Theoretical study on molten alkali carbonate interfaces

The properties and structure of relevant interfaces involving molten alkali carbonates are studied using molecular dynamics simulation. Lithium carbonate and the Li/Na/K carbonate eutectic mixture are considered. Gas phases composed of pure CO2 or a model flue gas mixture are analyzed. Similarly, the adsorption of these gas phases on graphene are studied, showing competitive CO2 and N2 adsorption that develops liquid-like layers and damped oscillation behavior for density. The interaction of the studied carbonates with graphene is also characterized by development of adsorption layers through strong graphene–carbonate interactions and the development of hexagonal lattice arrangements, especially for lithium carbonate. The development of molten salts–vacuum interfaces is also considered, analyzing the ionic rearrangement in the interfacial region. The behavior of the selected gas phases on top of molten alkyl carbonate is also studied, showing the preferential adsorption of CO2 molecules when flue gases are considered.European Union’s H2020- MSCA-RISE-2016-CO2MPRISE-73487

Insights into carbon nanotubes and fullerenes in molten alkali carbonates

The properties of single-walled carbon nanotubes and carbon fullerenes in molten alkali carbonates (MACs) were studied as a function of the considered nanomaterial and the ions into the molten salt using classical molecular dynamics simulations. The adsorption and confinement in carbon nanotubes is developed by efficient interaction of carbonate ions in the inner and outer walls of the nanotubes whereas alkali cations do not show a remarkable interaction with the nanomaterial. Analogous solvation mechanisms are inferred for carbon fullerenes with large disruption of the liquid structuring of MAC at high fullerene concentrations. The solvation ability of the studied lithium–sodium–potassium carbonate eutectic mixture for both types of nanomaterials is essential for considering this fluid in the development of composite materials for advanced technological applications.European Union H2020- MSCA-RISE-2016-CO2MPRISE-73487

PROMETHEUS: A Copper-Based Polymetallic Catalyst for Automotive Applications. Part I: Synthesis and Characterization

According to the strict European exhaust emissions standards that have been imposed by European legislation there is an elevated need for the decrease of the toxic gas emissions from vehicles. Therefore, car manufacturers have implemented a series of catalytic devices in the aftertreatment of the engine to comply with the standards. All catalytic devices (such as three-way catalysts, diesel particulate filters and diesel oxidation catalysts) accumulate concentrated loading of platinum group metals (PGMs, platinum, palladium, rhodium) as the active catalytic phase. Thus, the demand for PGMs is constantly increasing with a subsequent increase in their market prices. As a result, the research on catalytic converters of high activity and reduced cost/PGM loading is of great interest. In the present work, the Prometheus catalyst, a polymetallic nanosized copper-based catalyst for automotive emission control applications, is presented in two different metal loadings (2 wt% and 5 wt%) and metal ratios (Cu/Pd/Rh = 21/7/1 and Cu/Pd/Rh = 21/7/3). For the first time, a three-metal (copper, palladium, rhodium) nano-catalyst has been synthesized and characterized on a large scale. By using copper as an active catalytic phase, a reduction of PGMs loading is achieved (up to 85%) resulting in a novel catalytic device with similar or improved catalytic performance compared to commercial ones. The Prometheus catalyst is prepared by a wet impregnation method, using as a carrier an inorganic mixed oxide (CeZrO4) exhibiting elevated oxygen storage capacity (OSC). The heterogeneous catalytic powders produced were characterized by both spectroscopic and analytical methods. The metal content and ratio were determined by inductively coupled plasma mass spectrometry (ICP-MS), X-ray fluorescence (XRF) and energy-dispersive X-ray spectroscopy (EDS). The morphology and the catalyst particle size were determined with scanning electron microscopy (SEM) and X-ray diffraction (XRD). The investigation revealed homogeneous particle formation and dispersion. The deposition of the metal nanoparticles on the porous inorganic carrier was verified with N2 sorption. Catalytic performance and reactivity of a catalyst (pure wash coat) with molar ratio 21/7/1 and a full-scale Prometheus catalyst with the desired loading of 15 g/ft3 were tested on an in-house synthetic gas bench (SGB) for the abatement of CO, CH4 and NO, both presenting high catalytic activity

Ανακύκλωση πολύτιμων μετάλλων από καταλυτικούς μετατροπείς αυτοκινήτων με υδρομεταλλουργικές μεθόδους

