Lenz, Markus
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Life cycle assessment of a novel production route for scandium recovery from bauxite residues
2024, Hengevoss, Dirk, Misev, Victor, Feigl, Viktória, Fekete-Kertész, Ildikó, Molnár, Mónika, Balomenos, Efthymios, Davris, Panagiotis, Hugi, Christoph, Lenz, Markus
Scandium (Sc) has various technological applications, but the concentrations of Sc in ores are low. Both, the mining of low concentrated Sc and the production of industrial-grade Sc are a heavy burden on the environment. Bauxite residue (BR) from alumina production represents one of the major sources of Sc in Europe (Ochsenkühn-Petropulu et al., 1994). The goal of this study is to assess the environmental impacts from cradle to gate of a novel production route developed in the Scandium Aluminium Europe project (SCALE) to extract Sc at concentrations <100 ppm from BR, to concentrate and upgrade it to pure ScF3 and Sc2O3 and ultimately to refine it to an aluminium scandium master alloy with 2 % Sc mass fraction (AlSc2 %). Results show that the global warming potential (GWP), measured in CO2-eq per kg Sc2O3, generated with the novel route is about half the GWP of the state-of-the-art Sc2O3 production from rare earth tailings when applying equal allocation principles. The initial process step to dissolve BR and extract Sc consumes elevated amounts of acid and energy and is responsible for at least 80 % of the route’s total environmental impact. The amount of the generated filter cake (FC) is equal to the amount of the BR input and is a potential resource for cement clinker production. The ecotoxicological study indicates that both FC and BR are slightly ecotoxic.
Environmental selenium volatilization is possibly conferred by promiscuous reactions of the sulfur metabolism
2023, Liu, Ying, Schäffer, Andreas, Martinez, Mathieu, Lenz, Markus
Selenium deficiency affects many million people worldwide and volatilization of biogenically methylated selenium species to the atmosphere may limit Se entering the food chain. However, there is very little systematic data on volatilization at nanomolar concentrations prevalent in pristine natural environments. Pseudomonas tolaasii cultures efficiently methylated Se at these concentrations. Nearly perfect linear correlations between the spiked Se concentrations and Dimethylselenide, Dimethyldiselenide, Dimethylselenylsulfide and 2-hydroxy-3-(methylselanyl)propanoic acid were observed up to 80 nM. The efficiency of methylation increased linearly with increasing initial Se concentration, arguing that the enzymes involved are not constitutive, but methylation proceeds promiscuously via pathways of S methylation. From the ratio of all methylated Se and S species, one can conclude that between 0.30% and 3.48% of atoms were Se promiscuously methylated at such low concentrations. At concentrations higher than 640 nM (∼50 μg/L) a steep increase in methylation and volatilization was observed, which suggested the induction of specific enzymes. Promiscuous methylation at low environmental concentrations calls into question that view that methylated Se in the atmosphere is a result of a purposeful Se metabolism serving detoxification. Rather, the concentrations of methylated Se in the atmosphere may be “coincidental” i.e., determined by the activity of S cycling microorganisms. Further, a steep increase in methylation efficiency when surpassing a certain threshold concentration (here ∼50 μg/L) calls into question that natural methylation can be estimated from high Se spikes in laboratory systems, yet highlights the possibility of using bacterial methylation as an effective remediation strategy for media higher concentrated in Se. © 2023 The Authors
Nanofiltration-enhanced solvent extraction of scandium from TiO acid waste
2022-04-27, Yagmurlu, Bengi, Huang, Danyu, von Arx, Oliver, Dittrich, Carsten, Constable, Edwin, Friedrich, Bernd, Hedwig, Sebastian, Lenz, Markus
Scandium is a critical raw material with a technological potential to reduce transportation costs and CO2 emissions. However, global supply and market adoption are crucially impaired by the lack of high-grade Sc ores and recovery strategies. A tandem nanofiltration solvent extraction route is demonstrated to enable effective Sc recovery from real-world acid waste from the chloride TiO2 production route. The process involving several filtration stages, solvent extraction, and precipitation was optimized, ultimately producing >97% pure (NH4)3ScF6.
