Stefan Luidold

Recycling of waste printed circuit boards with simultaneous enrichment of special metals by using alkaline melts: A green and strategically advantageous solution

The increasing consumption of electric and electronic equipment has led to a rise in toxic waste. To recover the metal fraction, a separation of the organic components is necessary because harmful substances such as chlorine, fluorine and bromine cause ecological damage, for example in the form of dioxins and furans at temperature above 400°C. Hence, an alternative, environmentally friendly approach was investigated exploiting that a mixture of caustic soda and potassium hydroxide in eutectic composition melts below 200°C, enabling a fast cracking of the long hydrocarbon chains. The trials demonstrate the removal of organic compounds without a loss of copper and precious metals, as well as a suppressed formation of hazardous off-gases. In order to avoid an input of alkaline elements into the furnace and ensuing problems with refractory materials, a washing step generates a sodium and potassium hydroxide solution, in which special metals like indium, gallium and germanium are enriched. Their concentrations facilitate the recovery of these elements, because otherwise they become lost in the typical recycling processes. The aim of this work was to find an environmental solution for the separation of plastics and metals as well as a strategically important answer for the recycling of printed circuit boards and mobile phones.

Recycling von Seltene Erden aus Nickel-Metallhydrid-Akkumulatoren unter besonderer Berücksichtigung von Säurerückgewinnung

SummaryIt is possible to extract rare earth compounds out of used nickel-metal-hydride batteries by a hydrometallurgical treatment. During this process a high amount of spent acid which still contains various valuable metals is produced. produced. To remove metals from an aqueous solution many different ways such as electrolysis, precipitation, crystallisation, hydrogen reduction or solvent-extraction are applicable. The regeneration of spent acid makes also sense in order to use it again for the leaching of spent batteries. At industrial scale almost all hydrometallurgical processes are used for the extraction of nickel and cobalt out of aqueous solutions. Experiments for the selective cathodic deposition of nickel and cobalt did not achieve satisfactory results, because the solid showed a layered structure with included impurities. At the precipitation of nickel and cobalt in form of sulphides only a small portion of the theoretical performance was achieved, which was existent in form of a fine precipitate and contained a large amount of impurities. Further experiments for the selective separation of valuable metals from the residual solution by solvent extraction are the next step in the development of a closed recycling concept.ZusammenfassungAus Nickelmetallhydrid-Akkumulatoren können Verbindungen, welche Seltene Erden enthalten, auf hydrometallurgischem Wege gewonnen werden. Dabei entsteht eine große Menge an Restlösung, welche noch eine Vielzahl an Wertmetallen enthält. Die Metallgewinnung aus wässrigen Lösungen kann mit unterschiedlichsten Methoden erfolgen, wie beispielsweise Elektrolyse, Fällung, Kristallisation, Wasserstoffreduktion oder Solvent-Extraktion. Ebenfalls sinnvoll ist es, die dabei entstehende Säure zu regenerieren und wieder für die Laugung von Alt-Akkumulatoren zu nutzen. Großtechnisch wird für die Nickel- und Cobaltgewinnung aus wässrigen Lösungen eine Kombination aus fast allen hydrometallurgischen Verfahren verwendet. Bei Versuchen zur selektiven, kathodischen Abscheidung von Nickel bzw. Cobalt konnten keine zufriedenstellenden Ergebnisse erzielt werden, da der gewonnene Feststoff eine schichtartige Struktur aufwies und Verunreinigungen miteingeschlossen wurden. Bei der Fällung von Nickel und Cobalt in Form von Sulfiden ließ sich nur ein sehr geringer Teil des theoretischen Ausbringens erreichen, welcher zudem in Form eines feinen Niederschlags vorlag, welcher nach Filtration und Trocknung eine große Menge an Verunreinigungen enthielt. Weitere Versuche zur selektiven Trennung der Wertmetalle aus der Restlösung mittels Solvent-Extraktion sind der nächste Schritt zur Entwicklung eines Recyclingkonzeptes mit einem geschlossenen Lösungsmittelkreislauf.

