HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Figures Only Full Text Free Full Text (PDF) Free Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in ISI Web of Science Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via ISI Web of Science (20) Citing Articles via Google Scholar Google Scholar Articles by Glover, L. J. Articles by Brady, P. V. Search for Related Content PubMed Articles by Glover, L. J., II Articles by Brady, P. V. GeoRef GeoRef Citation Agricola Articles by Glover, L. J. Articles by Brady, P. V. Related Collections Soil Kinetics Soil Pollution Soil Chemistry

DIVISION S-2—SOIL CHEMISTRY

Desorption Kinetics of Cadmium²⁺ and Lead²⁺ from Goethite

Influence of Time and Organic Acids

^a Dep. Crop and Soil Environmental Sciences, 236 Smyth Hall, Virginia Polytech. Inst. & State Univ., Blacksburg, VA 24061
^b Sandia National Laboratories, Albuquerque, NM 87185

* Corresponding author (eick{at}vt.edu)

It is generally accepted that trace metal concentrations in soil solution are primarily controlled by sorption and desorption reactions at the particle-water interface. While numerous studies have been conducted to understand adsorption of these metals to soil minerals, less is known about long-term adsorption-desorption processes. The objective of this study was to examine the influence of residence time and organic acids on the desorption of Pb²⁺and Cd²⁺ from goethite. Adsorption experiments were conducted at pH 6.0 for 1 wk (short-term) and 20 wk (long-term). Lead adsorption was nearly complete after 4 h, with very little additional sorption occurring during a 20-wk period. In contrast, Cd showed a continuous slight increase in the remaining adsorption. Desorption experiments were conducted at pH 4.5 and desorption kinetics for Pb²⁺and Cd²⁺ were slow compared with the sorption reaction. Trace metal removal from the goethite surface was not completely reversible during an 8-h desorption period for all of the experiments, except for short-term Cd²⁺ in the presence of salicylate. For all experiments except long-term Pb²⁺ desorption, the quantity of metal desorbed from goethite followed the order salicylate > NaNO₃ > oxalate. It is postulated that the greater effectiveness of salicylate compared with oxalate was related to the ability of oxalate to form bridging or ternary complexes between the metal and the goethite surface. For all experiments except Pb²⁺ sorption in the presence of oxalate a greater quantity of metal was desorbed for the short-term compared with the long-term experiment. However, these results were only statistically significant for Pb²⁺ in the presence of salicylate. These results suggest that residence time effects observed by many researchers are much less prevalent at low pH values, and hence natural or anthropogenic reduction in soil pH may reduce the ability of the soil to naturally sequester trace metal cations over time.

Abbreviations: AA, atomic absorption • Fe_o, oxalate extractable Fe • Fe_t, total Fe • ICP-AES, inductively coupled plasma atomic emission spectrometer • TEM, transmission electron microscopy • TGA, thermogravimetric analysis • XRD, x-ray diffraction

This article has been cited by other articles:

				Nanogeochemistry: Geochemical reactions and mass transfers in nanopores Geology, May 1, 2003; 31(5): 387 - 390.