Ozonolysis of ketoprofen in polluted water: Reaction pathways, kinetics, removal efficiency, and health effects.

Ketoprofen (KET), as a non-steroidal anti-inflammatory drug frequently detected in aqueous environments, is a threat to human health due to its accumulation and low biodegradability, which requires the transformation and degradation of KET in aqueous environments. In this paper, the reaction process of ozone-initiated KET degradation in water was investigated using density functional theory (DFT) method at the M06-2X/6-311++g(3df,2p)//M06-2X/6-31+g(d,p) level. The detailed reaction path of KET ozonation is proposed. The thermodynamic results show that ozone-initiated KET degradation is feasible. Under ultraviolet irradiation, the reaction of ozone with water can also produce OH radicals (HO·) that can react with KET. The degradation reaction of KET caused by HO· was further studied. The kinetic calculation illustrates that the reaction rate (1.99 × 10-1 (mol/L)-1 sec-1) of KET ozonation is relatively slow, but the reaction rate of HO· reaction is relatively high, which can further improve the degradation efficiency. On this basis, the effects of pollutant concentration, ozone concentration, natural organic matter, and pH value on degradation efficiency under UV/O3 process were analyzed. The ozonolysis reaction of KET is not sensitive to pH and is basically unaffected. Finally, the toxicity prediction of oxidation compounds produced by degradation reaction indicates that most of the degradation products are harmless, and a few products containing benzene rings are still toxic and have to be concerned. This study serves as a theoretical basis for analyzing the migration and transformation process of anti-inflammatory compounds in the water environment.

Synthesis of δ-MnO2 via ozonation routine for low temperature formaldehyde removal.

Nowadays, it is still a challenge to prepared high efficiency and low cost formaldehyde (HCHO) removal catalysts in order to tackle the long-living indoor air pollution. Herein, δ-MnO2 is successfully synthesized by a facile ozonation strategy, where Mn2+ is oxidized by ozone (O3) bubble in an alkaline solution. It presents one of the best catalytic properties with a low 100% conversion temperature of 85°C for 50 ppm of HCHO under a GHSV of 48,000 mL/(g·hr). As a comparison, more than 6 times far longer oxidation time is needed if O3 is replaced by O2. Characterizations show that ozonation process generates a different intermediate of tetragonal ß-HMnO2, which would favor the quick transformation into the final product δ-MnO2, as compared with the relatively more thermodynamically stable monoclinic γ-HMnO2 in the O2 process. Finally, HCHO is found to be decomposed into CO2 via formate, dioxymethylene and carbonate species as identified by room temperature in-situ diffuse reflectance infrared fourier transform spectroscopy. All these results show great potency of this facile ozonation routine for the highly active δ-MnO2 synthesis in order to remove the HCHO contamination.

Relative humidity-dependent evolution of molecular composition of α-pinene secondary organic aerosol upon heterogeneous oxidation by hydroxyl radicals.

Heterogeneous oxidation by gas-phase oxidants is an important chemical transformation pathway of secondary organic aerosol (SOA) and plays an important role in controlling the abundance, properties, as well as climate and health impacts of aerosols. However, our knowledge on this heterogeneous chemistry remains inadequate. In this study, the heterogeneous oxidation of α-pinene ozonolysis SOA by hydroxyl (OH) radicals was investigated under both low and high relative humidity (RH) conditions, with an emphasis on the evolution of molecular composition of SOA and its RH dependence. It is found that the heterogeneous oxidation of SOA at an OH exposure level equivalent to 12 hr of atmospheric aging leads to particle mass loss of 60% at 25% RH and 95% at 90% RH. The heterogeneous oxidation strongly changes the molecular composition of SOA. The dimer-to-monomer signal ratios increase dramatically with rising OH exposure, in particular under high RH conditions, suggesting that aerosol water stimulates the reaction of monomers with OH radicals more than that of dimers. In addition, the typical SOA tracer compounds such as pinic acid, pinonic acid, hydroxy pinonic acid and dimer esters (e.g., C17H26O8 and C19H28O7) have lifetimes of several hours against heterogeneous OH oxidation under typical atmospheric conditions, which highlights the need for the consideration of their heterogeneous loss in the estimation of monoterpene SOA concentrations using tracer-based methods. Our study sheds lights on the heterogeneous oxidation chemistry of monoterpene SOA and would help to understand their evolution and impacts in the atmosphere.

