Facile Synthesis of Lanthanum-Doped Fe-Based MOF for Phosphate Removal from Water: High Adsorption Capacity, Tuneability, and Reproducibility

A novel lanthanum-doped MIL-101 (La-MIL-101) material was synthesized through the solvothermal method and used for phosphate adsorption in water. XRD and FT-IR characterization results showed that lanthanum was successfully doped into MIL-101, and changed the structure of the crystal of MIL-101. The adsorption process of phosphate by 0.5La-MIL-101 conformed to the Langmuir model and the pseudo-second-order kinetic model. Its saturated adsorption capacity was 344.02 mg·g −1 , which was significantly greater than that of MIL-101 (133.08 mg·g −1 ). Moreover, 0.5La-MIL-101 had a wide-range pH operation (3.0–10.0) and good reusability. Utilizing FT-IR and XPS characterization, it can be indicated that the mechanism of phosphate adsorption by 0.5La-MIL-101 is through electrostatic attraction and the exchange of ligands to form Fe/La–O-P internal complexes. The 0.5La-MIL-101 adsorbent prepared in this paper can provide a useful guideline for the design of high-performance and reusable phosphate adsorbent.