Sorption and desorption kinetics of cadmium from soils: Influence of phosphate

Journal Article · Wed Dec 01 04:00:00 EST 1999 · Soil Science

DOI:https://doi.org/10.1097/00010694-199912000-00002· OSTI ID:20080447

Krishnamurti, G S.R.; Huang, P M; Kozak, L M

The mobility and availability of heavy metals is controlled by sorption-desorption characteristics of the soils. There is much literature available about the sorption characteristics of heavy metals by soils. However, the influence of ionic environments on the desorption kinetics of heavy metals, particularly Cd, have not been studied in detail. The present study reports the kinetic data of desorption of Cd from two soils, with contrasting Cd availability characteristics, using 1 M NH{sub 4}Cl. The soils were preadsorbed with different amounts of Cd in the presence of monoammonium phosphate. The Cd was sorbed onto the soils almost instantaneously in the absence of phosphate, with >97% of the Cd added to the soils sorbed within the first 15 min of reaction time. The Freundilich parameter a, the sorption coefficient, which is related to the Cd sorption capacity, indicated that the phosphate retarded Cd sorption by both soils by at least one order of magnitude. The overall diffusion coefficient of Cd release from the Luseland soil by 1 M NH{sub 4}Cl, obtained using the parabolic diffusion model for the desorption kinetics, was 1.62 to 10.1 times higher than that of the Judburgh soil, depending on the initial amount of Cd preadsorbed. The lower the amount of initial Cd preadsorbed, the greater the difference in the rate of Cd released between the two soils. The presence of phosphate during Cd adsorption by the soils increased the amount of Cd released in the initial 30-min reaction period as well as the overall diffusion coefficients of Cd release. The kinetic data of Cd desorption reflect well the Cd availability index and grain Cd content of the durum wheat crops, Kyle and Arcola, grown in the two soils.

• Research Organization: Univ. of Saskatchewan, Saskatoon, Saskatchewan (CA)
• OSTI ID: 20080447
• Journal Information: Soil Science, Journal Name: Soil Science Journal Issue: 12 Vol. 164; ISSN SOSCAK; ISSN 0038-075X
• Country of Publication: United States
• Language: English

Related Subjects

54 ENVIRONMENTAL SCIENCES
ADSORPTION
BIOLOGICAL AVAILABILITY
CADMIUM
DESORPTION
SOIL CHEMISTRY
SOILS