The objective of this experiment was to investigate the influence of SO32-dosage, pH value, initial perfluorooctane sulfonate(PFOS)concentration as well as coexisting substances on the degradation and defluorination of PFOS by VUV-SO32- process. The results indicated that the increase of SO32- dosage could lead to rise in the concentration of active species hydrated electron(eaq-) and thus enhance the degradation and defluorination of PFOS. As the concentration of SO32- increased from 1 mmol·L-1 to 20 mmol·L-1, the degradation and defluorination rates of PFOS increased from 45% and 40% to 97% and 63%, respectively. The degradation and defluorination of PFOS were also enhanced with the increment of the solution pH values, and the defluorination was more sensitive to the pH values. In addition, more PFOS was degraded with the increase of initial PFOS mass concentration, although the degradation and defluorination rates of PFOS were reduced. When the initial PFOS mass concentration changed from 1 mg·L-1 to 50 mg·L-1, the degradation amount of PFOS after four hrs increased by about 50 times, probably due to the higher utilization proportion of eaq- at high pollutants concentration. Last but not least, the influence of co-existing substances, Cl- and HCO3-, on PFOS degradation could be neglected, whereas their effects on defluorination were observed. Defluorination of PFOS was enhanced with the increased Cl- concentration, however, increased first and then decreased with the increment of HCO3- concentration. It was also found that the presence of humic acid(HA) lowered degradation as well as defluorination of PFOS owing to the blockage of effective UV light and trapping of active species for photochemical reaction.
Keywords: VUV-SO32-; hydrated electron(eaq-); influencing factors; perfluorooctane sulfonate(PFOS); photochemical reduction.