Scalable Synthesis of Aragonite Whiskers Under Higher Initial Ca2+ Concentrations

Calcium carbonate (CaCO3) whiskers are promising materials for the high-value utilization of calcium-based resources. Here, aragonite whiskers were synthesized at a carbonation temperature of 90 °C using carbide slag ammonium leachate as the calcium source and CO2 as the precipitant. The effects of control agents, carbonation temperature, Ca2+ solution feeding rate, CO2 flow rate, and stirring speed on whisker morphology and aspect ratio were systematically investigated. Characterization via SEM and XRD revealed that the optimal conditions—carbonation temperature of 90 °C, Ca2+ feeding rate of 1.2 mL∙min−1, ethanol addition of 2 mL, CO2 flow rate of 150 mL∙min−1, and stirring speed of 300 rpm—yielded uniform CaCO3 whiskers with an average length of ~10 μm, an aspect ratio of ~24, and an aragonite purity of 99.42%. TEM confirmed that the whiskers are single crystals growing preferentially along the [001] direction. Hydroxyl groups were found to suppress lateral growth on the (200) facet, favoring elongation along the c-axis and enabling high-aspect-ratio whisker formation. These findings provide useful guidance for the scalable synthesis and industrial application of aragonite whiskers.