Microwave-induced synthesis of pyrophosphate Zr1-xTixP2O7 and TiP2O7 with enhanced sorption capacity for uranium (VI)

A series of nanostructured pyrophosphates Zr1-xTixP2O7 (x=0, 0.2, 0.4, 0.5, 0.6, 0.8, and 1.0), have been prepared via a facile microwave induced route in which zirconium hydroxide, titanium hydroxide and phosphoric acid were used as Zr, Ti and P sources, respectively. It is demonstrated the isomorphous substitution of Zr(4+) by Ti(4+) results in a decrease of the size and an enhancement of the adsorption capacity of the obtained particles for U(VI) in aqueous solution. The maximum amount of TiP2O7 for U(VI) reached up to 309.8 mgg(-1) under the experimental conditions (pH=5, t=60min and T=303K). The as-obtained specific metal pyrophosphates exhibit a considerably higher adsorption capability for U(VI) in aqueous solution compared with Zr1-xTixP2O7 prepared by calcined method, showing a high potential for U(VI) sequestration applications. The adsorption kinetics and thermodynamic analysis of Zr1-xTixP2O7 on adsorption of U (VI) were performed, and a possible adsoprtion mechanism was also proposed.