Mechanisms of strontium removal by a Ba-titanate material for the wastewater treatment

Growing interest in radioactive effluent treatment, especially after the Fukushima nuclear accident, has led to the development of new, increasingly efficient mineral sorbents. The sorbents currently attracting the most attention are materials dedicated to strontium extraction. The Ba-titanate material investigated here, combining several sorption mechanisms, has a high capacity and selectivity for strontium with a distribution coefficient, Kd, of 863 mL g(-1), obtained from a batch sorption test with seawater ([Sr] = 9 x10(-5) mol L-1; titanate concentration, 1 g L-1). This Kd is six times higher than that of Na-titanate, one of the strontium sorbents used for multi-nuclide removal at the Fukushima-Daiichi nuclear power station. Upon contact with the sulfate-containing effluent, Sr extraction proceeds by ion exchange with the Ba ions inserted in the material and by coprecipitation with insoluble barium sulfate formed at the surface of the titanate grains.