چكيده به لاتين
In recent decades, with the growth of industries and population, environmental pollution, especially the presence of heavy metals in industrial wastewater, has become a major problem. Metals such as cadmium (Cd), mercury (Hg), lead (Pb), arsenic (As), and chromium (Cr) are considered a serious threat to human health and aquatic ecosystems due to their high toxicity and carcinogenic effects. Especially chromium (VI), which is more toxic than chromium (III) and causes problems such as liver damage, lung problems, severe diarrhea, and vomiting. Therefore, the removal of these dangerous pollutants from water sources has attracted the attention of many researchers. Various methods have been proposed to reduce the concentration of heavy metals in polluted waters, including chemical precipitation, ion exchange, membrane filtration, adsorption, and electrochemical treatment. However, in recent years, the use of photocatalysts has attracted attention as a new solution due to their high efficiency, good stability, and favorable performance in the degradation of organic and inorganic pollutants. Among various photocatalysts, metal-organic frameworks (MOFs) have shown great potential in the removal of pollutants due to their properties such as high porosity, large surface area, diverse structures, and chemical stability. Among them, iron-containing MOFs (Fe-MOFs) are considered an ideal option for water purification due to their low toxicity, abundance of iron element, good stability, and ease of production. However, one of the main challenges in the use of nano-photocatalysts is their separation after the purification process. Suspended nanoparticles are difficult to separate from water and, in some cases, can become a new pollutant themselves. To overcome this problem, immobilization of photocatalysts on solid substrates such as glass, ceramics, polymers, carbon nanotubes and zeolites has been proposed as an effective solution. In this study, the metal-organic framework MIL-88-A(Fe) was used as the photocatalyst and the stainless steel mesh was used as the support. The stainless steel mesh was chosen due to its features such as cost-effectiveness, mechanical stability, high corrosion resistance and reusability. The prepared photocatalyst support containing MIL-88-A(Fe) showed significant photocatalytic activity for the reduction of chromium (VI) under visible light irradiation. The chromium (VI) reduction efficiency after 60 min was approximately 93% for the powder state of the metal-organic framework and 91% for the prepared photocatalytic support containing the same amount of MOF. The coating on the metal mesh was performed with a combination of MIL-88-A(Fe) and PVDF, which showed strong adhesion and high stability after five recovery cycles. The performance of this catalyst was investigated under two processes of photocatalysis and sonocatalysis, and the results indicated a significant increase in the efficiency of chromium (VI) reduction in the presence of simultaneous light and ultrasound irradiation, which was attributed to the synergistic effects between ultrasound and the photocatalyst. In addition, the effects of factors such as pH changes, MOF content, presence and absence of hole scavenger and their effects on the chromium (VI) reduction process were evaluated. The synthesized samples were examined using XRD, FT-IR, UV-Visible, SEM and EDS analyses to carefully examine their structure and composition. The results of this study showed that the sonocatalysis method has a better performance in the removal of chromium (VI) compared to photocatalysis. Also, this research demonstrated the high potential of combining MOFs with polymer adhesives in the manufacture of stable and efficient photocatalysts for the purification of polluted water, which could be an important step towards the development of new environmental technologies. The results of this research can help develop new and efficient solutions in the field of water purification and reducing environmental pollution. Given the increasing growth of industries and the increasing need for clean water resources, the use of advanced materials such as Fe-MOFs along with new stabilization methods can be an effective step towards improving water quality and protecting the environment.
