Synthesis Of Octahedron TiO₂ And Its Adsorption And Photocatalysis For Arsenic

As an efficient, environmentally friendly, non-toxic absorbent material and photocatalytic material, TiO2 is widely used in the treatment of arsenic contamination of drinking water. Since pH value, the concentrations of the adsorbent and arsenic reaction time, and the light source have significant impact on the adsorption and catalytic of arsenic, it is necessary to explore these factors and the adsorption and catalytic mechanism.In this work, Octahedral TiO2 nanocrystals (OTNs) with the main (101) surface have been prepared by hydrothermal method using the hexamethylenetetramine as the morphology controlling agent. XRD, SEM, BET was used for structural characterization. XRD results showed that all three were pure anatase phase. SEM results showed that anatase with (101) surface dispersed uniformly, uniform morphology, and the average size was 96.34nm. BET results showed that anatase with (101) surface specific surface area was 17.6m2·g-1, and there was a lot of mesoporous on the crystal surface. Anatase with (101) surface was used to adsorb As(III) and As(V) in the solution. When the arsenic concentration was 0.2mg·L-1 and the OTNs concentration was 0.1g·L-1, the adsorption reached equilibrium at pH 4,7,9 three solutions in 150min. Kinetic fitting results showed the adsorption behavior of As(III) and As(V) was more in line with false second-order equation, indicating chemical adsorption was dominant. Adsorption isotherm results showed that the adsorption was more in line with Langmiur adsorption isotherm model, adsorption capacity for As(III) and As(V) were 1.8930 mg·g-1 and 1.8566 mg·g-1 respectively. Total of 14 kinds of adsorption results with pH range from 1 to 13.5 showed that OTNs had a good adsorption ability for As(III) at neutral and alkaline solutions and for As(V) at acidic solutions. At pH range from 1 to 13 total of 13 kinds of uv photolysis results showed that OTNs could oxidize As(III) to As(V) within 30 min at pH range from 8 to 12. The adsorptions of As(III) and As(V) are simulated by the density functional theory (DFT) method. Qualitatively, the adsorption abilities of arsenic species, water and OH- follow the order of AsO33-> OH-> HAsO32-> H2AsO3-> H20> H3As03 for As(III) and AsO43->OH-> HAsO42-> H2AsO4-> H3As04> H2O for As(V). It implies that H2AsO3- should be the major As(III) species at pH 8 and H2AsO4- should be the major As(Ⅴ)species at pH 4,and the most negative charged ions AsO33- and AsO43-should correspond to the adsorptions at the high pH values 13 and 13.5.