Comparison On The Degradation Performance And Mechanism Of Tylosin By Plasma And Photocatalysis Based On Pyrite

The abuse and unregulated discharge of veterinary antibiotics has led to their widespread in the environment through various pathways,Which results in serious threat to the ecosystem and human health.Treatment of antibiotic-containing wastewater at the source is one of the important ways to solve the problem of antibiotic residues in environmental.Among them,the advanced oxidation process（AOP）is widely used in antibiotic wastewater treatment due to its advantages of high efficiency and no secondary pollution.Glow discharge plasma（GDP）technology and photocatalytic technology stand out from many AOPs.Because their advantage performances are as follow:ease operation,simple installation and high treatment capacity.However,the energy utilization efficiency of GDP is low.And the catalyst in photocatalysis suffers from narrow light absorption range and easy electron-hole complexation.Pyrite（FeS₂）has the advantages of narrow band gap（0.95 e V）,wide range of photoresponse,low price and wide distribution,which can compensate for the defects of GDP and photocatalyst.Therefore,FeS₂ was used to synergize GDP and photocatalysis for the degradation of Tylosin（TYL,veterinary antibiotic）with a large-molecule.Based on the comparative analysis of the degradation effect,degradation mechanism and degradation products of TYL by FeS₂ coupled with two techniques,three-dimensional rGOA-FeS₂ was prepared to address the problems of FeS₂for its poor reuse and difficult recycling.The photocatalytic effect,reuse and recycling performance of rGOA-FeS₂were investigated.The degradation mechanism of composite photocatalysis and the degradation products of TYL were discussed.The results of the study are as follows:（1）The results of GDP/FeS₂ degradation for TYL showed that the degradation efficiency of TYL increased with the increase of voltage,while the initial p H had little effect on the GDP/FeS₂ degradation of TYL.The degradation rate of GDP system for TYL was27.3%and the mineralization rate was 3.6%.The degradation rate and mineralization rate of GDP for TYL reached 56.3%and 17.7%after adding FeS₂,which increased by 29%and13.4%,respectively.The significant increase of ammonia nitrogen and nitrate nitrogen in the degradation solution of TYL after adding of FeS₂ indicated the mineralization of TYL.The results of active species trapping experiments and degradation product tests showed that all of the·OH,·O₂^-,h⁺and e^-played a role in degradation process.The e^-playing a major role.The TYL was attacked by these active oxide species and form small organic molecules through the breaking of C-C,C-N,and C-O bonds.And it was eventually mineralized to CO₂and H₂O.（2）In the FeS₂ photodegradation of TYL system,the degaradation and mineralization effciency of TYL with initial concentration of 10 mg/L reached 99.43%and 13.69%after 30min.The results of ammonia nitrogen and nitrate nitrogen tests and mineralization results indicated that the addition of raw FeS₂ promoted the mineralization of TYL.The active species capture experiments showed that the contributions of·O₂^-,·OH,h⁺and e^-in the degradation of TYL were not significantly different.Compared with the GDP/FeS₂degradation system,the efficiency of pyrite photocatalytic degradation for TYL increased by 43.1%.The mineralization rate decreased by 4.1%and the degradation intermediates were less.the degradation pathway of TYL was not significantly different from that of the GDP system.We concluded that FeS₂ photocatalytic technology is more suitable for degrading TYL by comparing the degradation efficiency,mechanism,stability and safety between the two system.（3）Three-dimensional rGOA-FeS₂ composites were successfully prepared by in situ hydrothermal method.The results of SEM,XRD,FT-IR,XPS and Raman showed that the crystalline shape of composites was unchanged.A stable three-dimensional mesh structure was formed between graphene and FeS₂ with Fe-O-C bond.The mechanical properties and elasticity of the composite were good.The photocatalytic degradation experiments and stability experiments showed that rGOA-FeS₂ has good photocatalytic performance and excellent recovery performance:the removal rate of TYL reached 92.4%at 120 min,which is 16.3%higher than that of synthetic FeS₂（76.1%）.The Fe-O-C bonds,π-πbonds,and three-dimensional structures of rGOA-FeS₂ are beneficial to the rapid transfer of electrons and the effective separation of photocarriers,which effectively enhances the photocatalytic performance of rGOA-FeS₂.The degradation rate of TYL remained around 85%after 5cycles.UV-vis DRS test results showed that rGOA-FeS₂ has a narrower band gap（1.08 e V）.The TRPL and PL test results indicated that rGOA-FeS₂promoted separation of photogenerated electrons and holes.Besides,it prolonged the lifetime of photogenerated carriers.The conduction band（CB）and valence band（VB）of rGOA-FeS₂ were positively shifted,which affected the generation of active oxide species.The EPR results showed that all of e^-,·O₂^-,h⁺,·OH and·SO₄^-played roles in the rGOA-FeS₂ photodegradation system.The active species capture experiments indicated that·O₂^-was the main active species.TYL was effectively degraded to small molecule organic substances,as well as CO₂ and H₂O by these active oxide species.The results of this study are expected to provide a possible solution for the defects of GDP and traditional photocatalyst.By comparing the degradation effects,mechanisms and degradation pathways of the two technologies,it provides a reference for the practical application of FeS₂ synergistic advanced oxidation technology for the degradation of antibiotics wastewater.To address the problem of difficult recycling of FeS₂,a method to prepare aerogel composites from graphene and FeS₂ is provided to improve their recyclability and photocatalytic performance,which further enriches the theoretical basis for the photocatalytic degradation of antibiotic wastewater.