Zirconia silicate modified with phytic acid (IP6) and its effect on uranyl sorption

In this work the sorption capacity of uranyl ions on zirconium silicate (ZrSiO₄) extracted from sea sand of Baja California Sur was studied, the effect of phytic acid (IP6) accompanied by a perchlorate salt of sodium (NaClO₄) on the surface of the mineral. In the first stage, ZrSiO₄ was obtained from sea sand by extraction using hydrofluoric acid, the purified and hydrated material was later characterized by instrumental techniques such as X-ray diffraction to determine its purity and crystallinity. The ZrSiO₄-purified, ZrSiO₄/NaClO₄ and ZrSiO₄/IP6 were studied by physicochemical and surface characterization. By scanning electron microscopy was observed that ZrSiO₄ initially is formed by flat structures, however, when it is hydrated with NaClO₄ the formation of particles on the material exists, whereas when the IP6 is added the crystals on the surface are elongated forming structures geometric shapes. This modification on the surface of the ZrSiO₄ was corroborated by atomic force microscopy where significant changes were observed in the topography of the purified and hydrated material. By Fourier transform infrared spectroscopy is identifies the presence of functional groups from hydration with IP6 and NaClO₄ on the surface of SrSiO₄. Characterization of surface properties was performed by determining the surface area of the purified ZrSiO₄, SrSiO₄/NaClO₄ and ZrSiO₄/IP6 systems using the Bet multipoint and fractal dimension technique; the hydration time, zero loading point was evaluated by means of a bulk titration and surface site density (Ds). The fluorescence and phosphorescence techniques allowed determining the optimum hydration point and the uranium species sorbed on the surface of the ZrSiO₄ as in the systems hydrated with IP6 and with NaClO₄. This technique provided relevant information about the speciation and complex formation of IP6 with uranyl ions on the surface of ZrSiO₄. Sorption isotherms and kinetics were prepared by the liquid scintillation technique, and this technique allowed corroborating the quantification of uranium at the surface. Surface acidity constants at the solid/liquid interface for both systems were obtained by modeling the acid-base titration curves with FiTEQL 4.0 software, where the chemical species and complexes formed on the mineral surface were identified. The results show that the ZrSiO₄/NaClO₄ system has a maximum percentage of 98.8% sorption at ph 7, whereas with the proposed system ZrSiO₄/IP6 it was 99.2% from a ph of 3, from an initial concentration of uranium of 1 x 10^-3 M. (Author)