Removal of organic template from magnetic porous silica: a thermogravimetric analysis

In the PUREX process, uranous nitrate (U(IV)) is employed for the conversion of Pu(IV) to Pu(III). Large quantities of U(IV) is required for Pu(IV) reduction due to presence of higher concentration of plutonium in the feed solution during reprocessing of fast reactor fuel. A number of methods have been referred in literature for the preparation of U(IV). These methods involve the reduction of U(VI) to U(IV) by suitable catalytic process. Platinum group metal impregnated silica catalyst has been reported for the reduction of U(VI) to U(IV) by many researchers. To facilitate the easy separation after the usage of catalyst from solution, magnetic silica catalyst was synthesized by encapsulating silica over Fe₃O₄ nano particles. For excellent metal loading capacity porous silica was synthesized with the help of hexadecyltrimethylammonium bromide (CTAB) as template material. Various techniques are available for the removal of template from porous silica. Fe₃O₄-SiO₂-CTAB was treated with 50% H₂ at 300 °C for 15 hours to remove the CTAB template. To understand the CTAB removal efficiency, a thermogravimetric analysis was performed with virgin CTAB, porous silica-CTAB, Fe₃O₄-SiO₂-CTAB, H₂ treated porous silica-CTAB and H₂ treated Fe₃O₄-SiO₂-CTAB. Virgin CTAB decomposes in two steps before 375 °C with no residue