Lanthanum-Doped iron MOFs: A sustainable solution for Arsenic(V) and phosphate pollution in water

In this study, lanthanum-doped iron-based metal-organic framework materials (MOFs) were fabricated by solvothermal method and evaluated for their capability to removal As(V) and phosphate from water. The characterization results exposed structural alterations following doping, emphasizing the necessity for careful control of lanthanum amount to prevent surplus La-BDC-NH2 aggregation at the defect sites. By adjusting the molar ratio of lanthanum to iron, the material exhibiting the utmost treatment efficacy towards As(V) and phosphate was identified as La0.75Fe1.0-MOF. Adsorption isotherms, kinetics, and thermodynamics revealed that the adsorption of As(V) and phosphate by La0.75Fe1.0-MOF is a spontaneous chemical adsorption process, monolayer adsorption. Furthermore, La0.75Fe1.0-MOF exhibited enhanced treatment performance for As(V) and phosphate compared to MIL-53-NH2, with a maximum adsorption capacity of 242.28 mg/g and 307.15 mg/g for As(V) and phosphate, respectively. Notably, in complex water bodies, competition from anions did not hamper the outstanding treatment efficacy of La0.75Fe1.0-MOF for As(V) and phosphate. Analysis from FTIR and XPS revealed the capture mechanism of As(V) and phosphate by La0.75Fe1.0-MOF involves primarily electrostatic interaction and inner layer complexation via hydroxyl substitution. Considering these characteristics, La0.75Fe1.0-MOF can be regarded as an ideal adsorbent for removing As(V) and phosphate from polluted waters.