| With the rapid development of printing and dyeing industry,more and more pollutants in printing and dyeing wastewater are released into the water environment,which has a bad impact on the environment.Photocatalytic degradation technology could completely decompose dyes by sunlight,and has broad application prospects in printing and dyeing wastewater treatment.Nano-Ti O2 material has become the preferred material for photocatalytic research because of the high photocatalytic activity,stability,non-toxicity and low cost.Due to the large band gap of Ti O2,the light absorption range is narrow,and the electron-hole pair recombination rate is fast,which greatly limits the further application of Ti O2.In order to improve the photocatalytic activity of Ti O2,Ti O2 nanosheets with high activity（001）crystal plane exposure were synthesized by hydrothermal method,and modified by semiconductor compounding.The crystal structure,microstructure,element valence,specific surface area and optical property of the prepared samples were characterized by XRD,SEM,XPS,BET and PL.The photocatalytic activity of the samples was evaluated by using Rh B dye solution to simulate printing and dyeing wastewater.The photocatalytic degradation mechanism of the heterojunction catalyst was preliminarily discussed.The specific research contents are as follows:（1）The binary Ag Br/Ti O2 composites were constructed using Ag Br and Ti O2 by deposition precipitation method.The effect of different mass fractions of Ag Br on the morphology,structure and degradation performance of organic dyes were investigated.The results showed that when the mass fraction of Ag Br was 60%,the composite photocatalyst had the highest visible light degradation efficiency for Rh B solution,and the degradation effierency reached 92.3%within 30 min.This was because the construction of heterojunction effectively inhibited the recombination of photogenerated electron-hole pairs.（2）Ti O2/g-C3N4 binary catalysts were prepared by ball milling method.The effect of Ti O2 content on the morphology,structure and photocatalytic performance of Ti O2/g-C3N4binary composites were investigated.The results showed that the construction of binary heterojunction improved the transfer efficiency of photogenerated carriers,broadened the absorption range to the visible light region,and promoted the photocatalytic degradation reaction process.When the mass fraction of Ti O2 was 20%,the photocatalytic degradation efficiency of the composite catalyst toward Rh B was 98.5%within 90 min.This can be explained that the construction of heterojunction broadened the response range to visible light and increased the specific surface area of the photocatalyst.（3）Based on Ti O2 and g-C3N4 binary composites,the Ag Br/Ti O2/g-C3N4 ternary heterojunction photocatalysts was prepared by deposition precipitation method.The results of photocatalytic experiments showed that the degradation rate of Rh B by ternary heterojunction photocatalyst was 99.7%within 30 min,which was attributed to the fact that the ternary heterojunction increased the light absorption range in the visible light region and improved the photocatalytic activity by improving the transfer efficiency of photogenerated carriers.Combining with free radical trapping experiments,the double Z-type reaction mechanism of Ag Br/Ti O2/g-C3N4 ternary composites in the degradation process was deduced. |
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