Andosols of the Bambouto Mountains (West Cameroon): Characteristics, Superficial Properties - Study of the Phosphate Ions Adsorption

ABSTRACT

The present work is focussed on the characterisation and the study of the surface properties of the Mount Bambouto andosols in view of their use in the adsorption of phosphate ions. The particle size distribution analysis has revealed a low clay content (9 %) meanwhile the silt content is high (70 %). Some surface properties like zero point charge (4.4), cationic exchange capacity (32.2 meq/100g), surface area (50.12 m²/g) of the material were measured. The adsorption kinetics of the phosphate ions is of second order. The removal of organic matter using hydrogen peroxide aqueous solutions enables to increase the quantity of the adsorbed phosphate ions at pH 6.6 from 4.15 mg/g to 6.10 mg/g. Minerals with hydroxyl groups like allophane, gibbsite and goethite are responsible for the phosphate ions adsorption but these hydroxyl groups are destroyed in acidic medium. The raw andosol adsorbs much more phosphate ions than its fine fraction (0-2 µm) because of the destruction of the allophane – humus complex during various extraction operations (crushing and dispersing).

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