Synthesis of α-Ti(HPO4)2·H2O and sorption of Eu (III)

Abstract

This paper presents the synthesis, physical–chemical characterization and preliminary evaluation of α-Ti(HPO4)2·H2O (α-TiP) sorption of Eu (III), an analogous chemical to Ac3+ and heavy 3+ valence metals (As3+, Cr3+). α-TiP was synthesized by direct chemical precipitation of concentrated TiCl4 and H3PO4 at a stoichiometric Ti/P ratio of 1:2. The following analyses were performed: elemental and morphological (SEM-EDS), spectral (FT-IR), and thermal (TGA), as well as X-ray diffraction studies (DRX). Surface area of the solid was established by the BET method and pHpzc by mass titration. Sorption kinetics measurements for Eu were conducted at different contact times at a constant pH. The results showed that the synthesis method generates a crystalline solid of homogeneous composition that is thermally unstable at temperatures greater than 623K. The specific area (As) of the solid was 20±4m2g−1 at a pHpzc of 2.8±0.1. Sorption kinetics showed that initial sorption velocity was 0.0754mgg−1min−1, and the sorption capacity at equilibrium was 40.6mgg−1. The evidence indicates that the retention process for Eu can take place on the surface and in the cavities of the solid in two stages: (a) diffusion into the cavities of the material and (b) chemisorption. Chemisorption would occur due to the interaction of the negatively charged (XO−) surface sites (TiO and P-OH) with the species in solution, Eu3+ and EuNO2+.