Adsorption/Desorption in a System Consisting of Humic Acid, Heavy Metals, and Clay Minerals

Cu2+ and Ca2+adsorption to goethite in the presence of fulvic acids

“…The presence of divalent cations generally increases the adsorption of NOM to the minerals (Tipping, 1981;Vermeer et al, 1998;Liu and Gonzalez, 1999;Christl and Kretzschmar, 2001). The effect of NOM on the adsorption of metal ions is, however, less conclusive.…”

“…The macroscopic outcome in the ternary system is the result of various interactions between metal ions and NOM at the mineral surface and in the solution. Possible mechanisms include (i) NOM and ion competition for the reactive sites of the surface; (ii) formation of ion-NOM complexes in solution that reduces the adsorption to the surface; (iii) formation of ternary surface complexes and (iv) electrostatic interactions (Tipping, 1981;Stumm, 1992;Ali and Dzombak, 1996;Spark et al, 1997b;Vermeer et al, 1998;Liu and Gonzalez, 1999;Alcacio et al, 2001). In principle, two types of ternary complexes can be formed: (1) ternary complexes in which the cations form bridges between the surface sites and NOM (type A); (2) ternary complexes in which cations are bound to the ligands on NOM that are not involved in complexation with surface sites (type B).…”

Interactions of calcium and fulvic acid at the goethite-water interface

“…Humic substances adsorb readily onto oxide minerals (Tipping, 1981;Davis, 1982;Murphy et al, 1992;Gu et al, 1994;Spark et al, 1997a;. Moreover, the presence of metal ions affects the adsorption of humic substances (Tipping, 1981;Liu and Gonzalez, 1999;Weng et al, 2002) and vice versa (Robertson and Leckie, 1994;Zachara et al, 1994;Murphy and Zachara, 1995;Vermeer et al, 1999;Christl and Kretzschmar, 2001). The final outcome with respect to both the humics adsorption to the oxides and the metal ion binding to the complex is the net result of various interactions, and depends on the nature of the surface and the humics, the type of metal ion and factors such as pH and ionic strength.…”

“…It is also possible to extend the LCD model for the formation of the ternary complexes in which the metal ions form bridges between the surface sites of the mineral oxides and the ligands of the organic molecules. This type of ternary complexes has been suggested in literature (Liu and Gonzalez, 1999;Alcacio et al, 2001). So far, the LCD model has only been tested for the pH and salt concentration dependency of the adsorption of simple organic acids and fulvic acid to iron (hydr)oxides (Filius et al, 2001(Filius et al, , 2003.…”

Contrasting Roles Of Natural Organic Matter On Colloidal Stabilization And Flocculation In Freshwaters

“…Liu et al (Liu and Gonzalez 1999) have studied the phenomenon of metal adsorption/desorption in a ternary system composed of metal ions, humic acids and clays (montmorillonite). They showed that for a constant ionic strength, the quantity of humic acid adsorbed on clay decreased when the pH increased.…”