Synthesis, Weathering and Machine Learning Modeling of Nutrient-Doped Fast-Weathering Silicate Minerals for Carbon Capture, Utilization and Sequestration (CCUS)

Abstract

Mineral carbonation is a promising carbon capture, storage and utilization (CCUS) technology that has enormous potential for capturing atmospheric CO2 (a greenhouse gas) and converting it into environmentally stable products. Slow weathering of naturally occurring silicate minerals is a key challenge for mineral carbonation, as some minerals can take centuries to weather and convert leached calcium and magnesium cations into carbonates. Some silicates, such as akermanite and calcio-olivine minerals, have shown faster weathering capabilities. The present research investigated the synthesis process of nutrient-doped akermanite and calcio-olivine via solid-state sintering methodology and the weathering capabilities of synthesized minerals compared with those of naturally occurring silicate minerals. A machine learning model is developed to help forecast the weathering capabilities of silicate minerals for deployment. X-ray diffraction (XRD), scanning electron microscopy (SEM), scanning electron microscopy-energy-dispersive X-ray spectroscopy (SEM‒EDS), Brunauer–Emmett–Teller (BET), and inductively coupled plasma‒mass spectrometry (ICP-MS) were used to characterize and analyze the performance of the synthesized minerals. The synthesis conditions of akermanite and calcio-olivine were adapted from literature by tuning the temperature conditions for synthesizing these minerals, resulting in successful synthesis. SEM analysis helped elucidate the morphological characteristics of akermanite and calcio-olivine. During the sintering experiments, swelling of the calcio-olivine tablet was observed, which was confirmed by cracks in the fused calcio-olivine particles at one micrometer scale. The weathering experiments resulted in the release of calcium and magnesium cations, where fast-weathering silicate minerals resulted in faster release of alkaline earth metal cations, creating more opportunities for capturing atmospheric CO2. The ICP-MS results also revealed the release of potassium cations, confirming that nutrients take part in the weathering process. The release of micro-nutrients is relatively fast, which opens future research direction to investigate other methodologies of nutrient’s incorporation during the synthesis process. The machine learning modeling results indicated fast weathering of synthesized silicate minerals compared with naturally occurring silicates, where calcio-olivine provided relatively more CO2 sequestration than did akermanite. The results provide research insights and future research directions in the fast-weathering silicate mineral research area for the scientific community to fill potential knowledge gaps.