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

Autor(es)

Soares, Marcio Roberto ^[1] ; Casagrande, Jose Carlos ^[1] ; Mouta, Ernesto Rinaldi ^[1]

Afiliação do(s) autor(es)

^[1] Univ Fed Sao Carlos, Agr Sci Ctr, Dept Nat Resources & Environm Protect, BR-13600970 Araras, SP - Brazil

• Tipo de documento: Artigo Científico
• Fonte: Communications in Soil Science and Plant Analysis; v. 40, n. 13-14, p. 2132-2151, 2009.
• Citações Web of Science: 12

Resumo

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)

• Processo FAPESP: 04/00445-3 - Avaliacao comparativa da adsorcao de cadmio, cobre, niquel e zinco em solos com cargas eletricas variaveis.
• Beneficiário: Ernesto Rinaldi Mouta
• Modalidade de apoio: Bolsas no Brasil - Iniciação Científica