Catalytic Ozonation Of Phenol Research Articles

Catalytic ozonation of phenol by magnetic Mn0.7Ce0.3Ox/CNT@Fe3C

A high-efficient and stable catalyst is highly desired to catalyze ozone for refractory organic pollutants removal. In this work, Mn-Ce bimetallic oxide loaded CNT@Fe3C (Mn0.7Ce0.3Ox/CNT@Fe3C) was synthesized with Mn0.7Ce0.3Ox as the active component and magnetic CNT@Fe3C as the support. The catalytic performance of Mn0.7Ce0.3Ox/CNT@Fe3C towards catalytic ozonation was evaluated. The TOC removal efficiency of phenol degradation after 45 min of reaction was 98%, which was 1.5 times and 1.8 times that of monometallic CeO2/CNT@Fe3C (65%) and MnxOy/CNT@Fe3C (54%), respectively. The synthesized-Mn0.7Ce0.3Ox/CNT@Fe3C possessed good reusability during five successive cycles and remained efficient over a wide range of pH 4.2–8.3. The results of EPR measurements and quenching experiments demonstrated that hydroxyl radicals (·OH) were the dominant reactive oxidation species (ROS) for phenol mineralization in the Mn0.7Ce0.3Ox/CNT@Fe3C/O3 system. Moreover, the magnetic Mn0.7Ce0.3Ox/CNT@Fe3C is easily recovered and reused.

Catalytic ozonation of phenol by ZnFe2O4/ZnNCN: performance and mechanism.

A novel magnetic catalyst was synthesized and applied in heterogeneous catalytic ozonation process. The ZnFe2O4/ZnNCN material was synthesized by hydrothermal and high-temperature calcination method and characterized by XPS, XRD, FTIR, VSM, and SEM techniques. In the system of O3/ZnFe2O4/ZnNCN, the removal rates of phenol and chemical oxygen demand (COD) reached 93% and 43% at 60 min. Further analysis shows that ZnFe2O4/ZnNCN has a significant catalytic effect on O3, which is demonstrated by the first-order kinetic constant being 1.93 times than O3 alone. The catalyst exhibits excellent cycling stability during repeated catalytic ozonation process and can be fully recycled under an applied magnetic field. The role of hydrogen peroxide (H2O2) and surface hydroxyl groups was investigated, and a mechanism for catalytic ozonation was proposed. This work not only builds an efficient catalytic ozonation system, but also provides a potential modification strategy for spinel oxides.

Preparation of SnOx-MnOx@Al2O3 for Catalytic Ozonation of Phenol in Hypersaline Wastewater

ABSTRACT The catalytic ozonation process (COP) is an effective and advanced oxidation technology for the treatment of organic wastewater. However, high salinity has a negative impact on catalytic ozonation performance. In this work, tin oxide (SnOx) and manganese oxide (MnOx) doped γ-Al2O3 catalysts (SnOx-MnOx@Al2O3) were prepared by the incipient wetness impregnation method and characterized by SEM, XRD, BET, XRT, XPS and FT-IR techniques. The SnOx-MnOx@Al2O3 catalyst was applied to the catalytic ozonation of phenol in hypersaline wastewater, and the catalytic performance was evaluated by COD removal efficiency. When the mass ratio of MnOx to SnOx was 1:3, the pH was 7, the catalyst dosage was 40 g/L, the ozone dosage was 6 mg/(L·min), the NaCl concentration was 15 g/L and the COD removal efficiency of hypersaline phenol wastewater reached 93.8% after 240 min of catalytic ozonation treatment. Compared with the single ozonation process (SOP), the introduction of SnOx-MnOx@Al2O3 catalyst improved the COD removal efficiency by 32.3%. Cl− may quench surface •OH species and ozone to form Cl• and Cl2•− with low activity and high selectivity, resulting in the reduction of catalytic ozonation efficiency. The catalytic activity of the SnOx-MnOx@Al2O3 catalyst remained high after eight cycles. In conclusion, the SnOx-MnOx@Al2O3 catalytic ozonation system exhibits efficient and stable mineralization performance and is a promising strategy for the treatment of hypersaline organic wastewater.

Phenol Removal Performance and Mechanism Using Catalytic Ozonation with the Catalyst of Cobalt-doped α-MnO2

In this paper, Cobalt-doped α-MnO2 (i.e., Co-α-MnO2) were synthesized through hydrothermal method. Phenol was employed as targeted pollutants to investigate the catalytic ozonation performance of Co-α-MnO2. Results showed that Co-α-MnO2 significantly improved the phenol removal increased to 97.47 % after 40 min, which was 16.46 %, 38.92 % higher than that of α-MnO2 catalytic ozonation and single ozonation without catalyst. Additionally, the physicochemical properties of α-MnO2 and Co-α-MnO2 were analyzed using technologies such as XRD, TEM, BET and XPS. Compared to α-MnO2, Co-α-MnO2 has larger specific surface area (79.496 m2/g) and pore volume (0.0396 cm3/g), higher Mn3+ relative content (41.16 %) and adsorbed oxygen content (18.99 %). Also, the oxygen vacancy content, lattice defect content and surface hydroxyl content of Co-α-MnO2 are higher than that of α-MnO2, which could result in higher catalytic oxidation performance of Co-α-MnO2. The influence of masking agent showed that surface hydroxyl group, •OH and •O2- were involved in the catalytic ozonation of phenol. This study could help recognize the role of surface hydroxyl groups and active free radicals and demonstrate the contribution of reactive oxygen species on phenol removal in Co-α-MnO2 systems.

