Enhanced basalt weathering for CO2 sequestration: Phase dissolution rates, carbon sequestration mechanisms and practical application.

Enhanced rock weathering, particularly using basalt, is a promising method for atmospheric CO2 reduction. However, the complex mineral phases of basalt and challenges in post-application soil separation hinder experimental determination of phase-specific dissolution rates in real-world settings. This study innovatively combines magnetic separation and XRD-Rietveld full-spectrum fitting to isolate basalt from soil and quantify post-weathering phase changes. The normalized dissolution rates of labradorite, augite, hortonolite, ilmenite, and amorphous phases in soil were determined as 4.33 × 10-6, 3.05 × 10-5, 3.01 × 10-5, 2.48 × 10-5, and 1.73 × 10-6 g m-2 d-1, respectively, with a carbon sequestration rate of 9.728 t ha-1 a-1. Weathering dynamics revealed early-stage decomposition of augite, hortonolite, and amorphous phases, while labradorite degraded predominantly in later stages. Dissolved cations either adhered to basalt particles, forming secondary phases (e.g., carbonates), or entered soil through adsorption, mineral formation, or leaching. Key weathering products included zeolite, hornblende, and serpentine. Furthermore, a comprehensive feasibility assessment for China highlighted practical considerations for carbon sequestration, land use, water demand, cost, and energy consumption. These findings underscore the critical role of enhanced basalt weathering in climate change mitigation strategies.