Lead Sorption by Pre-sorbed Phosphate on Kaolin. (6344)
Authors:
R.W. Taylor - Alabama A&M University T.D. Ranatunga - Alabama A&M University D.R.A. Ranatunga - Oakwood College Z.N. Senwo - Alabama A&M University
Abstract:
Presence of lead (Pb) in soils is of a major concern because of its highly toxic effects. Phosphate (P) is ubiquitous in the soil whether from fertilizer or organic matter. Therefore, all soils have surface adsorbed P which may influence metal adsorption processes. Thus, investigation of the role of soil phosphate in influencing retention of heavy metals is important from an environment point of view.
Batch equilibrium studies indicate that sorption of Pb onto kaolin and P pre-sorbed kaolin is rapid.
Presence of P on kaolin significantly increased the amount of Pb sorbed onto the surface at low solution pH (4-6). Sorption on both surfaces was pH dependent, and sorption at high solution pH (7-10) was greater than the maximum sorption at low solution pH (4-6). Sorption on both surfaces fitted the Langmuir and Freundlich isotherms well at pH 4, 6, and 8. Presence of P on kaolin at all pH ranges resulted in a significant increase in the Pb binding constant over all pH ranges indicating that Pb is held more tightly on surfaces containing pre-sorbed P. Lead speciation studies indicate that Pb(II) ion is the predominant species in solution at pH 4,6, and 7. Hydroxy forms of Pb are predominant in solution above pH 8. The increase in Pb sorption onto kaolin surfaces at higher pH ranges implies the possibility of formation of Pb hydroxy species/complex clusters on the surface.
Speaker Information: Robert Taylor, Alabama A@M University, Department of Plant and Soil Science.
P.O.Box 1208, Alabama A&M University, Normal, AL 35762; Phone: (256)372-4187; E-mail:
Session Information: Monday, November 1, 2004, 4:30 PM-6:00 PM Presentation Start: 4:30 PM (Poster Board Number: 2814) Keywords: Lead; phosphate; kaolin; sorption
