| Carbamazepine（CBZ）as a refractory organic drug,has appeared frequently and in relatively high concentrations in various aquatic environments,posing a potential threat to humans and the ecological environment.The conventional water treatment process cannot effectively remove CBZ,and the advanced treatment technology cannot be applied on a large scale due to the disadvantages of complex processes and high operating costs.Based on the degradation of CBZ by Mn O2,the role of Mn（Ⅲ）in the oxidation of CBZ byδ-Mn O2 was studied,and the effect of chemical structure on the oxidation of CBZ by Mn O2 was discussed.The main results are as follows:Through the study of the degradation effect of amorphousδ-Mn O2 on CBZ before and after the removal of Mn（Ⅲ）,it is preliminarily verified that Mn（Ⅲ）does not play a leading role in the oxidation of CBZ by amorphousδ-Mn O2.（1）After pyrophosphate（PP）complexed amorphous amorphousδ-Mn O2 with"solid"Mn（Ⅲ）,amorphous free-Mn（Ⅲ）δ-Mn O2 was obtained.At p H=1.8～3.0,the oxidation of CBZ by amorphous free-Mn（Ⅲ）δ-Mn O2 was better than that by amorphousδ-Mn O2.Through a series of physical characterization,it is proved that the better oxidation effect of amorphous Mn（Ⅲ）-freeδ-Mn O2 on CBZ can be attributed to its less Mn（Ⅲ）.（2）In the reaction process of Mn O2and CBZ,“soluble”Mn（Ⅲ）will be formed.By adding PP to two kinds of amorphousδ-Mn O2 to limit the reactivity of“soluble”Mn（Ⅲ）,the addition of PP significantly reduces the kinetic rate of oxidation of CBZ by amorphousδ-Mn O2 and amorphous Mn（Ⅲ）-freeδ-Mn O2,because PP or Mn（Ⅲ）-PP complexes occupied the Mn O2 active sites.Mn（Ⅲ）from different sources was prepared,which directly proved that Mn（Ⅲ）could not effectively oxidize CBZ.（1）Mn（Ⅲ）produced by 50mg/L Mn（OAC）3·2H2O has no removal effect on 1mg/L CBZ,but can completely degrade 1mg/L DCF and BPA within 20min.（2）The"solid"Mn（Ⅲ）contained in amorphousδ-Mn O2 can be dissolved in hydrochloric acid solution,and the"solid"Mn（Ⅲ）can degrade 5～6%of DCF and BPA,but has no removal effect on CBZ.（3）Different kinds and concentrations of organic drugs react with two kinds of amorphousδ-Mn O2 to produce“soluble”Mn（Ⅲ）.The separated“soluble”Mn（Ⅲ）can significantly degrade 14.4%～25.3%of DCF and BPA,and has no removal effect on CBZ.It is confirmed that the newly formed“soluble”Mn（Ⅲ）and"solid"Mn（Ⅲ）don’t play a leading role in the oxidation of CBZ by amorphousδ-Mn O2.There are significant differences in the oxidation of CBZ by Mn O2 with different crystal structures,and the degradation of CBZ by Mn O2 is mainly surface reaction.The Oxidation Reactivity of Mn O2 with different structures to CBZ is as follows:δ-Mn O2>>α-Mn O2≈γ-Mn O2>β-Mn O2.The kinetic rate ofδ-Mn O2 is 17 times higher than that ofα-Mn O2.Density functional theory calculation shows thatδ-Mn O2（110）crystal surface has higher adsorption energy and lower desorption energy,which is conducive to promoting CBZ oxidation.In conclusion,Mn（Ⅲ）does not play a key role in the oxidation of CBZ byδ-Mn O2.The crystal structure will significantly affect the oxidation of organic pollutants.Surface reaction is an important link in the oxidation of CBZ by Mn O2. |
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