Transforming Single Domain Magnetic CoFe2O4 Nanoparticles from Hydrophobic to Hydrophilic By Novel Mechanochemical Ligand Exchange

TL;DR

This paper presents a novel mechanochemical ligand exchange method to convert hydrophobic oleic acid coated CoFe2O4 nanoparticles into water-dispersible, superhydrophilic citric acid coated nanoparticles, enhancing their application in emulsion demulsification.

Contribution

A new single-step mechanochemical process for transforming hydrophobic CFO nanoparticles into hydrophilic ones using citric acid ligand exchange.

Findings

OA-CFO nanoparticles are hydrophobic; CA-CFO are superhydrophilic.

Mechanochemical ligand exchange effectively replaces oleic acid with citric acid.

CA-CFO nanoparticles successfully demulsify stabilized water-in-oil and oil-in-water emulsions.

Abstract

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.