Activation Of Peracetic Acid By Natural Iron-based Minerals To Degrade Typical PPCPs

In recent years,pharmaceutical and personal care products（PPCPs）have gradually attracted widespread attention as a new emerging organic pollutant that is frequently detected in the environment such as water,soil and sediment.However,conventional water treatment technologies are not effective in removing PPCPs,therefore,finding an efficient and green method to degrade PPCPs in water is of great importance to human health and the ecological environment.Advanced oxidation techniques based on peracetic acid（PAA）have been extensively investigated due to their ability to achieve effective water purification and disinfection at the same time.Researchers have developed a number of strategies to activate PAA to generate free radicals,with Fe²⁺emerging as the most promising activation method due to its non-toxic and environmentally friendly advantages.However,the conventional Fe²⁺/PAA system suffers from inadequate Fe²⁺/Fe³⁺cycling and the tendency to mask free radicals by adding large amounts of Fe²⁺.In order to overcome these shortcomings,this study used three natural iron-based minerals including siderite（FeCO₃）,pyrite（FeS₂）and chalcopyrite（CuFeS₂）as solid sources of Fe²⁺to activate PAA,and constructed the FeCO₃/PAA,FeS₂/PAA and CuFeS₂/PAA systems to degrade typical PPCPs in water,respectively.The oxidation performance and reaction mechanism of the systems were investigated as follows:The FeCO₃/PAA system was used to degrade naproxen（NAP）in water.The effect of the reaction parameters on the oxidation performance was investigated and the experimental conditions were optimized.NAP removal efficiency was achieved at 95.8%under FeCO₃dosage of 1.2 g L^-1,PAA concentration of 115μmol L^-1 and initial solution pH of 3.Free radical masking experiments,probe experiments,electron paramagnetic resonance spectrometer（EPR）and mass spectrometry determined that the main active substances in the system were hydroxyl radicals（·OH）,organic radicals（R-O·）and high-valent iron（Fe（IV））.Mechanistic studies showed that Fe²⁺released from the surface of FeCO₃dominated the activation process of PAA.Finally,the degradation mechanism of NAP and the toxicity of the products were analysed.The FeS₂/PAA system was used to degrade sulfamethoxazole（SMX）in water.The effect of the reaction parameters on the oxidation performance was investigated and the optimum experimental conditions were determined.The experimental results showed that the system could remove 93.7%SMX at FeS₂ dosage of 0.3 g L^-1,PAA concentration of460μmol L^-1 and initial solution pH of 5.8.The results of radical masking experiments,probe experiments,EPR and mass spectrometry showed that·OH,R-O·,singlet oxygen（¹O₂）and Fe（Ⅳ）were all involved in the degradation of SMX,but the most dominant ones were·OH,R-O·and ¹O₂.Characterisation and mechanistic studies suggest that Fe²⁺released from the FeS₂ surface dominates the activation process of PAA,while the presence of reducing S species can promote the Fe²⁺/Fe³⁺cycle in the system.The CuFeS₂/PAA system was used to degrade metronidazole（MTZ）in water.The effect of the reaction parameters on the oxidation performance was investigated and the optimum experimental conditions were determined.The experimental results showed that the system could achieve 83.9%removal efficiency of MTZ at CuFeS₂ dosage of 4 g L^-1,PAA concentration of 460μmol L^-1 and initial solution pH of 3.The results of the radical masking experiments,probe experiments and EPR tests indicated that·OH,R-O·and Fe（Ⅳ）were all involved in the degradation of MTZ,with the main active substance being·OH.The mechanism experiments showed that Cu（Ⅰ）and Fe（Ⅱ）bonded on the surface of chalcopyrite were the main active sites for the activation of PAA,while the presence of their own reducing S species could promote the dual cycle of Cu（Ⅰ）/Cu（Ⅱ）and Fe（II）/Fe（Ⅲ）in the system.After 5 cycles of experiments,the system still achieved 71.8%removal efficiency of MTZ,indicating that CuFeS₂ has excellent reusability performance.