  Single phase, uniform size (~9 nm) Cobalt Ferrite (CFO) nanoparticles have
been synthesized by hydrothermal synthesis using oleic acid as a surfactant.
The as synthesized oleic acid coated CFO (OA-CFO) nanoparticles were well
dispersible in nonpolar solvents but not dispersible in water. The OA-CFO
nanoparticles have been successfully transformed to highly water dispersible
citric acid coated CFO (CA-CFO) nanoparticles using a novel single step ligand
exchange process by mechanochemical milling, in which small chain citric acid
molecules replace the original large chain oleic acid molecules available on
CFO nanoparticles. The contact angle measurement shows that OA-CFO
nanoparticles are hydrophobic whereas CA-CFO nanoparticles are superhydrophilic
in nature. The potentiality of as synthesized OA-CFO and mechanochemically
transformed CA-CFO nanoparticles for the demulsification of highly stabilized
water-in-oil and oil-in-water emulsions has been demonstrated.
