Preparation of superhydrophobic nanocalcite crystals using Box–Behnken design

Abstract

Superhydrophobic nanocalcite crystals were prepared via an adjusted aqueous reaction of CaO, CO2 gas and sodium oleate. Box–Behnken design was used to optimize the preparation parameters such as CaO concentration, CO2 gas flow rate and surfactant concentration. The results revealed that the produced CaCO3 is indexed to the calcite phase. The crystallite size, particle size, morphology, hydrophobicity and surface charge of CaCO3 are significantly affected by changing the preparation parameters. The addition of sodium oleate helps in reducing the crystallite size from 101 nm to 48 nm, reducing the particle size from 1.5 μm length scalenohedral particles to 40 nm rhombohedral particles and modifying the properties of pure CaCO3 from highly hydrophilic to superhydrophobic. Keywords: Nanocalcite crystals, Bubbling carbonation, Box–Behnken design, Surface modification, Hydrophobicity, Particle surface charge