Synthesis And Photocatalytic Activity Of Reduction Of Cr（Ⅵ） Over Bean Sprout Template TiO₂ Series Material

China is a large producer of chromium salts.Metallurgy,electroplating,electronics,metal processing and other industries need a large number of chromium and its compounds into use.And the lack of technology has led to serious Cr（Ⅵ）pollution problems.Cr（Ⅵ）has high biological toxicity and cannot be completely degraded by the organism,which causes serious environmental pollution.Photocatalytic reduction technology possesses the advantages of energy-save,no secondary pollution,safe operation and eco-friendliness,and has become one of the most mature technologies to solve the Cr（Ⅵ）pollution problem.TiO₂is one of the most common transition metal semiconductor materials.It possesses strong resistance to light corrosion,high potential energy,very strong oxidation and reducibility and other advantages.Currently,it has become the most commonly used catalyst for photocatalytic reduction of Cr（Ⅵ）.However,at the same time,TiO₂is still suffering from a number of problems in practical application.For example,the problems such as high utilization rate only for UV light and easy recombination of photogenerated electrons and hole need to be solved urgently.Many reports have shown that the morphology and structure of TiO₂have an important influence on its photocatalytic activity.In addition,metal element doping and incorporation of semiconductor materials can also improve the photocatalytic performance of TiO₂.Therefore,in this work,bean sprouts with natural pipe structure was selected as biological template to prepar tubulare TiO₂nanomaterials,and the catalyst was further modified by doping of transition metal elements and incorporating semiconductor materials.Cr ion-doped bio-templated TiO₂and ZnO semiconductor/bio-templated TiO₂composites were prepared.The characterization and photocatalytic performance experiments of these catalysts were performed,and the following main results were obtained:（1）Using cheap and easily available bean sprouts as a template,bean sprouts templated TiO₂was prepared by simply immersing the bean sprouts in the titanium precursor solution.The catalyst was characterized by XRD,BET,SEM,TEM,XPS,UV-vis and PL.Its performance of photocatalytic reduction of Cr（Ⅵ）under UV light was further investigated.Under the condition of cave sacrificial agent,the photocatalytic reduction rate of the BSS-TiO₂material reached 100%in 60 minutes,which is 22%higher than that of pure TiO₂.All materials show good stability.（2）The bean sprout stem templated TiO₂materials doped with different proportions of metal Cr（Cr/BSS-TiO₂）were synthesized by impregnation and biological template method.The catalyst was characterized by XRD,BET,SEM,TEM,XPS,UV-vis and PL.Its performance of photocatalytic reduction of Cr（Ⅵ）under ultraviolet light was further investigated.The results showed that under the condition of using formic acid as the hole sacrificial agent,the photocatalytic reduction rate of 1%Cr/BSS-TiO₂reached 100%in 60minutes,which is 22%higher than that of pure TiO₂.All materials show good stability.（3）The bean sprout stem templated TiO₂material incorporated with different proportions of ZnO（ZnO/BSS-TiO₂）were synthesized by impregnation and biological template method.The catalyst was characterized by XRD,BET,SEM,TEM,XPS,UV-vis and PL.Its performance of photocatalytic reduction of Cr（Ⅵ）under ultraviolet light was further investigated.The results showed that under the condition of using formic acid as the hole sacrificial agent,the photocatalytic reduction rate of 30%ZnO/BSS-TiO₂composite reached100%in 40 min,which is 31%and 86%higher than those of pure TiO₂and pure ZnO,respectively.All materials show good stability.This work,bean sprouts with was selected as biological template to prepar tubulare TiO₂nanomaterials,and the catalyst was further modified by doping Cr ion and incorporating ZnO.The material preparation method is simple and possesses strong resistance to acid corrosion,doping Cr ion and incorporating ZnO can also improve the photocatalytic performance of TiO₂.