Effect of pH, foreign ions and temperature on radionickel sorption onto bentonite from Inner Mongolia, China

The development of nuclear power releases large amounts of radionuclides into the natural environment. Herein, the sorption of radionuclide 63 Ni on bentonite from Gaomiaozi county (Inner Mongolia, China) at different experimental conditions such as pH, contact time, ionic strength, foreign cations and anions, and temperatures were investigated by using batch technique. The results indicated that the sorption of 63 Ni on the bentonite was quickly at first contact time and then increased slowly with increasing contact time. The sorption of 63 Ni was strongly dependent on ionic strength at low pH values and independent of ionic strength at high pH values. The sorption of 63 Ni on bentonite was mainly dominated by outer-sphere surface complexation or ion exchange at low pH values, whereas inner-sphere surface complexation was the main sorption mechanism at high pH values. The Langmuir, Freundlich, and D–R models were applied to simulate the sorption isotherms of 63 Ni at three different temperatures, and the thermodynamic parameters (i.e., Δ H °, Δ S ° and Δ G °) calculated from the temperature-dependent sorption isotherms indicated that the sorption of 63 Ni on bentonite was an endothermic and spontaneous process. Experimental results indicate that the bentonite is a suitable material for the preconcentration and solidification of 63 Ni from large volume of solutions in radionickel pollution cleanup.