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Novel Catalyst for Organic Pollutants Degradation

Researchers from Xiangtan University synthesized a novel photo-Fenton catalyst named Ag/AgCl/MIL-101(Fe)

Dyes find application in various industries such as printing, painting, textile, paper, and leather. According to ‘Removal of Dyes from the Effluent of Textile and Dyestuff Manufacturing Industry: A Review of Emerging Techniques With Reference to Biological Treatment’— a paper published in the journal – Critical Reviews in Environmental Science and Technology – in 2007, around 7 × 105 tons of commercial dyes are produced worldwide annually and around 5–10% of them are eventually lost in the waste water. Therefore, an efficient method of treating dye wastes is required.

Now, a team of researchers from Xiangtan University synthesized a new catalyst called Ag/AgCl/MIL-101(Fe). The team used MIL-101(Fe) as a host material to load Ag/AgCl with high visible light driven-Fenton catalytic activity under neutral pH. Methylene blue, also known as methylthioninium chloride— a medication and dye – was used as a target contaminant to assess the photo-Fenton catalytic activity of Ag/AgCl/MIL-101(Fe). The team optimized the effects of variables such as initial concentration of methylene blue, water concentration, irradiation intensity, and catalyst dosage on the degradation of methylene blue with the help of Box–Behnken design (BBD) method. Plackett-Burman design was used to screen and enhance the variables that have an impact on the degradation of methylene blue.

The team found that Ag/AgCl/MIL-101(Fe) demonstrated high catalytic activity in the visible light-Fenton system. 99.75% of methylene blue decolorization efficiency and 65.43% of total organic carbon removal efficiency was achieved under the optimal conditions. The stability of Ag/AgCl/MIL-101(Fe) in the photo-Fenton reaction was studied by means of recycling experiments. The results demonstrated that the as-prepared catalyst had high stability. The team conducted electron spin resonance spin trapping experiment using 5,5-dimethyl-1-pyrroline N-oxide as a spin trap to confirm the generation of ·OH and O2·− in the photo-Fenton system with Ag/AgCl/MIL-101(Fe) and found that OH·, O2·− and h+ exhibited synergistic effects in the photo-Fenton system using Ag/AgCl/MIL-101(Fe) as catalysts for methylene blue degradation. The research was published in the journal MDPI Materials on May 5, 2019.