Christian Ludwig

Biographie

2005 - today: Adjunct Professor at EPFL in the field of Solid Waste Treatment and head of the Chemical Processes and Materials research group (CPM) at Paul Scherrer Institute (PSI). Joint EPFL-PSI Professorship on Solid Waste Treatment. 2000 - today: Head, Group of Chemical Processes and Materials (CPM) at Paul Scherrer Institut (PSI). In 2009 the LEM unit was closed and the CPM group is now affiliated to the Bioenergy and Catalysis Laboratory (LBK) of the Energy and Environment Research Division (ENE). Since June 2002 permanent position ("tenure"). 1997 - 1999: Senior Scientist. Paul Scherrer Institut (PSI), General Energy Research Department, Element Cycles Section. 1995 - 1997: Research Fellow. Swiss Federal Institute for Environmental Science and Technology (EAWAG), Department of Resource and Waste Management. 1993 - 1995: Post-doc Fellow. University of California Davis, Department of Land, Air, and Water Resources (LAWR). 1990 - 1993: PhD Student. University of Berne, Department of Inorganic, Analytical, and Physical Chemistry. 1989 - 1990: Master Student. University of Berne, Department of Inorganic, Analytical, and Physical Chemistry.

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https://people.epfl.ch/christian.ludwig?lang=fr

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The soluble fraction of atmospheric transition metals is particularly associated with health effects such as reactive oxygen species compared to total metals. However, direct measurements of the soluble fraction are restricted to sampling and detection units in sequence burdened with a compromise between time resolution and system bulkiness. Here, we propose the concept of aerosol-into-liquid capture and detection, which allowed one-step particle capture and detection via the Janus-membrane electrode at the gas–liquid interface, enabling active enrichment and enhanced mass transport of metal ions. The integrated aerodynamic/electrochemical system was capable of capturing airborne particles with a cutoff size down to 50 nm and detecting Pb(II) with a limit of detection of 95.7 ng. The proposed concept can pave the way for cost-effective and miniaturized systems, for the capture and detection of airborne soluble metals in air quality monitoring, especially for abrupt air pollution events with high airborne metal concentrations (e.g., wildfires and fireworks).

2023

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Surfactant-based enrichment of rare earth elements from NdFeB magnet e-waste: Optimisation of cloud formation and rare earths extraction

Christian Ludwig, Ajay Bhagwan Patil, Rudolf Paul Wilhelm Jozef Struis, Mohamed Tarik

Appropriate waste and resource management are essential for a sustainable circular economy with reduced environmental impact. With critical resources, e-waste may serve as indirect raw material. For example, with NdFeB permanent magnets, Neodymium (Nd) and the co-present Dysprosium (Dy) are critical rare earth elements (REEs). However, there exists no economically viable technology for recycling them from electronic waste (e-waste). Here, a method is presented based on cloud point extraction (CPE). The work involves basic complexation chemistry in a cloud medium with pure REE salts, as well as, with real NdFeB-magnets (nearly 28% REE content by weight) from an old hard disk drive (5.2 g magnet in a 375 g HDD). High extraction efficiency (>95%) was achieved for each REE targeted (Nd, Dy, Praseodymium (Pr)). With the magnet waste, the cloud phase did hardly contain any Nickel (Ni), Cobalt (Co), or Boron (B), but some Aluminium (Al) and Iron (Fe). Dynamic light scattering results indicated aggregation of ligand-surfactant micelles with the cloud phase. The preconcentrated products can be used for new Nd magnet manufacturing or further enriched using established transition metal removal techniques. Reuse of solvent, low chemical inventory demand, and using non-inflammable, non-volatile organic extractants promise safe large-scale operation, low process costs, and less environmental impact than using hydrometallurgical methods used with urban or primary mining.

2023

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A long-term study on structural changes in calcium aluminate silicate hydrates

Sonya Barzgar, Barbara Lothenbach, Christian Ludwig, Mohamed Tarik, Yu Yan

Production of blended cements in which Portland cement is combined with supplementary cementitious materials (SCM) is an effective strategy for reducing the CO2 emissions during cement manufacturing and achieving sustainable concrete production. However, the high Al2O3 and SiO2 contents of SCM change the chemical composition of the main hydration product, calcium aluminate silicate hydrate (C-A-S-H). Herein, spectroscopic and structural data for C-A-S-H gels are reported in a large range of equilibration times from 3 months up to 2 years and Al/Si molar ratios from 0.001 to 0.2. The Al-27 MAS NMR spectroscopy and thermogravimetric analysis indicate that in addition to the C-A-S-H phase, secondary phases such as stratlingite, katoite, Al(OH)(3) and calcium aluminate hydrate are present at Al/Si >= 0.03 limiting the uptake of Al in C-A-S-H. More secondary phases are present at higher Al concentrations; their content decreases with equilibration time while more Al is taken up in the C-A-S-H phase. At low Al contents, Al concentrations decrease strongly with time indicating a slow equilibration, in contrast to high Al contents where a clear change in Al concentrations over time was not observed indicating that the equilibrium has been reached faster. The Al-27 NMR studies show that tetrahedrally coordinated Al is incorporated in C-A-S-H and its amount increases with the amount of Al present in the solution.

SPRINGER2022

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