Extraction and separation of petroleum pollutants from oil-based drilling cuttings using methanol/n-hexane solvent

Oil-based drilling cuttings (OBDC) have a high content of petroleum pollutants with strong mutagenic, carcinogenic and teratogenic properties. Solvent extraction can effectively separate petroleum pollutants from OBDC. However, single solvent has preferred solubility for different types of petroleum pollutants in OBDC, resulting in a lower oil removal efficiency. Therefore, based on the polarity difference between methanol (Me) and n-hexane (He), a method was developed to extract petroleum pollutants from OBDC using Me&He. Compared with methanol or n-hexane alone, the oil removal efficiency of compound Me&He was significantly increased to 94.58 %, and 37, 37 and 77 petroleum pollutants were extracted using Single methanol, Single n-hexane and Compound Me&He, respectively. Methanol extraction preferentially solubilised polar molecules such as alcohols and carboxylic acids, while n-hexane extraction preferentially solubilised alkanes and other nonpolar molecules. Compound Me&He compensated for the low solubility of single solvents for petroleum pollutant extraction from OBDC. Additionally, because methanol and n-hexane are not mutually soluble, it was easy to separate the recycled components. Compared with other common solvent extraction technologies, compound Me&He had advantages including simple operation and high oil removal efficiency. This study provided a theoretical basis and technical reference for the efficient processing and resource recycling of OBDC.