Mutual Adsorption of Lead and Phosphorus onto Selected Soil Clay Minerals

Mutual adsorption of lead (Pb) and phosphorus (P) at pH 5 onto three soilclays materials (kaolinite, montmorillonite, and allophane) was studied toknow interaction of the anion and the cation at surface of the clays. Adsorptionof Pb was determined on montmorillonite, kaolinite and allophane withthe following pretreatments; 1) untreated clay (control), 2) phosphate treatedclay (P-clay) and 3) clay pre-treated with both P and Pb (P-Pb-clay). Adsorptionof P was determined on montmorillonite, kaolinite and allophane withthe following pretreatments; 1) control 2) Pb treated clay (Pb-clay) and 3)P-Pb-clay. The adsorption of Pb on the untreated clays was in the order:montmorillonite u003e allophane u003e kaolinite. On allophane and kaolinite Pb adsorptionwas in the order P-clay u003e P-Pb-clay u003e control. For montmorillonite,the trend was: P-Pb-clay = control u003e P-clay. Phosphorus adsorption was in theorder Pb-clay = P-Pb-clay u003e control for montmorillonite and kaolinite,Pb-clay u003e control u003e P-Pb-clay for allophane. The findings suggested thatpre-treatment with phosphate increases Pb adsorption on kaolinite and allophane,and decrease on montmorillonite, while pretreatment with Pb increasesphosphate sorption on all clays, and both Pb and P increased adsorptionon montmorillonite and kaolinite and decrease on allophane.