Adsorption of heavy metals in andisols, vertisols and humic acids

This research studied the adsorption of five heavy metals (Cd, Cu, Ni, Pb and Zn) in three adsorbents, two Colombian agricultural soils (Typic Melanudand and fine clay 1% isohyperthermic-Ustic Epiaquert) and Humic Acids (HA) extracted from leonardite samples of Spain. In both, HA and soils, the chemical properties determined were: PH, cation exchange capacity (CEC), organic carbon (% OC), exchangeable bases and total content of metals. The chemical composition of HA was determined using spectrometric techniques as ICP-MS, FTIR, UV-Vis, and CPMAS C NMR and Py-GC/MS-THMA. The results from the adsorption of metals in the three adsorbents were adjusted to Freundlich model, and these show a different behavior of the absorbers relative to the metals studied, in the same way the maximum adsorption capacity (K) and the retention strength (n) of metals is significantly different (p <0.05). According to K and n of each adsorbent, the adsorption selectivity sequences of the metals has the following order of preference for K: In Humic Acids: Cd> Pb> Cu> Ni> Zn, Andisol: Pb> Cu> Cd> Zn> Ni, and Vertisol: Cd> Pb> Cu> Ni> Zn. For n, Humic Acids: Pb> Zn> Cd> Cu> Ni, Andisol: Cu> Ni> Zn> Pb> Cd, and Vertisol: Zn> Ni> Cu> Pb> Cd.