γ-Al2O3 doped with cerium to enhance electron transfer in catalytic ozonation of phenol

Ozone decomposition into free radicals, which can be facilitated by enhancing electron transfer between ozone and catalyst, is an important segment in catalytic ozonation. We doped cerium uniformly on γ-Al2O3 with an impregnation–calcination method to enhance electron transfer in catalytic ozonation of phenol in aqueous solution. The removal efficiency of phenol is raised from 39.7% by ozonation alone to 46.3% by catalytic ozonation with Ce/Al2O3 in 50 min reaction. A higher Ce3+/Ce4+ ratio in Ce/Al2O3 witnesses a higher electron transfer rate in catalytic ozonation and thus a higher degradation efficiency of phenol, illustrating that the activity of Ce/Al2O3 depends on the valence state of Ce. The electron transfer cycle is formed by the electron donation from Ce3+ to ozone molecule and the electron acceptance of Ce4+ from adjacent lattice oxygen. After getting the electron, the ozone molecule is decomposed to generate free radical of ·OH on the surface of Ce/Al2O3. The continuous flow experiments exhibit a stable and high catalytic activity of Ce/Al2O3 for catalytic ozonation, implying the feasibility in practical application.

Heterogeneous Catalytic Ozonation of Phenol over Iron-based Catalysts in a Trickle Bed Reactor

The use of continuous reactors for heterogeneous catalytic ozonation is yet to be investigated in order to develop a viable technology for industrial applications. This paper presents hydrodynamic and degradation studies on the use of a co-current down flow trickle bed reactor for heterogeneous catalytic ozonation of phenol (as model pollutant) over Fe-Diatomite pellets and Fe-coated glass beads. It was found that the reactor can operate under trickle or pulsing flow regimes, promoting mass transfer augmentation. Residence time distribution data, fitted with n-CSTR and axial dispersion (ADM) models, showed low axial dispersion and high flow distribution. Just the Fe-diatomite pellets showed important phenol adsorption (16 %). Degradation experiments demonstrated that phenol conversion was substantial when using both catalysts, up to 19,7 % pollutant conversion with liquid-phase space times of just 6 s. Compared to direct ozonation, the use of the Fe-diatomite pellets and Fe-coated glass beads enhanced the reactor performance by 48 % and 23 %, respectively. It was confirmed that mass transfer is an important factor that restricts this reaction system performance; consequently, further improvement in mass transport rate is necessary for system optimization.

The influence of the substituent on the phenol oxidation rate and reactive species in cubic MnO2catalytic ozonation

Shape-controlled MnO2, Mn2O3 and Mn3O4 were prepared and applied in catalytic ozonation of phenol (Ph), p-cresol (Ph-CH3) and p-chlorophenol (Ph-Cl). Their textural properties were characterized by XRD, SEM, TEM, nitrogen physical adsorption and CV. MnO2 was found to be more active than Mn2O3 and Mn3O4 for its higher electron transfer ability and higher amount of oxygen defects or surface hydroxyl groups. The degradation order was Ph-Cl > Ph-CH3 > Ph in the mixed solution, while the trend became Ph-CH3 > Ph-Cl > Ph in the single component solution, indicating that an electron donating group (EDG) and an electron withdrawing group (EWG) both benefit phenol degradation. The co-existing phenol had a different effect on the degradation of the other in the ozonation and catalytic ozonation of the mixed solution, but their influence on each other was universally opposite. Superoxide radical, singlet oxygen and molecular ozone were mainly responsible for phenol degradation in bulk solution. The contribution of ozone and singlet oxygen to the phenol degradation follows the order Ph-CH3 > Ph > Ph-Cl, indicating an electrophilic attack reaction, while the trend is opposite for superoxide radical oxidation, possibly due to a nucleophilic reaction pattern.

Catalytic ozonation of phenol using copper coated pumice and zeolite as catalysts.

Catalytic ozonation has recently been applied as a new method of contaminant removal from water and wastewater. In this study, copper coated pumice and zeolite were used to catalyze the ozonation of phenol as a target pollutant from aqueous solutions. The pumice and zeolite stone were modified by CuSO4 (1N). Modified pumice and zeolite were characterized by Adsorption/Desorption Porosimetry (BET) and Scanning Electron Microscope analyses. Ozonation and catalytic ozonation experiments were performed in a 1 L semi-batch reactor containing a prepared phenol solution. The efficiency of catalytic ozonation was investigated by different variables: pH value, contact time, initial phenol concentration, catalyst dose, and radical scavenger. Experimental data indicated that as the pH solution increased, phenol removal increased. pH = 8 was measured as the optimum pH. The removal efficiency in single ozonation process (SOP) was 32% and in the catalytic ozonation process (COP) using modified zeolite and pumice was 51% and 63%, respectively. Moreover, these processes showed a great ability to mineralize phenol (up to 30%). Using the radical scavenger determined the indirect oxidation as the main pathway of phenol removal in both catalytic processes. The copper modified zeolite and pumice had good performance to remove phenol through catalytic ozonation method.

