Effect of biomass adsorbent on non-thermal plasma activated treatment of oil-based drilling cutting: Residual toxicity assessment

Abstract

The oil-based drilling cutting (OBDC), which contain petroleum hydrocarbons produced during the oil and shale gas exploration process, are considered toxic solid waste for the environment. In this study, we introduce a promising technique by coupling non-thermal dielectric barrier discharge (DBD) plasma with biomass adsorbents (wheat stalk, straw fiber, or rice husk) to remove toxic compounds from OBDC. The results show the plasma treatment can achieve up to 90.9% degradation rate of total petroleum hydrocarbons (TPH). The introduction of 3 wt% of biomass adsorbent exhibited a significant enhancement of the energy efficiency (up to 21.9% increase using rice husk). Importantly, toxicity evaluations, such as the corn seed germination test, demonstrate a substantial reduction in the toxicity of drilling cuttings after plasma treatment, with seed germination and growth rates (using straw fiber) comparable to uncontaminated soil. Adding biomass adsorbents can also enhance the hydrophilicity of treated OBDC, increasing the presence of HCOO–, CH3HCOO–, NO3- species which further contributes to the safety and fertility of treated OBDC. Coupling non-thermal DBD plasma discharge with biomass adsorbents presents an efficient and environmentally friendly choice for the environmental treatment of OBDC in deep shale gas development.