Photocatalytic Reduction Of Chromium From Aqueous Solution By Fe-MIL-101 And Bi₂Ti₂O₇/TiO₂

With the development of industry,heavy metal pollution has become one of the major pollutants.Hexavalent chromium is one of the three most serious carcinogenic heavy metals.Once hexavalent chromium came into the nature,it will accumulate in plants and animals,causing deadly damage to the human body through the biological chain.Therefore,the treatment of waste water which contains hexavalent chromium can not be delayed anymore.In this study,hexavalent chromium will be reducted to trivalent chromium which has low toxicity by photocatalysis.We improved the synthesis methods in which we can prepared Fe-MIL-101 and Bi₂Ti₂O₇/TiO₂ with high surface areas successfully and easily.We took a series of material characterization to verification that they were successfully to be made.At last they were used for the photocatalytic reduction of chromium in the wastewater.During the photocatalytic activity study of Fe-MIL-101 and Bi₂Ti₂O₇/TiO₂,the influence of initial reaction concentration,addition amount of catalyst,light source and sacrificial agent to the reduction rate were considered.And we also studied the reuse of catalysts.XRD characterization were taken of the reuse materials before and after the reaction to verify the good stability of the materials.All these experiments show that:?1?When Fe-MIL-101 was used as the catalyst,20 mg of the catalyst and 2 mL of ethanol were added into 50 mL of the initial concentration of 40 ppm solution.The photocatalytic reduction rate was reached to 100%after 50min illumination with a 400w metal halide lamp.What's more important,its reduction rate can also reach 95%after reusing for three times.And the XRD characterization of the reused materials keep same with before,which proved the material's good stability and catalytic activity in the photo reaction.?2?When Bi₂Ti₂O₇/TiO₂ was used as the catalyst,20 mg of the catalyst and 2 mL of ethanol were added into 50 mL of the initial concentration of 20ppm solution.The photocatalytic reduction rate was reached to 100%after 50min illumination with a 500w mercury lamp.What's more important,its reduction rate can keep 100%without any decrease after reusing for three times.And the XRD characterization of the reused materials keep same with before,which proved the material's good stability and catalytic activity in the photo reaction.