Oleic acid-coated magnetic particles for removal of oil from produced water

Abstract

Efficient removal of residual oil from produced water (PW) is a challenging but crucial task to meet the increasingly stringent environmental regulations. The current study presents lab-made magnetite particles coated with different amounts of oleic acid (OA) as an efficient and environment-friendly solution for the removal of low concentrations of oil from PW. Performance of the particles in oil removal experiments was studied as a function of the coating factor, adsorption time, oil to the particle concentration ratio and concentrations of emulsifier and salt. Furthermore, reusability of the particles after regeneration through solvent washing and centrifugation was studied. It was observed that the oil removal efficiency of the particles improves by increasing the OA coating factor up to 32 and decreases thereafter. Increasing oil to the particle concentration ratio boosted oil removed per unit time as well as the final oil removal efficiency. Salinity alone did not disturb the oil removal efficiency of the particles whereas oil adsorption efficiency was negatively affected due to the presence of emulsifier alone or in combination with the salinity. Adsorption of oil on the particles followed a Freundlich isotherm model and the kinetic was described by the pseudo-second-order model. Solvent washing completely restored the performance of the particles and was found to be more effective than centrifugation. It was concluded that the proposed particles offer a promising and highly efficient solution for the removal of residual oil from PW. • Magnetic particles were synthesized by coating oleic acid on magnetite. • The coated particles lowered the oil concentration in produced water as low as 1 ppm. • The oil removal efficiency could be customized by changing the oil to particle concentration ratio. • The particles were regeneratable through solvent washing.