Disclosure of the Kinetic Relations of Semidirect Cemented Carbide Leaching in Acid Media

The purpose of this investigation is to provide a basis for the semidirect recycling of hard metals. Accordingly, the present investigation focuses on revealing the fundamental chemical kinetic aspects during cemented carbide leaching in hydrochloric acid including an oxidant. In contrast to literature, the experiments are performed with pieces of cemented carbide specimen. This displays a crucial condition since the disintegration of hard metal scrap causes trouble and the tests should provide feasible information. Appropriate preliminary sample preparations combined with an adequate arrangement in the reaction vessel eliminate shrinking surface effects on the leaching kinetics. Moreover, an implementation of a design of experiments allows a statistical evaluation and regression analysis of the obtained results. During the experiments the influence of several parameters such as the temperature, the acid- as well as the oxidant concentration on the leaching behavior is examined. Finally a proposed empirical kinetic law describes the lixiviation performance of cobalt out of the hard metal substrate.

EXTRACTION OF LANTHANIDES FROM SPENT POLISHING AGENT

Abstract The polishing of glass substrates or wafers requires fine-grained particles, frequently based on oxides of the lanthanides cerium and lanthanum. During processing the slurries become enriched with different elements depending on the specific production program and the chemical composition of the work piece. Concentrations of these impurities can reach critical values and may negatively influence the surface quality of the substrates. Therefore, the polishing agents have to be removed from the system and are sent to a landfill or recycled. This chapter describes options for processing such secondary rare earth resources using different hydrometallurgical methods including mineral acids for extraction. In some cases, the focus is also on the evaluating precipitation methods by carbonate or oxalate carriers to produce a rare earth concentrate that meets requirements for reuse in fabricating new polishing powders.

RFID-Reststoff-Anfall und Recyclingpotenziale der Metallanteile

SummaryThe RFID technology (Radio Frequency Identification) represents an extensive field of application for logistic topics.. The application of RFIDs is unlimited. Particularly the simple replacement of the established bar-code system by smart labels and also the tracking/tracing of various objects, animals and people exhibit a high market potential. Due to the estimated future market development and penetration difficulties in the supply of RFID manufacturer with silver (antenna material) could be expected. An increase in primary production of lead and copper and accordingly the recycling of this metal from consumed RFID tags alleviate this problem. For the recovery it is necessary to find technologies for the separation of smart labels from the tagged objects. The build-up of appropriate infrastructures for the RFID recycling is also a future topic. The recovery of the two antenna metals copper and silver are thereby in focus. The increased accumulation of RFIDs in the established recycling routes (glass, plastic, paper and metal) may lead to a decrease of quality of secondary products. An upstream separation of smart labels avoids problems in the subsequent recycling processes (i. e. glass melting furnace – glass bottle production).ZusammenfassungDie RFID-Technologie (Radio Frequency Identification) stellt ein weitreichendes Einsatzgebiet für logistische Themenstellungen dar. Ausgehend vom einfachen Ersatz des heute gängigen Bar-Code-Systems bis hin zur Nachverfolgung (Tracking & Tracing) diverser Gegenstände, Tiere und Personen sind die Anwendungsmöglichkeiten praktisch unbegrenzt. Aufgrund der zu erwartenden zukünftigen starken Marktentwicklung und -durchdringung könnte es zu Schwierigkeiten bei der Versorgung der RFID-Hersteller mit dem Antennenmetall Silber kommen. Der steigenden Nachfrage ist mit einer Erhöhung der primären Blei- und Kupferproduktion beizukommen. Eine alternative Lösung für dieses Versorgungsproblem stellt die Sekundärmetallurgie dar. Hierbei ist es jedoch notwendig, Verfahren für die Separation der Etiketten mit den RFIDs (Smart-Labels) von den gekennzeichneten Objekten zu finden und geeignete Infrastrukturen für das Recycling dieser Art der Elektrokleingeräte aufzubauen. Die Rückgewinnung der beiden Antennenmetalle Kupfer und Silber stehen hierbei im Fokus. Durch den vermehrten Anfall von RFIDs in den bereits etablierten Recyclingprozessen (Glas, Kunststoff, Papier und Metall) könnte es zu Qualitätseinbußen bei den jeweiligen sekundären Produkten kommen. Eine vorhergehende Abtrennung der Smart-Labels von den gekennzeichneten Objekten schützt die nachfolgenden Prozesse vor diesen Problemen.

