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- Permeable reactive barriers (2)
- Radioindicator (2)
- Uranium (2)
- Carrier gas hot extraction (1)
- High purity metals (1)
- Hydroxyapatite (1)
- Nitrogen determination (1)
- Oxygen determination (1)
- Photon activation analysis (1)
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)×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.
This study was undertaken to investigate the long-term performance of elemental iron as reactive material for the removal of uranium in passive groundwater remediation systems. By using 237U as a radioindicator it was possible to track the movement of the contamination front through a test column without taking samples or dismantling the apparatus. The stoichiometric ratio between uranium and iron was found to be 1:(1390±62). The reaction between iron and uranium is of pseudo first-order kinetics and the rate constant was measured to be (1.1±0.09)×10-3 s-1. These data enable the calculation of ideal lifetime for permeable reactive barriers (PRB) using iron for uranium removal neglecting hydrological factors that may impair the function of PRBs.
The special importance of the analysis of non-metals in high purity metals, which will serve as national standards for elemental analysis in Germany, is illustrated for oxygen and nitrogen. The typical range of the mass fraction of oxygen and nitrogen in these materials is below 10.MU.g/g, often close to 1.MU.g/g. The two methods applied at BAM for these measurements are classical carrier gas hot extraction (HE) and carrier gas hot extraction after activation with photons (PAA-HE). The approach, the methods and their advantages and limitations are discussed. Comparative results from the measurement of oxygen and nitrogen in Cu, Fe, Ga, Pb, Sn and W are presented. (author abst.)