关键词: MOF, UiO-66, 复合材料, 光催化降解, MB

Abstract:  As the printing and dyeing industry grows by leaps and bounds, a large amount of industrial wastewater is produced, making the dyestuff in it one of the major water pollutants. However, dyestuff is not easy to break down into harmless substances by natural forces in water due to its stable chemical properties. By absorbing and reflecting sunlight, it hinders the growth and reproduction of microorganisms in water bodies and weaken their abilities to degrade pollutants, which makes it one of the largest sources of pollution that damages the natural water environment. Azo dyes are the most widely used dyes in the textile industry, which can decompose and produce a variety of carcinogens in the environment. They will not only significantly increase the color of the water, but also upset the balance of the water ecosystem and change the DNA structure of the human body to cause lesions.
At present, the commonly used methods for treating azo dyes include precipitation, adsorption, membrane separation, photochemical and biological treatment. However, these methods are difficult to completely destroy the structure of azo dyes and convert them into organic compounds that are less toxic or can be degraded by microorganisms. Therefore, it has been a hot research topic to develop a low-cost method with certain market economic benefits to remove the dyestuff from printing and dyeing wastewater. In recent years, photocatalytic degradation, as a low-cost, simple-to-operate, and highly reusable technology, has arouse wide concern both domestically and internationally. It has also become a focused area in wastewater treatment. Photocatalytic degradation technology can convert solar energy into chemical energy, and it is a new technology to reduce environmental pollution and ease energy shortage. This paper uses metal-organic frameworks (MOF) as photocatalysts. UiO-66 is a type of MOF with good thermal stability, excellent chemical stability and resistance to high external pressure. These properties ensure it with many potential applications in wastewater treatment. However, UiO-66 has its downsides, such as poor visible light absorption, easy electron-hole recombination, proness to agglomeration, and poor stability and dispersion in water, which seriously affect its further application. Research has found that graphene oxide (GO) has good electrical conductivity. And the combination of UiO-66 and GO can reduce the electron-hole recombination, thereby improving the photocatalytic performance of UiO-66. In this article, a post-synthesis method was used to prepare the  composite material UiO-66@GO, and methylene blue (MB) was adopted as a substrate to explore the photocatalytic degradation performance of this composite material. The results showed that the pH value and the mass ratio of UiO-66 and GO had a significant impact on the photocatalytic performance of the composite material UiO-66@GO. When the pH value was 3 and the mass ratio of UiO-66 to GO was 5:1, the photocatalytic degradation efficiency of the prepared UiO-66@GO on MB reached 96.4%, higher than that of the homogenous UiO-66 material. The degradation efficiency was increased by 1.1 times.
Based on the results of the above experiments in this article, it can be concluded that the  composite material UiO-66@GO was successfully prepared and its photocatalytic performance was improved compared to the homogenous UiO-66 material. These conclusions can provide reference for the adsorption and photocatalytic degradation of dyestuff in printing and dyeing wastewater in the future.

Key words: metal-organic framework materials, UiO-66, composite materials, photocatalytic degradation, MB