Biological synthesis of Fe2O3 nanomaterials with different morphologies: A comparative study for fluoride remediation.

[Display omitted] • Different shaped Fe 2 O 3 nanomaterials were synthesized by a greener method. • Guava leaf extract used as precipitating agent instead of harmful chemicals. • Nanoparticles and nanorods were obtained after hydrothermal and reflux respectively. • Nanomaterials were effectively used for fluoride adsorption. • Fe 2 O 3 nanoparticles showed higher adsorption efficiency than nanorods. A greener approach was used for the preparation of iron oxide (α-Fe 2 O 3) nanomaterials with different morphologies using guava leaf extract. After reflux and hydrothermal treatment, the 0D spherical nanoparticles (Fe 2 O 3 (H)) and 1D rod-shaped nanomaterial (Fe 2 O 3 (R)) were produced. The prepared nanomaterials were used for fluoride adsorption from water by batch adsorption method. Rhombohedral crystal structure of the α-Fe 2 O 3 phase was formed, according to XRD investigation. The FESEM analysis revealed the development of spherical nanoparticles and nanorods with sizes of 40–50 nm and 70–90 nm, respectively. The surface area of Fe 2 O 3 (H) is found to 82 m2/g, whereas Fe 2 O 3 (R) is found to be and 60 m2/g. The fluoride adsorption process was pH dependent and extreme adsorption occurred at pH = 5 to 7 with maximum adsorption capacity of 52 mg/g for Fe 2 O 3 (H) and 40 mg/g for Fe 2 O 3 (R). The fluoride adsorption process follows pseudo-second-order kinetic and Langmuir isotherm models. The common co-existing ions showed dissimilar effects towards fluoride adsorption. The primary factors in the fluoride adsorption mechanism include electrostatic interactions, anion exchange, and inner-sphere complexation. The adsorbed adsorbents were recovered and can be reused up to five cycles. [ABSTRACT FROM AUTHOR]