Objective Due to large amount of complex and stable organic matters in oilfield fracturing flowback fluid, the effects of traditional treatment method would be limited, and the photocatalytic technology was assessed in this study.

Methods BiOI/BiOBr and U-BiOI/BiOBr complexes were prepared by in-situ synthesis method using BiOBr and BiOI as monomers. Their structures, compositions, thickness, morphology and pore size were characterized by XRD, AFM, SEM, TEM, DRS and BET. Taking hydroxypropyl guanidine gum in fracturing flowback fluid as the photocatalytic degradation reaction model, the photocatalyst activity was investigated, and the effects of the dosage of photocatalyst and the concentration of hydroxypropyl guanidine gum on the degradation effect were determined.

Results For 100 mL hydroxylpropyl guanidine gum solution with mass concentration of 200 mg/L, when the dosages of BiOI/BiOBr and U-BiOI/BiOBr were 120 mg and the reaction time was 60 min, the degradation rate of hydroxylpropyl guanidine gum could reach 73.0% and 77.2%, respectively. Besides, the degradation rate of hydroxypropyl guanidine gum by U-BiOI/BiOBr was better than that by BiOI/BiOBr.

Conclusions The degradation of hydroxypropyl guanidine gum by photocatalytic oxidation technology provides a new idea and theoretical support for treating high contents of organic pollutants in fracturing flowback fluid from oil and gas fields.