Functionalization and characterization of iron oxide nanoparticles recovered from acid mine drainage and application in the enhanced oil recovery

•Iron oxide nanoparticles recovered from the acid mine drainage treatment are suitable to produce nanofluids.•Iron oxide nanoparticles in concentration 0.10–0.75 wt% can be used to produce stable nanofluids.•Additional 7–10% oil recovery is achieved after flooding due to injection of iron oxide-based nanofluids. Oil is one of the most intensively used energy sources in the world and, as a fossil fuel, it is a finite resource. Different methods have been explored to increase oil recovery from mature fields, particularly using enhanced oil recovery (EOR) with the help of nanofluids. This study performed EOR tests using iron oxide nanoparticles added to brine and sodium dodecyl sulfate solutions. Three types of iron oxide nanoparticles were examined: commercial (IO), derived from the acid drainage of an underground coal mine (SIO), and temperature-sensitive functionalized (TSIO). The nanoparticles were well characterized by X-ray diffraction, Fourier-transform infrared spectroscopy, high-resolution X-ray photoelectron spectroscopy, and transmission electron microscopy. The nanofluids were evaluated through dynamic light scattering measurements and determination of the viscosity, turbidity, contact angle and surface tension. There was not significant variation in the surface tension of the samples, which ranged between 25.46 and 28.28 mN m−1. However, the contact angle exhibited notable fluctuations depending on the nanoparticles concentration, ranging from 7.39° to 24.43°. Furthermore, the zeta potential suggests that the stability of the nanofluid samples falls within the moderate to medium range. An improvement in oil recovery reached 10% with the commercial nanoparticles (0.50 wt%), followed by 8.5% using the synthesized (0.25 wt%) and 7.5% using the functionalized (0.25 wt%). Moreover, all nanofluids showed good stability for up to 30 days, and their viscosity showed a direct relationship with the enhancement in oil recovery.