Cadmium sorption on alumina nanoparticles, and mixtures of alumina and smectite: An experimental and modelling study


Cadmium sorption on alumina nanoparticles, and mixtures of alumina and smectite: An experimental and modelling study

Mayordomo, N.; Missana, T.; Alonso, U.

Cadmium (Cd) is one of the most toxic transition metals for living organisms. Thus, effective measures to remediate Cd from water and soils need to be developed. Cd immobilization by alumina, and mixtures of alumina and smectite have been analyzed experimentally and theoret-ically by sorption experiments and sorption modelling, respectively. Cd aqueous removal was dependent on pH and Cd concentration, being maximum for pH>7.5. A two-site non-electrostatic sorption model for Cd sorption on alumina was developed and it successfully reproduced the experimental Cd immobilization on alumina. Cd sorption on mixtures of alumina and smectite depended on pH, ionic strength, and alumina content in the mixture. Cd removal in mixtures increased when alumina content increased at high pH and ionic strength values. On the contrary, Cd sorption decreased when alumina content increased under acidic conditions and low ionic strength due to the dissolution of alumina and the release of Al³⁺ into the suspension. Cd sorp-tion model on mixtures of alumina and smectite was reproduced by considering the individual Cd sorption models for alumina and smectite. The model of Cd sorption on mixtures was addi-tive when the competition of Al³⁺ with Cd²⁺ for cation exchange in smectite was included.

Keywords: Cd; sorption model; retention; immobilization; heavy metals; Al2O3

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