Efficient degradation of evaporative condensing liquid of shale gas wastewater using O3/UV process

In this study, a batch experiment was used to investigate the degradation of real evaporative condensing liquid of shale gas wastewater (ECLSGW). We showed that compared to the O 3 , ultraviolet (UV), UV/TiO 2 , and O 3 /UV/TiO 2 processes, the O 3 /UV process has better performance in removing the chemical oxygen demand (COD) and total organic carbon (TOC) of ECLSGW under the same conditions. The effects of initial pH (3–12), ozone flow rate (0.1–0.5 L/min), UV power (15–50 W), and reaction time (0–60 min) on the degradation of ECLSGW via the O 3 /UV process were investigated using a single-factor experiment. Moreover, the optimal experimental conditions were obtained using a quadratic polynomial prediction model (R Adj 2 =0.9961) that was obtained from the central composite design (CCD) of the response surface methodology (RSM). Under optimal experimental conditions, the COD and TOC removal efficiency reached 93.12 and 95.5%, respectively. In addition, gas chromatography–mass spectrometry analysis showed that the O 3 /UV process could nearly completely mineralize organic pollutants in the ECLSGW. Hydrogen peroxide (H 2 O 2 ) and hydroxyl radical ( OH) were identified by manganese dioxide (MnO 2 ) and tert-butanol (TBA). The mechanism research showed that OH plays an important role in the degradation of organic pollutants. In summary, the O 3 /UV process is an effective method to degrade ECLSGW.