Xu, Lin; Zheng, Tao; Yang, Shitong; Zhang, Linjuan; Wang, Jianqiang; Liu, Wei; Chen, Lanhua; Diwu, Juan; Chai, Zhifang; Wang, Shuao, Uptake Mechani**s of Eu(III) on Hydroxyapatite: a Potential Permeable Reactive Barrier Backfill Material for Trapping Trivalent Minor Actinides, 2016, Accepted.
ABSTRACT: The permeable reactive barrier (PRB) technique has attracted increasing attention for the in situ remediation of contaminated groundwater. In the present study, the macroscopic uptake behaviors and microscopic speciation of Eu(III) on hydroxyapatite (HAP) were investigated by a combination of theoretical modeling, batch experiments, powder X-ray diffraction (PXRD) fitting and X-ray absorption spectroscopy (XAS). The underlying removal mechani**s were identified to further assess the application potential of HAP as an effective PRB backfill material. The macroscopic ****ysis revealed that nearly all dissolved Eu(III) in solution was removed at pH 6.5 within an extremely short reaction time of 5 min. In addition, the thermodynamic calculations, desorption experiments, and PXRD and XAS ****yses definitely confirmed the formation of the EuPO4·H2O(s) phase during the process of uptake of dissolved Eu(III) by HAP via the dissolution-precipitation mechani**. The detailed comparison of the present experimental findings and related HAP-metal systems suggests that the relative contribution of precipitation to the total Eu(III) removal increases as the P:Eu ratio decreases. The dosage of HAP-based PRB for the remediation of groundwater polluted by Eu(III) and ****ogous trivalent actinides (e.g., Am(III) and Cm(III)) should be strictly controlled depending on the dissolved Eu(III) concentration to obtain an optimal P:M (M represents Eu, Am or Cm) ratio and treatment efficiency.