Molecular modeling of interactions between heavy crude oil and the soil organic matter coated quartz surface

Molecular dynamic (MD) simulation was applied to evaluate the mobility, diffusivity and partitioning of SARA (saturates, aromatics, resins, asphaltenes) fractions of heavy crude oil on soil organic matter (SUM) coated quartz surface. Four types of SUM were investigated including Leonardite humic acid, Temple-Northeastern-Birmingham humic acid, Chelsea soil humic acid and Suwannee river fulvic acid. The SUM aggregation at oil-quartz interface decreased the adsorption of SARA on the quartz surface by 13-83%. Although the SUM tended to promote asphaltenes aggregation, the overall mobility of SARA was significantly greater on SUM-quartz complex than on pure quartz. Particularly, the diffusion coefficient of asphaltenes and resins increased by up to one-order of magnitude after SUM addition. The SUM increased the overall oil adsorption capacity but also mobilized SARA by driving them from the viscous oil phase and rigid quartz to the elastic SOM. This highlighted the potential of SUM addition for increasing the bioavailability of heavy crude oil without necessarily increasing the environmental risks. The MD simulation was demonstrated to be helpful for interpreting the role of SUM and the host oil phase for the adsorption and partitioning of SARA molecules, which is the key for developing more realistic remediation appraisal for heavy dude oil in soils. (C) 2014 Elsevier Ltd. All rights reserved.