Thermal delamination of end-of-life crystalline silicon photovoltaic modules

Thermal delamination – meaning the removal of polymers from the module structure by a thermal process – as a first step in the recycling of crystalline silicon (c-Si) photovoltaic (PV) modules in order to enable the subsequent recovery of secondary raw materials was investigated. A correlation between treatment temperature and duration was established by an iterative process. Furthermore, chemical characterization of the resulting solid outputs (glass, cell, ribbons and residues) was performed in order to assess their further processing options. Additionally, the effect of removing the backsheet as a pre-treatment before the actual delamination process was investigated in relation to the aforementioned aspects of treatment duration and output quality. Results show that increased temperatures reduce the necessary treatment duration (65 minutes at 500°C, 33 minutes at 600°C) while generating the same output quality. The backsheet removal leads to an additional duration decrease of more than 45% at each considered temperature, while also having positive effects relating to fewer solid residues and easier flue gas handling. In regard to the main output specifications no significant influence of the pre-treatment is observed. Overall thermal delamination can be seen as a feasible method in order to obtain high value secondary raw materials from c-Si PV modules, while backsheet removal as pre-treatment should be considered as advantageous from multiple standpoints

Das urnenfelderzeitliche Gräberfeld von Mannersdorf am Leithagebirge

Das Gräberfeld in der Flur „Reinthal Süd“ gehört zur Stadtgemeinde Mannersdorf am Leithagebirge und liegt auf einer Schotterterrasse des Flusses Leitha 2,8 km von der Pfarrkirche entfernt. Das Areal wurde schon in der frühen und mittleren Bronzezeit als Friedhof genutzt. Die nächsten Belegungen erfolgten in der älteren Spätbronzezeit und einige Jahrhunderte später in der Latènezeit. Zunächst führten die Lokalhistoriker Friedrich Opferkuh und Heribert Schutzbier Bergungen der Funde durch. Von 1978–1984 fanden Notgrabungen durch die Abteilung für Bodendenkmalpflege des Bundesdenkmalamtes unter der Leitung von Gustav Melzer statt. Es konnten 55 urnenfelderzeitliche Gräber nachgewiesen werden, wovon ein Großteil leider gestört bzw. ganz zerstört waren. Bei den Gräbern handelte sich um typische Flachgräber der mitteldonauländischen Urnenfelderkultur, die seicht unter der Humusschicht eingetieft waren. Die Architektur der Grabformen lässt sich grundsätzlich in zwei Typen einteilen, nämlich in länglich-rechteckige Gräber mit oder ohne Steinsetzungen (Typ I) und rundovale-kreisrunde Gräber (Typ II). Bei Typ I kommt nur die Brandschüttung als Bestattungsart vor, bei Typ II tritt neben dieser auch die Urnenbestattung hinzu. Die länglich-rechteckigen Gräber sind vorwiegend NW-SO orientiert. Ausnahmen bilden die Gräber 72 und 194, die NO-SW ausgerichtet sind, und Grab 53, das O-W ausgerichtet ist. Möglicherweise spielten markante Punkte des Leithagebirges bei der Orientierung der Gräber eine gewisse Rolle. Der Leichenbrand kam vorwiegend in der dem Westen näher gelegenen Hälfte des Grabes zu liegen, manchmal auch in der Grabmitte. Die Keramik hingegen wurde an verschiedenen Stellen platziert, sei es zum Beispiel aufgereiht auf der Längsachse oder in der südöstlichen Hälfte der Grube. In 40% der Gräber befanden sich nachweislich Beigaben aus Bronze. Meist wurden die Trachbestandteile, wie Nadeln, Fibeln, Ringgehänge, Anhänger/Rasiermesser, aber auch Messer mit dem Toten auf dem Scheiterhaufen verbrannt und sind nur mehr im verformten Zustand erhalten. Einige Bronzegegenstände, wie zum Beispiel Messer oder Pfeilspitzen, wurden dem Toten auch unverbrannt ins Grab mitgegeben. Alle Stücke weisen Gebrauchsspuren auf. Die meisten Keramikformen wie auch die Bronzebeigaben sind typische Vertreter der Fazies der älteren mitteldonauländischen Urnenfelderkultur der Stufe Baierdorf-Velatice. Das Gräberfeld ist in die Stufen HaA1 bis HaA2 zu datieren. Anhand einiger Beigaben lassen sich kulturelle und wirtschaftliche Kontakte in den süddeutschen-bayerischen Raum, in den Norden Europas sowie nach Zentral- und Nordniederösterreich sowie Mähren und zur Lausitzer Kultur nachweisen.The prehistoric necropolis in the area “Rheintal-Süd” is part of the municipality of Mannersdorf am Leithagebirge. It is located on a gravel terrace of the river Leitha, about 2, 8 km off the townchurch. That area had already been used as graveyard during the early and the middle Bronze Age. It was used again as graveyard in the older late Bronze Age and several hundred years later during the Latène. The local historians Friedrich Opferkuh and Heribert Schutzbier started to rescue the first findings. From 1978 – 1984 the departement for maintaining soil monuments of the Federal Office for preservation of monuments undertook rescue excavations guided by Gustav Melzer. 55 graves of the “Urnenfelder” Culture could be identified, a majority of which had been disarranged or completely destroyed. All graves were typical flat graves of the “Mitteldonauländische Urnenfelder” Culture dug shallowly under humus soil. The architecture of the graves can principally be classified into two types: Type I is longish-rectangle-shaped with or without rests of stone covering, Type II round oval to circle round. Type I showed only one way of burials: cremation heaped on the ground, whereas Type II in addition contained cremation in urns. The longish-rectangle pits were mostly oriented toward northwest-southeast. Tomb 72 and tomb 194 are exceptions as they are directed to northeast-southwest, grave 53 is aligned with east-west. Possibly some characteristic points of the nearby hills, the so called “Leithagebirge”, played a special role within the orientation of the tombs. The ashes of the cremated corpses were mostly placed in that part of the grave pits, which pointed to the west, sometimes they were in the middle of the graves. Ceramics however were placed on different positions, for example alongside the longitudinal axis, or on the southeast part of the pit. Bronze artefacts could be traced in 40 % of the tombs. In most cases parts of the traditional costumes, as needles, fibulas, rings, pendants/razors, and knives were cremated with the corps and thus are only preserved in deformed condition. Some Bronze artefacts as knives and arrowheads, were put intact into the tombs. All pieces show traces of having been used. A large part of the ceramics and bronze objects typically represent the older “Mitteldonauländische Urnenfelder” Culture of the period “Baierdorf-Velatize”. Therefore the necropolis has to be dated in the period HaA1 until HaA2. Cultural and economic contacts with the South German area, Northern Europe, Central and Northern Lower Austria as well as Moravia and the Lausitz Culture can be identified through some objects

