Nanoparticle contrast agent Mn3O4/SiO2/C as an ozonation catalyst with unexpected synergy in degrading organic contrast agent iopamidol: an effective “treat-waste-with-waste” strategy for medical wastewater

Mixed refractory organic wastewater containing both organic molecular and nanoparticle contrast agents poses a significant challenge for wastewater treatment. In this study, heterogeneous catalytic ozonation (HCO) technology was employed, creatively using the nanoparticle contrast agent Mn 3 O 4 /SiO 2 /C as a catalyst for the degradation of the organic molecular contrast agent iopamidol (IPM). This study aims to provide new insights and approaches to address the challenge of mixed contrast agent treatment in medical wastewater through a “treat-waste-with-waste” strategy. Mn 3 O 4 /SiO 2 /C exhibited an excellent IPM degradation efficiency, reaching 99.3 % within 30    min, compared with only 9.6 % IPM removal in the absence of catalyst ([cat] = 0.1 g L −1 , [IPM] 0  = 5 μM, [O 3 ] 0  = 3 mg L −1 , at pH 6.8 and 278 K). The Mn 3 O 4 , SiO 2 , and C in Mn 3 O 4 /SiO 2 /C were extensively integrated, and the proportion of Mn(II) in Mn 3 O 4 /SiO 2 /C was 39.9 %, as compared to 33.1 % in Mn 3 O 4 , which facilitated the generation of hydroxyl radicals. The siloxide and carbonaceous materials in Mn 3 O 4 /SiO 2 /C provided abundant sites for ozone adsorption and pollutant enrichment, promoting interfacial ozone contact with pollutants and subsequent catalytic reactions. The presence of structures such as Mn-O-Si and Mn-O-C in the material helps accelerate electron transfer, thus promoting electron capture and ozone decomposition. This strategy provides new insights for refractory pollutant elimination and serves as a guide for advancing green catalysis in water purification.