O3 Process Research Articles

Degradation of clofibric acid by ozonation assisted by Co-Ce-SBA-15: Role of interfacial electron migration

Restrained by the sluggish Ce redox cycle, Ce-SBA-15 exhibited the low electron transfer toward O3 activation. To this end, cobalt‑cerium co-doped SBA-15 with three-dimensional pore structure was designed using urea-assisted hydrothermal method and its activity was evaluated using Clofibric acid (CA) as target pollutant. XRD and N2 adsorption-desorption characterizations suggested that Co-Ce-SBA-15 possessed a three-dimensional pore structure with high order degree. py-FTIR, O2-TPD, H2-TPR, and in situ electrochemical characterizations indicated that compared with Ce-SBA-15 and Co-SBA-15, Co-Ce-SBA-15 had greater Lewis acid strength, electron transfer ability and oxygen reducibility. Co-Ce-SBA-15/O3 achieved the greater CA removal and mineralization rate, with 98.7 % CA removal and 58.3 % TOC removal were obtained in 90 min. Co-Ce-SBA-15/O3 process would be inhibited by the coexisting Cl−, NO3− and SO42−. Co-Ce-SBA-15 demonstrated the greater ozone utilization rate than those of monometallic SBA-15. Lewis acidic sites of Co and Ce were the main sites for activating O3. DFT results suggested that the obvious electron transfer existed among O3, Co and Ce Lewis acid sites. The conversion of Co3+/Co2+ and Ce4+/Ce3+ accelerated the interfacial electron transfer, which favored for conveying O3 into •OH. •OH was the primary reactive oxygen species involved in degrading CA. 8 kinds of intermediates were found during CA degradation and the possible degradation route was proposed. This study deepened the understanding of the cooperative effect of Co and Ce in catalytic ozonation process.

Ferromanganese oxide-functionalized TiO2 for rapid catalytic ozonation of PPCPs through a coordinated oxidation process with adjusted composition and strengthened generation of reactive oxygen species

Ferromanganese oxide (MFOx) was first utilized to functionalize TiO2 and an MFOx@TiO2 catalyst was developed for catalytic ozonation for rapid attack of pharmaceutical and personal care products (PPCPs) with adjusted reactive oxygen species (ROSs) composition and strengthened ROSs generation. Unlike Al2O3, which strongly relied on adsorption and was significantly influenced by MFOx loading, synergistic catalytical effects of MFOx and TiO2 were observed, and optimal MFOx doping of 2 wt% and MFOx@TiO2 dosage of 500 ppm were obtained for catalyzing ozonation. In ibuprofen (IBP) degradation, MFOx@TiO2-catalyzed ozonation (MFOx@TiO2/O3) obtained 2.0-, 4.7- and 6.9-folds the kobs of TiO2/O3, MFOx/O3 and bare ozonation (B/O3). Stronger O3 decomposition was observed by MFOx@TiO2 over bare TiO2 with the participation of redox pairs Fe(II)/Fe(III) and Mn(II)/Mn(III)/Mn(IV) and increased surface oxygen vacancies (SOVs) from 9.8 % to 33.7 % was detected. The results revealed that Fe(II), Mn(II) and Mn(III) with low valance accelerated Ti(III) generation from Ti(VI), obtaining an unprecedented high Ti(III) composition occupying 35.3 % of the total Ti atoms. Ti(III) catalyzed the direct reduction of SOVs-O2 to •O2–, and it accelerated the formation of Ti(VI)-OH and Ti(VI)-O which catalyzed O3 decomposition into •O2–. •O2– was found to primarily initiate IBP degradation with nucleophilic addition and dominated over 66 % IBP removal. The enhanced •O2– generation further strengthened •OH and 1O2 production. MFOx@TiO2/O3 obtained 17 %, 21 % and 30 % higher TOC removal over TiO2/O3, MFOx/O3 and B/O3, respectively. Acute toxicity tests confirmed the effective toxicity control of organics by MFOx@TiO2/O3 process (inhibition rate: 10.9 %). Degradation test of atenolol and sulfamethoxazole confirmed the catalytic effects of MFOx@TiO2. MFOx@TiO2 performed strong resistance to water matrix in application test and showed good stability and reusability. The study proposed an effective catalyst for strengthening the ozonation process on PPCPs degradation and provided an in-depth understanding of the mechanisms and characteristics of the MFOx@TiO2 catalyst and MFOx@TiO2/O3 process.