Influence of Substrate Properties on the Selective Leaching Performance of Cobalt from Cemented Carbides

Lack of basic knowledge on the semi-direct recycling methods for hard metals hinders the application on an industrial scale. However, advantages like reduced expenses and lower environmental impact draw interest at future potentials. Consequently, this report aims to offer insight into the influence of varying bulky hard metal substrates during their lixiviation in acidic media with an oxidant. The statistical software Modde 11 assisted in the development of a design of experiments (DOE) for evaluation of the impact of average grain size, binder and tantalum carbide (TaC) content on the leaching characteristics. The other experimental parameters were constant. Among them were temperature, solution concentration and quantity, duration and substrate surface exposed to liquid volume. Eventually, prediction plots and factors of the computed model equation describe the effects of varying substrate qualities on leached binder metal and selectivity.

High Temperature Phase Formation at the Slag/Refractory Interphase at Ferronickel Production

Corrosion mechanisms between high melting synthetic ferronickel slags and refractory were investigated. The used slags were prepared by mixing and melting of specific oxides. Substrates of the applied refractory material and specimens of FeNi slags were heated in a hot stage microscope up to 1650 °C. The experiments were performed under a defined gas atmosphere of 60% CO and 40% CO2. A further examination of the formed phases between slag and refractory occurred by scanning electron microscope. The investigations indicate that the slag penetrates between magnesia grains and partly dissolves magnesia. Spot analyses show that iron diffuses into the magnesia grains, which transform to magnesiawustite, meanwhile SiO2 forms different types of olivine like forsterite and monticellite. Thermodynamic calculations confirm the formation of these phases. The combination of practical lab scale experiments and thermodynamic calculations should finally contribute to an improvement of the refractory lifetime and performance.

Evaluation of High Temperature Refractory Corrosion by Liquid Al2O3–Fe2O3–MgO–SiO2

Corrosion mechanisms have been investigated between MgO refractory substrates and synthetic FeNi slags. The materials taken into consideration comprised a simple synthetically mixed slag with specific oxides of slags from a ferroalloy producer. The MgO refractory substrates with the slag specimens on it were heated in a hot stage microscope to two different characteristic temperatures, 1350 and 1650 °C. The experiments proceeded under a controlled gas atmosphere that simulates the relevant process conditions. The corrosion mechanisms of each system were determined by SEM analyses. The obtained results showed that slag corrosion is dominating with a pronounced partial dissolution of refractory. It was also observed that iron oxide present in the slag diffused into the coarse refractory grains forming the relative low melting magnesia wuestite. Finally, the comparison of these findings with those predicted by thermodynamic calculation (FactSage) indicated the corrosion mechanisms and draw implications for improving the refractory performance and lifetime.

New preparation and recycling procedure to recover rare earth elements from magnets by using a closed loop treatment

The use of critical raw materials also increases due to the higher demand on electrical and electronic equipment (EEE). The high content of valuable substances in EEE in relation to primary ores secures a potential for its use as new raw materials sources, the so-called ‘urban mining’. Positive effects of urban mining are to save existing mineral resources as well as to relieve the primary production and get a new opportunity instead of landfilling. The subsequently described research work at the Chair of Nonferrous Metallurgy at the University of Leoben is concentrated on the preparation of hard disc drives (HDDs). Currently, the main problem to recover neodymium–iron–boron (NIB) magnets is the missing technology for preparation. A disassembling of HDD by hand is not economic and a treatment by a shredding machine destroys the NIB magnets, so that they cannot be separated and fed into a proper recycling process. Therefore, the investigation leads to a thermal treatment to obtain the components of a HDD in separated form. The investigation also focuses on a metallurgical way to recover the technological metals like neodymium, copper, gold as well as a reusable aluminium alloy. Therefore, a closed loop treatment was found to clean the leaching agent and reuse it to reduce the amount of waste streams.

High temperature corrosion mechanisms of refractories and ferro-alloy slags

Refractory linings in pyrometallurgical furnaces are attacked by various process phases (e.g. metal, slag, gas). However, refractories are the barrier between these phases and the environment: refractory damages and consequent furnace failure can cause severe damages including potential danger for workers/operators. Hence, refractory corrosion and attack of molten phases require attention to study the mechanisms and effects on refractory performance and lifetime. This is of special importance in ferroalloys production, where temperatures are generally even higher than in base metal processes and the corrosion effects therefore more pronounced.