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Gasification of heavy metal–contaminated biochar: Experimental investigation and thermodynamic analysis
No full textThe thermochemical conversion of heavy-metal (HM)–contaminated biomass offers a pathway to produce syngas and functional biochar while simultaneously remediating the environment. Here, Zn/Pb-contaminated birch biomass from a phytoremediation site was carbonized and the resulting char was gasified under two oxidizing atmospheres (100 vol% CO₂ and 50/50 vol% H₂O/CO₂) at 700–900 °C. Gas composition, char conversion, biochar properties (SEM, Raman, N₂ adsorption), and solid-phase metal retention (ICP-OES) were evaluated together with thermodynamic equilibrium calculations (FactSage 8.4/FactFlow) based on measured elemental inputs (C, H, O, N, S, ash-forming elements, and trace metals). Gasification in an H₂O/CO₂ atmosphere markedly increased reactivity, achieving > 60 % conversion at 700 °C compared with < 20 % under CO₂ alone. The product gas was dominated by CO and CO₂, with enhanced H₂ under H₂O/CO₂. Zn retention decreased from 52.1 % at 700 °C to < 2 % at 900 °C, while Pb retention decreased from 86.1 % to 13.1 % under H₂O/CO₂. Activation produced biochars with BET surface areas up to ∼ 673 m2 g⁻¹ and average pore diameters up to ∼ 1.50 nm. Equilibrium calculations indicated increased Zn volatilization above ∼ 800 °C and predicted Pb stabilization as condensed PbO/PbS at lower temperatures, while K, Ca and Al were predicted to form stable condensed silicates/oxides. Overall, the combined experimental and equilibrium analysis quantifies trade-offs between conversion/activation performance and HM retention during CO₂ and H₂O/CO₂ gasification of contaminated biomass
Retaining crystallinity of as-deposited thermoelectric Fe₂VAl-based thin films grown from DCMS and HiPIMS
No full textThermoelectric materials have gained much attention in recent years due to their ability to directly interconvert electrical and thermal energy via the Seebeck/Peltier effect. Their appeal for application in energy harvesting and solid-state cooling is however currently held back, as current state-of-the-art systems rely on rare and/or hazardous elements. Efforts to replace them with more abundant and environmentally benign alternatives have shown Heusler-alloys to be attractive candidates with thin film Fe2V0.8W0.2Al achieving a massive Figure of Merit, but requiring extensive post-processing to achieve crystallinity.
Here, we report the direct deposition of this material in a crystalline, fully disordered W-type body-centered cubic (bcc) structure using direct current magnetron sputtering (DCMS) and high-power impulse magnetron sputtering (HiPIMS). Structural analyses confirm the formation of crystalline Heusler Phases in the as-deposited state, even at room temperature, eliminating the need for prolonged annealing. Transport measurements reveal low thermal conductivity (2.12 W/m∙K), low resistivity (≈240 μΩ∙cm) and a moderate Seebeck-coefficient (−55 μV/K), resulting in a viable Figure of Merit (ZT ≈ 0.1). These findings demonstrate an energy-efficient route in the fabrication of thermoelectric thin films from earth-abundant, non-toxic elements to be used for sustainable energy conversion
ÖWAV-Expert:innenpapier : Per- und polyfluorierte Alkylsubstanzen (PFAS) in der aquatischen Umwelt
No full textSynCat: molecule-level attention graph neural network for precise reaction classification
No full textChemical reactions typically follow mechanistic templates and hence fall into a manageable number of clearly distinguishable classes that are usually labeled by names of chemists who discovered or explored them. These “named reactions” form the core of reaction ontologies and are associated with specific synthetic procedures. Classification of chemical reactions, therefore, is an essential step for the construction and maintenance of reaction-template databases, in particular for the purpose of synthetic route planning. Large-scale reaction databases, however, typically do not annotate named reactions systematically. Although many methods have been proposed, most are sensitive to reagent variations and do not guarantee permutation invariance. Here, we propose SynCat, a graph-based framework that leverages molecule-level cross-attention to perform precise reagent detection and role assignment, eliminating unwanted species. SynCat ensures permutation invariance by employing a pairwise summation of participant embeddings. This method balances mechanistic specificity derived from individual-molecule embeddings with the order-independent nature of the pairwise representation. Across multiple benchmark datasets, SynCat outperformed established reaction fingerprints, DRFP and RXNFP, achieving a mean classification accuracy of 0.988, together with enhanced scalability
