Oral Presentation Royal Australian Chemical Institute National Congress 2026

From atmosphere to stone: integrated direct air capture and mineralisation of CO2 utilising aqueous amino acid salt solutions (136918)

Sofia Lazareva 1 , Nouman Mirza 2 , Debra Fernandes 2 , Graeme Puxty 2 , Robert Bennett 3 , Sam Chen 1
  1. The University of Newcastle, Shortland, NSW, Australia
  2. CSIRO Energy, Mayfield West, NSW, Australia
  3. CSIRO Manufacturing, Clayton, VIC, Australia

Direct Air Capture (DAC) is a critical technology for mitigating rising atmospheric CO2, yet conventional amine-based absorbents suffer from high volatility, toxicity, and energy-intensive regeneration [1–3]. These issues can be solved by utilising amino acid (AA) salt solutions (more stable towards oxidation, non-volatile and biodegradable) in an integrated DAC – mineralisation process [4,5], where the CO2 loaded absorbents coming out of DAC’s absorber unit are regenerated through the mineralisation of absorbed CO2 using alkaline materials. However, the number of studies on the integrated DAC – mineralisation process employing AA salt solutions and the correlation between the structure of AAs with the outcomes of capture and mineralisation reaction is limited [6]. This work demonstrates an influence of steric hindrance in AAs on the performance of an integrated DAC – mineralisation process employing glycine, α- and β-alanine as precursors for AA salt solution-based DAC, and CaO and MgO as alkaline materials to induce mineralisation of absorbed CO2 and regenerate the absorbents.

The density and viscosity of these AA salt solutions were determined, their overall mass transfer coefficients (Kov) of CO2 absorption under DAC conditions were studied using a wetted wall column (WWC). After mineralisation of absorbed CO2 using MgO, the absorbents were studied for the impact on their Kov values in the wetted wall column, with the results indicating that they were partially regenerated. Using 13C NMR spectroscopy, the evolution of carbamate and (bi)carbonate species with the increase in CO2 loading in the absorbents was observed. These speciation profiles were directly correlated with the structure of amino acids and the kinetics of the subsequent mineralisation reaction with CaO and MgO. The progress of mineralisation reactions was monitored in real-time by collecting data about the pH, temperature, and the CO2 loading of the absorbents. The solid precipitates resulting from the mineralisation reaction were characterised using powder X-ray diffraction (PXRD) and Fourier transform infrared spectroscopy (FTIR) analyses, confirming the benefits of steric hindrance on the mineralisation outcomes. This work offers a non-toxic, potentially energy-efficient pathway for transforming atmospheric carbon dioxide into stable rock materials.

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