Preparation and characterization of magnetic Co0.5Zn0.5Fe2O4-chitosan nanoparticles as surfactants in oilfield

Chitosan nanoparticles with magnetic properties can be potentially used as separation materials in adsorption of oil for enhanced oil recovery. Different from the traditional surfactants, the novel magnetic Co0.5Zn0.5Fe2O4-chitosan nanoparticles are of excellent biodegradation and a high level of controllability. The Co0.5Zn0.5Fe2O4-chitosan nanoparticles with core-shell structure were prepared successfully. The image of transmission electron microscope and the scanning electron microscopy showed that the cubic-shape magnetic Co0.5Zn0.5Fe2O4-particles were encapsulated by the spherical chitosan nanoparticles. The size of the Co0.5Zn0.5Fe2O4-chitosan nanoparticles was below 100 nm. The saturated magnetization of the Co0.5Zn0.5Fe2O4-chitosan nanoparticles could reach 80 emu g−1 and showed the characteristics of superparamagnetism at the same time. The evaluation on the interfacial properties of the product demonstrated that the interfacial tension between crude oil and water could be reduce to ultra-low values (to about 10−3 mN m−1) when the magnetic Co0.5Zn0.5Fe2O4-chitosan nanoparticle was used in several blocks in Shengli Oilfield without other additives. Meanwhile, the magnetic Co0.5Zn0.5Fe2O4-chitosan nanoparticles possessed good salt-resisting capacity.