Fluoride (F-) is one of the common naturally occurring anions present in groundwater worldwide that may be beneficial or detrimental depending on the total amount ingested and the duration of exposure. Among all the remediation techniques, adsorption using nanomaterials shows superior efficiency and the process can be eco-friendly and economical. We report cellulose nanofiber-polyaniline (PANI)-templated ferrihydrite nanocomposite synthesized by a green one-pot process where the iron precursor not only acts as an oxidant for the polymerization of aniline to give emaraldine base-emaraldine salt (EB-ES) form of PANI but also forms 2-line ferrihydrite (FeOOH) nanoparticles in situ. These nanoparticles get embedded into the cellulose-PANI blend to give a granular nanocomposite having double action sites for adsorption and robustness which also prevent nanoparticle leaching. Doped PANI and FeOOH act as synergistic adsorption sites for F- removal which results in an enhanced uptake capacity. The materials' adsorption mechanism and removal performance have been evaluated by diverse analytical techniques. The investigations led to the conclusion that the material is suitable to be used as adsorption media in the form of simple cartridges for gravity-fed water purification. In addition, the impact of such materials on the environment has been assessed by evaluating the relevant sustainability metrics and socio-economic parameters.