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- 4 Material und Umwelt (55)
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Municipal sewage sludge is a carrier of nutrients most important phosphorus (P) but also contains organic pollutants and heavy metals. A two steps thermal treatment based on 1. mono-incineration of sewage sludge under destruction of organic pollutants and 2. thermochemical treatment of the resulting ashes to remove heavy metals and increase P-bioavailability is suggested by the authors. The process aims at P-fertilisers production from sewage sludge. Seven sewage sludge ashes of different origin and composition and one residue from gasification of sewage sludge were thermochemically treated. The raw ashes were mixed with a chlorine donor (e.g. MgCl2) and thermally treated in a gas tight lab-scale rotary furnace. The distributions of the heavy metals between solid and gas phase were determined. The heavy metals concentrations of the treated ashes matched the legislative limits in most cases. The products from thermochemical treatment are suited raw materials for P-fertiliser production. Relevant process parameters such as temperature, type and concentration of Cl-donor and retention time were optimised for the thermochemical treatment step.
Recovery of rare earth elements - optimized elemental analysis of fluorescent lamp shredder waste
(2016)
Rare earth elements (REE) are a crucial component of fluorescence lamps. Several procedures have been developed to recovery these technological important elements. Nevertheless, actual REE recycling from fluorescence lamps is scarce so far (recovery rate of less than 1 %), with current recycling approaches concentrating on glass recovery. Since most recycling processes include several, also wet-chemical steps, a complete knowledge of the actual elemental composition of the respective mass flows is necessary for an efficient REE recovery. We tested seven different reagent mixtures for microwave-assisted digestion of fluorescent lamp shredder, including HF, HClO4, and H2O2. We determined the concentrations of 25 of the most relevant rare earth and other trace elements in the respective dilutions. Two independent digestions, one a mixture of perchlorid/nitric/hydrofluoric acid and the other aqua regia, showed the highest concentrations of 23 of these elements, excluding only Sn and Tb. The REE concentrations in the tested lamp shredder sample (stated in g/kg) were 10.2 (Y), 12.1 (La), 7.77 (Ce), 6.91 (Eu), 1.90 (Gd), and 4.11 (Tb).
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.
Da das Recycling von tantalhaltigen Post-Consumer-Abfällen praktisch nicht existiert, stellen metallurgische Reststoffe eine äußerst wichtige Rohstoffquelle für das Tantalrecycling dar. Die meisten Zinnerze enthalten von Natur aus erhebliche Mengen an Refraktärmetallen. Diese Elemente werden in den Schlacken der pyrometallurgischen Primärzinngewinnung angereichert. Aufgrund ihrer vergleichsweise hohen Wertstoffkonzentration und ihrer Funktion als zusätzlicher Schlackenbildner stellen diese Schlacken einen wertvollen Rohstoff für die Verhüttung tantalhaltiger Reststoffe dar. In der vorliegenden Arbeit wird ein existierendes Verfahren zur Tantalrückgewinnung diskutiert, dem hauptsächlich pyrometallurgische Rückstände geringer Wertstoffkonzentration als Einsatzstoff dienen. Mit Hilfe des Verfahrens sollte dasoxidisch vorliegende Tantal vollständig reduziert und in der Metallphase angereichert werden. Weiterhin sollte vermieden werden, dass unerwünschte Elemente wie Titan in die Metallphase überführt werden. Ziel der Untersuchung war es, die ablaufenden Reduktionsprozesse besser zu verstehen, um so Ansätze für die Prozessoptimierung identifizieren zu können.