| Water resources are precious resources for human exitence.However,a large number of pharmaceuticals and personal care products(PPCPs)have been developed,which be widely used in people's daily life and social production process.The removal efficiency is low in traditional sewage treatment process due to their nondegradable,biotoxic and inhibitory.This kind of organic matter will be discharged into the water environment along with the effluent of wastewater treatment plants,which pose serious threat to natural water environment ecology and water resources security.Therefore,it is urgent to develop an effective depth treatment method for PPCPs pollutants in water.Sulfate radical(SO4·-)has a redox potential of 2.6-3.IV,which is very reactive towards many organic compounds,and is expected to provide a solution for the deep treatment of PPCPs pollutants in water.SO4,·-can be generated from the activation of persulfate by Fe?,but the acidic reaction condition(pH 2.0-3.0)is the potential limiting factors in application.In order to make this process work under circumneutral pH conditions,the effect and mechanism of typical PPCPs degradation(such as ibuprofen(IBP)and carbamazepine(CBZ))in water by Fe?/?-NTA(nitrilotriacetic acid)activated persulfate(S2O82-)at neutral pH were investigates in the present study.The obtained results are summarized as follows:.Firstly,the degradation efficiency of IBP,which was selected as the model compound,in Fe?-NTA/S2O82-system at neutral pH was investigated.The results showed that the degradation of IBP by Fe?-NTA/S2O82-process was not successful(<10%)due to the rapid oxidation of Fe?-NTA complex by dissolved oxygen.In order to improve the regeneration rate of Fell-NTA,we evaluated the effect of hydroxylamine hydrochloride(HA)in Fe?-NTA/S2O82-system.The results showed that the yield of SO4·-and the degradation efficiency of IBP were significantly improved because of the quick regeneration of Fe?-/?-NTA complex by HA.Secondly,the effects of important factors such as NTA:Fe?,S2O82-:Fell and HA:Fe?molar ratios on the degradation kinetics of IBP were evaluated in Fe?-NTA/S2O82-/HA process.The suitable conditions were obtained at[Fe?]=0.1 mM,[NTA:Fe?]=1:1,[HA:Fe?]=20:1 and[S2O82-:Fe?]=30:1,and almost complete degradation of IBP was achieved within 20 min of the reaction time.In addition,radicals scavenging experiments were conducted to identify the primary reactive species in Fe?-NTA/S2O82-/HA process.The results showed that SO4·-and hydroxyl radical(HO·)contributed to?80%of IBP degradation.Fell-NTA complex was more effective than Fe?-EDDS([S,S]-ethylendiaminedisuccinic)or Fe?-EDTA(ethylene-diaminetetraacetic acid)complex in the activation of S2O82-.The major intermediates in IBP degradation were identified by high performance liquid chromate-graphy(LC-QTOF-MS)analysis and the degradation pathways were proposed.Thirdly,due to the toxicity of HA limiting the practical application of the Fe?-NTA/S2O82-/HA system,we further proposed a new method of photochemical reduction of Fe?-NTA by long-wave ultraviolet light(UVA),and constructed a UVA/Fe?-NTA/S2O82-system.The results showed that UVA irradiation-induced Fe?-NTA reduction can enhance Fe?/Fe? redox cycle,which can help degrade CBZ effectively in water at neutral pH.Electron spin resonance spectroscopy(ESR)and radicals quenching tests indicated that the major reactive species included SO4·-and HO· in UVA/Fe?-NTA/S2O82-process,which contributed more than 80%degradation of CBZ.The rate constant of SO4·-reacting with NTA was determined at 5.89×107 M-1 s-1 by the transient-state photolysis method.The critical NTA:Fe? molar ratio was determined at 1:1,above this ratio the excess NTA would act as a scavenger of SO4·-/HO· thereby inhibiting the degradation rate of CBZ.Moreover,the degradation of CBZ by UVA/Fe?-NTA/S2O82-process in real water matrix(lake water,groundwater and tap water)with environmentally relevant concentration were conducted,the degradation mechanism and pathway of CBZ were proposed on the basis of the identified intermediates by using LC-QTOF-MS technique.The results of this study can provide a new method for the advanced treatment of PPCPs in water,which provided scientific and guidance for the construction of SO4·-advanced oxidation system under neutral pH conditions. |
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