Persulfate–derived porous wollastonite granules for accelerated CO2 mineralization and suitability for aggregate applications

• Porous wollastonite-based granules were synthesized • The fresh granules exhibited good initial strength for pre–carbonation handling • Granules synthesized with 20% pore forming agent achieved the best carbonation • Granules exhibited good mechanical strength and lightweight as artificial aggregates • Esterified variant of granules were thermally and water stable Mineral carbonation technology is a promising solution for CO 2 capture and utilization. To achieve large scale application of the technology, the challenges related to CO 2 diffusion and passivation by carbonate precipitation must be overcome. In this work, we demonstrate a route to high volume CO 2 capture by granulation and carbonation using wollastonite, polyvinyl alcohol (pva) and potassium persulfate. The wollastonite powder was granulated with 10% pva solution, incorporating 10–100 wt% of granulation fluid of potassium persulfate as pore–forming agent. The utility of some granules was extended by esterification reaction in citric acid solution. The granules were carbonated in a pressured reactor (10 bar, 100 °C) and the influence of pore–forming amount on carbonate passivation and CO 2 diffusion was studied by thermogravimetry, optical, electron microscopy and N 2 adsorption. The experiments revealed that 20% persulfate produced highly porous granules with an interconnected pore structure that reduced carbonate passivation and captured the highest amount of CO 2 (44mol%). Comparatively, mix designs with 0, 10 and 100 wt% persulfate showed low carbonation due to poor CO 2 diffusion attributed to surface passivation by carbonates and sulfates. Additionally, pore structure and surface modelling using Frankel–Halsey–Hill (FHH) fractal analysis concludes that 20% persulfate in both fresh and esterified granules produced a less tortuous and uniform pore structure with high interconnectivity, aiding CO 2 diffusion within the granules which resulted in high amount of carbonation products while preventing passivation. After carbonation, the aggregates maintained high strength and light weight, confirming their high potential as a high-volume CO 2 negative artificial lightweight aggregate in construction.