Removal of total petroleum hydrocarbons from oil-based drilling cuttings by a heat activation persulfate-based process.

Oil-based drilling cuttings (OBDC) are typical hazardous wastes generated during shale gas extraction. In this study, two persulfate-based advanced oxidation processes (AOPs), heat/PMS and heat/PDS, have been used to treat OBDC. The results showed that for the heat/PMS process, within a certain range, the oxidant dosage, temperature, and reaction time were significantly positively correlated with the degree of total petroleum hydrocarbon (TPH) removal. When these parameters were increased from their initial values to 3.57 mmol/g, 70°C, and 80 min, respectively, TPH removal rates increased significantly, by 20.95%, 18.68%, and 16.41%, respectively. However, further increases in these parameters had little effect on the TPH removal rate. Similar observations were made for the heat/PDS process. There are other differences between the two processes, including that the heat/PDS process required less oxidant to reach an effective activation state than the heat/PMS process, but required a higher temperature and a longer reaction time. Fourier-transform infrared spectrometry and gas chromatography-mass spectrometry have shown that both processes could effectively remove the light components of linear paraffins contained in OBDC. The heat/PMS process performed significantly better than the heat/PDS process in removing aromatic hydrocarbons and long-chain alkanes. Scanning electron microscopy, energy-dispersive spectrometry, and X-ray diffraction analysis implied that the elemental and mineral compositions of OBDC were not significantly modified by reaction in the heat/PMS and heat/PDS processes. This study may provide theoretical support for the technological development of heat activation and persulfate-based AOPs to remove TPH from OBDC.