The Activation Of Peroxymonosulfate And The Synergetic Removal Of Atrazine And Cr（Ⅵ） By CuFe-MoS₄ LDH Under Visible Light Irradiation

The compound pollution characteristics of organic and heavy metal commonly exist in wastewater.It is a great challenge for collaborative treatment process how to achieve organic oxidation degradation and heavy metal reduction removal simultaneously in the same system.In this paper,the Mo S₄^2-intercalated Cu Fe layered double hydroxide（LDH）has been designed and synthesized as a catalyst to realize activation of permonosulfate（PMS）with visible light assisted.The catalytic reaction system of CuFe-MoS₄LDH/PMS/vis has been constructed to achieve the synergistic removal of refractory organic matter atrazine（ATZ）and heavy metal pollutant Cr（Ⅵ）.Firstly,Cu Fe-LDH was prepared by hydrothermal method,and the Mo S₄^2-intercalation was successfully realized by ion exchange method,and the CuFe-MoS₄ LDH series catalyst was constructed.XRD,FTIR,Raman,SEM,TEM,BET and elemental analysis were used to confirm the formation of LDH structure,the successful exchange of intercalated ions and the properties of specific surface area.Then,the effects of catalyst dosage,PMS concentration,initial ATZ concentration,light intensity,initial p H,coexisting anions and HA（Humic Acid）on the reaction of catalytic oxidation degradation of organic pollutants were investigated.The influence of ionic strength and ATR-FTIR results indicated that CuFe-MoS₄ LDH was combined with PMS by inner-sphere complexation and formed complexs of≡M-（OH）OSO₃（M=Cu,Fe）through hydroxyl group on catalyst surface.The quenching experiments and EPR results revealed that the main active species in the degradation process of ATZ were·O₂^-,·OH and SO₄·^-.In addition,photogenerated electron also plays an important role by directly activating PMS or promoting M^（n+1）+/Mⁿ⁺cycling of the active center metal.Furthermore,the effect of different atmosphere and the change of oxygen vacancy（O_v）before and after the reaction proved that·O₂^-did not come from the dissolved oxygen in water but from PMS.Through UV-vis DRS,EIS and transient photocurrent response photocatalytic characterization and XPS analysis,it can be found that the addition of Mo S₄^2-gives CuFe-MoS₄ LDH excellent PMS activation performance and photocatalytic performance,by changing the photocatalytic properties of the material to narrow down its energy band gap or by acting as an electron donor to promote the cycle of active center metal M^（n+1）+/Mⁿ⁺,in which S^2-is the main electron donor.In addition,the synergistic catalytic effect of Cu Fe bimetal also can promote the activation of PMS.In the second part,the synergistic removal of ATZ and Cr（Ⅵ）by CuFe-MoS₄LDH/PMS/vis system was studied.The effects of catalyst dosage,PMS concentration,initial concentration of ATZ,initial concentration of Cr（Ⅵ）and light intensity on the synergistic removal of ATZ and Cr（Ⅵ）were investigated.Under the optimal conditions of0.4 g/L CuFe-MoS₄ LDH and 2 m M PMS,the removal rate of 0.05 m M ATZ and 20 mg/L Cr（Ⅵ）can reach 99.9%within 20 min.Quenching experiments and EPR results revealed that the addition of Cr（Ⅵ）changed the main active species of ATZ oxidative degradation,from mainly·O₂^-,·OH and SO₄·^-to·OH and SO₄·^-.And·O₂^-and e^-were the main active species for Cr（Ⅵ）reduction removal.The determination of the total chromium and Cr（Ⅵ）concentration in the solution over time and the Cr 2p XPS analysis of CuFe-MoS₄LDH proved the existence of Cr（Ⅲ）in the solution and on the surface of the catalyst,indicating that Cr（Ⅵ）has been reduced into Cr（Ⅲ）which has lower mobility and toxicity.