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  • 1 School of Nuclear Science and Technology, Lanzhou University, 730000 Lanzhou, People’s Republic of China
  • 2 School of Materials and Chemical Engineering, Anhui University of Architecture, Hefei, 230601 People’s Republic of China
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Abstract  

This work contributed to the adsorption of radiocobalt on goethite as a function of contact time, pH, ionic strength and foreign ions in the absence and presence of fulvic acid (FA) under ambient conditions. The results indicated that adsorption of Co(II) was dependent on ionic strength and foreign ions at low pH values (pH < 7.8), and independent of ionic strength and foreign ions at high pH values (pH > 7.8). Outer-sphere surface complexation and/or ion exchange were the main mechanisms of Co(II) adsorption on goethite at low pH values, whereas inner-sphere surface complexation was the main adsorption mechanism at high pH values. The presence of FA enhanced Co(II) adsorption at low pH values, but reduced Co(II) adsorption at high pH values. The thermodynamic data (ΔH 0, ΔS 0, ΔG 0) were calculated from the temperature dependent adsorption isotherms, and the results suggested that adsorption process of Co(II) on goethite was spontaneous and endothermic. The results are crucial to understand the physicochemical behavior of Co(II) in the nature environment.