Removal of asphaltenes from heavy oil improves the quality of oil and makes it easier to process. To this end, Nassar et al. [1] recently showed that NiO nanoparticles have high affinity toward asphaltene adsorption. This investigation, however, involved toluene model solutions and commercially available nanoparticles. In the current work, we show that NiO nanoparticles prepared in situ within heavy oil display much higher affinity toward asphaltenes adsorption, and uptake in the order of 2.8 g asphaltene/g nanoparticles is reported. This uptake way exceeds asphaltene adsorption onto conventional porous adsorbents and commercial nanoparticles from toluene model solutions. Nanoparticle preparation followed a method developed by our group [2], and XRD. EDX, and TEM analyses confirmed the formation of NiO nanoparticles of 12 +/- 5 nm mean diameter. Kinetic experiments showed that, while equilibrium could be achieved in less than 2 h for both in situ prepared and commercial NiO particles, much higher adsorption took place onto the in situ prepared ones, owing to their better dispersion. Contrary to literature findings on adsorption from model solutions onto nanoparticles, surface coverage calculations revealed multilayer adsorption. (C) 2012 Elsevier Inc. All rights reserved.