| This research was supported by the project of National Science and Technology Support Program of China, which was the key technology of large-scale production and application of Konjac Glucomannan (2007BAE42B04) and Postgraduate Innovation Fund sponsored by Southwest University of Science and Technology, which was the Photo and thermocatalytic degradation of polyethylene films over TiO2and NiCoMnO4catalyst (Grant No.13ycjjl2). The catalytic activity of TiO2and NiCoMnO4powders was studied by catalytic degradation of methylene blue. Afte that, these two kinds of catalysts were added into polyethylene films, the aging temperature, aging time, catalyst dosage, etc were all discussed. Finially, the antioxidant1010was added into the LDPE/TiO2/NiCoMnO4composite films and the degradable properties of LDPE/TiO2/NiCoMnO4/1010composite films under photo and heat irradiation were also investigated. It is the hope that this research may offer some references and guidance for the treatment of organic effluents and degradation of polyethylene. The main results are as follows:(1) The thermocatalytic activity of TiO2powders is weak when decomposing methylene blue molecules. After reacting for40h, the removal efficiency just reached35.6%. The thermocatalytic activity of NiCoMnO4is higher than TiO2powders and after reacting for40h, the degradation efficiency was up to92.3%under the optimal condition. The methylene blue molecules were degraded into toluenes, or even CO2an H2O over NiCoMnO4catalyst. Meanwhile, the thermocatalytic degradation process fitted well with the pseudo first-order kinetic model and was found similarly to Langmuir-Hinshelwood behavior.(2) In the thermal aging test, the aging degree is greater with higher aging temperature and longer aging time, and the films were degraded more serious in air than in water. Both TiO2and NiCoMnO4powders can lead to drastic thermal degradation, besides, NiCoMnO4powders can cause crosslinking. The optimal dosages of TiO2and NiCoMn04in polyethylene films are2%and1%. After thermal aging in air at50℃for90days, the carbonyl index of pure films, LDPE/TiO2and LDPE/NiCoMnO4with the best filler content reached0.06,0.29and0.74, the decomposition temperatures of these films decreased by22.8℃,65.6℃and53.4℃, respectively. There is a synergistic effect between TiO2and NiCoMnO4, the composite films filled with both catalysts were aged most violent than films with only one kind of catalyst. The carbonyl index and decomposition temperature of LDPE/TiO2/NiCoMnO4composite films reached0.8and decreased by75.9℃after thermal aging in air at50℃for90days.(3) In the photo and thermal aging test, both TiO2and NiCoMnO4powders can degrade polyethylene, while TiO2present more excellent photocatalytic activity and NiCoMnO4powders can cause crosslinking. The optimal dosages of TiO2and NiCoMnO4in polyethylene films are2%and5%. After UV accelerate aging in air at50℃for14days, the carbonyl index of pure films, LDPE/TiO2and LDPE/NiCoMnO4with the best filler content reached0.18,0.7and0.39, the decomposition temperatures of pure films and LDPE/TiO2composite films decreased by15.2℃and61℃, while the decomposition temperature of LDPE/NiCoMnO4composite films increased by11.5℃. With the increasing of aging time, the decomposition temperature of LDPE/TiO2composite films decreased all the time, while the decomposition temperature of LDPE/NiCoMnO4composite films increased first, and then decreased. There is a synergistic effect between TiO2and NiCoMnO4, the composite films filled with both catalysts were aged most violent than films with only one kind of catalyst. The carbonyl index and decomposition temperature of LDPE/TiO2/NiCoMnO4composite films reached0.7and decreased by49.2℃after UV accelerate aging in air at50℃for14days. The antioxidant1010can control the photo and thermocatalytic degradation behavior of LDPE/TiO2/NiCoMnO4composite films effectively. When added with1.5%antioxidant, the carbonyl index of LDPE/TiO2/NiCoMnO4composite films dereased from0.7to0.17, the decomposition temperature increased from375℃to423.3℃. |
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