ADSORPTION AND RELEASE OF CADMIUM IN SOME SOILS OF EGYPT. | ||
| Journal of Soil Sciences and Agricultural Engineering | ||
| Article 2, Volume 30, Issue 3, March 2005, Pages 1725-1738 PDF (649.78 K) | ||
| Document Type: Original Article | ||
| DOI: 10.21608/jssae.2005.226350 | ||
| Author | ||
| M. G. A. Rehan | ||
| Soils, Water and Environment. Res. Institute, ARC, Giza, Egypt. | ||
| Abstract | ||
| Cadmium adsorption by and release from five soils representing the soils of Egypt; alluvial, calcareous, and sandy soils, were studied. Soil samples collected from the top 20 cm were equilibrated with CdCl2 solutions containing up to 800 µg Cd/ml. The absorbed Cd was subsequently extracted with 1M ammonium acetate (exchangeable-Cd) and 0.125 M copper (II) acetate (complexed-Cd). The adsorption of Cd by soils was highly fitted to Langmuir and Freundlich isotherms with (r2) values ranging from 0.962 to 0.993 with the former and from 0.945 to 0.987 with the later. The Cd adsorption maxima calculated from Langmuir isotherm ranged from 1.885 to 8.830 mg/g soil (3.35 to 15.71 meq/100g soil) and was significantly correlated with clay + silt content, cation exchange capacity (CEC), and organic matter content (OM). The corresponding values calculated from Freundlich isotherm ranged from 0.18 to 0.88 mg Cd/g soil and were not correlated with any of the studied soil properties. About 80 to 95 percent of adsorbed Cd was retained by cation exchange and complexing sites. Cation exchange sites assumed to play more important role in adsorbing Cd than complexing sites with increasing adsorption, except in calcareous soil, which exhibited a comparable importance of the two kinds of sites. Such results are important to understand the fate of Cd added to the soil through applications of contaminated sludges and wastes and to develop useful environmental guidelines for its potential toxic hazards. | ||
| Keywords | ||
| Cadmium; Adsorption; Desorption; Heavy metals; Soils of Egypt | ||
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