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Fluoride ion pollution is a problem that needs attention, as it is considered a hidden type of pollution due to its lack of direct or immediate effects. This study aimed to achieve comprehensive environmental treatment by preparing a high-performance adsorbent from non-valuable materials and then using it in the treatment of polluted water. The ability of cobalt oxide nanoparticles (prepared by green method) to treat aqueous solutions contaminated by high fluoride concentrations was investigated, using a batch adsorption unit and under various operating conditions. The obtained results showed that the prepared material was within the nanoscale range with an average size of 271.48 nm, with a surface area of 329 m2/g, possessing multiple functional groups, and a porous structure that qualifies it to be an effective adsorption medium, while its zero-charge point was 7.88. The treatment efficiency varied directly with the nano cobalt oxide dose, contact time, and agitation speed, while it had an inverse relationship with temperature and the fluoride initial concentration. While, the acid function had a dual effect, as the treatment efficiency increased between pH 1-5.5, then began to decrease, reaching the lowest value at pH=9. Nano-cobalt oxide contributed to recover 87% of the contaminated fluoride, with an adsorption capacity of 7.43 mg/g, recorded at 450 rpm, 94 ppm, 5.5, and 1.1 g, for each of the agitation speed, initial fluoride concentration, pH, and nano-cobalt oxide dosage, respectively, after three hours of treatment and at room temperature. The morphological study showed that the prepared nanomaterial suffered from obvious changes represented by the displacement and disappearance of peaks and the appearance of new peaks, a decrease in the surface area by 97%, agglomeration and blockage in the porous structure, dispersion of magnetic particles, increased roughness of the adsorption surface, and modification in the crystallization phases, as indicated by FTIR, BET, AFM, VSM, FESEM, and XRD tests, respectively, which reflects the effectiveness of the preparation method and the efficiency of the nanomaterial as an adsorption medium.