关键词: 光敏剂, 锌酞菁, 纤维素, 纳米纤维膜, 单线态氧, 染料降解

Abstract: In recent years, wastewater discharge accounts for a large proportion of environmental pollution, posing a great threat to the environment and human health. Printing and dyeing wastewater has been paid much attention in the field of wastewater treatment and reuse for its high chroma, complex components and large amounts of discharge. The available dye-degradation methods including physical adsorption and biological treatment have problems like secondary pollution, high cost and energy-consuming, while the photocatalytic dye-degradation method based on the inorganic semiconductor, though famous for its high efficiency, also has defects such as difficult material recovery and requiring UV light illumination. Therefore, it is necessary to develop new recyclable photocatalytic materials for efficient dye decomposition in wastewater treatment.
In order to construct highly-efficient, recyclable and visible light responsive dye degradation materials, we started from the excellent photocatalytic performance of organic photosensitizers and the high specific surface area of nanofiber membrane, synthesizing and characterizing tetracarboxyl modified symmetric zinc phthalocyanine organic photosensitizer, and then covalently grafted it onto the cellulose nanofiber obtained by electrospinning technology via N,N'-carbonyldiimidazole catalytic esterification method. The zinc phthalocyanine photosensitive group has strong visible light absorption and high singlet oxygen quantum yield. However, due to the high planarity of the structure, the intermolecular aggregation can lead to the reduction of photosensitive activity. In this paper, zinc phthalocyanine photosensitizer was covalently loaded on the surface of nanofiber membrane to provide space for molecular extension, which could reduce the aggregation of zinc phthalocyanine derivatives and improve the photosensitivity. The chemical structure and appearance of the novel zinc phthalocyanine functionalized nanofiber membrane were analyzed, its photocatalytic mechanism was further studied through reactive oxygen capture technology, and its dye degradation performance and recycling ability under visible light condition were explored. It is found that the zinc phthalocyanine photosensitizer functionalized nanofiber membrane has excellent singlet oxygen generation ability under near-infrared light irradiation, and the adsorption ability of the nanofiber membrane to dyes can help alleviate the problem of weak degradation ability caused by short singlet oxygen lifetime. The zinc phthalocyanine functionalized nanofiber membrane has the degradation performance to methylene blue under visible light irradiation, and it can be recycled for reuse.
The photosensitive activity of zinc phthalocyanine photosensitizer provides new enlightenment for photocatalytic degradation of dyes. The covalent grafting of zinc phthalocyanine photosensitizer onto the cellulose nanofiber membrane can achieve efficient degradation of dyes under visible light catalysis, and it is easy to recover, which provides a new idea for the development of new efficient and recyclable wastewater treatment materials.

Key words: photosensitizer, zinc phthalocyanine, cellucose, nanofiber membrane, singlet oxygen, dye degradation