Impact of thermal soil treatment on heavy metal mobility in the context of waste management

Thermal soil treatment is a well-established remediation method to remove organic contaminants from soils in waste management. The co-contamination with heavy metals raises the question if thermal soil treatment affects heavy metal mobility in soils. In this study, four contaminated soils and a reference sample were subjected to thermal treatment at 105°C, 300°C and 500°C for 7 day. Thermogravimetry and differential scanning calorimetry were used to understand the reactions, and resulting gases were identified by Fourier-transformed infrared spectroscopy. Treated and untreated samples were characterised by X-ray diffraction (XRD) and electron microprobe analysis and subjected to pH-dependent leaching tests, untreated samples additionally by X-ray-fluorescence (XRF) and inductively coupled plasma mass spectroscopy (ICP-MS). Leachates were analysed using ICP-MS and ion chromatography. Maximum available concentrations were used for hydrogeochemical modelling using LeachXS/Orchestra to predict leaching control mechanisms. Leaching experiments show that thermal treatment tends to decrease the mobility at alkaline pH of Pb, Zn, Cd, As and Cu, but to increase the mobility of Cr. In the acidic to neutral pH range, no clear trend is visible. Hydrogeochemical modelling suggests that adsorption processes play a key role in controlling leaching. It is suggested that the formation of minerals with a more negatively charged surface during thermal treatment are one reason why cations such as Pb2+, Zn2+, Cd2+ and Cu2+ are less mobile after treatment. Future research should focus on a more comprehensive mineralogical investigation of a larger number of samples, using higher resolution techniques such as nanoscale secondary ion mass spectrometry to identify surface phases formed during thermal treatment and/or leaching