Co-doped cryptomelane-type manganese oxide in situ grown on a nickel foam substrate for high humidity ozone decomposition.

Monolithic catalysts with excellent O3 catalytic decomposition performance were prepared by in situ loading of Co-doped KMn8O16 on the surface of nickel foam. The triple-layer structure with Co-doped KMn8O16/Ni6MnO8/Ni foam was grown spontaneously on the surface of nickel foam by tuning the molar ratio of KMnO4 to Co(NO3)2·6H2O precursors. Importantly, the formed Ni6MnO8 structure between KMn8O16 and nickel foam during in situ synthesis process effectively protected nickel foam from further etching, which significantly enhanced the reaction stability of catalyst. The optimum amount of Co doping in KMn8O16 was available when the molar ratio of Mn to Co species in the precursor solution was 2:1. And the Mn2Co1 catalyst had abundant oxygen vacancies and excellent hydrophobicity, thus creating outstanding O3 decomposition activity. The O3 conversion under dry conditions and relative humidity of 65%, 90% over a period of 5 hr was 100%, 94% and 80% with the space velocity of 28,000 hr-1, respectively. The in situ constructed Co-doped KMn8O16/Ni foam catalyst showed the advantages of low price and gradual applicability of the preparation process, which provided an opportunity for the design of monolithic catalyst for O3 catalytic decomposition.

The Synergetic Reduction of the Condensation Degree of Dissolved Lignin (DL) during the Refining Process of Wheat Straw Biomass Based on the MA/O3 System.

Lignin, a natural pol2ymer with a complex structure that is difficult to separate, is prone to C-C bond condensation during the separation process. To reduce the condensation of lignin, here, a novel method is proposed for separating the components by using a combination of maleic acid (MA)/ozone (O3) to co-treat wheat straw. The removal of lignin, glucan, and xylan was 38.07 ± 0.2%, 31.44 ± 0.1%, and 71.98 ± 0.1%, respectively, under the conditions of ball-milling of wheat straw for 6 h, reaction temperature of 60 °C, and O3 holding time of 9 min. Lignin-rich solutions were collected to extract the dissolved lignin (DL) after washing the treated samples. The DL obtained under MA/O3 conditions had a carboxyl group (-COOH) content of 2.96 mmol/g. The carboxyl group of MA underwent esterification with the hydroxyl group (-OH) at the γ position of lignin and O3 reacted on the positions of the lignin side chain or the phenolic ring, resulting in a break in the side chain and the opening of the phenolic ring to introduce the carboxyl group. The 2D-HSQC-NMR results revealed that the phenolic ring-opening reaction of lignin in the presence of O3 was essentially free of ß-ß and ß-5 condensation bonds.

Effective degradation of various bacterial toxins using ozone ultrafine bubble water.

Infectious and foodborne diseases pose significant global threats, with devastating consequences in low- and middle-income countries. Ozone, derived from atmospheric oxygen, exerts antimicrobial effects against various microorganisms, and degrades fungal toxins, which were initially recognized in the healthcare and food industries. However, highly concentrated ozone gas can be detrimental to human health. In addition, ozonated water is unstable and has a short half-life. Therefore, ultrafine-bubble technology is expected to overcome these issues. Ultrafine bubbles, which are nanoscale entitles that exist in water for considerable durations, have previously demonstrated bactericidal effects against various bacterial species, including antibiotic-resistant strains. This present study investigated the effects of ozone ultrafine bubble water (OUFBW) on various bacterial toxins. This study revealed that OUFBW treatment abolished the toxicity of pneumolysin, a pneumococcal pore-forming toxin, and leukotoxin, a toxin that causes leukocyte injury. Silver staining confirmed the degradation of pneumolysin, leukotoxin, and staphylococcal enterotoxin A, which are potent gastrointestinal toxins, following OUFB treatment. In addition, OUFBW treatment significantly inhibited NF-κB activation by Pam3CSK4, a synthetic triacylated lipopeptide that activates Toll-like receptor 2. Additionally, OUFBW exerted bactericidal activity against Staphylococcus aureus, including an antibiotic-resistant strain, without displaying significant toxicity toward human neutrophils or erythrocytes. These results suggest that OUFBW not only sterilizes bacteria but also degrades bacterial toxins.

Nanoscale Sequential Reactor Design Achieves Effective Removal of Disinfection Byproduct Precursors in Catalytic Ozonation.