Application of hybrid oxidative processes based on cavitation for the treatment of methyl blue solutions

Over the past few decades, the scientific community has developed an increasing interest in high-performance water treatment systems based on cavitational processes. Hydrodynamic cavitation (HC) is one of the promising technologies for wastewater treatment, especially for dyeing solutions, since it shows high efficiency in treating dyes, even at low concentrations. Both strategies have been shown to be efficient ways to get rid of pathogenic bacteria by disinfecting waters and achieving the mineralization of numerous organic pollutants. This makes cavitation-based techniques an attractive choice for use in water treatment facilities' post-treatment stages. Modern techniques have been presented that combine advanced oxidation processes (AOPs) with cavitation for increased oxidation capacity. When used together, cavitation and AOPs (such as O3, H2O2, and Fenton's process) can cause materials to decay much more quickly. This work aims to investigate the degradation of Methyl Blue (MB) with HC and evaluate the effectiveness of a hybrid process (O3 + HC). The experimental tests were conducted to determine the optimal operating conditions (pressure, pH, O3 dosage). Furthermore, the feasibility of MB mineralization at a high concentration range (10–100 mg/l) was performed. Cost estimation and energetic analysis were discussed. As a result, the optimal conditions were: P = 4.5 bar, pH 2, O3 = 7.5 mg/L. For the initial concentration of 10 mg/L, the MB decolorization yield of HC, O3, and HC + O3 were 10%, 99%, and 100%, respectively, after 30 min of treatment. The addition of O3 promoted the degradation efficiency above 95%, decreasing the treatment time. Increasing the O3 feed rate can reduce the treatment time. A flow rate of 8 L/min of ozone was adopted in the optimal flow value. The hybrid process has an important effect in improving the performance of wastewater treatment by reducing treatment time, causing saving in energy consumption and process cost.

Hybrid O3/UV/Fe process using rebar flakes waste for removal of congo red dye in wastewater

In Indonesia, textile is one of the labour-intensive industries that makes an important contribution to the national economy sectors. This industry tends to develop rapidly to meet domestic and export needs. This phenomenon increases wastewater generation from the textile industry. Textile wastewater contains dyes that are designed to be durable to resist sunlight and washing process. These properties pose a challenge to the treatment of dye wastewater. The complex structure of dye molecules is generally difficult to degrade by conventional biological processes, while the physical-chemical precipitation process will generate hazardous sludge. Therefore, alternative treatment processes for dye removal are urgently required. In this work, ozonation (O3), ozone and ultraviolet (O3/UV), and catalytic ozone coupling with ultraviolet (O3/UV/Fe) processes were tested for decolourisation of synthetic Congo red dye wastewater. Laboratory assays were carried out under various operating conditions: pH (3-7); ozonation mode (continuous, sequential); and catalyst dose (0.5-2 g/L). Ozonation in sequential mode and the utilisation of rebar flake waste from building construction project as iron catalyst presents a degree of novelty in this work. Congo red decolourisation up to 97% was achieved in less than one-hour of reaction by the continuous O3 process. Mineralisation in terms of COD reduction (50%) can be increased by either performing ozonation in sequential mode (79%) and coupling with UV irradiation (86%). Nevertheless, the effect of the iron catalyst was found to be negligible.

Enhanced removal strategy towards organic matter with low coagulability: Immediate entrapment and complexation of oxidized intermediates by the hybrid ozonation-coagulation process

