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Eingeladener Vortrag
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Along with the globally increasing energy demand the application of renewable energy sources is
urgently required. According to national regulations and international treaties (e.g. Kyoto Protocol)
these sources shall be sustainably available at reasonable financial effort and non-polluting during
production, use and waste treatment. Using photovoltaic sources (PV), these requirements can
clearly be met. All industry has to follow the best available technology and an integrative life cycle
approach for their products and production. PV thin film technology strictly responds to this obligation.
In order to save material resources and to minimise undesirable landfill recycling of spent PV
modules is necessary. Recycling of multi-component materials containing mixed metals typically
consists of three parts: liberation, separation, and recovery. In our study (RESOLVED an EU
Demonstration Project) the focus is on liberation and separation. The converting layer (CdTe) was
liberated (removed) from the glass carrier by sandblasting and separated subsequently from the
blast material (e.g. corundum) and other components using stepwise different separation techniques.
Both the glass substrate and CdTe are subject to re-use. The overall feasibility of the recycling
process is primarily governed by the efficiency of the procedure applied to the separation of CdTe
from the rest (blasting material, glass residues, etc.). This was performed by water-based flotation.
Several flotation procedures were studied regarding their separation yields. The distribution of
CdTe in the phases involved (flotate, water, residue) was measured using energy dispersive X-ray
fluorescence spectrometry (EDXRS) intended for future routine application and by instrumental
large-volume photon activation analysis (IPAA) as a reference procedure. The results of both analytical
methods were in satisfactory agreement.
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.