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(Reference retrieved automatically from Web of Science through information on FAPESP grant and its corresponding number as mentioned in the publication by the authors.)

Effect of Ionic Strength and pH on Cadmium Adsorption by Brazilian Variable-Charge Soils

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Author(s):
Soares, Marcio Roberto [1] ; Casagrande, Jose Carlos [1] ; Mouta, Ernesto Rinaldi [1]
Total Authors: 3
Affiliation:
[1] Univ Fed Sao Carlos, Agr Sci Ctr, Dept Nat Resources & Environm Protect, BR-13600970 Araras, SP - Brazil
Total Affiliations: 1
Document type: Journal article
Source: Communications in Soil Science and Plant Analysis; v. 40, n. 13-14, p. 2132-2151, 2009.
Web of Science Citations: 12
Abstract

Batch adsorption experiments were conducted to assess the effects of pH and ionic strength (I) on cadmium (Cd) adsorption by two Brazilian Oxisols. Adsorption envelopes were constructed through soil sample reactions with 0.01, 0.1, and 1 mol L(-1) calcium nitrate {[}Ca(NO(3))(2)] solutions containing 5 mg L(-1) of Cd, with an increasing pH value from 3 to 8. The adsorption increased drastically with increasing pH, varying from 20 to 90% in a narrow pH range (4-6 in topsoil and 5-6 in subsoil). Gibbs energy (Delta G) for Cd adsorption was negative, and the phenomenon became more thermodynamically spontaneous with an increase in pH. Under the standard 0.01 mol L(-1) and at pH close to natural, the Delta G values ranged from -796 to -3427 J mol(-1). No effect of I was observed on the Delta G values for Cd adsorption at pH values less than 6. At values greater than pH6, sharp changes in the Cd adsorption pattern were observed on subsoil samples. The only soil attribute significantly correlated with the spontaneity of Cd adsorption was the effective cation exchange capacity, ECEC (r = 0.97; p < 0.1). (AU)