title: Pretreatment of shale gas drilling flowback fluid (SGDF) by the microscale Fe0/persulfate/O3process (mFe0/PS/O3).
abstract: Shale gas drilling flowback fluid (SGDF) generated during shale gas extraction is of great concern due to its high total dissolved solid, radioactive elements and organic matter. To remove the toxic and refractory pollutants in SGDF and improve its biodegradability, a microsacle Fe0/Persulfate/O3process (mFe0/PS/O3) was developed to pretreat this wastewater obtained from a shale gas well in southwestern China. First, effects of mFe0dosage, O3flow rate, PS dosage, pH values on the treatment efficiency of mFe0/PS/O3process were investigated through single-factor experiments. Afterward, the optimal conditions (i.e., pH = 6.7, mFe0dosage = 6.74 g/L, PS = 16.89 mmol/L, O3flow rate = 0.73 L/min) were obtained by using response surface methodology (RSM). Under the optimal conditions, high COD removal (75.3%) and BOD5/COD ratio (0.49) were obtained after 120 min treatment. Moreover, compared with control experiments (i.e., mFe0, O3, PS, mFe0/O3, mFe0/PS, O3/PS), mFe0/PS/O3system exerted better performance for pollutants removal in SGDF due to strong synergistic effect between mFe0, PS and O3. In addition, the decomposition or transformation of the organic pollutants in SGDF was analyzed by using GC-MS. Finally, the reaction mechanism of the mFe0/PS/O3process was proposed according to the analysis results of SEM-EDS and XRD. It can be concluded that high-efficient mFe0/PS/O3process was mainly resulted from the combination effect of direct oxidation by ozone and persulfate, heterogeneous and homogeneous catalytic oxidation, Fenton-like reaction and adsorption. Therefore, mFe0/PS/O3process was proven to be an effective method for pretreatment of SGDF prior to biological treatment.
authors.affiliation: Department of Environmental Science and Engineering, School of Architecture and Environment, Sichuan University, Chengdu 610065, China.
authors.forename: Heng
authors.initials: H
authors.lastname: Zhang
authors.affiliation: Department of Environmental Science and Engineering, School of Architecture and Environment, Sichuan University, Chengdu 610065, China.
authors.forename: Zhaokun
authors.initials: Z
authors.lastname: Xiong
authors.affiliation: Department of Environmental Science and Engineering, School of Architecture and Environment, Sichuan University, Chengdu 610065, China.
authors.forename: Fangzhou
authors.initials: F
authors.lastname: Ji
authors.affiliation: Department of Environmental Science and Engineering, School of Architecture and Environment, Sichuan University, Chengdu 610065, China. Electronic address: laibo@scu.edu.cn.
authors.forename: Bo
authors.initials: B
authors.lastname: Lai
authors.affiliation: Department of Environmental Science and Engineering, School of Architecture and Environment, Sichuan University, Chengdu 610065, China.
authors.forename: Ping
authors.initials: P
authors.lastname: Yang
mesh_terms: D002681:China; D052918:Environmental Restoration and Remediation / Q000379:methods*; D008401:Gas Chromatography-Mass Spectrometry; D006861:Hydrogen Peroxide / Q000737:chemistry; D007501:Iron; D059206:Natural Gas; D061329:Oil and Gas Fields; D010084:Oxidation-Reduction; D010126:Ozone / Q000737:chemistry; D014865:Waste Disposal, Fluid / Q000379:methods*; D062065:Wastewater / Q000737:chemistry*; D014874:Water Pollutants, Chemical / Q000302:isolation & purification*
chemical_list: D006861:Hydrogen Peroxide; D007501:Iron; D059206:Natural Gas; D010126:Ozone; D062065:Wastewater; D014874:Water Pollutants, Chemical; C045076:Fenton's reagent
keywords: Reaction mechanism; Response surface methodology; Shale gas drilling flowback fluid; Synergistic effect; mFe(0)/PS/O(3) process