Flake channels construction of hydroxyapatite/gelatin cryogel with excellent flame retardant properties for enhancing the capturing of iodine

Abstract

Safe and efficient capturing of volatile radioiodine is of extremely important significance in the treatment of spent fuel. Herein, the flake channels in gelatin-hydroxyapatite (HAP@Ge) cryogel with excellent flame retardant properties were constructed by immobilizing hydroxyapatite nanorods (HAP) on Gelatin (Ge) cryogel for enhancing the capturing of iodine. The immobilization of HAP nanorods enhanced thermal stability, provided low rates of dynamic heat transfer and dissipation, and remarkably improved the flame retardant and smoke suppression properties of the Ge cryogel, which can effectively prevent the occurrence of safety incidents caused by further thermal degradation or combustion of this cryogel. More importantly, it was effective in improving the rapid enrichment of iodine, resulting in a high adsorption capacity. The maximum adsorption capacity of HAP@Ge cryogel for iodine vapor reached 2693 mg/g at equilibrium. The high adsorption capacity for iodine was attributed to the multi-scale porous structure in HAP@Ge cryogel, which offered effective channels for iodine diffusion, whereas the numerous complex and irregular flakes provided sufficient number of active sites for iodine capture. The adsorption process was chemical in nature and involved the -PO₄³⁻, –OH, –C=O, and –NHR groups on HAP@Ge cryogel. Moreover, the complex porous structure of HAP@Ge cryogel enhanced the physical capturing of iodine. These advantages, such as low-cost raw material, simple preparation method, good flame retardancy, and excellent capturing performance for iodine indicated that HAP@Ge cryogel is a potential candidate for the removal of radioactive iodine in the exhaust gas stream of post-treatment plants.

Graphical Abstract