Novel hydrophobic vaterite particles for oil removal and recovery

Abstract

This paper describes a simple, cost-effective and ‘green’ route for the synthesis of highly hydrophobic and oleophilic CaCO₃ particles in the absence of any solvent and at ambient temperature conditions. Oleic acid as an additive promotes polymorph selectivity from calcite to vaterite with ‘flaky-floret’ like morphology with concomitant changes in its surface wettability from hydrophilic to hydrophobic. The gradual polymorph transformation from pure calcite to almost pure vaterite coupled with changes in morphology induced by increasing concentration of oleic acid have been systematically studied by powder X-ray diffraction and scanning electron microscopy techniques. Fourier transform infrared spectroscopy and thermo-gravimetric analyses establish the presence of Ca-oleate soap in the samples which leads to surface hydrophobicity. Water and oil contact angle measurements establish the extent of hydrophobicity and oleophilicity of the CaCO₃ samples. The synthesized materials have been successfully employed for selectively mopping up a variety of oils like sunflower oil, engine oil and diesel from the surface of water. This has been established in its powder form as well as in the format of a ‘spill-pouch’. In addition, the material has been used to fabricate functionalized polyurethane foam which mops up oil spillage from water and renders easy recovery of oil.