Atrazine degradation using Fe3O4-sepiolite catalyzed persulfate: Reactivity, mechanism and stability

Highlights: • Fe₃O₄ NPs supported on sepiolite was applied as persulfate activator. • Small size and good dispersion of Fe₃O₄ NPs were observed by FESEM and TEM. • 71.6% of ATZ and 20% of solution TOC can be removed by Fe₃O₄-Sep/PS after 60 min. • The structure stability and catalytic activity were proved during recycle runs. • Pathways included dealkylation, chain oxidation and dechlorination-hydroxylation. -- Abstract: In this study, with sepiolite as a support, a novel magnetic Fe₃O₄-sepiolite composite was fabricated by coprecipitation method. The characterization results reveal that the sepiolite support could anchor Fe₃O₄ nanoparticles with good dispersion. The composite was used as a catalyst to activate persulfate (PS) for atrazine (ATZ) degradation. 71.6% of ATZ and 20.9% of solution TOC could be removed after 60 min with 92 mmol/L of PS ([ATZ]₀ = 10 mmol/L). Due to the good adsorption capacity of Fe₃O₄-sepiolite composite toward ATZ, the degradation was considered to be facilitated by an adsorption process, since the adsorbed ATZ can be more easily transported to the active sites and be degraded in situ. Operation factors, including PS dose and solution pH, were investigated and found to be influential for the ATZ removal. The Fe₃O₄-sepiolite composite maintained its catalytic activity and structural stability with negligible Fe leaching during the recycling batch experiments. The intermediate products were further identified and the possible transformation pathway was then proposed based on the results. The findings of this research promote the application of Fe₃O₄-sepiolite composite as efficient and recyclable heterogeneous catalyst for organic degradation, and provide insights into the development of alternative catalysts with good adsorptive properties.