The influence of aminopolycarboxylates on the sorption of copper (II) cations by (Hydro)oxides of iron, Aluminum, and manganese

Resumo

The influence of some complexing agents of (poly)aminopolycarboxylic acids (diethylenetriaminopentaacetic acid (DTPA), ethylenediaminotetraacetic acid (EDTA), nitrilotriacetic acid (NTA), and iminodiacetic acid (IDA)) on the sorption of Cu²⁺ by crystal and amorphous (hydr)oxides of Fe(III), Al(III), and Mn(IV) that are widespread mineral components of soils was studied. The obtained results are considered in terms of complex-formation in the solution and on the sorbent’s surface. The effect of the complexing agents on the metal sorption (mobilization/immobilization) is determined by (1) the stability, structure, and sorption capability of compexonates formed in the solution; (2) the acidity, and (3) the nature of the sorbent. The desorption effect on Cu²⁺ cations was found to change in the following sequence of complexing agents: EDTA > DTPA ≫ NTA > IDA. The high-dentate complexing agents (EDTA, DTPA) had the greatest impact on ?u²⁺ cations bound with crystalline (hydr)oxides of Fe, Al, and Mn. The low denticity of the complexing agents (IDA, NTA) and binding of ?u²⁺ with amorphous sorbents leads to the weakening of desorption. The decrease in acidity promoted the mobilization of the metal under the influence of complexing agents; the increase in acidity caused its immobilization. The growth in the mobility of heavy metals bound with soil (hydr)oxides of Fe, Al, and Mn due to the complexing agents entering the surface and ground water is considered a factor of ecological risk.