Influence of phosphate on the transport properties of lead in sand

Temporal moment analysis was used to examine the transport of lead species in sand columns. The influence of sodium phosphate (PO4(aq)) and hydroxyapatite (HA) on lead transport was also evaluated. Transport properties of lead microparticles (diameter > 0.45 μm) were a function of electrophoretic mobility: those particles with electrophoretic mobility less than −1 × 10−8 m2/V s exhibited significantly lower dimensionless first temporal moment (θ) and second temporal moment (σθ2). The forms of lead investigated in this work had a tendency to move in sand over a wide pH range. Although the PO4(aq) amendment substantially reduced lead mass recoveries in the sand column effluent, lead microparticles were formed that had a tendency to move rapidly and with minimal dispersion when compared with controls. Treatments with HA provided limited reduction in lead mass recovery and minimal changes in lead transport properties. A colloid stability model was used to predict attachment of lead particles in sand.