Microwave-assisted rapid synthesis of cerium phosphates and their adsorption on uranium(VI)

Cerium phosphates have been successfully synthesized under microwave irradiation in the absence of organic solvent. The effects of different molar ratios of phosphoric acid (85 %) to cerium hydroxide on the product phosphates were investigated. A single-phase CeP2O7 compound and a mixture of tetravalent cerium pyrophosphate (CeP2O7 ) and metaphosphate (Ce(PO3)4 ) were synthesized at 800 W for 5 min under microwave irradiation when the mole ratio of H3PO4 to Ce(OH)4 was equal to 2 and 2.5–4, respectively. In the presence of chemometric excess of H3PO4 (mole ratio of H3PO4 to Ce(OH)4 is between 5 and 6), a single-phase Ce(PO3)4 compound can be prepared at 480 W for 10 min under microwave irradiation. Scanning and transmission electron microscope images showed that particle sizes of CeP2O7 and Ce(PO3)4 were 0.1–3 and 1–5 μm, respectively. The adsorption properties of CeP2O7 and Ce(PO3)4 on uranium(VI) were examined. In the same condition, uranium(VI) was removed by Ce(PO3)4 more effectively than CeP2O7, and there are greater advantages for products synthesized under microwave irradiation than those calcination products on adsorption of uranium(VI).