Every modern vehicle equipped with an internal combustion engine possess catalysts (Τhree-Way Catalytic Converters for petrol engines, or Diesel Oxidation Catalysts for diesel engines), in order to reduce efficiently the emission of harmful compounds like carbon oxides (CO), hydrocarbons (HC) and nitrogen oxides (NOx). Car manufacturers mainly use platinum group metals (PGMs) such as platinum, palladium and rhodium to perform these catalytic functions. In general, the platinum group metals are comprised of six similar elements: iridium, osmium, palladium, platinum, rhodium and ruthenium. These elements are included by the European Commission in the list of critical raw materials, based on their economic importance and supply risk. The long-term demand fundamentals for PGMs are strong, with their consumption closely related to the global green energy transition and imposition of stricter emissions standards – particularly in the automotive sector. Recycling could contribute to the reduction of supply risk and increasingly cover the future PGM demands in the EU and globally. Moreover, concerning the advantages of recovering precious metals over their mining, these are mainly their limited resources, scarcity, expensive and energy-intensive mining process and the significant amount of waste generated during this process. Platinum group metal ores contain very small amounts of these metals. For example, in South Africa (the largest producer of platinum), PGM bearing ores have a low content of between 2 and 6 g/t . At the same time, it should be noted that automotive catalytic converters typically contain up to 2000 g/t PGM in the ceramic catalyst brick, the active part of the converter. Therefore, due to the high value of PGMs and the fact that autocatalysts comprise a rich source of PGMs, the attractiveness to recover those metals from end-of-life products such as spent autocatalysts, is extremely high. In the specific thesis, an industrial driven, integrated circular economy model is proposed for the sustainable valorization of platinum group metals (PGMs) contained in automotive catalytic converters. The 4 main steps of the cycle are, a) pre-processing, b) leaching/recovering c) new catalyst preparation from recovered (impure) material, and d) introduction to the market of the new catalysts. The circular economy model is based on leaching/recovering of PGMs with an industrially optimized hydrometallurgical method from spent automotive catalytic converters and the preparation of new catalyst from recovered material. State of the art methods, principles and theory on PGMs extraction are described in detail providing an insight of the advantages and difficulties of each process. Several parameters, such as temperature, acidity and time, have been studied and examined for the hydrometallurgical method to be optimized for automotive catalysts. A novel hydrometallurgical process has been developed, resulting in recovery rates for Pt, Pd and Rh, namely, 100%, 92% and 61%, respectively. In order to highlight the importance and significance of recovering PGMs, alternative secondary sources, such as membrane electrode assemblies from spent fuel cell and electrolyzers and emission control devices derived from Euro6 heavy duty vehicles have been examined. Recovered material has been used to produce new three-way catalysts and diesel oxidation catalysts and their catalytic activity has been validated on a synthetic gas bench. Their performance has been discussed in terms of commercial benchmarks. Finally, the essential market analysis has been conducted for the manufacturing of automotive catalytic converters (ACC) integrating 100% recycled PGMsΌλα τα σύγχρονα οχήματα που λειτουργούν με μηχανές