Enhanced weathering of lizardite-rich sand in seawater: effects of pH and CO₂ pressure on carbonate formation for climate change mitigation

Enhanced weathering (EW) of serpentinized peridotites is being investigated as a potential approach for ex situ CO₂ sequestration in both coastal and open-ocean environments. Previous studies on serpentine minerals have provided important insights into their geochemical reactivity, highlighting their preferential dissolution behavior and enhanced weathering potential under natural conditions. This study examines the CO₂ sequestration potential of lizardite-rich sand and evaluates the formation of hydrated and carbonated mineral phases under varying CO₂ conditions. Mineralogical analyses indicate the presence of aragonite, magnesite, and other secondary minerals associated with CO₂ uptake, suggesting successful carbonation. Changes in pH and dissolved inorganic carbon (DIC) point to differing geochemical dynamics under ambient and elevated CO₂ conditions, with acidification observed in both scenarios. While the findings support the feasibility of using lizardite-rich materials for EW-based carbon sequestration, the associated pH decline raises concern about potential ocean acidification. However, incorporating lime derived from industrial marble waste into sand presents a promising approach to mitigate both climate change and ocean acidification. This mixed sand offers dual environmental benefits by facilitating carbon mineralization and promoting the sustainable utilization of industrial by-products, thereby contributing to climate resilience and environmental sustainability. The results underscore the need for careful selection of rock types and operational conditions to ensure both carbon removal efficacy and environmental compatibility. Ongoing work aims to identify optimal materials for sustainable deployment in marine environments.