Sulfur amino acid status controls selenium methylation in pseudomonas tolaasii. Identification of a novel metabolite from promiscuous enzyme reactions
2021-05-26, Liu, Ying, Hedwig, Sebastian, Schäffer, Andreas, Lenz, Markus, Martinez, Mathieu
Selenium (Se) deficiency affects many millions of people worldwide, and the volatilization of methylated Se species to the atmosphere may prevent Se from entering the food chain. Despite the extent of Se deficiency, little is known about fluxes in volatile Se species and their temporal and spatial variation in the environment, giving rise to uncertainty in atmospheric transport models. To systematically determine fluxes, one can rely on laboratory microcosm experiments to quantify Se volatilization in different conditions. Here, it is demonstrated that the sulfur (S) status of bacteria crucially determines the amount of Se volatilized. Solid-phase microextraction gas chromatography mass spectrometry showed that Pseudomonas tolaasii efficiently and rapidly (92% in 18 h) volatilized Se to dimethyl diselenide and dimethyl selenyl sulfide through promiscuous enzymatic reactions with the S metabolism. However, when the cells were supplemented with cystine (but not methionine), a major proportion of the Se (∼48%) was channeled to thus-far-unknown, nonvolatile Se compounds at the expense of the previously formed dimethyl diselenide and dimethyl selenyl sulfide (accounting for <4% of total Se). Ion chromatography and solid-phase extraction were used to isolate unknowns, and electrospray ionization ion trap mass spectrometry, electrospray ionization quadrupole time-of-flight mass spectrometry, and microprobe nuclear magnetic resonance spectrometry were used to identify the major unknown as a novel Se metabolite, 2-hydroxy-3-(methylselanyl)propanoic acid. Environmental S concentrations often exceed Se concentrations by orders of magnitude. This suggests that in fact S status may be a major control of selenium fluxes to the atmosphere. IMPORTANCE Volatilization from soil to the atmosphere is a major driver for Se deficiency. “Bottom-up” models for atmospheric Se transport are based on laboratory experiments quantifying volatile Se compounds. The high Se and low S concentrations in such studies poorly represent the environment. Here, we show that S amino acid status has in fact a decisive effect on the production of volatile Se species in Pseudomonas tolaasii. When the strain was supplemented with S amino acids, a major proportion of the Se was channeled to thus-far-unknown, nonvolatile Se compounds at the expense of volatile compounds. This hierarchical control of the microbial S amino acid status on Se cycling has been thus far neglected. Understanding these interactions—if they occur in the environment—will help to improve atmospheric Se models and thus predict drivers of Se deficiency.
Ecotoxicity attenuation by acid-resistant nanofiltration in scandium recovery from TiO2 production waste
2023, Fekete-Kertész, Ildikó, Stirling, Tamás, Vaszita, Emese, Berkl, Zsófia, Farkas, Éva, Hedwig, Sebastian, Remmen, Kirsten, Lenz, Markus, Molnár, Mónika, Feigl, Viktória
Magnesium sensing via LFA-1 regulates CD8+ T cell effector function
2022, Lötscher, Jonas, Martí i Líndez, Adrià-Arnau, Kirchhammer, Nicole, Cribioli, Elisabetta, Giordano Attianese, Greta Maria Paola, Trefny, Marcel P., Rothschild, Sacha I., Strati, Paolo, Künzli, Marco, Lotter, Claudia, Schenk, Susanne H., Dehio, Philippe, Löliger, Jordan, Litzler, Ludivine, Schreiner, David, Koch, Victoria, Page, Nicolas, Lee, Dahye, Grählert, Jasmin, Kuzmin, Dmitry, Burgener, Anne-Valérie, Merkler, Doron, Pless, Miklos, Balmer, Maria L., Reith, Walter, Huwyler, Jörg, Irving, Melita, King, Carolyn G., Zippelius, Alfred, Hess, Christoph, Lenz, Markus
The relevance of extracellular magnesium in cellular immunity remains largely unknown. Here, we show that the co-stimulatory cell-surface molecule LFA-1 requires magnesium to adopt its active conformation on CD8+ T cells, thereby augmenting calcium flux, signal transduction, metabolic reprogramming, immune synapse formation, and, as a consequence, specific cytotoxicity. Accordingly, magnesium-sufficiency sensed via LFA-1 translated to the superior performance of pathogen- and tumor-specific T cells, enhanced effectiveness of bi-specific T cell engaging antibodies, and improved CAR T cell function. Clinically, low serum magnesium levels were associated with more rapid disease progression and shorter overall survival in CAR T cell and immune checkpoint antibody-treated patients. LFA-1 thus directly incorporates information on the composition of the microenvironment as a determinant of outside-in signaling activity. These findings conceptually link co-stimulation and nutrient sensing and point to the magnesium-LFA-1 axis as a therapeutically amenable biologic system.
