Adsorption–Desorption and Interfacial Distribution Characteristics of Petroleum Hydrocarbons in Soil Systems

The adsorption of organic pollutants on soil surfaces impedes their oxidative degradation efficiency within the soil medium. Understanding the distribution patterns of different petroleum hydrocarbon components on the soil medium surface can provide effective theoretical guidance for the technical regulation and efficiency improvement of in situ chemical oxidation (ISCO). Therefore, this study designed experiments involving interface diffusion, static desorption, and intensive desorption, and investigated adsorption patterns and component analysis. Fast-desorbing petroleum hydrocarbon components in on-site oil sludge were identified, including amines (e.g., 2-Phenylethylamine, 2,4,6-Trimethyl-m-phenylenediamine), acids (e.g., Benzoic acid, Octadecanoic acid). Relatively fast-desorbing components included phenols (e.g., Phenol), alcohols (e.g., Phenylmethanol, Dihydroxybenzene), ketones (e.g., Cyclohexa-2,5-dien-1-one, Cyclohepta-2,4,6-trien-1-one, and Pyrimidine-2,4,6(1H,3H,5H)-trione). Slow-desorbing components comprised carboxylic esters (e.g., Ethyl carboxylic acid ester), benzenoid olefins (e.g., 1'-(Cyclopenta-2,4-dien-1-yl)-1,4'-bipiperidine, 6-Allyl-1-methylnaphthalene). Finally, the remaining components in the soil were measured by extraction method as strongly adsorbed petroleum hydrocarbon components, including long straight-chain alkanes (e.g., Tetradecane, Hexadecane, Heptadecane, Octadecane, Icosane), and benzene esters (e.g., Dimethyl 5-methyl-1,3-benzene-dicarboxylate). It provides a theoretical basis for the accurate desorption of petroleum hydrocarbons from the soil surface.

Graphical Abstract