Catalytic ozonation of aqueous phenol over metal-loaded HZSM-5

The performances of HZSM-5 and transition metal-loaded HZSM-5 (Mn, Cu, Fe, Ti) catalysts during catalytic ozonation of phenol have been investigated. It was observed the performance order for removal of phenol and COD was Mn/HZSM-5 > Fe/HZSM-5 > Cu/HZSM-5 > Ti/HZSM-5 > HZSM-5. The presence of metals on HZSM-5 enhanced the phenol removal capability of HZSM-5. Mn loading on HZSM-5 was optimized due to its high phenol removal capability amongst metal-loaded HZSM-5 catalysts. Experimental results suggested that low amount of Mn loading on HZSM-5 was sufficient for HZSM-5 to act as catalyst and adsorbent. A maximum of 95.8 wt% phenols and 70.2 wt% COD were removed over 2 wt% Mn/HZSM-5 in 120 min. It was supposed that transition metals mainly acted as ozone decomposers due to their multiple oxidation states that enhanced the ozonation of phenol.

Catalytic Ozonation of Phenol in Aqueous Solution by Co3O4Nanoparticles

The degradation efficiencies of phenol in aqueous solution were studied by semi-continuous experiments in the processes of ozone alone, ozone/bulky <TEX>$Co_3O_4$</TEX> and ozone/<TEX>$Co_3O_4$</TEX> nanoparticles. Catalyst samples (bulky <TEX>$Co_3O_4$</TEX> and <TEX>$Co_3O_4$</TEX> nanoparticles) were characterized by X-ray diffraction and transmission electron microscopy. The Brunauer-Emmett-Teller surface area, <TEX>$pH_{pzc}$</TEX> and the density of surface hydroxyl groups of the two catalyst samples were also measured. The catalytic activity of <TEX>$Co_3O_4$</TEX> nanoparticles was investigated for the removal of phenol in aqueous solutions under different reaction temperatures. Tert-butyl alcohol had little effect on the catalytic ozonation processes. Based on these results, the possible catalytic ozonation mechanism of phenol by <TEX>$Co_3O_4$</TEX> nanoparticles was proposed as a reaction process between ozone molecules and pollutants.

Catalytic ozonation of phenol and oxalic acid with copper-loaded activated carbon

A novel heterogeneous catalytic ozonation process in water treatment was studied, with a copper-loaded activated carbon (Cu/AC) that was prepared by an incipient wetness impregnation method at low temperature and tested as a catalyst in the ozonation of phenol and oxalic acid. Cu/AC was characterized using XRD, BET and SEM techniques. Compared with ozonation alone, the presence of Cu/AC in the ozonation processes significantly improves the degradation of phenol or oxalic acid. With the introduction of the hydroxyl radical scavenger, i.e., turt-butanol alcohol (t-BuOH), the degradation efficiency of both phenol and oxalic acid in the Cu/AC catalyzed ozonation process decreases by 22% at 30 min. This indicates that Cu/AC accelerates ozone decomposition into certain concentration of hydroxyl radicals. The amount of Cu(II) produced during the reaction of Cu/AC-catalyzed ozonation of phenol or oxalic acid is very small, which shows that the two processes are both heterogeneous catalytic ozonation reactions.

A Facile Hydrothermal Method to Synthesize Nanosized Co3O4/CeO2 and Study of its Catalytic Characteristic in Catalytic Ozonation of Phenol

In this paper nanosized Co3O4/CeO2 was successfully synthesized by a simple hydrothermal method and was applied as catalyst in catalytic ozonation of phenol in solution. The observed results show that nanoparticles have a pleasant special surface. Ozonation experiments indicate that the nanoparticles present a certain catalytic effect on the degradation of phenol and a remarkable acceleration on the chemical oxygen demand removal. Further investigations reveal that a mechanism of solid–liquid interface reactions exists in this system.

Catalytic ozonation of phenol in water with natural brucite and magnesia

Natural brucite and magnesia were applied as catalysts in catalytic ozonation of phenol in this work. It was found that both brucite and magnesia had remarkable accelerations on degradation of phenol and removal of COD in water. On this basis, effective and feasible routes for catalytic ozonation of phenol in water were proposed. The influence of initial pH value, radical scavengers and reaction temperature were investigated. The results revealed that there were different ozonation mechanisms in two systems: molecular ozone direct oxidation mechanism was proved in catalytic ozonation with brucite, and hydroxyl radical mechanism was demonstrated to play a main role in catalytic ozonation with magnesia.

Catalytic ozonation of phenol in water with natural brucite and magnesia

Catalytic ozonation of phenol in water with natural brucite and magnesia