Investigation On Hydrothermal Synthesis And Photocatalytic Properties Of SnO₂ And ?-Fe₂O₃ Nanomaterials

With the development of the global economy and the improvement of people's environmental awareness,novel,environmental friendly and highly efficient degradation technology of the colored dyes in industrial wastewater has become a research hotspot.The application of semiconductor oxide nanomaterials as the photocatalysts has attracted more and more attention.In order to prepare semiconductor oxide nanomaterials with high photocatalytic properties and low cost,four morphologies of SnO₂ nanomaterials and three morphologies of?-Fe₂O₃ nanomaterials were synthesized by hydrothermal method.The phases,morphologies and microstructures of the synthesized products were carried out.The optimum synthesis processes of Sn O₂ and?-Fe₂O₃ nanomaterials arepresented by analyzing the effect of various process parameters on the micromorphologies of the synthetic products.The growth mechanismsof different morphologies of SnO₂ and?-Fe₂O₃ nanomaterials arediscussed.By testing the photocatalytic propertiesof the products with different morphologies to degrade methylene blue?MB?,methyl orange?MO?and rhodamine B?RhB?,the degradation abilitiesare evaluated,and the photocatalytic mechanismsareclarified.The specific surface areas and pore size distributions of SnO₂ and?-Fe₂O₃ nanomaterials were tested,and the effects of the specific surface areas of SnO₂ and?-Fe₂O₃ nanomaterials on the photocatalytic properties are investigeted.The synthetic parameters have a great influence on the morphologies of the products.Low temperature and short time induce the incompletion growth of the as-prepared products.High temperature and increased time make the surface coarse.The SnO₂ nanosheets assembled into flowers are thin and wide under the condition of hexadecyl trimethyl ammonium bromide?CTAB?,and they becomethicker and narrower under the condition of sodium dodecyl sulfate?SDS?.The mesoporous SnO₂ nanospheres with a diameter of about 40 nm were synthesized at160°C for 3 h using Na₂SnO₃·3H₂O and glucose as the source materials.The specific surface area is 48.39 m²g^-1.The degradation rates for MB,MO and RhB are 98.51%,97.62%and96.53%,respectively,and the degradation times are 30,40 and 70 min,respectively.The SnO₂nanoflowers assembled by the nanorods with a diameter of about 60 nm and the length of about 300 nm were synthesized at 200°C for 24 h using Na₂SnO₃·3H₂O and NaOH as the source materials.The specific surface area was 47.59 m²g^-1.The degradation rates for MB,MO and RhB are 98.48%,96.77%and 96.48%,respectively,and the degradation times are 30,55 and 35 min,respectively.The SnO₂ nanoflowers assembled by the nanosheets with a thickness of about 5 nm were synthesized at 140°C for 12 h using SnCl₂·2H₂O,NaOH and CTAB as the source materials.The specific surface area was 68.84 m²g^-1.The degradation rates for MB,MO and RhB are 99.42%,98.86%,97.73%,respectively,and the degradation times are 30,50 and 45 min,respectively.The urchin-like SnO₂ nanostructures assembled by the nanothorns with a diameter of about 20 nm were synthesized at 180°C for 24 h using SnCl₄·5H₂O,NaOH and Zn?CH₃COO?₂·2H₂O as the source materials.The specific surface area was 45.06 m²g^-1.The degradation rates for MB,MO and RhB are 98.43%,96.18%and95.87%,respectively,and the degradation times are 30,55 and 50 min,respectively.The?-Fe₂O₃ nanocubes with a side length of about 100 nm were synthesized at 140°C for 12 h using FeCl₃·6H₂O,NaOH and CTAB as the source materials.The specific surface area was 10.69 m²g^-1.The degradation rates for MB,MO and RhB are 97.62%,94.93%and96.81%,respectively,and the degradation times are 90,140 and 120 min,respectively.The urchin-like?-Fe₂O₃ nanostructures assembled by the nanothorns with a diameter of about 80nm were synthesized at 140°C for 12 h using FeCl₃·6H₂O and Na₂SO₄ as the source materials.The specific surface area was 40.88 m²g^-1.The degradation rates for MB,MO and RhB are99.34%,98.17%and 98.76%,respectively,and the degradation times are 80,110 and 100 min,respectively.The coral-like?-Fe₂O₃ nanostructures assembled by the nanospheres with a diameter of about 80 nm were synthesized at 140°C for 12 h using FeCl₃·6H₂O,H₂C₂O₄ and CH₄N₂O the source materials.The specific surface area was 28.16 m²g^-1.The degradation rates for MB,MO and RhB are 98.25%,95.76%and 98.18%,respectively,and the degradation times are 90,130 and 120 min,respectively.The as-preparedSnO₂ nanomaterials are tetragonal rutile phase,and the?-Fe₂O₃nanomaterials are cubic phase with high purity and well crystallinity.The as-prepared products possess excellent photocatalytic activity for MB,MO and RhB.Especially for MB,the degradation rate is the fastest and the degradation rate is the highest.The specific surface area of the products has an important influence on its photocatalytic performance.It is obvious that the specific surface area is larger,the degradation rate is higher.In addition,the as-prepared SnO₂ and?-Fe₂O₃ nanomaterials exhibit high degradation efficiency for MB after five cycles.It has great significance on eliminating organic pollutants in industrial effluent.