•An efficient defluorination of PFOA was obtained in the UV/BiOCl system.•The PFOA degradation was dominated by the direct photo-generated hole oxidation.•The PFOA defluorination corrected well with the oxygen vacancies of BiOCl.•The oxygen vacancies made BiOCl tightly bind PFOA for the hole transfer.•A hole-mediated mechanism was proposed for the photocatalytic degradation of PFOA on BiOCl.There remains a significant need for developing new photocatalytic system to degrade perfluorooctanoic acid (PFOA), a typical persistent organic pollutant. In this study, highly efficient BiOCl nanosheets were prepared by a simple hydrolytic method and employed to decompose PFOA. The UV irradiation BiOCl system decomposed nearly all the added PFOA after 12 h, yielding a defluorination of 59.3% and a minimization ratio of 52.5%. The photocatalytic defluorination rate constant of PFOA on BiOCl was 16.53 μmol L−1 h−1, being 1.7 and 14.6 times higher than that on commercial In2O3 and TiO2 (P25), respectively. It was demonstrated the photocatalytic degradation of PFOA on BiOCl mainly followed the direct hole-induced oxidative pathway, and the PFOA degradation was positively correlated with the amount of oxygen vacancies in BiOCl. The oxygen vacancies not only acted as the electron scavengers to suppress the charge recombination, but also favored to bind PFOA tightly on the BiOCl surface through a special monodentate coordination, which is beneficial for the hole oxidation of PFOA.Download high-res image (106KB)Download full-size image

•PFOA significantly quenched the fluorescence emission of quantum dots (QDs).•A rapid and simple fluorescence sensor was proposed for determining PFOA by QDs.•PFOA determination could be completed within approximately 10 min.•The developed method had a working range of 0.5 to 40 μmol L−1 and a detection limit of 0.3 μmol L−1.Analysis of perfluorooctanoic acid (PFOA) usually requires a combination of high-performance liquid chromatography and mass spectrometry, which is expensive and time-consuming. In the present work, water-soluble CdS quantum dots (QDs) were employed to develop a simple and rapid fluorometric method for the determination of PFOA. Strongly fluorescent CdS QDs were prepared by using 3-mercaptopropionic acid (MPA) as a stabilizer. It was observed that PFOA strongly quenched the fluorescence emission of the MPA-CdS QDs because PFOA promotes the aggregation of MPA-CdS QDs through a fluorine–fluorine affinity interaction. Under optimum conditions, the fluorescence intensity of MPA-CdS QDs was observed to decrease linearly with an increase in the concentration of PFOA from 0.5 to 40 μmol L−1, with a limit of detection of 0.3 μmol L−1. This new method was successfully implemented for the analysis of PFOA-spiked textile samples, with recoveries ranging from 95% to 113%.

The present work investigated the mechanochemical (MC) treatment of powdery decabromodiphenyl ether (BDE209) with Bi2O3 and/or Fe powders as co-milling reagents. The simultaneous use of Bi2O3 and Fe with a Bi:Fe:Br molar ratio of 1:1:1 led to a BDE209 degradation of 96.6% within 2 h of ball milling at rotation speed of 400 rpm, whereas only 66.0% and 24.0% of BDE209 was removed in the MC-Bi2O3 and MC-Fe system, respectively. It was demonstrated that the MC process activated the lattice oxygen (O2−) of Bi2O3 and promoted its reaction with BDE209, whereas Fe initiated the reduction of BDE209. The MC treatment of BDE209 through a single reductive in the MC-Fe system or oxidative process in the MC-Bi2O3 system was not efficient, due to that BDE209 is rather difficultly oxidized and the debrominated intermediates are resistant to reduction. When combining Bi2O3 with Fe, the reductive debromination of BDE209 over Fe and the subsequent oxidation of debrominated products over Bi2O3 were integrated into a concerted process. The rapid reduction of BDE209 over Fe not only released Br− ions, which acted as the dopant to improve the activity of O2− in Bi2O3, but also generated less brominated intermediates, which were more susceptible to the O2−-participating reaction over Bi2O3. Thus, a strong synergistic effect between Bi2O3 and Fe was observed on the MC degradation of BDE209.