Adsorption of High-Fluoride Brackish Water from the Ndame Senegal Borehole on Coconut Shell Activated Carbon

Abstract

The populations of the peanut basin are facing a groundwater quality problem due to high salinity and excess fluoride. The consumption of these waters constitutes a risk to public health through poisoning and cases of severe fluorosis. This study aims to propose a small-scale treatment accessible to the rural population. The methodology for defluoridation of hyperfluorinated water from the Ndame borehole by adsorption adopted consists of developing an activated carbon from coconut shells. Acidification of the medium with sulfuric acid, vinegar, and hibiscus is studied to improve treatment efficiency. The characterization of the activated carbon obtained gives iodine indices of 788.95 mg/g and 691.32 mg/g for methylene blue. Fluoride ions (F − ) are adsorbed at 64.50% ( i.e. 4 mg/L to 1.17 mg/L) for water acidified with hibiscus, 70% ( i.e. 4 mg/L to 1.42 mg/L) for water acidified with sulfuric acid, 70.75% ( i.e. 4 mg/L to 1.20 mg/L) for raw water, and 72.75% ( i.e. 4 mg/L to 1.09 mg/L) for water acidified with vinegar. Analysis of these results shows that in addition to the good adsorption capacity of activated carbon, the acidity of the medium and the presence of magnesium (Mg 2 + ) and calcium (Ca 2 + ) ions promote the elimination of fluorides. However, acidification with hibiscus is not an optimal method due to its high fluoride concentration. Thus, the physicochemical parameters of the environment impact the effectiveness of fluoride treatment. This study demonstrates that the activated carbon derived from coconut shells, in conjunction with a simple neutralization using locally available materials, can serve as a cost-effective and long-lasting solution for the elimination of fluoride in rural Senegal.