Immobilization of iodine into a hydroxyapatite structure prepared by cementation

Abstract

International audienceIn order to manage radioactive iodine-129 coming from nuclear spent fuel, robust host matrices with durable long term behaviour need to be developed. In this work, a new process of synthesis of an iodate-substituted hydroxyapatite by means of a cementation route is described. This material was obtained from a mixture of tetracalcium phosphate (TTCP), tricalcium phosphate (αTCP) and sodium iodate (NaIO3), taken in a molar ratio of 1/2/0.5. The progress of the reaction leading to the setting and hardening of cement paste was monitored by combined measurements of electrical conductivity and heat flux release, together with XRD characterization of materials at definite times of hydration. Sodium iodate acts as a set retarder, by leading to the precipitation of non-cohesive transient phases, which are then destabilized when the massive precipitation of hydroxyapatite occurs. These delays can however be limited by adding hydroxyapatite seeds to the cement paste, which means that it is possible to control the setting time in view of an industrial application. This novel cementitious system leads to a porous material composed of iodine-substituted hydroxyapatite needles covering residual TTCP and αTCP particles. Iodine has entered the hydroxyapatite structure in the form of iodate anions only. An iodine incorporation rate of 6.5 wt% has been obtained by this cementitious system, which is a promising value in view of using these materials for the conditioning of radioactive iodine

Anion exchange on hydrous zirconium oxide materials: application for selective iodate removal

“…12 Other removal techniques for I − include for example ion exchange resins, 13 activated carbons, 14 organoclays 14–16 and hydrotalcites. 17 For the removal of IO 3 − , a wide range of different adsorbent materials have been studied including zero valent iron, 18 hydroxyapatites 19,20 and hydrotalcites. 17,21,22 Despite the intensive research, no selective, highly performing state-of-art iodate removal technique has yet been established.…”

“…, a wide range of different adsorbent materials have been studied including zero valent iron, 18 hydroxyapatites 19,20 and hydrotalcites. 17,21,22 Despite the intensive research, no selective, highly performing state-of-art iodate removal technique has yet been established.…”

Pure and Sb-doped ZrO2 for removal of IO3− from radioactive waste solutions

“…In addition, hydrotalcites (Levitskaia et al 2016) and organoclays (Bors et al 2000) have shown significant capability of removing iodide. The iodate removal methods studied previously include hydroxyapatites (Campayo et al 2011;Coulon et al 2014), sulphurcontaining minerals (Strickert et al 1980), hydrotalcites (Levitskaia et al 2016;Liang and Li 2007;Toraishi et al 2002), zero-valent and sulphur-modified iron (Lawter et al 2018) and co-precipitation with calcite (Truex et al 2017;Zhang et al 2013). Despite the studies, the removal of iodate in the industrial scale still remains a difficult task and further studies as well as novel approaches are required.…”

Iodate interactions with calcite: implications for natural attenuation

“…Under natural environments, IO 3 − is often associated with carbonate minerals (Xu et al 2015;Podder et al 2015Podder et al , 2017. In addition, the potential for IO 3 − to be incorporated in carbonates, mainly calcite, has been demonstrated in recent laboratory and/or computational studies (Saslow et al 2019;Lu et al 2010;Campayo et al 2011;Zhang et al 2013;Coulon et al 2014;Podder et al 2017). The interactions of IO 3 − with calcite are important in environments where detrital and/or pedogenic calcite are present in significant abundance (Serne et al 2008).…”