Impact of environmental conditions on the adsorption behavior of radionuclide 63Ni(II) on γ-Al2O3

The fate and transport of toxic metal ions and radionuclides in the environment is generally controlled by adsorption reactions. The removal of 63Ni(II) from wastewaters by γ-Al2O3 was studied as a function of various environmental parameters such as shaking time, pH, ionic strength, foreign ions, and humic substances under ambient conditions. The results indicated that the adsorption of 63Ni(II) on γ-Al2O3 was strongly dependent on pH and ionic strength. At low pH, the adsorption of 63Ni(II) was dominated by outer-sphere surface complexation and ion exchange with Na+/H+ on γ-Al2O3 surfaces, whereas inner-sphere surface complexation was the main adsorption mechanism at high pH. The Langmuir and Freundlich models were used to simulate the adsorption isotherms of 63Ni(II) at three different temperatures of 298.15, 323.15 and 343.15 K. The thermodynamic parameters (ΔH°, ΔS° and ΔG°) calculated from the temperature dependent adsorption isotherms indicated that the adsorption process of 63Ni(II) on γ-Al2O3 was endothermic and spontaneous.

. To illustrate the variation and relationship of pH, Ce (mol/L, the concentration of 63Ni(II) remained in solution), and qe (mol/g, the concentration of 63Ni(II) adsorbed on solid phase), experimental data are plotted as three dimensional plots of qe, Ce, and pH.Figure optionsDownload as PowerPoint slideHighlights
► As an economical and efficient method, adsorption technique has been widely applied in the disposal of wastewaters.
► The study of 63Ni on γ-Al2O3, especially the thermodynamic data of 63Ni adsorption on γ-Al2O3 and the effect of humic substances on 63Ni uptake to humic γ-Al2O3 hybrids, is still scarce.
► In this paper, the adsorption of 63Ni on γ-Al2O3 is studied as a function of various environmental conditions such as contact time, pH, ionic strength, foreign ions, humic substances and temperature.
► Based on the obtained experimental results, the adsorption mechanism of 63Ni on γ-Al2O3 is stated in detail.
► This study will have an important reference value in evaluating the physiochemical behavior of radionuclide 63Ni.