Efficient PFOA degradation by persulfate-assisted photocatalytic ozonation

ZnO-reduced graphene oxide (ZnO-rGO) was synthesized successfully at 423 K by a hydrothermal method. The presence of reduced graphene oxide significantly improved the photocatalytic performance of ZnO and its optimal loading ratio was 0.6 wt%. The XRD, SEM, UV–vis and FT-IR were applied to characterize the prepared catalyst. Comparative experiments were conducted to evaluate perfluorooctanoic acid (PFOA) degradation efficiency and the results showed that 99.2% PFOA was degraded in persulfate-assisted photocatalytic ozonation with low dosage of ozone and persulfate at room temperature. The impact factors on PFOA degradation efficiency including loading ratios of GO on ZnO, reaction temperatures and persulfate concentration were inspected and analyzed. The sodium persulfate and ammonium persulfate were compared as common oxidants in photocatalytic ozonation for PFOA degradation and sodium persulfate showed the better PFOA removal. Chloride and humic acid (HA) were common substances in natural water, and they showed inhibition effects on PFOA degradation. Conversion of persulfate to sulfate ion was studied and persulfate concentration during PFOA oxidation was monitored. PFHpA, PFHeA, PFPeA and PFBA were main intermediates during PFOA degradation.