Ungebinnte Entfaltung des Energiekorrelators im Rahmen von Messungen der Top-Quark-Masse
No full textThis work explores the novel approach of unfolding the threefold energy correlator with generative machine learning methods. In recent investigations energy correlators (EEEC) were found to have a top quark mass sensitive peak which is also accessible analytically. To extract the top quark mass by comparing data with analytic calculations, the measured correlators must be unfolded to correct for detector effects. Normalizing flows with conditional invertible neural networks (CiNN) and conditional flow matching (CFM) are two generative machine learning methods, able to perform unbinned unfolding. In this work, simulated data from boosted tt_bar events was used to construct the correlators with emphasis on feasibility with machine learning methods, while allowing the comparison to theory. In contrast to latest studies, the jet p_T dependency of the mass peak, was solved via the construction of a new observable without this dependency. Configurations of the two models were found enabling the unfolding of these correlators. The concept of unfolding EEEC could be demonstrated and showed promising results. Supplementary investigations regarding the generalization capabilities of the models showed a mass bias towards distributions originating from samples with m_t = 172.5 GeV for both models
Leistungsfähigkeit von luftporenhaltigem Beton mit rezykliertem Betongranulat unter anspruchsvollen Umgebungsbedingungen
Get PDFDie zunehmende Erschöpfung der natürlichen Ressourcen und die mit der Rohstoffgewinnung verbundene Umweltbelastung treiben die Suche nach nachhaltigen Alternativen im Bausektor voran. Rezykliertes Betongranulat (RCA), das aus Betonabbruch gewonnen wird, stellt eine vielversprechende Alternative zu natürliche Zuschlagstoffe (NA) in der Betonherstellung dar. Bedenken hinsichtlich seines Einflusses auf die Betoneigenschaften, insbesondere unter extremen Umgebungsbedingungen, haben jedoch seine Verwendung auf nachrangige Anwendungen beschränkt. Diese Arbeit untersucht die Leistungsfähigkeit von B7-Beton (Expositionsklassen XC4, XW2, XD3, XF4, XA1L) unter Verwendung unterschiedlicher Anteile von vorgesättigtem RCA mit geringen Verunreinigungen. Ziel der Studie ist es, die Auswirkungen des RCA-Gehalts auf die physikalischen Eigenschaften von Frischbeton sowie auf die mechanischen Eigenschaften und die Dauerhaftigkeit von ausgehärtetem Beton zu bewerten. Durch den Einsatz eines zweistufigen Mischverfahrens (TSMA) wurden eine Abschwächung der negativen Auswirkungen von RCA auf die Verarbeitbarkeit und Festigkeit erreicht. Die experimentellen Untersuchungen umfassten Messungen der Verarbeitbarkeit, des Luftgehalts, der Dichte, der Druckfestigkeit und der Dauerhaftigkeitsmerkmale wie Chloridwiderstand, Frost-Tausalz-Beständigkeit, Wassereindringtiefe und Karbonatisierungsbeständigkeit. Zusätzlich wurde eine Luftporenanalyse durchgeführt, um die für die Frost-Tausalz-Beständigkeit relevanten mikrostrukturellen Poreneigenschaften zu charakterisieren. Die Zugabe von RCA verringerte die Verarbeitbarkeit von Frischbeton geringfügig, während die mechanischen Eigenschaften befriedigend waren. In Bezug auf die Dauerhaftigkeit nahmen der Chloridgehalt und die Karbonatisierungstiefe mit dem RCA-Gehalt aufgrund der höheren Porosität der rezyklierten Zuschlagstoffe zu. Die kritischste Einschränkung wurde bei der Frost-Tausalz-Beständigkeit beobachtet, die mit einer unzureichenden Mikroporenstruktur im RCA zusammenhängt. Insgesamt kann ordnungsgemäß vorbehandeltes und qualitätsgeprüftes RCA zur Herstellung von Beton mit hohen mechanischen Anforderungen verwendet werden; seine Dauerhaftigkeit unter anspruchsvollen Umgebungsbedingungen bleibt jedoch die wesentliche Herausforderung.The increasing depletion of natural resources and the environmental impacts associated with raw material extraction drive the search for sustainable alternatives in the construction sector. Recycled concrete aggregate (RCA), obtained from demolished concrete structures, presents a promising substitute for natural aggregates (NA) in concrete production. However, concerns regarding its influence on concrete performance, particularly under severe exposure conditions, have limited its use to non-structural applications. This thesis investigates the performance of B7 concrete (exposure classes