Theoretical Modelling of Immobilization of Cadmium and Nickel in Soil Using Iron Nanoparticles

Immobilization using zero valent using iron nanoparticles is a soil remediation technology that reduces concentrations of dissolved contaminants in soil solution. Immobilization of heavy metals in soil can be achieved through heavy metals adsorption and surface complexation reactions. These processes result in adsorption of heavy metals from solution phase and thus reducing their mobility in soil. Theoretical modelling of heavy metals, namely, cadmium and nickel, adsorption using zero valent iron nanoparticles was conducted using Visual MINTEQ. Adsorption of cadmium and nickel from soil solutions were modelled separately and when these metals were dissolved together. Results have showed that iron nanoparticles can be successfully applied as an effective adsorbent for cadmium and nickel removal from soil solution by producing insoluble compounds. After conducting the modelling of dependences of Cd+2 and Ni+2 ions adsorption on soil solution pH using iron nanoparticles, it was found that increasing pH of solution results in the increase of these ions adsorption. Adsorption of cadmium reached approximately 100% when pH ≥ 8.0, and adsorption of nickel reached approximately 100% when pH ≥ 7.0. During the modelling, it was found that adsorption of heavy metals Cd and Ni mostly occur, when one heavy metal ion is chemically adsorbed on two sorption sites. During the adsorption modelling, when Cd+2 and Ni+2 ions were dissolved together in acidic phase, it was found that adsorption is slightly lower than modelling adsorption of these metals separately. It was influenced by the competition of Cd+2 and Ni+2 ions for sorption sites on the surface of iron nanoparticles