| Textile and dyeing industry discharges large amount of dye effluents containing organic compounds with high concentration and chromaticity, which cause severe pollution to the environment. Therefore, it is necessary to treat the wastewater. However, low BOD5/COD makes it difficult to dispose these chemicals through conventional methods. Heterogeneous Fenton reaction can be carried out at mild conditions. What is more, the generated hydroxyl radicals can not only strongly degrade dye molecules without selectivity but also overcome shortcomings of traditional homogeneous Fenton reaction such as narrow pH range and unrecyclable property of homogeneous catalysts. As a result, heterogeneous Fenton reaction became the top concern of scientific research. The key of Heterogeneous Fenton reaction is the development of heterogeneous catalysts with good performance. In this paper, we prepared two heterogeneous catalysts of Cu-L zeolite and CuO/ZrO2and studied the catalytic activity in the heterogeneous Fenton reaction.According to the generation and degradation mechanism of hydroxyl radicals, the pore structure of porous material should have some influence on catalytic activity. Zeolite L has one-dimensional porous structure and a high surface area. This paper hydrothermally synthesized a series of Cu-L zeolites for the first time and tested the catalytic activity of peroxide degradation using methylene blue and acid scarlet as model compound. The study mainly focused on the influence of L zeolite porous structure on the degradation of dyes. The results showed that methylene blue with small molecular size could enter the Cu-L zeolite channels and cover the active sites of the catalyst, so the dye solution can get high decoloration efficiency according to adsorption, while oxidative degradation of dye was weak. However, the molecular size of acid scarlet was so big that it could not enter the zeolite channel. Hydroxyl radicals produced at the active sites degraded acid scarlet and ideal decoloration efficiency was observed. Catalytic activity of Cu-L zeolite was also influenced by Cu content. Cu-L zeolite could show high activity through adjusting Cu content of the catalyst. At50℃, decoloration efficiency of acid scarlet can reach98.6%for120min when catalyst prepared with the best proportion adding amount was50mg and3%H2O2adding amount was1ml. In addition, the study found that the Cu-L zeolite synthesized hydrothermally had a better catalytic performance than both the Cu-L zeolite synthesized through ion-exchange method and Fe-L zeolite synthesized hydrothermally.As a stable catalyst support, ZrO2can not only make active component highly dispersed, but also interact intensely with active components and affect the activity of the catalysts. CuO/ZrO2as the heterogeneous Fenton reaction catalyst has not been reported inland or oversea. This article focused on CuO/ZrO2preparation methods and the influencing factor of heterogeneous Fenton treatment with acid scarlet. The results showed that CuO/ZrO2prepared through immersion method had the best activity and CuO/ZrO2prepared through mixing method took the second place. CuO/ZrO2prepared through co-precipitation method was amorphous and the catalytic activity was quite different with various CuO content. The decoloration efficiency of acid scarlet was decreased with the increase of CuO content when CuO/ZrO2prepared through mixing and immersion method was used, while it was decreased with the increase of CuO content when CuO/ZrO2prepared through coprecipitation was used. At50℃, decoloration efficiency of200mg/L acid scarlet (50ml) can reach95.4%for120min when catalyst which was prepared through immersion with CuO content of5%was used. The catalyst adding amount was50mg and3%H2O2adding amount was1ml. In addition, the paper studied the influence of temperature, pH, initial dye concentration, catalyst loading and H2O2dosage on decoloration efficiency. What is more, CuO/ZrO2had a good decoloration efficiency of high concentration dye solution and could be operated in alkaline conditions, which was better than Cu-L Zeolite. Copper leaching amount of Cu-L zeolite and CuO/ZrO2were both quite low and the stability of Cu-L zeolite was better than CuO/ZrO2. |
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