Adsorption of metal-ethylenediaminetetraacetic acid chelates onto lake sediment.

The adsorption of Ethylenediaminetetraacetic acid (EDTA) and its metal complexes, Cu, Fe(III), Hg, Mn and Ni, onto lake sediment was studied. The results reveal that EDTA and metal-EDTA complexes, even though being hydrophilic compounds, are indeed adsorbed within one months' contact time to some extent (6.3-24.8%). Less than 10% of Ni-EDTA, Cu-EDTA and EDTA salt was adsorbed, while the mass amount of Mn EDTA, Hg-EDTA and Fe(III)-EDTA found in sediment exceeded 15% after the contact period. Thus, adsorption of metal-EDTA chelates might be a relevant process in their removal from the aquatic environment. The metal-EDTA chelates in aqueous and solid phases were determined by gas chromatography-nitrogen phosphorus detection (GC-NPD) system. The complexes were extracted by phosphate solution prior to analysis. The ability of EDTA to desorb adsorbed heavy metals from sediments is also discussed.