(46a) Dispersion of Magnetite Nanoparticles in Brine Solutions Via Coating with Sulfonated Phenolic Resin

It has been proposed to use superparamagnetic magnetite nanoparticles (MNP) as contrast agents for electromagnetic surveys of underground oil reservoir. However, underground oil reservoir has high salinity condition that may lead to particle agglomeration, preventing long-distance propagation of magnetite particles through the subsurface porous rocks. One method for preventing agglomeration is to increase repulsive forces between particles by introducing polymers or polyelectrolytes onto the particle surfaces. In this study, a surface modification was conducted by coating magnetite nanoparticles with sulfonated phenolic resin (SPR). SPR has numerous sulfonic groups in its molecular structure that can induce highly negative charge to the surface of the magnetite particles. SPR was synthesized from 4-hydroxybenzenesulfonic acid and formaldehyde. Coating magnetite nanoparticles with was implemented by mixing the SPR solution with the iron precursor solution and then adding the sodium hydroxide solution that induced in-situ co-precipitation. In order to further enhance the stability of the particle the various types of polymer such as polyethylene glycol (PEG), polyvinyl alcohol (PVA) and polyacrylic acid (PAA) was also introduced. As a result, the PAA treated SPR coated MNP formed stable dispersion in highly salt solutions containing NaCl up to 10 wt.% for a wide range of pH.