Transforming dissolved organic matter (DOM) is a crucial approach to alleviating the formation of disinfection byproducts (DBPs) in water treatment. Although catalytic ozonation effectively transforms DOM, increases in DBP formation potential are often observed due to the accumulation of aldehydes, ketones, and nitro compound intermediates during DOM transformation. In this study, we propose a novel strategy for the sequential oxidation of DOM, effectively reducing the levels of accumulation of these intermediates. This is achieved through the development of a catalyst with a tailored surface and nanoconfined active sites for catalytic ozonation. The catalyst features a unique confinement structure, wherein Mn-N4 moieties are uniformly anchored on the catalyst surface and within nanopores (5-20 Å). This design enables the degradation of the large molecular weight fraction of DOM on the catalyst surface, while the transformed smaller molecular weight fraction enters the nanopores and undergoes rapid degradation due to the confinement effect. The generation of *Oad as the dominant reactive species is essential for effectively reducing these ozone refractory intermediates. This resulted in over 70% removal of carbonaceous and nitrogenous DBP precursors as well as brominated DBP precursors. This study highlights the importance of the nanoscale sequential reactor design and provides new insights into eliminating DBP precursors by the catalytic ozonation process.

MnFe2O4/MoS2 catalyst used for ozonation: optimization and mechanism analysis of phenolic wastewater treatment.

The performance of catalytic ability of MFe2O4/MoS2 in the ozonation process was investigated in this work. The synthesized MnFe2O4/MoS2 was optimize prepared and then characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, X-ray photo-electron spectroscopy, and magnetic saturation strength. The results showed that when Cphenol = 200 mg/L, initial pH = 9.0, Q = 0.10 L/min, and CMnFe2O4/MoS2 = 0.10 g/L, MnFe2O4/MoS2 addition improved the degradation efficiency of phenol by 20.0%. The effects of pH, catalyst dosage, and inorganic ions on the phenol removal by the MnFe2O4/MoS2 catalytic ozonation were investigated. Five cycle experiments proved that MnFe2O4/MoS2 had good recyclability and stability. MnFe2O4/MoS2 also showed good catalytic performance in the treatment of coal chemical wastewater pesticide wastewater. The MnFe2O4 doped with MoS2 could provide abundant surface active sites for ozone and promote the stable cycle of Mn2+/Mn3+and Fe2+/Fe3+, thus generating large amounts of •OH and improving the degradation of phenol by ozonation. The MnFe2O4/MoS2/ozonation treatment system provides a technical reference and theoretical basis for industrial wastewater treatment.

N-Nitrosodimethylamine formation from anthropogenic nitrogenous compounds during preozonation and post-chloramination with characteristic low treatment dose.

One effective option to minimize N-nitrosodimethylamine (NDMA) in finished drinking water is to identify and control its precursors. However, previous works to identify significant precursors use formation potential (FP) tests using high doses to assure the maximum NDMA formation rather than the NDMA formation in finished waters. In this study, we applied characteristic low treatment doses of ozone (O3)-to-dissolved organic carbon (DOC) of target compounds of 0.8 mg/mg and NH2Cl of 2.5 ± 0.2 mg Cl2/L to evaluate the NDMAFP yields of organic compounds bearing N,N-dimethylamine (DMA) and N,N-dimethylhydrazine (DMH) during preozonation and post-chloramination. The results in pH-buffered Milli-Q water showed a significant decrease from ≤ 52% to non-detectable levels in the O3-NDMAFP yields of O3-reactive precursors (i.e., DMH-like compounds) after preozonation and post-chloramination. Similarly, a significant decrease from 0.5 to 12% to nonquantifiable levels was observed for the NH2Cl-NDMAFP yields of NH2Cl-reactive precursors; however, the NH2Cl-NDMAFP yields of N,N-dimethylbenzylamine (DMBzA)-like compounds only decreased from ~ 110 to ≤ 43%, suggesting that these compounds could contribute to NH2Cl-NDMAFPs even after preozonation. The effect of the matrix in sewage-effluent and lake water samples varied and was specific for precursors; for example, the O3-NDMAFP yield of 1,1,1',1'-tetramethyl-4,4'-(methylene-di-p-phenylene) disemicarbazide (TMDS), an important O3-reactive NDMA precursor, did not significantly decrease when tested in sewage-effluent samples. Based on the previous occurrence concentration of TMDS in sewage samples, we estimated an NDMAFP of ~ 315 ng/L. This estimate exceeds the guidance concentrations of NDMA (3-100 ng/L), highlighting the importance of TMDS and its related compounds for NDMA formation.