The existence of dissolved organic matter (DOM) with low coagulability poses great challenges for conventional coagulation (CC) in water treatment. As a kind of typical organochlorine pesticide, 2,4-dichlorophenoxyacetic acid (2,4-D) cannot be efficiently removed by CC. To enhance the 2,4-D removal, ozonation was applied with coagulation. The hybrid ozonation-coagulation (HOC) achieved 60.61% DOC removal efficiency, which was obviously higher than pre-ozonation coagulation (POC) (45.83%). Synchronous fluorescence spectroscopy revealed stronger complexation between modified 2,4-D and coagulants during the HOC than that in subsequent coagulation of the POC process. During the HOC process, ozone promoted the formation of polymeric Al species, such as Alb. To investigate the 2,4-D removal mechanism, γ-Al2O3/O3 process with the same oxidation ability as the HOC was established. 2,4-D was oxidized step-by-step to 2,4-dichlorophenol, 4,6-dichlororesorcin, 3,5-dichlorocatechol, 2-chlorohydroquinone, 4-chlorocatechol, 1,2,4,5-tetrahydroxybenzene, pentahydroxybenzene and oxalic acid in γ-Al2O3/O3 process. However, during the HOC process, these oxidized intermediates were readily complexed by coagulants and accumulated in flocs. Especially 1,2,4,5-tetrahydroxybenzene and pentahydroxybenzene, completely complexed by AlCl3•6H2O hydrolysates as soon as being formed. Immediate entrapment and complexation between coagulant hydrolysates and 2,4-D oxidized intermediates inhibited the generation of small-molecular-weight organics such as oxalic acid, which enhanced the removal of organics with low coagulability.

Cobalt species immobilized on nitrogen‑doped ordered mesoporous carbon for highly efficient catalytic ozonation of atrazine

The strategy of coupling transition metal and N-doped carbon catalysts have garnered great attention in catalytic ozonation. To overcome the inferior mass transfer of O3, we prepared a hetero-structure catalyst (Co3O4@Co-N-CMK3), which was composed of Co3O4 nanoparticles (NPs) and cobalt-nitrogen doped ordered mesoporous carbon. Co3O4@Co-N-CMK3 displayed a uniformly arranged long-range mesoporous channel structure with large surface area (537.24 m2/g). The adsorption efficiency of ATZ (10 μM) was 55% at 15 min in presence of 0.05 g/L catalyst. After aeration of 3.5 mg/L O3 gas (50 mL min-1), the ATZ removal increased to 99.6% with rate constant of 0.354 min-1 in Co3O4@Co-N-CMK3/O3, 35.4-fold that in ozonation. The turnover frequency (TOF) value of Co3O4@Co-N-CMK3 reached 7.08 min-1 g-1, which was 2.2-93.2 folds higher than the reported ozonation catalysts. Co3O4@Co-N-CMK3 displayed the adsorption performance for ATZ and could activate O3 into O2- and OH effectively. The ≡Co2+ and ≡Co-Nx were main active sites. The synergy between Co3O4 and Co-N-CMK3 accelerated interface electron transfer, which was conducive to the redox of ≡Co2+/≡Co3+. The degradation pathway and intermediates toxicity were speculated using HPLC-MS measurement and Toxicity Estimation Software Tool simulation. The stability of Co3O4@Co-N-CMK3 for ATZ removal was certified by five consecutive experiments in catalytic ozonation. Moreover, the Co3O4@Co-N-CMK3/O3 process had good applicability to common anions and humic acid, real water and different pollutants.

Efficient catalytic ozonation for ibuprofen through electron-deficient/rich centers over cerium-manganese doped carbon

The sluggish Me(n+m)+/Men+ redox cycle greatly restrained the catalytic ozonation performance of metal-based catalysts. To break this bottleneck, we adopted an interfacial oxidation reaction to create electron-deficient/rich centers within carbon skeleton derived from MOF (C-MOF) by utilizing the electronegativity difference between cerium (Ce) and manganese (Mn), and evaluated its catalytic ozonation activity with ibuprofen (IBP) as model pollutant. XPS, H2-TPR, LSV and EPR characterizations as well as DFT calculation demonstrated that there existed electron-deficient Ce sites and electron-rich Mn sites on CeOx/MnOx/C-MOF. Under the co-function of Ce and Mn sites, CeOx/MnOx/C-MOF/O3 process achieved 100% IBP removal in 90 min, which was 3.1 times of sole ozonation process. IBP could be absorbed at the electron-deficient Ce center and directionally donate its electron to the O3 around electron-rich Mn center. Singlet oxygen (1O2) played the major role in IBP degradation. Cl−, HCO3−, NO3− and SO42− demonstrated limited inhibitions on IBP degradation. This work provided a sustainable strategy for breaking the rate-limiting step in the traditional catalytic ozonation.

