| With the development of society,the demand for pharmaceuticals and personal care products（PPCPs）increases.However,the long half-life and complex composition of PPCPs and their poor biochemical properties make them difficult to remove by conventional wastewater treatment processes,and they are very harmful to living things after they entered the water.This requires us to develop a method with high oxidation capacity and high interference resistance to treat wastewater containing PPCPs.Advanced oxidation techniques based on sulphate radicals（SR-AOPs）have been demonstrated to be highly oxidative systems and are widely used for the removal of difficult to degrade organic matter.In the Fe（VI）/PMS system,ferrate（Fe（VI））was chosen as the activator of peroxymonosulfate（PMS）to form the SR-AOPs technology,Fe（VI）can act as an activator to activate PMS to produce two strongly oxidizing radicals SO4·-and·OH,it can also be used as an oxidizing agent to produce high-valent iron species with a selective degradation effect.Improving the oxidation effect of the system also protects it from the complexities of the external environment.In this study,sulfamethoxazole（SMX）was used as a representative of PPCPs for degradation,and the effectiveness of the system in removing PPCPs pollutants was investigated.The mechanism of the system in degrading pollutants was derived through qualitative and quantitative analysis of the active species in the system by means of experiments and calculations,and finally the process regulation provided a reference basis for the system in practical applications.The experimental results of SMX removal showed that at 10 mg/L SMX,the dosage of Fe（VI）and PMS is 0.2 m M could remove 75.4%of SMX at p H7 for 30 min;the removal rate of SMX was higher than 70%at p H=3-7,at an initial concentration of 1 mg/L of SMX,the Fe（VI）/PMS system removed60.5%of SMX,but when the initial concentration of SMX was 3-7 mg/L,the system could achieve more than 90%degradation of the pollutant.The addition of Cl-to the system showed a facilitative effect on the system,HCO3-showed an inhibitory effect on the system,while an increase in the concentration of NO3-and HA had little effect on the system.The system achieved over 90%removal of all three species of carbamazepine,phenol and ibuprofen,indicating that the system has good removal of PPCPs and strong anti-interference ability.Electron spin resonance（ESR）experiments showed the presence of SO4·-and·OH and the absence of reactive species such as singlet oxygen.The quenching experiments showed that the free radicals present in the system were not the only substances that played a role in the degradation,and that the high-valent iron species in the system also played a larger role in the degradation of SMX.The results of competitive oxidation kinetics showed that at neutral p H,when the molar ratio of PMS/Fe（VI）was1:1,the contribution of high-valent iron species and free radical to SMX degradation was 49.3%and 50.7%,respectively.In addition,the degradation contributions of the two active species were different for different pollutants.By comparing the Fe（VI）/PMS and Fe（VI）systems,it was found that PMS promotes the production of high-valent iron species in the Fe（VI）/PMS system,and the amount of high-valent iron species in the Fe（VI）/PMS system is four times higher than that in the Fe（VI）system.Density functional theory calculations suggest that SMX is more vulnerable to electrophilic attacks caused by expensive iron than free radicals.And more calculations show that electron-rich pollutants are more vulnerable to high-valent iron species.Notably,the use of methyl phenylsulfoxide（PMSO）as a probe for high-valent iron species showed that at p H 7.0,with an increase in the molar ratio of PMS/Fe（Ⅵ）,the predominant active species changed from f high-valent iron species to free radicals.As the p H changes from acidic to neutral,the main active species also have free radicals that become high-valent iron species.The results of this study can promote the process regulation and application of Fe（VI）/PMS system in water/wastewater treatment. |