εσωτερικής καύσης, διαθέτουν καταλυτικά συστήματα (τριοδικούς καταλύτες για τα οχήματα καυσίμου βενζίνης ή οξειδωτικούς καταλύτες για τα οχήματα καυσίμου πετρελαίου - diesel), με στόχο να μετατρέπουν τα τοξικά αέρια του μονοξειδίου του άνθρακα (CO), των υδρογονανθράκων (HC) και των οξειδίων του αζώτου (NOx) σε μη τοξικά, χρησιμοποιώντας πλατινοειδή μέταλλα, όπως Πλατίνα, Παλλάδιο και Ρόδιο. Τα πλατινοειδή μέταλλα περιλαμβάνουν τα μέταλλα της Πλατίνας, του Παλλαδίου, του Ροδίου, του Ιριδίου, του Οσμίου και του Ρουθηνίου, τα οποία ανήκουν σε μια μεγαλύτερη κατηγορία υλικών, αυτή των κρίσιμων. Η κρισιμότητα αυτών των υλικών εξαρτάται από την επαρκή τους προσφορά και την κάλυψη της ζήτησης τους για την παραγωγή νέων αγαθών, αλλά και τη συνεισφορά που έχουν στην οικονομική ανάπτυξη της βιομηχανίας και του τρόπου ζωής μας. Η μακροπρόθεσμη ζήτηση των πλατινοειδών διαφαίνεται να σημειώνει ιδιαίτερη αύξηση, λαμβάνοντας υπόψιν την βελτίωση και την ανάπτυξη νέων πράσινων τεχνολογιών, που στόχο έχουν τη συμμόρφωση με τις οδηγίες της Ευρωπαϊκής Ένωσης για αυστηρότερα όρια στις εκπομπές των καυσαερίων. Η κάλυψη αυτών των αναγκών θα μπορούσε να πραγματοποιηθεί είτε με αύξηση του ρυθμού εξόρυξης αυτών των μεταλλευμάτων είτε με την ανακύκλωση συσκευών/υλικών μετά το τέλος ζωής τους, ανακτώντας τις απαιτούμενες ποσότητες πολυτίμων μετάλλων. Καθώς η διαδικασία και οι μέθοδοι της εξόρυξης είναι πολύ κοστοβόρες και ενεργοβόρες, ενώ ταυτόχρονα παράγονται δυσανάλογα μεγάλοι όγκοι αποβλήτων σε σχέση με τη συγκέντρωση των μεταλλευμάτων, η ανακύκλωσης αποφαίνεται πιο οικονομικά συμφέρουσα και περιβαλλοντικά φιλική. Για παράδειγμα, τα μεταλλεύματα των πλατινοειδών της Νοτίου Αφρικής, η οποία είναι από τους κύριους εξαγωγείς Pt, παγκοσμίως, διαθέτουν μόλις 2-6g/t πολυτίμων μετάλλων, ενώ ένας απενεργοποιημένος καταλύτης αυτοκινήτου, περιέχει 2000g/t πολυτίμων μετάλλων, καθιστώντας τους ιδιαίτερα ελκυστική λύση για την εξαγωγή πολυτίμων μετάλλων. Στη παρούσα εργασία παρουσιάζεται ένα ολοκληρωμένο βιομηχανικό μοντέλο κυκλικής οικονομίας σύμφωνα με το οποίο περιγράφεται η χρήση των πολυτίμων μετάλλων τα οποία έχουν ανακτηθεί από δευτερεύουσες πηγές και πρόκειται να χρησιμοποιηθούν στην παραγωγή νέων υλικών, εξίσου αποδοτικών με αυτά εξ ων ανακτήθηκαν. Τα επιμέρους χαρακτηριστικά βήματα τα οποία συνθέτουν το κυκλικό μοντέλο περιγράφονται λεπτομερώς σε κάθε κεφάλαιο που ακολουθεί. Στα κεφάλαια που ακολουθούν αναλύονται τα βήματα της προ-επεξεργασίας των πηγών που περιέχουν τα πολύτιμα μέταλλα, θα περιγραφούν και μέθοδοι με τις οποίες γίνεται η εξαγωγή των μετάλλων (leaching) σε μορφή αλάτων του χλωρίου, η μετατροπή τους σε νιτρικά άλατα (όπου απαιτείται), η εναπόθεση τους σε νέα υποστρώματα και τέλος η δημιουργία νέων υλικών καθώς και η αξιολόγηση τους όσον αφορά στην καταλυτική τους ενεργότητα. Παράμετροι που επηρεάζουν την απόδοση της ανάκτησης των πλατινοειδών μετάλλων, όπως το είδος διαλυτών, τα οξειδωτικά μέσα, ο χρόνος ανάδευσης και η θερμοκρασία, μελετήθηκαν συζητούνται εκτενώς. Η υδρομεταλλουργική μέθοδος που αναπτύχθηκε, χρησιμοποιήθηκε για την ανάκτηση πολυτίμων μετάλλων από απενεργοποιημένους καταλυτικούς μετατροπείς αυτοκίνητων (τόσο μικρών οχημάτων – τριοδικοί καταλύτες – όσο και βαρέων οχημάτων – οξειδωτικοί καταλύτες) και πολυμερικές ηλεκτρολυτικές μεμβράνες από κελιά καυσίμου (Fuel Cells) και συσκευές παραγωγής υδρογόνου (electrolyzers). Τέλος, το μοντέλο της κυκλικής οικονομίας συμπληρώνεται με την παρασκευή νέων υλικών, τόσο τριοδικών όσο και οξειδωτικών καταλυτικών μετατροπέων και την αξιολόγηση της καταλυτικής τους ενεργότητας αναφορικά με τους καταλύτες πρώτης τοποθέτησης. Επιπλέον, πραγματοποιείται η ανάλυση της αγοράς για την παρασκευή καταλυτικών μετατροπέων εξ’ ολοκλήρου από ανακυκλωμένα μέταλλα

