Defluoridation plays a vital role in providing drinking water with
safe fluoride levels. The present work concentrated on the development
of fumaric acid-based metal–organic frameworks (MOFs) using
Zr4+, La3+, and Fe3+ metal ions,
viz., Zr@Fu, La@Fu, and Fe@Fu MOF composites by the hydrothermal method
for defluoridation studies. Fluoride removal from water was investigated
and optimized in batch mode. The fabricated Zr@Fu, La@Fu, and Fe@Fu
MOF composites have the maximum defluoridation capacities (DCs) of
4920, 4925, and 4845 mgF– kg–1, respectively. The fluoride adsorption studies were conducted by
optimizing various affecting parameters like contact time, adsorbent
dosage, adsorbate pH, influence of co-ions and temperature. The fabricated
Zr@Fu, La@Fu, and Fe@Fu MOF composites were characterized by Fourier
transform infrared (FTIR) spectroscopy, scanning electron microscopy
(SEM), energy-dispersive X-ray analysis (EDAX), X-ray diffractometry
(XRD), high-resolution transmission electron microscopy (HR-TEM),
selected area electron diffraction (SAED), and atomic force microscopy
(AFM) studies. The sorption data were fitted with different isotherm
models. The studies of thermodynamic parameters demonstrate the feasibility
and endothermic nature of the defluoridation process. The DCs of Zr@Fu,
La@Fu, and Fe@Fu MOF composites were compared with other reported
adsorbents. The regeneration and reusability studies were proposed
to adequately utilize Zr@Fu, La@Fu, and Fe@Fu MOF composites. The
field sample taken from a nearby fluoride rife village was also tested
with the synthesized Zr@Fu, La@Fu, and Fe@Fu MOF composites, which
reduce the fluoride content below the tolerance limit.