Organic solvent free PbI2 recycling from perovskite solar cells using hot water
2023-04-05, Schmidt, Felix, Amrein, Meret, Hedwig, Sebastian, Kober-Czerny, Manuel, Paracchino, Adriana, Holappa, Ville, Suhonen, Riikka, Schäffer, Andreas, Constable, Edwin C., Snaith, Henry J., Lenz, Markus
Perovskite solar cells represent an emerging and highly promising renewable energy technology. However, the most efficient perovskite solar cells critically depend on the use of lead. This represents a possible environmental concern potentially limiting the technologies’ commercialization. Here, we demonstrate a facile recycling process for PbI2, the most common lead-based precursor in perovskite absorber material. The process uses only hot water to effectively extract lead from synthetic precursor mixes, plastic- and glass-based perovskites (92.6 – 100% efficiency after two extractions). When the hot extractant is cooled, crystalline PbI2 in high purity (> 95.9%) precipitated with a high yield: from glass-based perovskites, the first cycle of extraction / precipitation was sufficient to recover 94.4 ± 5.6% of Pb, whereas a second cycle yielded another 10.0 ± 5.2% Pb, making the recovery quantitative. The solid extraction residue remaining is consequently deprived of metals and may thus be disposed as non-hazardous waste. Therefore, exploiting the highly temperature-dependent solubility of PbI2 in water provides a straightforward, easy to implement way to efficiently extract lead from PSC at the end-of-life and deposit the extraction residues in a cost-effective manner, mitigating the potential risk of lead leaching at the perovskites’ end-of-life.
Rapid sequestration of perovskite solar cell-derived lead in soil
2022-08, Schmidt, Felix, Ledermann, Luca, Schäffer, Andreas, Snaith, Henry J., Lenz, Markus
Efficient and stable perovskite solar cells rely on the use of Pb species potentially challenging the technologies’ commercialisation. In this study, the fate of Pb derived from two common perovskite precursors is compared to cationic lead in soil-water microcosm experiments under various biogeochemical conditions. The rapid and efficient removal of Pb from the aqueous phase is demonstrated by inductively coupled plasma mass spectrometry. Sequential soil extraction results reveal that a substantial amount of Pb is associated with immobile fractions, whereas a minor proportion of Pb may become available again in the long term, when oxygen is depleted (e.g. during water logging). X-ray absorption spectroscopy results reveal that the sorption of Pb on mineral phases represents the most likely sequestration mechanism. The obtained results suggest that the availability of leached Pb from perovskite solar cells is naturally limited in soils and that its adverse effects on soil biota are possibly negligible in oxic soils. All three Pb sources used behaved very similar in the experiments, wherefore we conclude that perovskite derived Pb will have a similar fate compared to cationic Pb, so that established risk assessment considerations for Pb remain legitimate.
Recovery of scandium from acidic waste solutions by means of polymer inclusion membranes
2022, Hedwig, Sebastian, Kraus, Manuel, Amrein, Meret, Stiehm, Johannes, Constable, Edwin C., Lenz, Markus
Scandium is a raw material with properties that promise considerable potential for application in alloys to enable aviation fuel savings and as dopants for use in sustainable energy production using solid oxide fuel cells. Despite these attractive properties, scandium is rarely used due to its scarcity and unreliable supply. Therefore, new strategies for scandium recovery are of economic priority. In this study, polymer inclusion membranes (PIMs) consisting of PVDF-HFP, 2-NPOE and DEHPA, were optimised for selective scandium separation from real TiO2 production waste. With the optimised system, >60% of the scandium was recovered with high selectivity, resulting in scandium mole fraction at more than two orders of magnitude higher in the receiving phase than in the original waste. This suggests PIMs may be an effective way to recover scandium from bulk waste, thus easing the scarcity and insecurity that currently limit its bulk application.