Phosphate Sorption on Boehmite with Eu(III): P K-edge EXAFS Fingerprinting

Actinide sorption to the geological materials can reduce the mobility and bioavailability of radionuclides released to the environment through the development of nuclear weapons and nuclear energy. Under circumneutral pH conditions, actinide sorption can be enhanced by phosphate anions sorbed on oxide mineral surfaces as indicated by the sorption of trivalent lanthanide ions (), the chemical analog for trivalent actinide ions (). In this paper, we examined a ternary sorption system of trivalent europium ions () sorbed onto boehmite (-AlOOH) surfaces pre-sorbed with phosphate anions (), using extended X-ray absorption fine structure (EXAFS) spectroscopy. In the Eu--boehmite ternary sorption system, surface precipitates were formed as implicated by Eu -edge EXAFS spectroscopy. Phosphorus K-edge EXAFS fingerprinting indicated a bidentate mononuclear surface complex formation of phosphate sorbed on boehmite surfaces as well as surface precipitate formation.