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

Abstract

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, K d , of 863 mL•g −1 , obtained from a batch sorption test with seawater ([Sr] = 9 × 10 −5 mol•L −1 ; titanate concentration, 1 g•L −1). This K d 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.

Efficient separation of strontium radionuclides from high-salinity wastewater by zeolite 4A synthesized from Bayer process liquids

“…In the literature, more than 99% removal of Sr at the initial concentration in SW of 0.2 mg/L was reported using > 20 g/L of zeolite 4A and 5 g/L of Ba-impregnated zeolite 4A 15 . Given that the target efficiency for decontamination is usually 99% of the 90 Sr in solution (i.e., targeted decontamination factor (DE) is 100) 14 , the results from Fig. 9 a,b, demonstrate that the dose of Z4A can be successfully optimized for water salinity so that Sr activity is reduced to the required level.…”

“…For the liquid waste with more than 50% SW, the application of selective sorbents was found necessary 13 . The survey of the latest scientific literature demonstrates the intensified efforts to develop Sr-selective sorbents/ion-exchangers for application in SW. Materials tested in SW encompass inorganic, organic, and composite materials: BaSiO 3 and BaMnO 4 13 , Ba-titanate 14 , Ba-impregnated 4A zeolite 15 , macroporous LTA-monoliths 16 apatite-based, and non-apatite phosphates 17 , 18 , granulated Na-birnessite 19 , alginate microsphere 20 , MnO 2 -alginate and zeolite-alginate composites 21 , 22 , magnetic zeolite nanocomposites 23 , and composite magnetic nanoparticles derived from industrial sludge 24 .…”

“…Regarding both the selectivity towards Sr and the sorption capacity, all novel materials display advantages over the conventional sorbents and ion-exchange resins, however, the most promising were the ones displaying either the chemical reactivity or ion-sieving effects. The efficacy of the sorption-reagent materials, including BaSiO 3 , BaMnO 4 13 , Ba-titanate 14 , Ba-impregnated 4A zeolite 15 , is enhanced as a result of their chemical reaction with the anionic components of LRW (SO 4 2− ), and co-precipitation of Sr with insoluble barium-sulfate. On the other hand, granulated Na-birnessite 19 , a low crystallized layered modification of manganese oxide, exhibited structural benefits for efficient Sr removal in the presence of chemically close elements.…”