Efficient treatment of surfactant containing wastewater by photocatalytic ozonation with BiPO4 nanorods

In this study, monoclinic BiPO4 nanorods were fabricated by one-pot solvothermal method. Its catalytic capability in photocatalytic ozonation process was tested by degradation and mineralization of sodium dodecyl benzene sulfonate (SDBS) solution. The results demonstrated that the TOC removal rate was dramatically improved to 90.0% at 75 min for UV/O3/BiPO4 process, which was 4.9 and 3.8 times more than that of UV/BiPO4 and O3. Moreover, the pseudo-first-order kinetic constant (0.337 min−1) and mineralization rate (90.0%) for SDBS degradation using BiPO4 in UV/O3 process were 1.6 and 1.3 times as great as that of conventional TiO2 photocatalyst (0.206 min−1, 67.3%). The influence of BiPO4 dosage, O3 concentration initial pH and coexisted ions on SDBS degradation in UV/O3/BiPO4 process were also investigated. The outcome of quenching studies illustrated both ·OH and h+ contributed prominently to SDBS degradation in UV/O3/BiPO4 process, implying that high valence band position of BiPO4 could promote the synergism between photocatalysis and ozonation. The degradation pathway of SBDS was proposed by combination of intermediates analysis and DFT calculation. Real carwash wastewater was chosen as typical surfactant containing wastewater to explore the practical application of UV/O3/BiPO4 technology. During 30 min, COD and LAS removal efficiency reached 59.7% and 70.6%, respectively. The quality indices of effluent could meet the requirements for reuse of carwash water in Water Quality Standard for Urban Miscellaneous Use in China. Energy consumption in the process was calculated as 13.9 kW h m−3, which was about 3.6 and 2.2 times less than that of UV/BiPO4 and O3 process, respectively. The results suggest that UV/O3/BiPO4 system has an application potential for surfactant containing wastewater treatment or recycle.

Magnetic nanohybrid derived from MIL-53(Fe) as an efficient catalyst for catalytic ozonation of cefixime and process optimization by optimal design

The catalytic activity of metal-organic frameworks (MOFs) in the degradation of environmental pollutants has garnered considerable interest recently. FTIR, FE-SEM, EDS, XRD, XPS, VSM, TEM, and N2 sorption-desorption isotherms were used to characterize Fe-based nanohybrids derived from MIL-53(Fe). In the catalytic ozonation of cefixime (CFX), the nanohybrid (CM-500) synthesized at 500 °C exhibited high efficiency. The enhanced catalytic activity of CM-500 may have been caused by Lewis acid sites (LAS), iron oxides, and oxygenated functional groups of the mesoporous carbon substrate that remained after pyrolysis of the organic framework. During 15 min of continuous ozonation, the CM-500/O3 process was the most effective at removing CFX with a removal efficiency of 97%, significantly higher than single ozonation with a degradation efficiency of 43% under the same conditions. Modeling and optimization of process conditions were conducted using a novel and efficient class of experimental design, namely optimal design with the fewest possible runs. Calculated CFX degradation kinetic rate constants were 0.212 min-1 with CM-500, 0.043 min-1 with MIL-53 (Fe), and 0.038 min-1 for ozonation alone. Mineralization (measured COD and TOC) is significantly higher in the CM-500/O3 system compared to single ozonation. Moreover, the scavenging experiment confirmed that the reactive oxygen species in the catalytic ozonation of CFX are surface-adsorbed superoxide and hydroxyl radicals. Due to CM-500's sustained activity and magnetic properties, it is expected that it has a high catalytic capacity for treating pharmaceutical wastewater.

