[S-CG46] New Insights of Fluid-Rock Interactions: From Surface to Deep Subduction Zone

[SCG46-P16] Natural chelating agents accelerate weathering of minerals in natural environments

*Jiajie Wang¹, Sena Kikuchi¹, Noriaki Watanabe¹, Noriyoshi Tsuchiya^1,2 (1.Graduate School of Environmental Studies, Tohoku University, Japan, 2.National Institute of Technology, Hachinohe College, Hachinohe, Japan)

Keywords:enhanced weathering, CO2 reduction, natural chelating agent, congruent dissolution

The enhanced weathering of silicate minerals has garnered significant attention for its potential in reducing atmospheric carbon dioxide (CO₂) and mitigating climate change. This is attributed to the fact that the dissolution processes of silicate minerals consume protons, leading to an increase in the alkalinity of the water body. Despite the promise of this method, the dissolution of silicate minerals in ambient environments is notably slow, emerging as a rate-controlling step for CO₂ reduction. Therefore, there is an urgent need for environmentally friendly approaches to accelerate mineral dissolution for CO₂ reduction. In recent years, the revelation of chelating agents' ability to promote mineral dissolution has been noteworthy. In recent years, the ability of chelating agents to promote mineral dissolution due to their ability to binding metal ions in solution or in mineral structure was revealed. Given that chelating agents are potentially widespread in the natural environment, a system for CO₂ reduction involves enhanced mineral dissolution using potential natural chelating agents was proposed, and the feasibility of this approach was verified through lab-scale dissolution experiments in this study.
The experimental results revealed that among various potential natural chelating agents, amino acids, specifically glutamic acid, demonstrated a strong ability to accelerate the dissolution of silicate minerals at a neutral pH, and the dissolution process tends to be congruent. This can be attributed to the presence of amine groups in amino acids, which facilitate the adsorption of amino acids on the mineral surface for effective metal extraction. Furthermore, it was observed that while the presence of natural chelating agents accelerates mineral dissolution under a variety of environmental conditions, Fe-bearing minerals (e.g., olivine) are not always suitable for use in CO₂ reduction systems. This is due to the generation of Fe(OH)₂ with the enhanced extraction of Fe from minerals, which leads to a decrease in pH and subsequent CO₂ adsorption reduction. In addition, this study revealed that the presence of NaCl assisted the chelating agent in approaching and leaving the minerals, thereby significantly augmenting the enhancement in mineral dissolution by the natural chelating agent, suggesting the potential application of the CO₂ reduction system to coastal seawater systems.