Task 4 – Adsorption and activation under hydrothermal conditions
Task leader Isabelle Daniel
Participants LGL LRS PhENIx LIEC JHU
Evaluation of biomolecule condensation reactions under hydrothermal conditions
This includes the dependency of the reactions on pressure, temperature, W/R ratio and dissolved H2, the reversibility of condensation and adsorption and should lead to the determination of robust thermodynamic parameters for those reactions.
Description of work
Adsorption isotherms will be measured according to the mineral-molecule plan described in table 1. Experiments will be performed in the hydrothermal vessels that have very recently become availabl and measurements will be done using ex situ UV absorption, up to 100 MPa and 200°C. Adsorbed biomolecules and mineral surfaces will also be characterized after hydrothermal reaction using microRaman and micro-IR spectroscopies to investigate adsorption mechanisms as viewed by changes in bonds strength in the biomolecule, XPS, AFM or STXM to characterize the detailed physical chemistry at the surface of the clay minerals upon adsorption. As Near-Ambient Presssure XPS becomes available at the French synchrotron facility SOLEIL for instance, those characterizations could also be performed in presence of water if required.
After desorption, the newly formed biomolecules will be identified in solution by MALDI-TOF spectroscopy.
The most interesting systems will also be investigated in situ at HP-HT the LGL, thanks to the diamond anvil cells that can be coupled to the microRaman spectrometers.
Role of participants
I. Daniel: task leader, coordination with tasks 2 and 3; design of the experiments, in situ spectroscopy under hydrothermal conditions
H. Cardon: in charge of the hydrothermal vessels and training the new high-pressure users
U. Pedreira-Segade: polymerization of amino- and nucleic acids under hydrothermal conditions and adsorption on iron and magnesium rich phyllosilicates
Postdoctoral fellow: adsorption on iron oxides or sulfides
L. Michot (PhENIx): Spectroscopic characterization (NAP XPS, STXM)
Risks and contingency plan
- Although we have planned for hydrothermal vessel volumes that can accommodate a series of 1ml capsules for experiments in absolutely similar conditions, this volume might be too small for some further analysis like NMR. If necessary, larger autoclaves are available at the LGL (up to 100 ml).
- If the hydrothermal conditions alter mineral characteristics by dissolution for instance, we shall work under more moderate hydrothermal conditions. However, this is unlikely to occur in the (P,T) range considered as clays are used for nuclear waste repository and their stability under extreme conditions has been studied in great details (e.g., Guillaume et al., 2004).
- If we observe that the quenching technique is not fast enough to prevent desorption, we shall improve the quenching rates by adding fluid circulation, or work in situ as much as possible, install a sampling system such as the sampling system that will connect our large autoclave to a GC-MS.
Deliverables / milestones
D4.1 – adsorption isotherms under hydrothermal conditions
D4.2 – Identification of adsorption mechanisms and comparison with the results of task 3
D4.3 – effect of hydrothermal conditions on condensation reactions
M4.1 – delivery and installation of the new hydrothermal reactors (m6)
M4.2 – effect of hydrothermal conditions on the condensation of amino acids (m12)
M4.3 – effect of hydrothermal conditions on the adsorption of nucleotides on Fe-Mg phyllosilicates (m18)
M4.4 – Effect of hydrothermal conditions on the condensation of nucleotides (m24)
M4.5 – effect of hydrothermal conditions on the adsorption of nucleotides on iron oxides or sulfides (m36)
Guillaume, D., Neaman, A., Cathelineau, M., Mosser-Ruck, R., Peiffert, C., Abelmoula, M., Dubessy, J., Villiéras, F. and Michau, N. (2004) Experimental study of the transformation of smectite at 80 and 300°C in the presence of Fe oxides, Clay Minerals, 39, 17-34.