Abstract
Fluoride ion contamination in drinking water poses a considerable environmental and health risk. Thus, novel sustainable and economic removal techniques are needed. This study examined the biosorption of fluoride ions from aqueous solutions utilizing the dead biomass of the green alga
Chara vulgaris
as an adsorbent. First, the biomass was studied for its structural and functional characteristics using Fourier transform infrared spectroscopy (
FTIR
), scanning electron microscopy (
SEM
), transmission electron microscopy (
TEM
), X-ray diffraction (
XRD
), and Brunauer–Emmett–Teller (
BET
) techniques. The optimal conditions for the biosorption were studied experimentally. Dead
Chara vulgaris
biomass achieved fluoride removal efficiency of 91% under optimal conditions (pH 2, 35 °C, 0.4 g adsorbent dose, and 300 min contact time). The surface characteristics and functional groups of the algal biomass were assessed to enable effective fluoride adsorption via a spontaneous, exothermic mechanism. The examination of fluoride biosorption indicated that the process was best explained by a Langmuir model with a high fit (
R
2
= 0.99). It shows that fluoride adheres to the surface in a monolayer. The kinetics of the process followed the pseudo-second-order model (
R
2
= 0.98), with the internal movement of particles being of lesser significance. The findings indicate that dead
Chara vulgaris
biomass can be used as an efficient material for fluoride removal, making it highly beneficial for purifying natural water and treating industrial effluent.
