La-MOFs in situ loaded Al₂O₃ particles for effective removal of phosphate in water: characterization, application...

Excessive phosphorus in water would cause eutrophication and deterioration of the ecological environment. Herein, the La-MOFs/Al₂O₃ composite was successfully prepared by the in situ hydrothermal synthesis method for granulation, which was conducive to exerting the phosphate adsorption capacity and facilitating practical application. The materials were characterized by SEM, EDX, XRD, BET, FTIR, and Zeta. In addition, the adsorption performance of La-MOFs/Al₂O₃ was evaluated through adsorption kinetics and isotherms, showing that the Langmuir adsorption capacity was 16.34 mgP·g^-1 (25 °C) and increased with the water temperature. Moreover, the batch influence experiments of intimal pH, adsorbent dosage, coexisting ions, and stability tests were performed to analyze the potential for practical applications and verified through the natural micro-polluted water samples from Houxi River and Bailu Lake (China). The results indicated that the La-MOFs/Al₂O₃ was suited to a wide pH range of 4 to 10 and the phosphate removal efficiency remained above 70% after continuous use for four times, exhibiting excellent stability. It also had excellent selectivity in the presence of SO₄^2-, Cl^-, NO₃^-, and HCO₃^-, only decreased to 70.24% at high HCO₃^- ion concentration of 60 mg/L, respectively. And the La-MOFs/Al₂O₃ had excellent adsorption of total phosphorus, phosphate, and organic phosphorus in the actual river and lake water and completely removed dissolved phosphorus. Finally, a phosphate adsorption mechanism model involved in electrostatic interaction and ligand exchange was proposed. Therefore, La-MOFs/Al₂O₃ could be considered to be an excellent phosphorus adsorbent for application in the actual water environmental remediation.