Application of magnetic nanoparticles for the removal of oil from oil-in-water emulsion: Regeneration/reuse of spent particles

The recovery of oil from produced water (PW) is integral for minimizing energy resource loses and creating an appropriate treatment method for a sustainable environment. In this study, Fe3O4 magnetic nanoparticles (Fe-MNP) were synthesized using the combustion synthesis method (CSM) in the temperature range of 150 to 350 degrees C. The Fe-MNP were characterized using various analytical techniques and were used to recover oil from oil-inwater emulsion (O-in-W-emu) at various concentrations. The effects of the process parameters including, pH, oil concentration (C-oil), Fe-MNP dose (D-MNP), the surfactant concentration (C-sur) on the demulsification efficiency (%(eta dem)), and the percentage oil removal (%R-oil) were studied. Further, the re-usability of the assynthetized Fe-MNP were examined and reported. The as-synthetized Fe-MNP achieved a %(eta dem) >= 98% for C-oil in the range of 200-660 mg/L. Up to 98.6% of the %(eta dem) was attained for C-oil in the range from 0 to 800 mg/L using only a DMNP of 10 mg/L. A lower D-MNP of 5 mg/L recovered up to 55.6% of the oil, while increasing the D-MNP > 50 mg/L did not significantly affect the %(eta dem) nor the %(eta dem). The observed %(eta dem) at a pH of 4 and C-sur of 0.05 g/L was observed to be > 90 + 0.1% and decreased by either rising the pH to 7 or increasing the C-sur to 0.1 g/L. This change is due to the decrease in the emulsion stability and the formation of fine oil droplets. Stability and re-usability tests of the as-synthetized Fe-MNP exhibited an effective oil recovery of up to 90% after 7 cycles. The as-synthesized Fe-MNP demulsifier exhibited an excellent adsorption capacity of 51 mg/g and best fit the Langmuir and Freundlich models. The kinetics of the oil recovery process are properly adapted to fit the pseudosecond-order model for the C-oil and D-MNP. The tests indicated that the fastest and highest adsorption capacity was achieved at a D-MNP (100 mg/L). As such, the results indicate that the developed Fe-MNP are an effective and reusable demulsifier, which are suitable for the oil recovery of produced water (PW).