Dielectric barrier discharge non-thermal plasma treatment of oil-based drilling cuttings: Operating windows, energy coupling characteristics, and aqueous-extract phytotoxicity response

Oil-based drilling cuttings (OBDC) are hazardous solid wastes generated during oil and gas drilling, and their management requires effective pollutant removal with controlled energy demand and appropriate residual-risk assessment. In this study, a plate-to-plate dielectric barrier discharge (DBD) non-thermal plasma reactor was used to treat petroleum hydrocarbons in field-derived OBDC. The effects of electrode diameter, discharge gap width, and input power on discharge characteristics, solid-phase total petroleum hydrocarbon (TPH) removal, and energy efficiency were systematically investigated. The highest solid-phase TPH removal efficiency of 98.62% was achieved after 40 min using a 60 mm electrode, a 10 mm gap, and an input-power setting of 220 W. The maximum energy efficiency of 58.6 mg kJ −1 was obtained after 10 min using a 150 mm electrode. Optical emission spectroscopy revealed emission features assigned to excited OH, CH, C 2 , and atomic O species. Fourier transform infrared spectroscopy and gas chromatography–mass spectrometry analyses showed attenuation of hydrocarbon-related signatures and endpoint changes in the extractable-organic composition, consistent with plasma-induced hydrocarbon transformation, although a unique elementary pathway was not established. Wheat-seed assays showed reduced germination inhibition for the aqueous extract of DBD-treated OBDC relative to fresh OBDC, while extract conductivity and salinity increased after treatment. These results demonstrate the potential of DBD for rapid reduction of the solid-phase TPH burden in OBDC while confirming the need for broader direct-contact and environmental-risk assessments.