Importance of the Adsorption Method Used for Obtaining the Nanoparticle Dosage for Asphaltene-Related Treatments

The primary objective of this study is to show the importance of the adsorption method used in obtaining the nanoparticle dosage for inhibiting/remediating asphaltene-related problems. In this work, two methods for determining the adsorption isotherms for different asphaltenes onto three different types of nanoparticles were evaluated. The adsorption equilibrium of n-C-7 asphaltenes was determined using batch-mode adsorption experiments that were performed in two different ways: (i) by exposing a certain mass of nanoparticles in a fixed volume of liquid with a varying initial concentration of asphaltenes and (ii) by exposing a given amount of asphaltenes in a fixed volume of liquid while varying the dosage of nanoparticles. The results obtained using these two methods were sufficient to determine the type I and III adsorption isotherms, respectively. These differences in behavior in adsorption isotherms can be due complexity of the n-C-7 asphaltenes, which are self-associative molecules that impact directly the interaction between the adsorbate (i-mers depending on their concentration) and adsorbent. These results were proven through the aggregate size distribution of asphaltenes as estimated by dynamic light scattering (DLS) measurements. The experimental data was well described with the solid liquid equilibrium (SLE) model. The adsorption isotherms obtained using the second method deviated significantly from those typically reported in the literature. However, this method is a useful tool for determining the required amount of nanoparticles based on the interactions of adsorbate-adsorbate and adsorbate-nanoadsorbent. Indeed, this method is of practical significance because the amount of asphaltenes at reservoir conditions can be considered constant when treatments are performed.