Characterization of raw clay from N'Djamena (Chad) used in water treatment: the case of lead (Pb) in aqueous systems

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Résumé

This study evaluates the potential of a natural clay from N’Djamena (Chad) for removing Pb²⁺ ions from aqueous solutions under static conditions. The adsorption performance was interpreted using Langmuir and Freundlich isotherm models. Mineralogical characterization classified the raw material as a clay soil, predominantly composed of kaolinite (49.3%), with contributions from goethite (15.8%), quartz (18.1%), vermiculite (1.5%), and k-feldspar* (15.4%). The clay is primarily composed of silica (40.46%), alumina (23.84 %), and iron oxide (14.44%). Its specific surface area is 86.82 m²/g. It has a cation exchange capacity of 46 meq/100 g and a swelling index of 2.71 cm³/g. Optimal lead removal was achieved under the following conditions: 25 mL of solution per reactor; a clay-solute contact time of 90 minutes; an initial Pb²⁺ concentration of 20 µg/L; and a pH of 7. The adsorption of lead onto the studied clay is well described by the Langmuir isotherm, with a maximum adsorption capacity of 14.64 µg/g. Kinetic analysis suggests that the pseudo-second-order model accurately represents the adsorption process. These results show that the clay is an effective natural material for removing lead from water, suggesting its potential use in water treatment.

Mots-clés

clay; characterization; Pb²⁺ ions; water treatment