Innowacyjne technologie odzysku metali grupy platynowców z katalizatorów – studium przypadku wybranych projektów

The growing increase in the use of cars and transportation in general is causing an increase the emission of pollutants into the atmosphere. The current European Union regulations impose the minimization of pollution through the use of automotive catalytic converters on all member countries, which stops toxic compounds from being emitted into the atmosphere thanks to their contents of platinum group metals (PGMs). However, the growing demand for cars and the simultaneous demand for catalytic converters is contributing to the depletion of the primary sources of PGMs. This is why there is now increasing interest in recycling PGMs from catalytic converters through constantly developing technologies. There are newer and more sustainable solutions for the recovery of PGMs from catalytic converters, making the process part of a circular economy (CE) model. The purpose of this article is to present two innovative methods of PGM recovery in the framework of ongoing research and development projects.Rosnący wzrost wykorzystania samochodów i generalnie środków transportu przyczynia się do emisji zanieczyszczeń do atmosfery. Obecne przepisy UE narzucają na wszystkie kraje członkowskie minimalizacje zanieczyszczeń poprzez stosowanie katalizatorów samochodowych, które dzięki zawartości metali z grupy platynowców (PGM) zatrzymują toksyczne związki przed emisji do atmosfery. Jednak rosnący popyt na samochody i jednoczesny popyt na katalizatory przyczynia się do zubożania pierwotnych źródeł pozyskiwania PGM. Dlatego też obecnie coraz więcej mówi się o recyklingu PGM z katalizatorów poprzez ciągle rozwijające się technologie. Powstają coraz nowsze, bardziej zrównoważone rozwiązania odzysku PGM z katalizatorów, dzięki czemu proces ten wpisuje się w model gospodarki o obiegu zamkniętym (CE). Celem artykułu jest przedstawienie dwóch innowacyjnych metod odzysku PGM w ramach prowadzonych obecnie projektów badawczo-rozwojowych

Platinum Recovered from Automotive Heavy-Duty Diesel Engine Exhaust Systems in Hydrometallurgical Operation

The current study is focused on platinum recovery from the secondary sources of end-of-life heavy-duty diesel oxidation catalysts (DOCs) and heavy-duty catalyzed diesel particulate filters (c-DPFs) in order to reduce the supply–demand gap within the European Union. The extraction of platinum was based on a hydrometallurgical single-step low acidity leaching system (HCl-H2O2-NaCl) and a calcination step that takes place before the leaching process. The parameters of calcination and leaching process were thoroughly investigated in order to optimize recovery efficiency. The optimized results proved that a calcination step (at 800 °C for 2 h) improves the recovery efficiency by a factor of 40%. In addition, optimal Pt recovery yield was achieved after 3 h of leaching at 70 °C, with a solid-to-liquid (S/L) ratio of 70 g/100 mL (70%) and 3 M HCl-1% vol H2O2-4.5 M NaCl as leaching conditions. The optimum Pt recovery yield was 95% and 75% for DOC and c-DPF, respectively. Since the secondary feedstock investigated is highly concentrated in platinum, the pregnant solution can be used as a precursor for developing new Pt-based catalytic systems

Platinum Recovered from Automotive Heavy-Duty Diesel Engine Exhaust Systems in Hydrometallurgical Operation

The current study is focused on platinum recovery from the secondary sources of end-of-life heavy-duty diesel oxidation catalysts (DOCs) and heavy-duty catalyzed diesel particulate filters (c-DPFs) in order to reduce the supply–demand gap within the European Union. The extraction of platinum was based on a hydrometallurgical single-step low acidity leaching system (HCl-H2O2-NaCl) and a calcination step that takes place before the leaching process. The parameters of calcination and leaching process were thoroughly investigated in order to optimize recovery efficiency. The optimized results proved that a calcination step (at 800 °C for 2 h) improves the recovery efficiency by a factor of 40%. In addition, optimal Pt recovery yield was achieved after 3 h of leaching at 70 °C, with a solid-to-liquid (S/L) ratio of 70 g/100 mL (70%) and 3 M HCl-1% vol H2O2-4.5 M NaCl as leaching conditions. The optimum Pt recovery yield was 95% and 75% for DOC and c-DPF, respectively. Since the secondary feedstock investigated is highly concentrated in platinum, the pregnant solution can be used as a precursor for developing new Pt-based catalytic systems

Preprocessing and Leaching Methods for Extraction of REE from Permanent Magnets: A Scoping Review

The demand for REEs is continuously increasing in the European Union due to the rapid development of high-tech applications that contain REEs, mainly those based on electrification. However, the REE supply in Europe is limited because of the exclusive production of these metals by third-world countries. The European supply/demand gap for REEs can be covered with the development of recycling technologies from secondary resources, such as REE permanent magnets. NdFeB and SmCo magnets are the two main categories of REE-containing permanent magnets. In the following work, studies focusing on the preprocessing and leaching methods in order to extract REEs were identified and discussed. Although preprocessing includes controversial steps, i.e., milling and demagnetizing, numerous studies have focused on the leaching of REEs from NdFeB magnets using either inorganic or organic solvents. Meanwhile, the literature based on Sm recovery methods from SmCo magnets has been limited