Dual functional amorphous aluminosilicate sorbents for removing and cold-immobilizing cesium/cobalt/nickel-ions

Abstract

Direct cold immobilization of the spent amorphous aluminosilicate adsorbent was achieved via a low-temperature sintering process at 200 °C without the addition of any binder or liquid agent for the first time. In this study, the amorphous aluminosilicates were synthesized as adsorbents for cesium/cobalt/nickel-ions and the measured maximum adsorption capacities of cesium, cobalt, and nickel-ions were 53.0, 18.8, and 21.2 mg/g, respectively. The cold-sintered as-spent aluminosilicate sorbent formed a dense monolith (density = 2.05 × 103 kg/m3 with a microhardness value of 3 ± 0.3 GPa). Pressure-induced consolidation of the amorphous phase and dehydration of the structurally bound water are attributed to the cold sintering mechanism. The normalized leaching rates through a 7-day product consistency test for cesium/cobalt/nickel-ions are 5.18 × 10−7, 6.27 × 10−6, and 3.25 × 10−6 g∙m−2∙d−1, respectively, much lower than crystalline aluminosilicates and other immobilization matrices. Furthermore, the measured leachability indices for all target ions and sodium, as per the American National Standards Institute/American Nuclear Society 16.1 (ANSI/ANS 16.1) for 90 days, are the highest value among other immobilization processes. To our best knowledge, the results present the first example of cold-immobilized used amorphous aluminosilicate sorbents, with a unique benefit of avoiding volatile radio-nuclides loss.