Degradation of cytostatics methotrexate and cytarabine through physico-chemical and advanced oxidative processes: influence of pH and combined processes on the treatment efficiency

ABSTRACT Environmental release of wastewater that contains cytostatic drugs can cause genotoxic impact, since these drugs act directly on the genetic material of aquatic organisms. Thus, the aim of this study was to evaluate the removal of the cytostatic drugs cytarabine (CTR) and methotrexate (MTX) using different physico-chemical methods individually (i.e. US, O3, H2O2 and UV) and combined (i.e. O3/US, US/H2O2, O3/H2O2 and O3/US/H2O2) under different pH conditions (4, 7 and 10). In the degradation tests, the efficiency of the methods applied was found to be dependent on the pH of the solution, with the degradation of CTR being better at pH 4 and MTX at pH 7 and pH 10. The US, H2O2 and US + H2O2 methods were the least efficient in degrading CTR and MTX under the pH conditions tested. The highest MTX degradation rate after 16 min of treatment at pH 7 was achieved by the O3 + H2O2 method (97.05% – C/C0 = 0.0295). For CTR, the highest degradation rate after 16 min of treatment was achieved by the O3 process (99.70% – C/C0 = 0.0030) at pH 4. In conclusion, most of the treatment methods tested for the degradation of CTR and MTX are effective. Notably, ozonolysis is an efficient process applied alone. Also, in combination with other methods (US + O3, O3 + H2O2 and O3 + H2O2 + US) it increases the degradation performance, showing a rapid removal rate of 70–94% in less than 4 min of treatment.

Oxidation of ibuprofen in water by UV/O3 process: Removal, byproducts, and degradation pathways

Owing to the huge consumption of ibuprofen (IBP), its risk of exposure in water is of concern. The UV/O3 process has advantages in IBP degradation compared with the single UV and O3 processes. To promote the utilization of UV/O3, further exploration is necessary. In this study, the degradation mechanisms, byproduct security and cost of the UV/O3 process were investigated. Degradation kinetics showed that adding of UV irradiation into 0.6 mg/L of O3 increased the IBP degradation rate by 10 times, subsequently achieving a superior mineralization result. When the pH values changed (4.0–10.0) or humic acid existed in water, the UV/O3 efficiency was less affected compared with that of O3 process, which mainly attributed to the promotion of HO formation during UV/O3. Eleven byproducts with OH/COOH groups were identified in UV/O3, most of which contained 2–6 carbons. Ozonation produced the same types of byproducts, but the byproducts from UV irradiation were aromatics. Toxicity evaluation indicated that the 4′-(2-Methylpropyl)acetophenone formed in the UV process had stronger bioaccumulation potential than IBP, and some byproducts produced in the O3 and UV/O3 processes were more harmful based on the oral rate LD50 values. Because the byproduct transformations in UV/O3 accomplished within 10 min compared with the 100 min in the separate processes, the UV/O3 technology could better ensure byproduct security. In addition, the cost of UV/O3 was most acceptable among the three technologies under the same IBP degradation target. The UV/O3 technology had the promotion potential in IBP wastewater treatment.

Treatment of complex sulfur-containing solutions in ammonia desulfurization ammonium sulfate production by ultrasonic-assisted ozone technology

In this work, the cause of abnormal color in ammonium sulfate products formed by flue gas desulfurization is revealed by investigating the conversion relationship between different sulfur-containing ions and their behavior in a sulfuric acid medium. Both thiosulfate (S2O32−) and sulfite (SO32− ＆ HSO3−) impurities affect the quality of ammonium sulfate. The S2O32− is the main reason for the yellowing of the product due to the formation of sulfur impurities in concentrated sulfuric acid. To address the yellowing of ammonium sulfate products, a unified technology (US/O3), using ozone (O3) and ultrasonic waves (US) simultaneously, is exploited to remove both thiosulfate and sulfite impurities from the mother liquor. The effect of different reaction parameters on the degree of removal of thiosulfate and sulfite is investigated. The synergistic effect of ultrasound and ozone on ion oxidation is further explored and demonstrated by the comparative experiments with O3 and US/O3. Under the optimized conditions, the thiosulfate and sulfite concentration in the solution is 2.07 and 5.93 g/L, respectively, and the degree of removal is 91.39 and 90.83%, respectively. The product obtained after evaporation and crystallization is pure white and meets the national standard requirements for ammonium sulfate products. Under the same conditions, the US/O3 process has apparent advantages, such as saving reaction time compared with the O3 process alone. Introducing an ultrasonically intensified field improves the generation of oxidation radicals ·OH, 1O2, and ·O2– in the solution. Furthermore, the effectiveness of different oxidation components in the decolorization process is studied by adding other radical shielding agents using the US/O3 process supplemented with EPR analysis. The order of the different oxidation components is O3(86.04%) > 1O2(6.53%) > •OH(4.45%) > •O2–(2.97%) for the oxidation of thiosulfate, and it is O3(86.28%) > •OH(7.49%) > 1O2(4.99%) > •O2–(1.25%) for the oxidation of sulfite.