[Research Progress on Pollution Characteristics, Degradation, and Transformation of Typical PPCPs in the Process of Wastewater Treatment].

Pharmaceuticals and personal care products (PPCPs) have received extensive attention as a new type of pollutant inin the 21st century, and the ecological and health risks caused by PPCPs have gradually been recognized by government regulatory agencies. Daily use of PPCPs has led to their frequent detection and high concentrations in the influent, effluent, and sludge of wastewater treatment plants, but traditional wastewater treatment processes can't remove them effectively. Most research about enhancing the removal of PPCPs through microbial degradation, photodegradation, and ozonation is still in the laboratory research stage, and the removal effects are not satisfactory when applied to actual sewage treatment. Therefore, the effective removal of PPCPs from domestic wastewater is a critical technical problem that urgently needs to be studied and solved in the coming years. At present, many scholars do not have a comprehensive understanding about the degradation and transformation behaviors of microbes, ultraviolet, and ozone for typical PPCPs in the wastewater treatment process, so it is necessary to conduct a systematic analysis and discussion. In this study, 16 typical PPCPs frequently detected in sewage treatment plants were selected as research objects through a literature review. The occurrence, removal characteristics, and sludge adsorption properties of typical PPCPs in wastewater treatment plants were analyzed and summarized. The degradation and transformation behavior of typical PPCPs under microbial, ultraviolet, and ozone treatments in the wastewater treatment process were also discussed. Finally, based on current research gaps, some research directions for the removal and transformation of PPCPs in wastewater were proposed:① investigation into the removal characteristics of PPCPs by actual biochemical treatment; ② study on the mechanism of microbial degradation and transformation of typical PPCPs during biochemical treatment; ③ study on the degradation and transformation mechanism of typical PPCPs by UV/ozone in an actual sewage system; and ④ research on the application technology of removing PPCPs from sewage via microbial degradation, photodegradation, ozone oxidation, etc. The relevant results of this study can provide a reference for the pollution control of typical PPCPs in the sewage treatment process.

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.

Catalytic ozonation of reverse osmosis membrane concentrates by catalytic ozonation: Properties and mechanisms.

Ni-Mn@KL ozone catalyst was prepared for the efficient treatment of reverse osmosis membrane concentrates. The working conditions and reaction mechanism of the ozone-catalyzed oxidation by Ni-Mn@KL were systematically studied. Then, a comprehensive CRITIC weighting-coupling coordination evaluation model was established. Ni-Mn@KL was characterized by scanning electron microscopy, BET, X-ray diffraction, X-ray photoelectron spectroscopy, energy-dispersive spectrometry, and X-ray fluorescence spectrometry and found to have large specific surface area and homogeneous surface dispersion of striped particles. Under the optimum working conditions with an initial pH of 7.9 (raw water), a reaction height-to-diameter ratio of 10:1, an ozone-aeration intensity of 0.3 L/min, and a catalyst filling rate of 10%, the maximum COD removal rate was 60.5%. Free-radical quenching experiments showed that OH oxidation played a dominant role in the Ni-Mn@KL-catalyzed ozone-oxidation system, and the reaction system conformed to the second-order reaction kinetics law. Ni-Mn@KL catalysts were further confirmed to have good catalytic performance and mechanical performance after repeated utilization. PRACTITIONER POINTS: Ni-Mn@KL catalyst can achieve effective treatment of RO film concentrated liquid. High COD removal rate of RO membrane concentrated liquid was obtained at low cost. Ni-Mn@KL catalyst promotes ozone decomposition to produce ·OH and O2 -· oxidized organic matter. The Ni-Mn@KL catalyst can maintain good stability after repeated use. A CRITIC weight-coupling coordination model was established to evaluate the catalytic ozonation.

High-efficiently utilizing micro-nano ozone bubbles to enhance electro-peroxone process for rapid removal of trace pharmaceutical contaminants from hospital wastewater.

