A Preliminary Study On The Detection Of Singlet Oxygen In The Sodium Pyrophosphate/Monopersulfate And Base-Hydrogen Peroxide Systems

Alkali/peroxide systems are widely used in the fields of industrial wastewater treatment,material modification and pulp bleaching.Singlet oxygen（¹O₂）may play an important role in it,but its identification is difficult due to problems such as short life,rapid reaction,and detection easily interfered by reaction coexisting substances.For alkali/peroxide systems,the qualitative and quantitative results of various ¹O₂identification techniques that have been developed are still controversial.In this study,taking sodium pyrophosphate（PA）/monopersulfate（PMS）and alkali/hydrogen peroxide（H₂O₂）system as an example,electron paramagnetic resonance（EPR）method,ultraviolet-visible spectrophotometry（UV-vis）method and fluorescence photometric method,by changing conditions such as p H,concentration,solvent and reaction time,the generation of ¹O₂ in PA-PMS and alkali-H₂O₂ system was identified,and the following main conclusions were obtained:（1）In the PA-PMS system,the suspected ¹O₂ triple signal peak TEMPO was detected by the ¹O₂ probe（2,2,6,6-tetramethylpiperidine,TEMP）method,but according to a series of the quenching experiment using furfuryl alcohol（FFA）as the¹O₂ quencher shows that PMS can also directly oxidize TEMP to generate TEMPO signals,so it cannot be simply considered that all TEMPO signals are contributed by¹O₂ oxidation of TEMP.Based on the 9,10-anthracendiyl-bis（methylene）dimalonic acid（ABDA）probe,UV-vis,fluorescence and quenching experiments confirmed that PA can promote the formation of ¹O₂ in the PA-PMS system,Affects the intensity of the fluorescent signal and the UV signal of the probe.The contribution of ¹O₂ oxidation and PMS direct oxidation of TEMP to TEMPO signal needs to be judged by other quantitative experimental methods.（2）The Na₂CO₃-H₂O₂ system was identified based on the EPR experiment of the chemical probe TEMP,and the TEMPO signal suspected to be produced by ¹O₂ was obtained.H₂O₂ alone can also oxidize TEMP to generate TEMPO signal.Combined with FFA quenching experiments,it was proved that the TEMPO signal was generated by ¹O₂ oxidation of TEMP generated by Na₂CO₃ activation of H₂O₂ and H₂O₂ oxidation of TEMP.The ultraviolet experiment based on ABDA shows that ABDA is not suitable for identifying ¹O₂ in Na₂CO₃-H₂O₂ system.（3）In the CH₃CN-Na₂CO₃-H₂O₂ system,CH₃CN can cause the EPR triplet signal of the Na₂CO₃-H₂O₂ system to be significantly enhanced,because the CH₃CN-H₂O₂system can react to generate ¹O₂.The results of dye degradation experiments show that CH₃CN can significantly promote the decolorization efficiency of Na₂CO₃-H₂O₂system for various dyes.Concentration gradient experiments and quenching experiments prove that the ternary mixed CH₃CN-Na₂CO₃-H₂O₂ system can still generate ¹O₂,which may be an important reason for the improvement of dye decolorization efficiency.