal and recovery of phosphate from water and wastewater have received increasing attention. Herein, magnetically recyclable La₂O₂CO₃/γ-Fe₂O₃ adsorbents were rationally designed by derivation from La/Fe binary metal organic framework (MOF) precursors via calcination treatment. Based upon preliminary screening of as-prepared La₂O₂CO₃/γ-Fe₂O₃ nanocomposites with different La-to-Fe molar ratios in terms of phosphate sorption capacity and magnetic property as well as La content, La₂O₂CO₃/γ-Fe₂O₃ nanocomposite with a La-to-Fe molar ratio of 2:1 was selected for further characterization and adsorption performance evaluation. Batch adsorption experiments showed that La₂O₂CO₃/γ-Fe₂O₃ (2:1) adsorbent exhibited a remarkable phosphate sorption capacity of 134.82 mg P/g, a fast sorption kinetic, strong selectivity for phosphate in the presence of co-existing anions, and a wide applicable pH range of 3-9. Furthermore, La₂O₂CO₃/γ-Fe₂O₃ (2:1) sorbent displayed an excellent sorption performance for low-concentration wastewater, a low dosage of 0.1 g/L was sufficiently enough for reducing P-concentration from 0.5 mg P/L to below 10 μg P/L within 20 min. In a real sewage of 2.68 mg P/L, 0.2 g/L of sorbent could reduce the concentration of phosphate to <0.01 mg P/L within 50 min. Moreover, over 83.1 % of original sorption capacity could be retained after 5 consecutive regeneration cycles, showing great regenerative performance of the adsorbent. These development is expected to be meaningful for practical water purification.