The electro-peroxone (EP) process encounters two inherent challenges in wastewater treatment: sluggish O2/O3 transfer and substantial ozone waste. To overcome these limitations, we introduced micro-nano bubbles (MNBs) aeration to enhance O2/O3 dissolution and diffusion, ultimately aiming to improve the removal of trace pharmaceutical contaminants from hospital wastewater. In the MNBs aeration system, the ozone transfer coefficient ranging from 0.536 to 0.265 min-1, significantly surpassing that of conventional aeration (0.220 to 0.090 min-1) by approximately 2 to 4.5 times. Consequently, the EP process under MNBs aeration significantly enhanced ozone-resistant ibuprofen (IBU) removal, achieving a removal rate of 98.4 ± 1.5 %, far exceeding the 47.3 ± 4.7 % observed with conventional aeration. This significant improvement was attributed to the heightened production of hydroxyl radicals (•OH), reaching 0.97 × 10-9 M s, compared to only 0.28 × 10-9 M s in conventional aeration. The mechanism behind the enhanced •OH production in the MNBs-EP process relied primarily on two factors: improved O2/O3 dissolution due to high internal pressure/large surface and enhanced O3/H2O2 activation from high collapse energy. These factors together contributed to the robust oxidation capability of the MNBs-EP system. As a result, over 97 % removal efficiency was achieved for five representative pharmaceutical pollutants (sulfamethoxazole, ribavirin, norfloxacin, tetracycline and ampicillin) in just 1 min. Furthermore, when applied to real hospital wastewater, the MNBs-O3-E treatment system reduced all 15 detected trace pharmaceutical compounds to below 10 ng L-1 and achieved 14 types of pollutants with removal rates of over 85 % within 15 min, resulting in an ultrahigh total removal rate of 98.6 %, from an initial total concentration of 2108 ng L-1 to less than 30 ng L-1. Thus, micro-nano aeration endowed the EP process as a promising advanced oxidation system for rapid and highly-effective removal of trace pharmaceutical contaminants from hospital wastewater.

High-performance activation of ozone by sonocavitation for BTEX degradation in water.

This work presents a novel advanced oxidation process (AOP) for degradation of emerging organic pollutants - benzene, toluene, ethylbenzene and xylenes (BTEXs) in water. A comparative study was performed for sonocavitation assisted ozonation under 40-120 kHz and 80-200 kHz dual frequency ultrasounds (DFUS). Based on the obtained results, the combination of 40-120 kHz i.e., low-frequency US (LFDUS) with O3 exhibited excellent oxidation capacity degrading 99.37-99.69% of BTEXs in 40 min, while 86.09-91.76% of BTEX degradation was achieved after 60 min in 80-200 kHz i.e., high-frequency US (HFDUS) combined with O3. The synergistic indexes determined using degradation rate constants were found as 7.86 and 2.9 for LFDUS/O3 and HFDUS/O3 processes, respectively. The higher extend of BTEX degradation in both processes was observed at pH 6.5 and 10. Among the reactive oxygen species (ROSs), hydroxyl radicals (HO•) were found predominant according to scavenging tests, singlet oxygen also importantly contributed in degradation, while O2•- radicals had a minor contribution. Sulfate (SO42-) ions demonstrated higher inhibitory effect compared to chloride (Cl-) and carbonate (CO32-) ions in both processes. Degradation pathways of BTEX was proposed based on the intermediates identified using GC-MS technique.

Stable O3 Decomposition by Layered Double Hydroxides: The Pivotal Role of NiOOH Transformation.

Because ozone (O3) is a significant air pollutant, advanced O3 elimination technologies, particularly those under high-humidity conditions, have become an essential research focus. In this study, a nickel-iron layered double hydroxide (NiFe-LDH) was modified via intercalation with octanoate to develop an effective hydrophobic catalyst (NiFe-OAa-LDH) for O3 decomposition. The NiFe-OAa-LDH catalyst sustained its O3 decomposition rate of >98% for 48 h under conditions of 90% relative humidity, 840 L/(g·h) space velocity, and 100 ppm inlet O3 concentration. Moreover, it maintained a decomposition rate of 90% even when tested at a higher airflow rate of 2500 L/(g·h). Based on the changes induced by the Ni-OII to Ni-OIII bonds in NiFe-OAa-LDH during O3 treatment, catalytic O3 decomposition was proposed to occur in two stages. The first stage involved the reaction between the hydroxyl groups and O3, leading to the breakage of the O-H bonds, formation of NiOOH, and structural changes in the catalyst. This transformation resulted in the formation of abundant and stable hydrogen vacancies. According to density functional theory calculations, O3 can be effectively decomposed at the hydrogen vacancies with a low energy barrier during the second stage. This study provides new insights into O3 decomposition.

