ABSTRACT
The environmental applications of humic acid include metal removal by chelation, re moval of organics by adsorption, neutralization of acidic water streams, removal of oxo-anions and reduction of metal species. Ion exchange is the main mechanism for the metal removal by humic acid, in addition to complexation through the heteroatoms-oxy gen, nitrogen and sulfur. The cation exchange capacity of humic acid (2-5 meq/g) is much higher than other soil colloids such as vermiculite (1-1.5 meq/g) and montmorillonite (1 meq/g) [18].
