A sandy loam soil as a natural control for Pb contamination

The Pb (II) adsorption/desorption mechanism onto a natural sandy loam soil was studied by batch experiments at different pHs (3.0, 4.5, 6.0), at different ionic strength (0, 0.02 and 0.1 M) and with different electrolytes solutions of NaCl, NaAcO and NaNO₃. Pb was strongly adsorbed onto the soil due to the formation of a mix of inner-sphere and outer-sphere complexes. Experimental adsorption data fitted Freundlich and Langmuir isotherms. The desorption results with 0.1 M Mg (NO₃)₂ and 0.1 M NaAcO solutions corroborated the mechanisms proposed. The strong binding of Pb (II) to high affinity sites on soil minerals seems to be responsible for the extent of hysteresis. The sandy loam soil under study thus constitutes a natural control for Pb contamination.