Ozone Loss on Painted Surfaces: Dependence on Relative Humidity, Aging, and Exposure to Reactive SVOCs.

Ozone and its oxidation products result in negative health effects when inhaled. Despite painted surfaces being the most abundant surface in indoor spaces, surface loss remains one of the largest uncertainties in the indoor ozone budget. Here, ozone uptake coefficients (γO3) on painted surfaces were measured in a flow-through reactor where 79% of the inner surfaces were removable painted glass sheets. Flat white paint initially had a high uptake coefficient (8.3 × 10-6) at 20% RH which plateaued to 1.1 × 10-6 as the paint aged in an indoor office over weeks. Increasing the RH from 0 to 75% increased γO3 by a factor of 3.0, and exposure to 134 ppb of α-terpineol for 1 h increased γO3 by a factor of 1.6 at 20% RH. RH also increases α-terpineol partitioning to paint, further increasing ozone loss, but the type of paint (flat, eggshell, satin, semigloss) had no significant effect. A kinetic multilayer model captures the dependence of γO3 on RH and the presence of α-terpineol, indicating the reacto-diffusive depth for O3 is 1 to 2 µm. Given the similarity of the kinetics on aged surfaces across many paint types and the sustained reactivity during aging, these results suggest a mechanism for catalytic loss.

Synthesis of surficial-modified green biochar catalyst generated by biogas residue biochar and potential application for catalytic ozonation degradation of ciprofloxacin.

This study synthesized novel, green, and easily recoverable surface-modified economical catalysts via hydrothermal treatment (HT) successfully, utilizing biogas residue biochar (BRB), a food waste product from anaerobic fermentation, pyrolyzed at 500 °C for 50 min. Using autoclaves, a total of six solutions were prepared, each having 1 g fine-grinded BRB, surficial modified by adding glycerol (GL) (10 or 20 mL) and SDI water (70 or 60 mL), and heated in an oven at 240 °C, 180 °C, and 120 °C for 24 h. Afterward, the catalysts showed the potential for degradation of widely used emerging pollutants like ciprofloxacin. Taking advantage of catalytic surface modification, the catalytic ozonation degradation was more effective than that of a single ozonation. However, under similar conditions, catalyst amount 0.20 g, ozone dose 15 mg L-1, and ciprofloxacin 80 mg L-1, the performance of the 10 mL GL-180 °C catalyst was excellent. It showed a 92.45%-94.41% optimum removal rate in the 8-10 min interval. After five continuous cycles, the 10 mL GL-180 °C catalyst exhibited excellent stability and reusability. XPS, FT-IR, BET, XRD, and SEM before and after the reaction confirmed the successful synthesis and degradation mechanism. A possible degradation pathway was unrevealed based on a liquid chromatography-mass spectrometer (LC-MS) and scavenger test, proving the significant roles of superoxide radicals (O2•-), hydroxyl radicals (•OH), and singlet oxygen (1O2). Further, Electron paramagnetic resonance (EPR) analysis confirmed the presence of active oxygen species. Subsequently, 10 mL GL-180 °C showed promising degradation for the actual water environment, such as groundwater (73.55%) and river water (64.74%). This work provides a valuable economic strategy to convert biogas residue biochar into a low-cost catalyst for organic pollutant decomposition.

Fundamental insights and recent advances in catalytic oxidation processes using ozone for the control of volatile organic compounds.

The development of technologies for highly efficient treatment of emissions containing low concentrations of volatile organic compounds (VOCs) remains an important challenge. Catalytic oxidation with ozone (catalytic ozonation) is useful for the oxidative decomposition of VOCs, particularly aromatic compounds, under ambient temperature conditions. Only inexpensive transition metal oxides are required as catalysts, and Mn-based catalysts are widely used for catalytic ozonation. This review describes the oxidation reaction mechanisms, reaction pathways of aromatic hydrocarbons, and dependence of the catalytic ozonation activity on the reaction conditions. The reasons why Mn oxides are effective in catalytic ozonation are also explained. The structure of the catalytic active sites and the types of supporting materials contributing to the reaction are also discussed in detail, with the aim of establishing a VOC control technology. In addition, recent progress in catalytic oxidation processes using ozone as an oxidant has been outlined, focusing on catalyst materials and reaction conditions.