Tubular membrane photoreactor for the tertiary treatment of urban wastewater towards antibiotics removal: application of different photocatalyst/oxidant combinations and ozonation

A tubular membrane photoreactor, operated in continuous mode and low residence times (τ from 3.9 to 12.2 s), was applied for the removal of 14 antibiotics (sulfonamides, fluoroquinolones, macrolides, cephalexin, and trimethoprim) in demineralized water (DW) and secondary-treated urban wastewater (UWW). In this setup, the oxidant (hydrogen peroxide (H2O2), persulfate (S2O82−) or ozone (O3)) is permeated through the membrane pores and delivered to the catalyst (titanium dioxide (TiO2) or silver molybdate (Ag2MoO4)), embedded in the membrane shell side, and to the annular reaction zone (ARZ) where the DW or UWW fortified with the target antibiotics (50 µg L−1 each) flows. The antibiotics removal in the tested processes - photolysis (UVC), photocatalysis (UVC/TiO2 or UVC/Ag2MoO4), photochemical oxidation (UVC/H2O2 or UVC/S2O82−), their combinations (UVC/TiO2/H2O2, UVC/TiO2/S2O82‾, UVC/Ag2MoO4/H2O2 and UVC/Ag2MoO4/S2O82‾) and O3 - were evaluated at steady-state conditions by ultra-high performance liquid chromatography followed by quadrupole time-of-flight high-resolution mass spectrometry (UHPLC-QTOF-HRMS). In the DW, the treatment efficiency followed the sequence: UVC < UVC/TiO2 ≈ UVC/Ag2MoO4 < UVC/H2O2 < UVC/TiO2/H2O2 ≈ UVC/Ag2MoO4/H2O2 < UVC/S2O82‾ < UVC/TiO2/S2O82‾ < UVC/Ag2MoO4/S2O82‾ < O3. In the UWW, the O3 process proved again to be the most efficient (12 antibiotics removed >90%), followed by UVC/Ag2MoO4/S2O82‾ (five antibiotics removed >60%). UHPLC-QTOF-HRMS tentatively identified seven by-products stemming from macrolides for O3 treatment. This is a pioneer study on the application of Ag2MoO4 combined with H2O2 or S2O82- for advanced treatment of UWW, laying the groundwork for future research. The membrane reactor proves to be an effective technological approach for the O3 process.

Enhanced Mass Transfer of Ozone and Emerging Pollutants through a Gas-Solid-Liquid Reaction Interface for Efficient Water Decontamination.

Ozone (O3), as an environmentally friendly oxidant, is widely used to remove emerging pollutants and ensure the safety of the water supply, whereas the restricted accessibility of O3 and limited collision frequency between pollutants and O3 will inevitably reduce the ozonation efficiency. To promote the chemical reactions between O3 and target pollutants, here we developed a novel gas-solid-liquid reaction interface dominated triphase ozonation system using a functional hydrophobic membrane with an adsorption layer as the O3 distributor and place where chemical reactions occurred. In the triphase system, the functional hydrophobic membrane simultaneously improved the interface adsorption performance of emerging pollutants and the access pathway of O3, leading to a marked enhancement of interfacial pollutant concentration and O3 levels. These synergistic qualities result in high ciprofloxacin (CIP) removal efficiency (94.39%) and fast apparent reaction rate constant (kapp, 2.75 × 10-2 min-1) versus a traditional O3 process (41.82% and 0.48 × 10-2 min-1, respectively). In addition, this triphase system was an advanced oxidation process involving radical participation and showed excellent degradation performance of multiple emerging pollutants. Our findings highlight the importance of gas-solid-liquid triphase reaction interface design and provide new insight into the efficient removal of emerging pollutants by the ozonation process.

