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THE SPECIFIC ADSORPTION OF DIVALENT Cd, Co, Cu, Pb, AND Zn ON GOETHITE
Author(s) -
FORBES E. A.,
POSNER A. M.,
QUIRK J. P.
Publication year - 1976
Publication title -
journal of soil science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.244
H-Index - 111
eISSN - 1365-2389
pISSN - 0022-4588
DOI - 10.1111/j.1365-2389.1976.tb01986.x
Subject(s) - adsorption , metal , chemistry , goethite , inorganic chemistry , metal ions in aqueous solution , oxide , divalent , ion , oxide minerals , surface charge , qualitative inorganic analysis , chemical reaction , organic chemistry
Summary The specific adsorption of divalent Cd, Co, Cu, Pb, and Zn on goethite is measured as a function of pH. For each mole of heavy metal adsorbed approximately two moles of H+ ions are displaced from the interface. Using these results the heavy metal adsorption data are expressed as functions of the solution concentrations of both H+ and metal ions, and the interfacial reaction is described by the equation, 2 SH+M 2+ = S 2 M+ 2 H + . The adsorption data are consistent with an electrochemical model of the simultaneous adsorption of H + ions and divalent metal ions on to the oxide. The intrinsic affinities of the metal ions for the oxide surface increase in the order, Cd < Co < Zn < Pb < Cu. However, besides the affinity of the metal ion for the surface, the adsorption curves are considered to be influenced by surface charge, the adsorption density of the metal ions and their size. The analysis of the data in terms of H + and M 2+ ion adsorption is considered to be complementary to the hydrolysis model for heavy metal adsorption.