Synthesis Of TiO₂ Crystal Facet For Arsenic Removal

As a much toxic metallic element,elevated geogenic arsenic?As?in groundwater?>10 ?g/L?has becoming an urgent environmental problem in the world.Chronic exposure to As can lead to many diseases including cancer,thus groundwater As treatment has attracted worldwide interest.TiO₂ nanomaterials have been widely used in arsenic?As?remediation,although reports on their adsorption and photocatalytic capacity have been controversial.Recent intriguing studies have shown that the adsorption and photocatalytic activity of TiO₂ largely depend on its surface atomic structure and the degree of exposed reactive crystal facets.Anatase.The adsorption and photocatalytic performance of anatase TiO₂ depend on its size,shape,and surface atomic structure.6-8 Meanwhile,the properties of surface acid sites including type,concentration,and strength also play an important role in the activity of TiO₂This paper used TiO₂ to study the adsorption and photocatalytic activity of As and studies the major role in the process of reaction mechaniam The main results of the experiment are as follows:?1?Prepare the TiO₂ with different proportion of crystal materials,using a variety of in situ characterization methods to explore different physical properties of crystal materials,physical properties of the crystal morphology.According to the experimental results show that the TiO₂{101} crystal materials are octahedron configuration,its particle size is about 150 nm.The isoelectric point is 5.5.TiO₂{001} crystal materials are flat octahedron configuration,through the experiment condition to self-assemble into the spherical,the average particle size about 40 nm,The isoelectric point is 6.9.TiO₂{100} crystal materials are spindle configuration,the hammer body two paragraphs are 20% exposure to {101} crystal,the average particle size is about 750 nm.The isoelectric point is 4.1.?2?Using Langmuir and Freundlich adsorption isothermal model fits the three kinds of crystal adsorption for As???and As???.According to the experimental results show that TiO₂{001} crystal adsorption of As???solution is 53.7 mg/g and for the As???solution is 76.1 mg/g;TiO₂{100} crystal adsorption of As???solution is 32.9 mg/g and for the As???solution is 22.4 mg/g;TiO₂{101} crystal adsorption of As???solution for 148.3 mg/g and for the As???solution is 123.6 mg/g.The adsortion rate is {101}>{001}>{100}.The adsorption capacity of the crystal material is influenced by the material size,the surface area,the crystal surface energy,and the atomic form of the material.p H mainly influences the adsorption effect by affecting the presence of arsenic,which is the main factor affecting adsorption performance.?3?The experiment explored the three kinds of crystal materials photocatalytic degradation rate and properties for As???,founding that the three kinds of materials showed good catalytic oxidation properties for the As???.In the process of photocatalytic oxidation of {001} crystal materials,the reaction rate is the fastest.Within 30 minutes As???can be completely oxidized.The photocatalytic oxidation degradation reaction rate of the three kinds of materials for the As???solution is {001} > {101} > {100}.?4?Reactive oxygen species?ROS?,including ·OH andO₂·-,are commonly accepted as the main oxidants in the TiO₂/UV process.In the process of photocatalytic oxidation experiment,according to the fluorescence spectrum analysis and the ESR experimental spectrum analysis,the produce content of ·OH is in order of {001} > {101} > {100} while the {001} crystal materials can produce a large amount of · OH andO₂ – which lead to its excellent performance in the process of photocatalytic oxidation TiO₂ {001} facets,with stronger Lewis acid Ti4+ atoms,exhibit higher adsorption affinity than {101} facets.Furthermore,the strong interactions of {001} facets with oxygen molecules lead to more photoelectrons being transferred to the adsorbedO₂ to generate superoxide radical,which is the primary oxidant in the As???photooxidation.