A2O–MBR–BAF–O3 process for treating high organic wastewater with high ammonia nitrogen

In recent years, many WWTPs in China need to be upgraded and reconstructed due to the emission standards improvement. The WWTP influent is complex in composition and contains many hard-to-degrade organic matter. The indices (e.g., chroma, chemical oxygen demand (COD), ammonia nitrogen (NH4+–N), total nitrogen (TN), and suspended substance) are relatively high. In this paper, the anaerobic–anoxic–oxic (A2O)–membrane bioreactor (MBR)–biological aerated filter (BAF)–O3 process was proposed for the first time. The practical process was used to degrade COD and NH4+–N, TN, and chroma simultaneously. Under the adjusted optimal hydraulic retention time (12.5 h), internal reflux ratio of the intermixture (200 %), and O3 contact time (15 min), the removal efficiencies of COD, NH4+–N, TN, total organic carbon, UV254, and chroma were 94.50 %, 99.13 %, 78.21 %, 95.18 %, 90.60 %, and 78.66 %, respectively. The effluent quality satisfied the first grade A criteria (GB 18918–2002) in China. The ultraviolet-visible and excitation-emission-matrix spectra of water samples during the O3 oxidation were analyzed. It showed that the reaction was effective in removing chroma and hard-to-degrade organic matter that could not be treated by the previous process, and humic acids that was the main fluorescent organic matter in the wastewater.

Potable Water Treatment in a Batch Reactor Benefited by Combined Filtration and Catalytic Ozonation

Due to continuous contamination of groundwater by anthropogenic activities, potable water fetches numerous pollutants such as pathogens, pharmaceuticals, and heavy metals, with these being severe health hazards. The main aim of the current study was to develop a hybrid unit based on catalytic ozonation and the filtration process to effectively remove the contaminants in drinking water. To the best of our knowledge, in the current study, the Fe-Zeolite 4A (Fe-Z4A)/O3 process followed by filtration involving rice husk and activated carbons were studied for the first time in order to treat drinking water. In the current investigation, fecal coliforms, arsenic, pharmaceuticals, turbidity, and TDS removal were investigated in a novel hybrid reactor. The results showed 100%, 45%, 40%, 70%, and 95% fecal coliform, arsenic, TDS, paracetamol, and turbidity removal efficiency, respectively. The results further indicated that all the studied drinking water samples followed WHO guidelines and NEQS for drinking water quality after the proposed treatment. Therefore, it is concluded that the proposed hybrid process implies a single unit is highly efficient for drinking water treatment. The designed novel hybrid reactor treatment can be scaled up in the future for household or commercial use.

Exploring Formation of Ozone in Typical Cities in Beijing-Tianjin-Hebei Region Using Process Analysis

As the problem of O3 pollution in the Beijing-Tianjin-Hebei region becomes increasingly prominent, it is of great significance to explore and analyze the ozone variation characteristics and causes of the pollution process in the Beijing-Tianjin-Hebei region for regional air pollution prevention and control. The observations in this study showed that high O3 concentration in spring and summer of the Beijing-Tianjin-Hebei region was higher in the south and lower in the north. The high O3 concentration in Beijing, Tianjin, and Shijiazhuang was often accompanied by the influence of southern wind. Based on WRF-Chem model simulation and process analysis technology, the variation characteristics and causes of O3 in The Beijing-Tianjin-Hebei region in 2019 were deeply analyzed. The diurnal variations in chemical processes, vertical mixing, and transportation in typical cities showed distinct seasonal variations. In summer afternoons, chemical processes were the main source of O3 concentration increase in each city. Vertical mixing resulted in an increase in O3 concentration in Tianjin and Shijiazhuang but a decrease in Beijing. Tianjin and Shijiazhuang had a net output, whereas Beijing had a net inflow. In the polluted O3 process, the chemical process dominated the afternoon O3 concentration increasing in Beijing and Shijiazhuang, whereas vertical mixing dominated in Tianjin. In addition, there was a net input of O3 in Beijing and Shijiazhuang and a net output of O3 in Tianjin. In the clean O3 process, vertical mixing dominated the increase in O3 concentration in Beijing and Shijiazhuang in the afternoon, whereas in Tianjin it was chemical processes. At the same time, the net output of O3 existed in all three cities.

