Effect of viscosity and colloidal stability on the magnetic hyperthermia of petroleum-based nanofluids

Magnetic Hyperthermia (MH) is the increase in temperature of a colloid composed of suspended magnetic nanoparticles (NP), which occurs when subjected to high frequency alternate magnetic fields (AMF). When well controlled, this phenomenon has shown great potential for industrial and medical applications. In this work, we investigate the effect of important variables such as viscosity, NP concentration, and colloidal stability to maximize the heat transferred from the AMF to the colloid. Iron oxide nanoparticles with core size of 9 nm (σ=0.3) were used in the colloid, forming a stable system for six days in diesel, for both NP concentrations tested (0.5 and 1 wt.%). The NP and Diesel mixture was then added to two different viscosity crude oils (Heavy and Waxy). The maximum ΔT achieved in two minutes with 0.5 wt.% NP (770 kHz and 28 kA/m) was 59 ° C for diesel, 57 °C for heavy crude oil, and 43 °C for waxy crude oil, respectively, with up to 95 °C for 1.0 wt.% NP dispersed in diesel. It was therefore possible to observe a clear increase in the system‘s temperature by applying MH in high viscous liquids (>1000 mPa.s) with superparamagnetic nanoparticles.