Solution chemistry effects on sorption behavior of radionuclide 63Ni(II) in illite–water suspensions

Abstract In this work, a naturally occurring illite was characterized by using FTIR and XRD to determine its chemical constituents and crystal structure. A series of batch experiments were carried out to investigate the effect of various environmental factors such as contact time, pH, ionic strength, foreign ions, coexisting humic substances and temperature on the sorption behavior of illite towards radionuclide 63Ni(II). The sorption of 63Ni(II) on illite was strongly dependent on pH and ionic strength. A positive effect of HA/FA on 63Ni(II) sorption was found at pH 6.5. The Langmuir, Freundlich, and D-R models were used to simulate the sorption isotherms of 63Ni(II) at three different temperatures of 293, 313 and 333 K. The thermodynamic parameters (ΔH0, ΔS0 and ΔG0) of 63Ni(II) sorption on illite were calculated from the temperature dependent sorption isotherms, and the results indicated that the sorption of 63Ni(II) on illite was endothermic and spontaneous. At low pH, the sorption of 63Ni(II) was dominated by outer-sphere surface complexation and ion exchange with Na+/H+ on illite surfaces, whereas inner-sphere surface complexation was the main sorption mechanism at high pH. From the experimental results, it is possible to conclude that illite has good potentialities for cost-effective treatments of 63Ni(II)-contaminated wastewaters.