Treatment of real time textile effluent containing azo reactive dyes via ozonation, modified pulsed low frequency ultrasound cavitation, and integrated reactor

The common effluent treatment plant (CETP) of Kerala Industrial Infrastructure Development Corporation (KINFRA) at Kannur (District), Kerala (State), India undertakes the treatment of textile effluents containing the azo reactive dyes by using the stage-1 and stage-2 facilities. In this investigation, the stand-alone ozonation (O3) and modified pulsed low frequency ultrasound (US) cavitation as well as their integrated reactor are studied for the possible replacement of stage-1 facility which generates large amount of sludge. The major criteria for the replacement are to achieve minimum 90% of chemical oxygen demand (COD) removal, without the sludge formation, with the final COD level of less than 150 mg L − 1 as per the requirements of KINFRA, India. The stand-alone ozonation and modified pulsed low frequency US cavitation processes provide the COD removal of 90 and 65%; while, their integrated reactor provides 86% COD removal, without the sludge formation, with the final COD level less than 150 mg L − 1. Since all the conditions are satisfied only by the stand-alone O3 process, the latter is highly suitable for the replacement of stage-1 facility. The COD removal is possibly achieved via the generation and attack of ·OOH for the stand-alone O3 process; while, the same is achieved via the generation and attack of O2·- for the modified pulsed low frequency US cavitation process and their integrated reactor.

Catalytic ozonation of N, N-dimethylacetamide in aqueous solution by Fe3O4@SiO2@MgO composite: Optimization, degradation pathways and mechanism

BackgroundCatalytic ozonation is a commonly used technique in deep treatment of water. Magnesium oxide is an effective catalyst in ozonation, but how to effectively separate and improve its stability remains big challenge. MethodThe magnetic core-shell Fe3O4@SiO2@MgO was prepared by co-precipitation method, and the prepared catalyst could be easily recovered through magnetic separation. Significant findingsOzonation of N, N-dimethylacetamide (DMAC) was used to test the performance of Fe3O4@SiO2@MgO. The removal fraction of DMAC by Fe3O4@SiO2@MgO catalytic ozonation was 99.96% in 12 min, which was almost 4.3 times that of ozonation alone under the same conditions. In addition, the mineralization rate of DMAC at 12 min was 43.70%, much higher than that of ozone alone (11.90%). The recycling test manifested the excellent stability and recoverability of Fe3O4@SiO2@MgO, indicating the formed composite is a potential practical catalyst. The possible DMAC degradation pathways and reaction mechanism of Fe3O4@SiO2@MgO/O3 process were proposed.

Fe3O4 catalytic ozonation of iohexol degradation in the presence of 1-hydroxybenzotriazole: Performance, transformation mechanism, and pathways

This study explored the degradation of an iodine X-ray contrast media, iohexol, under heterogeneous ozone-catalyzed oxidation by adding Fe3O4 and 1-hydroxybenzotriazole (HBT). Results show that increasing the dosages of Fe3O4 catalyst and ozone as well as solution pH were beneficial to the degradation of iohexol. The presence of low background humic acid (HA) concentration (≤10 mg/L) promoted iohexol degradation, but high HA concentration (≥20 mg/L) inhibited it. Adding HBT exhibited a similar effect on iohexol degradation as HA. The degradation rate constant of iohexol was calculated as 0.07108 min−1 in the Fe3O4/O3/HBT process ([HBT] = 5 μM) at pH 7.0, which was approximately 1.5 times higher than that in the Fe3O4/O3 process (0.04533 min−1), and 4 times higher than that in the O3 process (0.01742 min−1). Fe3O4/O3/HBT process was pH-dependent with high degradation efficiency of iohexol at pH 5 or 7. Singlet oxygen (1O2), hydroxyl radical (OH∙), and superoxide radical (O2-∙) have been identified in the Fe3O4/O3/HBT process, and the conversion of Fe2+ to Fe3+ was more obvious on the surface of Fe3O4 compared to that in the Fe3O4/O3 process. Transformation intermediates were identified, and the degradation pathways of iohexol were proposed. Overall, Fe3O4/O3 could enhance iohexol degradation compared with ozone-only system, and adding trace HBT in Fe3O4/O3 system can further enhance heterogeneous ozone-catalyzed process for rapid organic matter degradation.