title: Behaviour of uranium in hydroxyapatite-bearing permeable reactive barriers: investigation using 237U as a radioindicator.
abstract: This study was undertaken to investigate the long-term performance of hydroxyapatite (HAP) as reactive material for the removal of uranium in passive groundwater remediation systems. 237U used as a radioindicator enabled tracking the movement of the contamination front through a test column without taking samples or dismantling the apparatus. The stoichiometric ratio between uranium and HAP was found to be 1:(487 +/- 19). Uranium removal by HAP is of pseudo first-order kinetics and the rate constant was measured to be (1.1 +/- 0.1) x 10(-3) s(-1). HAP can sorb more than 2900 mg/kg uranium. Possible reaction pathways of uranium and HAP are discussed. The data obtained enable the calculation of ideal lifetime for permeable reactive barriers (PRB) using HAP for uranium removal neglecting hydrological factors that may impair the function of PRBs.
authors.affiliation: Federal Institute for Materials' Research and Testing (BAM), Division Waste Treatment and Remedial Engineering, D-12200 Berlin, Germany. franz-georg.simon@bam.de
authors.forename: Franz-Georg
authors.initials: FG
authors.lastname: Simon
authors.forename: Vera
authors.initials: V
authors.lastname: Biermann
authors.forename: Christian
authors.initials: C
authors.lastname: Segebade
authors.forename: Martina
authors.initials: M
authors.lastname: Hedrich