Photocatalytic Degradatiob Of Congo Red In Wastewater By Nano-Ce/Nano-Fe Doped With Frestule And Activated Potassium Persulfate

The organic pollutants in wastewater can be degraded by photocatalysis technology,which can convert light energy into chemical energy,and has attracted great attention in the field of wastewater treatment.However,it still has some shortages such as poor photoresponse,excessive photo-generated charge carriers recombination,and severe photocorrosion.Therefore,the development of highly active and stable photocatalysts,and the construction of more efficient photocatalytic reaction system are the key of improving the efficiency of photocatalytic degradation.In the present paper,the Frustule,with unique porous and reticular structure,was used to dope CeO₂ to prepare Shell-Ce composite material.The degradation of Cogon red（CR）were studied by constructed Shell-Ce/UV system.The results showed that the decolorization rate of CR and the dye mineralization rate reached to 97%and 52%respectively under the suitable conditions（the concentration of CR:10 mg/L;pH:4;the dosage of Shell-Ce:0.7 g/L;the reaction time:90 min）.And the decolorization rate was still above 85%after 5 times recycle-degradation.The free radical inhibition experiment demonstrated that the order of active species in system is h⁺>·O₂^->·OH.In this photocatalytic system,the e^-and h⁺produced by Shell-Ce and reacted with O₂,H₂O and OH^-to generate·O₂^-and OH,these active substances participate the reaction with CR.According to the material properties of Shell-Ce,the Shell-Ce/PS/UV system was constructed.Peroxysulphate（PS）captures e^-to achieve efficient separation of photo-generated carriers,and activated PS to generate SO₄^·-,improve the photocatalytic capacity.In Shell-Ce/PS/UV system,the decolorization rate of CR and the dye mineralization rate reached to 97%and 70%respectively under the optimal conditions.And the decolorization rate was still above 94%after 5 times recycle-degradation.The free radical inhibition experiment demonstrated that the active species by the order of h⁺>SO₄^·->·O₂^->·OH in system.In this photocatalytic system,PS promote the efficient separation of photo-generated carriers of Shell-Ce,and the catalytic activity was improved.Meanwhile,cerium ion,e^-and other active substances are able to activated PS to generate SO₄^·-,improve the decolorization rate of CR.The Shell-Fe-Ce composite material was prepared by using Fe₃O₄ and Shell-Ce,and adopted to activate PS to degrade CR.The photocatalyst could be separated magnetically from an aqueous phase and the synergistic catalysis of Fe/Ce bimetallic can promote the activation of PS.In Shell-Fe-Ce/PS/UV system,the decolorization rate of CR and the dye mineralization rate reached to 98%and 67%respectively under the optimal conditions.And the decolorization rate was still above 96%after 5 times recycle-degradation.The free radical inhibition experiment confirmed that the order of active radical in system is SO₄^·->h⁺>·O₂^->·OH.The synergistic catalysis of Shell-Fe-Ce and PS can improve decolorization rate.Ce³⁺could not only activate PS,but also promoted the reduction of Fe³⁺to Fe²⁺.Fe²⁺could also reduced Ce⁴⁺to Ce³⁺,promoted the transform of Ce⁴⁺/Ce³⁺,Fe³⁺/Fe²⁺.In addition,the degradation products of CR in the above systems were determined by LC-MS,and it was found that CR had been degraded into small molecular organics,although CR was not fully mineralized.