The Effect Of Environmental Matrix On The Photodegradation Of Antidepressant By Humic Substances

Over the past decade,there have been numerous reports on the detection of anti-depressants in various water bodies,which has attracted widespread attention.Anti-depressants can accumulate and persist in the water environment,and traditional water treatment methods cannot effectively remove them.Humic substances（HS）,as an important photosensitizer,is widely found in natural water bodies such as lakes,rivers and oceans.For contaminants that are difficult to degrade directly,photochemical degradation can occur in HS solution through singlet oxygen oxidation or direct reaction with ³HS^*.And important environmental matrix in natural water bodies,such as metal ions(Ca²⁺,Mg²⁺,Fe³⁺,Mn²⁺,Cu²⁺,Zn²⁺,Cr³⁺,Al³⁺),halide ion（Cl^-,Br^-,I^-）,CO₃^2-,NO₃^-,SO₄^2-,etc.,they may have important effects on HS photochemical activity.In this study,the effects of environmental matrix on the photodegradation of anti-depressants by HS were discussed.The effects of metal ions and anions on the photochemical activity of HS were studied,and the main indexes were ³HS^*and singlet oxygen.The effect of metal ions and anions on the photodegradation of imipramine under deaerated conditions in the nitrogen was studied.The following points can be drawn from the study:Study on the effect of environmental matrix on the photochemical activity of HS suggested:.（1）Through the fluorescence characterization,both FA and HA will react with metal ions,the stability constants of FA and metal ions are in the order of Cu²⁺>Mn²⁺>Fe³⁺>Cr³⁺>Al³⁺>Zn²⁺>Ca²⁺>Mg²⁺,and the stability constant of HA is in the order of Cu²⁺>Mn²⁺>Fe³⁺>Al³⁺>Cr³⁺>Zn²⁺=Ca²⁺=Mg²⁺.We synthesized and characterized HS by fourier transform infrared spectroscopy（FT-IR）.It is found that FA has more oxygen-containing functional groups than HA.The coordination functional groups of metal ions and HS mainly contain oxygen-containing functional groups such as carboxyl,hydroxyl and aldehyde ketone.（2）Among the eight metal ions selected in the experiment,only the paramagnetic metal would have the quenching effect on ³FA^*and ³HA^*,and the inhibition decreasing order is:Cu²⁺>Mn²⁺>Fe³⁺>Cr³⁺,which is consistent with the stability constant.（3）The eight metal ions selected in the experiment will inhibit the production of ¹O₂.For FA,the inhibition decreasing order is:Cu²⁺>Mn²⁺>Fe³⁺>Cr³⁺>Al³⁺>Zn²⁺>Ca²⁺>Mg²⁺;For HA,the inhibition decreasing order is:Cu²⁺>Mn²⁺>Fe³⁺>Al³⁺>Cr³⁺>Zn²⁺=Ca²⁺=Mg²⁺,which is consistent with the stability constant.（4）The addition of 500μM I^-or 800μM Br^-have no effect on ³FA^*and ³HA^*.The addition of540 mM Cl^-will increase the concentration of ³FA^*and ³HA^*due to the effect of ion concentration,but there was no obvious effect of Cl^-.（5）Halide ions have no effect on¹O₂.（6）The addition of 500μM SO₄^2-、NO₃^-or CO₃^2-have no effect on ³HS^*and ¹O₂.Study on the effect of environmental matrix on the photodegradation of imipramine under deaerated conditions in the nitrogen suggested:（1）Only the paramagnetic metal ions of the eight metal ions selected in the experiment have inhibitory effects on FA and HA photosensitive degradation of IMP under deaerated conditions in the nitrogen,and the inhibition decreasing order is:Cu²⁺>Mn²⁺>Fe³⁺>Cr³⁺,which is consistent with the the effect of metal ions on ³FA^*and ³HA^*.（2）The addition of 500μM I^-inhabit the photodegradation of IMP.The addition of 800μM Br^-enhance the photodegradation of IMP due to the generation of Br₂^?-.By adding different concentrations of Cl^-,the degradation rate of IMP first increases and then decreases with the increase of ion concentration,while the generation of Cl₂^?-was helpful for the degradation of IMP.（3）The addition of 500μM SO₄^2-,NO₃^-or CO₃^2-have no effect on FA and HA photosensitive degradation of IMP under deaerated conditions in the nitrogen.（4）3 photodegradation products were detected.Demethylation and hydroxylation were two main processes for the photosensitized degradation of IMP in the FA aqueous solutions.