Effect of organic anions on heavy metal retention by soils of contrasting characteristics

Abstract

Sorptive interactions of metals with soils and soil constituents are affected by the presence of inorganic and organic ligands capable of combining with the metals to form soluble complexes and chelates. Whereas the influence of inorganic ligands on the sorption of metals has been extensively studied (Bolan et al., 1999), the effect of organic complexation has received limited attention. Nitrilotriacetic acid (NTA) is a synthetic complexing agent, which is currently marketed for a variety of agricultural and industrial uses and has also been considered as a substitute for phosphates in detergents. The NTA contains ca rboxy I and amino functional groups that are largely responsible for the metal-binding properties of organic material found in soils, as well as municipal and industrial wastes. The objectives of this research were (i) to compare the sorption patterns of Pb, Cu, Cd and Zn in three soils of contrasting characteristics and (ii) to determine the effect of NTA on metal sorption.