A novel insight of degradation ibuprofen in aqueous by catalytic ozonation with supported catalyst: Supports effect on ozone mass transfer.

Catalytic ozonation is an effective wastewater purification process. However, the low ozone mass transfer in packed bubble columns leads to low ozone utilization efficiency (OUE), poor organic degradation performance, and high energy consumption. Therefore, there is an urgent need to develop efficient supported catalysts that can enhance mass transfer and performance. However, the reaction mechanism of the support on ozone mass transfer remains unclear, which hinders the development of catalytic ozonation applications. In this study, lava rocks (LR)-supported catalysts, specifically CuMn2O4@LR and MnO2Co3O4@LR, were proposed for catalytic ozonation of IBP degradation due to their superior catalytic activity, stability, and high OUE. Addition of CuMn2O4@LR or MnO2Co3O4@LR increased IBP removal efficiency from 85% to 91% or 88%, and reduced energy consumption from 2.86 to 2.14 kWh/m3 or 2.60 kWh/m3, respectively. This improvement was attributed to LR-supported catalysts enhancing mass transfer and promoting O3 decomposition to generate •OH and •O2-, leading to IBP degradation. Furthermore, this study investigated the effects of ozone dose, supporter sizes, and catalyst components on ozone-liquid mass transfer. The results revealed that the size of the supporter influenced stacked porosity and consequently affected ozone mass transfer. Larger-sized LR (kLa= 0.172 min-1) exhibited better mass transfer compared to smaller-sized supports. Based on these findings, it was concluded that both CuMn2O4@LR and MnO2Co3O4@LR are potential catalysts for catalytic ozonation in residual IBP degradation of pharmaceutical wastewater, and LR showed good credibility as a catalyst supporter. Understanding the effects of supporters and active components on ozone mass transfer provides a fundamental principle for designing supported catalysts in catalytic ozonation applications.

Structure and molecular-level transformation for oxidation of effluent organic matters by manganese oxides.

As important organic components in water environments, effluent organic matters (EfOMs) from wastewater treatment plants are widely present in Mn-rich environments or engineered treatment systems. The redox interaction between manganese oxides (MnOx) and EfOMs can lead to their structural changes, which are crucial for ensuring the safety of water environments. Herein, the reactivities of MnOx with EfOMs were evaluated, and it was found that MnOx with high specific surface area, active high-valent manganese content and lattice oxygen content (i.e., amorphous MnO2) possessed stronger oxidizing ability towards EfOMs. Accompanying by EfOMs oxidation, Mn(IV) and Mn(III) were reduced into Mn(II), with Mn(III) as the significant active species. Through molecular-level transformation analysis by ultrahigh mass spectrometry (FT-ICR MS), the highly reactive compounds in EfOMs were clearly determined to be that with more aromatic and unsaturated structures, especially lignin-like compounds (the highest content in EfOMs (over 60 %)). EfOMs were oxidized by amorphous MnO2 into products with lower humification index (0.60 vs. 0.46), smaller apparent molecular weight (386.94 Da vs. 368.68 Da), and higher biodegradability (BOD5/COD: 0.12 vs. 0.78). This finding suggested that redox reactions between MnOx and EfOMs might alter their abiotic and biotic behaviors in receiving water environments.

Interfacial reactions of catalytic ozone membranes resulting in the release and degradation of irreversible foulants.

An efficient in-situ self-cleaning catalytic ceramic-membrane tailored with MnO2-Co3O4 nanoparticles (Mn-Co-CM) was fabricated. Density functional theory calculations result substantiated that molecular ozone could be effectively adsorbed by oxygen vacancies (OV) on the Mn-Co-CM surface and then direct activated into a surface-bound atomic oxygen (*Oad) and a peroxide (*O2, ad), ultimately producing ·OH. Mn-Co-CM coupling with ozone efficiently removed foulants from the permeate and the membrane surface simultaneously and leading to in-situ formation of ·OH that changed the nature of the irreversible foulants and ultimately resulted in the rapid release and degradation of humic acid-like substances causing irreversible fouling. However, the commercial CM with ozone mainly removed cake layer fouling including protein-like and fulvic acid-like substances, followed by the slow release and degradation of irreversible foulant, resulting in many humic acid-like substances remain on the membrane surface as irreversible fouling. Based on these, the flux growth rate of Mn-Co-CM was 3.5 times higher than that of CM with ozone. This study provides new insights into the mechanism of in-situ membrane fouling mitigation, when using an efficient catalytic ceramic-membrane. This will facilitate the development of membrane antifouling strategies.