Complexons as Reagents for Demetallization of Contaminated Sediments

Effect of various complexons [ethylenediaminetetraacetic acid, nitrilotriacetic acid, iminodiacetic acid, ethylenediaminetetra(methylenephosphonic acid), nitrilotris(methylenephosphonic acid)] on the sorption of heavy metal cations Cu2+, Ni2+, Pb2+, Zn2+ by crystalline and amorphous Fe(III), Al(III), and Mn(IV) oxides and hydroxides was studied. The sorption processes in systems constituted by a metal cation, complexon, and sediment were analyzed in terms of the theory of surface complexation. The factors affecting the processes of remobilization/immobilization of heavy metals under the action of complexons were studied. The desorbing effect of complexons becomes stronger with increasing stability and decreasing sorption capacity of complexonates formed in solution. A flow chart of recovery of heavy metals from contaminated sediments with ethylenediaminetetraacetic acid was developed.