Photoassisted-ferrocene/H₂O₂ Heterogeneous System To Degrade Sulfonamide Antibiotics

Antibiotics are well-acknowledged micropollutants in wastewaters and surface waters.They are of acute concern because they can trigger an increase of resistant bacterial flora.Therefore,the novel and efficient technology for the removal of antibiotics is urgently needed.In this study,heterogeneous Fenton-like reaction based on ferrocene?Fc?had been constructed,sulfamethoxazole?SMX?and sulfamethazine?SMZ?was selected as target compound due to its widely detected in water.The effects of initial pH,the dosage of Fc and H₂O₂ concentration on the degradation of these two target pollutants were investigated.The degradation kinetics,transformation pathway,and degradation products of SMX and SMZ in this system were also explored,and the main conclusions are as follow:?1?The Fc/H₂O₂/UV system had better degradation efficiency for SMX and SMZ relative to Fc,Fc/UV,H₂O₂,H₂O₂/UV,Fc/H₂O₂ systems,respectively.The results show that Fc-catalyzed heterogeneous photo-Fenton system established can be used as a feasible method for the removal of SMX and SMZ.?2?Combined with the observations above,we employed the degradation system to probe the degradation mechanism of antibiotics with the initial conditions of pH=3,the dosage of 0.25 g/L Fc and 25 mmol/L H₂O₂.Radical scavenger experiment confirmed that the photogenerated·OH was largely responsible for the photolytic enhancement of SMX and SMZ in Fc/H₂O₂/UV system.?3?The electron spin resonance?EPR?technique revealed that the photogenerated O₂·^-was found in the system,indicating that Fc can generate electrons under light conditions,and then H₂O₂ and dissolved oxygen underwent electron disproportionation to produce·OH and O₂·^-,which promoted the degradation of SMX and SMZ.?4?The degradation products of SMX and SMZ in Fc/H₂O₂/UV system were identified by LC/LTQ-Orbitrap MS,the removal of SO₂ and the products of breaking of C—S,S—N,N—C bonds were observed.and it was found that aniline group in sulfonamide antibiotics molecule was verified to be the primarily reactive site for·OH attack by degrading sulfonamides and their sub-structures.Finally,the degradation pathways of SMX and SMZ were deduced.?5?Common solubility components?such as DOM,HCO₃^-,Cl^-,Br^-?in water can quench the·OH,thus inhibit the photodegradation of SMX and SMZ.However,the ionic strength had no significant effect on the degradation of SMX and SMZ in Fc/H₂O₂/UV system,which showed that this technique had a good effect on the treatment of wastewater containing high salinity antibiotics.After cyclic experiments,it was found that ferrocene has good catalytic stability and recycling properties.The research results are expected to develop a new Fc/H₂O₂/UV oxidation technology,and provide new remediation strategies and technical support for dislodging new pollutants such as antibiotics in water.