Demulsification of Oleic-Acid-Coated Magnetite Nanoparticles for Cyclohexane-in-Water Nanoemulsions

Abstract

Oleic acid (OA)-coated magnetite (Fe3O4) nanoparticles, denoted Fe3O4@OA, were synthesized by co-precipitation in the presence of varying contents of OA. The Fe3O4@OA nanoparticles were characterized by X-ray diffraction, transmission and scanning electron microscopies, Fourier transform infrared spectroscopy, thermogravimetric–differential thermogravimetric analyses, and vibrating sample magnetometry. Increasing the OA content during preparation resulted in an increase of the OA-coating amount (A O, in units of g of OA/g of Fe3O4) on the Fe3O4 surface, before reaching an equilibrium value. The resulting magnetic nanoparticles were nearly spherical with a size of ∼12–14 nm. OA molecules formed a single layer coating on the Fe3O4 surface. The A O and area occupied by a single OA molecule at saturation coating were estimated to be 0.11 g g–1 (1.22 mg m–2) and 0.37 nm2, respectively. The Fe3O4@OA nanoparticles were applied in the demulsification of a cyclohexane-in-water nanoemulsion, under an external magnetic field. The effects of A O, demulsifier dosage, pH, and electrolytes on the demulsification efficiency (E D) were investigated. The E D increased and then decreased with increasing A O, which was attributed to a change in wettability of the magnetic nanoparticles. A maximum E D of ∼98% was observed at a ∼90° contact angle between water and the magnetic nanoparticles. The E D was independent of pH and electrolyte (NaCl or CaCl2) concentration, under the studied conditions. The magnetic demulsifier exhibited excellent stability after reuse over 6 cycles. Fe3O4@OA nanoparticles are effective for oil–water multiphase separation and treating oily wastewater.

Stable Colloidal Suspension of Magnetic Nanoparticles for Applications in Life Sciences

“…These values are also slighter higher than the theoretically estimated ones found for the cases of magnetic or non-magnetic stirring during ferrophase coating. The results of this experimental study are concordant with those reported by other authors [7,16] that yielded single layer oleic acid magnetic nanoparticle systems with 10 nm and respectively 12-14 nm size. The MNP suspension response to electromagnetic field with frequency from 100 Hz to 1MHz (Fig.…”

Iron oxide nanoparticles decorated oleic acid for high colloidal stability

“…[12] Figures 4 shows the TGA curves of the OA-decorated MNPs samples. [15] As presented in Figure 4, all OA-decorated MNPs samples exhibited two prominent weight loss stages at temperature F I G U R E 3 Raman spectra of MNPs with different loading amount of OA F I G U R E 4 TGA curves of MNPs with different loading amount OA below 600°C. A slight weight loss at temperature below 100°C could be noticed for all of the tested OA-decorated MNPs samples.…”

“…The weight loss of MNPs at below 100°C was attributed to the water content. [15] According to Mahdavi, Ahmad, [16] synthesized MNPs were reduced from magnetite phase to iron (II) oxide (FeO) phase because Iron (II) oxide is thermodynamically stable at temperature above 570°C (Equation 1). For undecorated MNPs, a weight loss of 3.68% was observed at 100-600°C.…”

An investigation on simultaneous effects of several parameters on the demulsification efficiency of various crude oils

“…With the help from magnets placed under sample containers, the magnetic property of MT and the rate of demulsification were improved. MT was also recyclable and reusable after each demulsification process, reducing the cost of chemicals in practical applications in the petroleum industry . Furthermore, DE was studied by undertaking demulsification tests within and without the magnetic field emitted from outside magnets for all types of crude oils in the presence of 0.98, 0.99, and 1.01 ppm MT, respectively, at 38.2, 45.2, and 50.1 °C (optimum conditions of concentration and temperature).…”

“…During the test, the quality of the separated water is also estimated (e.g. clear, cloudy, or containing crude oil) …”