Synergized Effects of Amino Acids and NaCl to Enhance Silicate Mineral Dissolution in Aqueous Environments for Efficient Atmospheric CO2 Removal

Abstract

Enhanced weathering of silicate minerals is a promising approach for reducing atmospheric CO₂ levels by increasing the aquatic pH and facilitating CO₂ dissolution. However, the slow and unsustainable dissolution of silicate minerals in natural environments remains a challenge. This study proposed a new CO₂ capture system that uses the combined effect of amino acids and NaCl to promote mineral dissolution, and its characteristics were investigated experimentally. The results showed that amino acids are promising for enhancing the near-congruent dissolution of silicate minerals, specifically at weakly alkaline pHs (i.e., 8), implying the long-term effectiveness of the system. Comprehensive findings revealed a 13-fold increase in the level of Ca extraction from wollastonite (CaSiO₃) in the presence of 0.1 mol/L glutamic acid (Glu) over 72 h at 35 °C and a 22-fold increase in the level of CO₂ capture efficiency. However, Fe-bearing minerals, such as olivine ((Mg,Fe)₂SiO₄), are unsuitable for application, because the enhanced Fe extraction results in the generation of Fe hydroxide, which lowers pH and consequently reduces CO₂ capture efficiency. Moreover, NaCl facilitates the release of the Ca–Glu complex from mineral surfaces into the solution, synergizing amino acids to promote mineral dissolution. A semiclosed application system is proposed, with future studies needed to assess ecological impacts and ensure long-term sustainability.