Study Of Preparation,modification Of Nanometer Cuprous Oxide And Its Photodegradation Performance Of Sulfamethoxazole

Cuprous oxide（Cu₂O）was a semiconductor with narrow band gap（2.17 e V）which responded to visible light and absorbed 42%-43%solar energy.A large number of experiments showed that the polycrystalline Cu₂O exhibited excellent stability and could be used repeatedly without being reduced to Cu or oxidized to Cu²⁺.However,photocatalytic efficiency of pure Cu₂O photocatalyst was reduced due to its low holes mobility and utilization.If the migration of carriers were accelerated and provided holes to capture and separate holes and electrons,it enhanced effectively the photocatalytic efficiency.In this paper,the Cu₂O was prepared,modified and studied on photocatalytic to methyl orange which was represented in dye and sulfamethoxazole which was represented in antibiotic in wastewater.（1）Preparation,modification and photocatalytic performance of CeO₂/Cu₂O.Cu₂O was a nanosphere with particles size about 500 nm which band gap was 2.28 e V.The CeO₂/Cu₂O composite materials were prepared by 1M hydrazine hydrate and the shape of it was spherical with an average particle size about 500 nm and improved response to visible light（2.13 e V）.The 10 mg/m L methyl orange solution was degraded under visible light irradiation.The degradation rate of cuprous oxide was 61.88%and that of CeO₂/Cu₂O reached85.11%which was increased by 23.23%.The TOC removal rate was approximately 68.98%.CeO₂/Cu₂O still maintained excellent catalytic activity after 4 times repeated experiments.The active species capture experiments proved that photo-generated electrons（e⁺）played negligible role in the degradation process,while photo-generated holes（h⁺）and superoxide radicals(O^2-·)exhibited major role in the degradation process.The bending of the energy band leads to the building of an internal electric field promoting photo-excited electrons and holes to move in opposite directions.The charges are effectively separated which outstandingly enhances the photocatalytic activity under visible-light irradiation.（2）Preparation,modification and photocatalytic performance of AgBr-Ag/Cu-Cu₂OThe average particle size of AgBr-Ag/Cu-Cu₂O composites materials was about 250 nm with mainly octahedron,a small amount of microspheres and hollow spheres,which was prepared by 0.1M hydrazine hydrate.The band gap of the AgBr-Ag/Cu-Cu₂O composite catalyst was 1.75 e V,indicating that the deposition of AgBr-Ag on Cu₂O-Cu reduced the band gap and improved the response to visible light.The degradation rate of AgBr-Ag/Cu-Cu₂O to10mg/L methyl orange solution reached 93.78%,which was higher than that of pure Cu₂O.The AgBr-Ag/Cu-Cu₂O composite materials still maintained excellent catalytic activity after 4times repeated experiments and the degradation rate was not significantly reduced.Active species capture experiments showed that the influence of each active material on the degradation rate was photogenerated holes（h⁺）>superoxide radicals(O^2-·)>photogenerated electrons（e⁺）.The Cu of AgBr-Ag/Cu-Cu₂O system enhanced transfer and separation carriers and played an important role in improving the photocatalytic efficiency and stability.When Cu was introduced between Cu₂O and AgBr,an ohmic contact was formed at the interface,so that the photogenerated electrons on the AgBr conduction band could be transferred easily to Cu,and then recombine with the photogenerated holes on the Cu₂O valence band to improve the separation of carriers.（3）Preparation,modification and photocatalytic performance of CuS/Cu₂O.The average particle size of CuS/Cu₂O（1M hydrazine hydrate）was about 650 nm with spherical.The band gap of the CuS/Cu₂O composite catalysts was 1.70 e V,which indicated that loading CuS on Cu₂O could reduce the band gap and improve response to visible light.The degradation rate of CuS/Cu₂O to 10 mg/L methyl orange solution reached to 92.65%,which increased 30.77%than that of Cu₂O.The degradation rate to methyl orange did not decrease obviously after 4 times repeated experiments and CuS/Cu₂O presented excellent catalytic activity.The active species capture experiments to methyl orange indicated that photo-generated holes and superoxide radicals showed major roles.While photo-generated holes played minor roles.The introduction of CuS on Cu₂O caused the photogenerated electrons in the valence band of Cu₂O to migrate to the valence band of CuS collecting easily carriers on the surface of Cu₂O due to the narrow band gap characteristic of CuS which enhanced the transfer and separation of the carriers when it was excited by visible light irradiation.（4）Research on Degradation Effect of Composite Catalysts on AntibioticsThe degradation process of CeO₂/Cu₂O composites to SMX was gentle,and the degradation rate was 89.81%.AgBr-Ag/Cu-Cu₂O composites and CuS/Cu₂O composites materials degraded intensely to SMX.The maximum degradation rates were 97.18%and95.68%,respectively.At different p H environment,the degradation rate of every catalyst showed the same pattern which was that of weak acidity（p H=5）>neutral（p H=7）>strong acidity（p H=3）>weak alkaline（p H=9）>Strong alkaline（p H=11）.The degradation rate of the three composite catalysts to SMX decreased with the increase of concentration of SMX,and the decrease rate remained about 8%,indicating that all catalysts were more suitable to apply at low concentrations of SMX.