Lauric acid triggered in situ surface modification and phase selectivity of calcium carbonate: its application as an oil sorbent

Abstract

This paper demonstrates a novel method for the in situ surface modification (from hydrophilic to hydrophobic/oleophilic) and phase selectivity of aragonite over calcite, induced by molten lauric acid, through a one-step, solvent-free route. The final product is extremely hydrophobic and is easy to isolate. While in the absence of lauric acid, formation of hydrophilic rhombohedral calcite particles is observed, lauric acid as an additive leads to the formation of hydrophobic CaCO₃ particles comprising of rosette-shaped aragonite as the predominant phase. In addition, increase in concentration of lauric acid increases the water contact angle gradually to 140°. Powder X-ray diffraction and scanning electron microscopy confirm the phase and morphology of different CaCO₃ particles, respectively. Fourier transform infrared spectroscopy and thermo-gravimetric analysis establish the presence of calcium laurate in the hydrophobic CaCO₃ samples. Water contact angle measurements demonstrate the extent of surface hydrophobicity. Moreover, the hydrophobic CaCO₃ particles show selective absorption of oil from an oil–water mixture. Thus, the current method of in situ synthesis of hydrophobic CaCO₃ particles may provide an environmentally friendly, cost-efficient technology to clean up catastrophic oil spills.