XC4, XW2, XD3, XF4, XA1L) incorporating varying proportions of pre-saturated RCA of high purity. The study aims to evaluate the effects of RCA content on the physical properties of fresh concrete, as well as on the mechanical and the durability performance of hardened concrete. The two-stage mixing approach (TSMA) was employed to optimise the use of pre-saturated RCA and mitigate its adverse effects on workability and strength. Experimental testing included measurements of workability, air content, density, compressive strength, and durability indicators such as chloride penetration resistance, freeze–thaw resistance with de-icing salts, water penetration depth, and carbonation resistance. Additionally, an air void analysis was carried out to assess the microstructural characteristics relevant to the freeze–thaw performance. The inclusion of RCA slightly lowered fresh concrete workability, while the mechanical performance remained adequate for structural applications. In terms of durability, chloride ingress and carbonation depth increased with RCA content due to the higher porosity of recycled aggregates. The most critical limitation was observed in freeze–thaw resistance, linked to an insufficient micropore structure in the RCA. Overall, properly pre-treated and quality-controlled RCA can be used to produce concrete with adequate mechanical performance; however, its durability under severe environmental conditions remains the main restriction
Barriers and gaps in the implementation of close-range remote sensing technologies in forestry
No full textClose-range remote sensing (CRRS) technologies are increasingly used in forestry, but there is a lack of awareness of the challenges, needs and expectations of both service providers and end users. We used a customised online questionnaire to interview professionals in the field, recruited through direct (existing networks) and indirect channels (social media). The main barriers we identified include the cost of equipment, the complexity of data processing workflows and insufficient access to specialised training. Our findings emphasise the need for interdisciplinary collaboration, the development of more intuitive and user-friendly tools and the expansion of specialised training programmes. The results of the questionnaire suggest that stronger partnerships between industry and academia should be encouraged to drive innovation and knowledge sharing. In addition, the development of standardised protocols for CRRS applications and the creation of accessible educational resources proved essential to support both novice and experienced users. Scientific conferences are the most important platform to gather all stakeholders in one place, and have underutilised potential to narrow the gap between theory and application. The recommendations we have made aim to facilitate the widespread adoption and efficient utilisation of CRRS technologies in practical forestry
Integrating AMR surveillance into wastewater monitoring systems in 2025: a position on the implementation of Article 17 of the Urban Wastewater Treatment Directive (UWWTD)
No full textThe recast Urban Wastewater Treatment Directive (UWWTD) calls for monitoring antimicrobial resistance (AMR) in wastewater of large European agglomerations (≥ 100,000 person equivalents). Guidance on scope and methods is currently in development. Two European Joint Actions share a goal to harmonise procedures and indicators: the European Union (EU)-Wastewater Integrated Surveillance for Public Health (EU-WISH), aiming to strengthen wastewater-based surveillance (WBS) for public health and the EU-Joint Action Antimicrobial Resistance and Healthcare Associated Infections (EU-JAMRAI) 2, providing among others, approaches for environmental surveillance of AMR. An EU-WISH survey in 2024, mapping WBS AMR-related activities across Europe, revealed that of 27 countries surveyed, 11 had an operative AMR WBS system and mainly employed WBS to determine AMR trends, primarily through culture-based analyses, in-depth characterisation of specific bacteria, and quantitative PCR for specific resistance genes. Occasionally metagenomics was used. We argue that prioritising AMR WBS targets should consider the intended objectives of surveillance, which could include uncovering AMR trends and emerging AMR determinants in humans, the assessment of antimicrobial/AMR environmental release, and wastewater treatment efficiency. Targets should be assessed for their public health relevance and the usefulness of complementary information they provide, while integrating measurability, resource efficiency, and expertise from different One Health domains