Research On The Degradation Of Diclofenac Sodium In Water By Potassium Ferrate(Ⅵ)/Sodium Sulfite System

The oxidant used in this study is potassium ferrate（K₂FeO₄）,which has strong oxidizing properties,and its oxidation products are environmentally friendly.A trivalent iron oxide or a trivalent iron hydroxide.However,K₂FeO₄ is a selective oxidant,so how to fully exert its oxidizing properties has become the focus of research in recent years.The target pollutant selected in this experiment is diclofenac sodium（DCF）,a common ECs.The way to strengthen K₂FeO₄ is to construct a K₂FeO₄/Na₂SO₃ system,which uses the co-oxidation of intermediate valence iron（Fe（V））and sulfate radicals to degrade the target.This study first explored the reaction kinetics of K₂FeO₄ and Na₂SO₃ and found that the reaction between them was greatly affected by pH.The rate constant at pH 6(1.24×10⁵ M^-1s^-1)differs from the rate constant at pH 9(2.4×10³ M^-1s^-1)by two orders of magnitude.It can be seen that the reactivity of K₂FeO₄ with Na₂SO₃ under acidic conditions is It is much stronger than alkaline conditions.Then,the factors affecting the degradation of DCF in K₂FeO4/Na₂SO₃ system were investigated from the pH of the reaction system,the dosage of Na₂SO₃,the dosage of K₂FeO₄,and the dissolved oxygen.The main active substances in the oxidation process of the system were also analyzed.The experimental results show that the main oxidizing substances of DCF degraded by K₂FeO₄/Na₂SO₃ system are different under different conditions.In the low concentration region of Na₂SO₃（≤100μM）,Na₂SO₃ promotes the formation of more oxidative Fe（V）in K₂FeO₄ to degradate DCF.In the high concentration region of Na₂SO₃（≥100μM）,K₂FeO₄ is used as a promoter to promote Na₂SO₃ to produce SO₄^·-to degradate DCF.From the pH point of view,since Fe（VI）and Fe（V）are more active under acidic conditions,the maximum degradation rate can be achieved in the low concentration region of Na₂SO₃.Under alkaline conditions,the activities of Fe（VI）and Fe（V）were inhibited,and the system reached the maximum degradation rate when SO₄^·-was formed in the high concentration region of Na₂SO₃.Under the actual water conditions（Songhua River water,groundwater）,the K₂FeO₄/Na₂SO₃ system still has a good degradation effect on DCF,even if the dosage of K₂FeO₄ is only 25μM,and the dosage of Na₂SO₃ is 400μM,in the condition of pine flower.In river water,the degradation efficiency of DCF in groundwater can reach 85%and 85%,respectively.