Nickel adsorption by variable charge soils: effect of pH and ionic strength

Author(s)

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

Affiliation

^[1] Univ Fed Sao Carlos, Dept Recursos Nat & Protecao Ambiental, Ctr Ciencias Agr, BR-13600970 Araras, SP - Brazil

• Document type: Journal article
• Source: Brazilian Archives of Biology and Technology; v. 54, n. 1, p. 207-220, JAN-FEB 2011.
• Web of Science Citations: 15

Abstract

The effects of pH and ionic strength (I) on Ni adsorption in variable charge soils were evaluated by laboratory batch experiments. Experimental results fitted the Langmuir model. Maximum adsorption (Ads max) ranged from 260-2818 mg kg-1 (topsoil) to 532-1541 mg kg-1 (subsoil). Nickel affinity (K L) was higher in the subsoil samples (0.022-0.236 L kg-1) than in topsoil (0.003-0.049 L kg-1). Adsorption envelopes showed sharp increase in Ni adsorption (20-90%) in the 4.0-6.0 pH range. Nickel adsorption was affected by I and specific adsorption predominated in the 3.0-5.0 pH range, while above pH 5.0, it was adsorbed by electrostatic mechanisms. Negative values of free energy variation (ΔG) and the separation factor K R<1 indicated that Ni adsorption reaction was favorable and occurred spontaneously, especially when pH increase. Chemical and mineralogical soil attributes should be considered as criteria for selecting the areas for disposal of residues containing Ni to minimize the impact on the environment. (AU)