Molecular-level simulations of oil-contaminated clays

Petroleum products, besides being the core of the energy source, frequently result in the contamination of subsurface soils. Clay minerals, being electrochemically active components of soils, are the most affected and hence lead to substantial change in behaviour and properties of the soils. This paper provides a multilevel study consisting of macro and micro testings coupled with molecular-level simulations of the behaviour of active clay mineral in the soil structure, pore fluids and dissolved salts when contaminated with crude oil. There was a significant change in the engineering behaviour of the contaminated clay. The coarse-grained soil-like behaviour was observed in the strength of the oil-contaminated clay. The contamination has affected the plasticity and the cation-exchange capacity of the investigated clay. The swelling pressure of the contaminated clay is reduced to about one third of that of the uncontaminated clay, while there was no change observed in the swelling percentage. The formation of oil-coated agglomerates due to the addition of the crude oil has been found to be responsible for most of the physical and mechanical processes in the contaminated clays. The study's molecular-level simulation modelling concepts can be used to describe the behaviour of clay minerals and other interacting compounds.