Sorption of Nuclear Waste Components by Layered Hydrazinium Titanate: a Straightforward Route to Durable Ceramic Forms
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Sorption of Nuclear Waste Components by Layered Hydrazinium Titanate: a Straightforward Route to Durable Ceramic Forms
Sergey N. Britvin1, Yulia I. Korneyko2, Boris E. Burakov2, Andriy Lotnyk3, Lorenz Kienle3, Wulf Depmeier4 and Sergey V. Krivovichev1 1 Department of Crystallography, Geological Faculty, St. Petersburg State University, Universitetskaya Nab. 7/9, 199034 St. Petersburg, Russia; Nanomaterials Research Center, Kola Science Center RAN, Fersman Str. 20, 184200 Apatity, Murmansk Region, Russia 2 V.G. Khlopin Radium Institute, 28, 2-nd Murinskiy Ave., St. Petersburg, 194021, Russia 3 Institute for Material Science, Synthesis and Real Structure, University Kiel, Kaiserstr. 2, 24143 Kiel, Germany 4 Institute for Geosciences, University Kiel, Olshausenstr. 40, 24118 Kiel, Germany ABSTRACT Layered hydrazinium titanate LHT-9, (N2H5)1/2Ti1.87O4 is a new nanohybrid material related to lepidocrocite-type titanates. Unique combination of ion exchange, reductive properties, surface activity due to Brønsted acid sites and occurrence of surface titanyl groups allows exploring LHT-9 for simultaneous uptake of almost all components of liquid nuclear wastes. LHT-9 irreversibly removes technetium, molybdenum, palladium and selenium from their aqueous solutions by specific mechanism of reductive adsorption. For removal of cesium, strontium, transition elements, actinides and lanthanides LHT-9 provides mechanisms of ion exchange and surface complexation. Products of adsorption are nanocrystalline and homogeneous powders loaded with 5 to 15 wt. % of radionuclides and non-radioactive elements. LHT-9 can be applied as ready-to-use precursor for one-step synthesis of durable titanate ceramic waste forms similar to SYNROC. An essential advantage of LHT-9 in comparison with other titanate sorbents (monosodium titanate and peroxo-titanate materials) is the absence of Na in its composition that permits arbitrary tailoring of sorbent properties by simple pre-treatment with the desired elements. Results on sorption of americium, cesium, strontium and lanthanides by LHT-9 are discussed. INTRODUCTION Employment of ion-selective adsorbents targeted for uptake of 137Cs and 90Sr is a common approach in treatment of high-level nuclear wastes [1,2]. High selectivity for certain ions is frequently pointed out as an advantage of different adsorbents, but that is not always true in case of nuclear wastes with very complex chemical composition. The idea of an "ultimate" sorbent which is capable of simultaneous uptake of chemically diverse constituents, such as Cs+, Am3+ and (TcO4)-, would require the development of the material with universal multiple adsorption properties. Such a universal sorbent should be characterized by the following features: 1) Efficient adsorption in acid as well as in alkaline environments; 2) Uptake of elements having diverse chemical behavior (i.e., both anions and cations); 3) High uptake capacity for adsorbed chemical elements of nuclear wastes;
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Ability to form highly homogeneous adsorbates, which are su
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