Reza Azin

Stability of nanofluid in the presence of salt is important during synthesis and application in oil reservoirs. In this study, the stability of alumina nanofluid was investigated in water/methanol base fluid in the presence of five different salts (NaCl, KCl, CaCl2, Na2 SO4 and Al(NO3)3) with various concentrations. The volume ratio of water/methanol in the base fluid was optimized and the best surfactant concentration was selected among cationic, anionic, and nonionic surfactants to achieve best stability conditions for nanofluid prepared by two-step method. The stability of nanofluid was characterized by sedimentation test, turbidity test, zeta-potential and dynamic light scattering. Results showed that the 70/30 vol% of water/methanol base fluid shows the highest zeta-potential. The highest stable nanofluid was obtained in the presence of 0.2 wt% arabic gum surfactant. The alumina nanofluid with 100000 ppm of NaCl, 25000 ppm of Na2SO4, 50000 ppm of CaCl2, 50000 ppm of KCl and 100000 ppm of Al(NO3)3 was stable or more than 50 days.