Degradation of petroleum pollutants in oil-based drilling cuttings using an Fe2+-based Fenton-like advanced oxidation processes.

Abstract

Oil-based drilling cuttings (OBDC) contain a large amount of total petroleum hydrocarbon (TPH) pollutants, which are hazardous to the environment. In this study, Fe2+-activating hydrogen peroxide (Fe2+/H2O2), peroxymonosulfate (Fe2+/PMS), and peroxydisulfate (Fe2+/PDS) advanced oxidation processes (AOPs) were used to treat OBDC due to the difference in the degradation capacity of TPH caused by the type of free radical generated and effective activation conditions observed for the different oxidants studied. The results showed that the oxidant concentration, Fe2+ dosage, and reaction time in the three AOPs were greatly positively correlated with the TPH removal rate in a certain range. The initial pH value had a significant effect on the Fe2+/H2O2 process, and its TPH removal rate was negatively correlated in the pH range from 3 to 11. However, the Fe2+/PMS and Fe2+/PDS processes only displayed lower TPH removal rates under neutral conditions and tolerated a wider range of pH conditions. The optimal TPH removal rates observed for the Fe2+/H2O2, Fe2+/PMS, and Fe2+/PDS processes were 45.04%, 42.75%, and 44.95%, respectively. Fourier transform infrared spectrometer and gas chromatography-mass spectrometer analysis showed that the alkanes in OBDC could be effectively removed using the three processes studied, and their degradation ability toward straight-chain alkanes was in the order of Fe2+/PMS > Fe2+/PDS > Fe2+/H2O2, among which Fe2+/PMS exhibited the optimal removal effect for aromatic hydrocarbons. Scanning electron microscope, energy dispersive spectroscopy, and X-ray diffraction results showed no significant changes in the elemental and mineral composition of OBDC before and after treatment. Therefore, this study provided a theoretical reference for the effective degradation of TPH pollutants in OBDC.