Carbon Capture Efficiency of Mechanically Activated Australian Halloysite-Rich Kaolin with Varying Iron Impurities and Its Potential Reuse for Removing Dyes from Water
2025
Siavash Davoodi | Bhabananda Biswas | Ravi Naidu
Sustainable strategies are required to mitigate elevated atmospheric CO2 levels. Achieving that by adsorption, especially by using clay-based adsorbents, drew attention. These are even more promising when these adsorbents are obtained by low-cost modifications. This study evaluates the effect of ball milling on the carbon capture performance of Australian halloysite nanotube (HNT)-rich kaolin samples: one without iron impurities (Hal) and the other with iron impurities (HalFe). The iron was mainly nested within illite/mica minerals in HalFe. Samples were ball-milled for 30 and 60 min, and their CO2 sorption was assessed at various pressures and temperatures. Crystallography, electronic microscopy, and surface area and charge characterization revealed reduced length and increased width of tubular structure following ball milling, leading to higher specific surface area without compromising crystallinity. CO2 sorption of Hal increased 14% at 20 bar and 15 °:C after 60 min milling, with a ~300% rise at near-atmospheric pressures. Conversely, milling negatively affected CO2 sorption of HalFe, likely due to iron/illite-mica-related damage during milling. Crystallography, infrared, and thermographic analyses revealed physisorption as the primary sorption mechanism. Since direct disposal of CO2-laden materials is against sustainability principles, these materials were tested for methylene blue removal from aqueous solutions, achieving ~83% (Hal) and ~91% (HalFe) removal efficiencies. This highlights HNTs-rich kaolin clays&rsquo: valorization potential for carbon capture and utilization (CCU).
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