Heterogeneous Catalytic Ozonation Process Research Articles

Treatment of pharmaceutical wastewater by a sequential KMnO4/CoFe2O4-mediated catalytic ozonation process

Pharmaceutical compounds, which are of utmost concern, have found their way into natural water bodies, causing numerous problems for both human health and ecosystems. In this study, an integrated system including potassium permanganate (PM) pre-oxidation, followed by a heterogeneous catalytic ozonation process (HCOP) using CoFe2O4 magnetic nanoparticles (CF MNPs), and an activated sludge-based biological treatment (BT) was employed for the first time to treat pharmaceutical wastewater (PWW). In this regard, the effluent from PM pre-oxidation process was used as a batch for the HCOP, and the effluent was used as a batch for the BT process. The results showed that PM pre-treatment of PWW (PM dose = 1264 mg/L and pH = 8.0) reduced the COD content of the PWW from 900 ± 50 to 443 ± 10 mg/L within 120 min of reaction time. The application of HCOP for further treatment of PWW dramatically enhanced COD and TOC removal compared with the single ozonation process (SOP). Under optimum conditions (pH = 10, O3 = 4.0 mg/L, and CF MNPs = 1000 mg/L), HCOP successfully reduced the COD and TOC contents of PWW by 37 % and 46.1 %, respectively, after 120 min of treatment. The consecutive combination of PM pre-treatment followed by HCOP exhibited good potential and reduced COD by over 69 %, resulting in a residual COD of less than 280 mg/L. A biodegradability ratio of over 81 % and residual COD of 54 mg/L for the PWW treated by the PM/HCOP/BT integrated system indicated that biodegradability was enhanced, and a high fraction of refractory organic compounds was effectively removed. In conclusion, the PM/HCOP/BT integrated system is an efficient, synergistic, and easy-to-operate technique for enhancing the biodegradability of PWW.

Preparation of catalyst of cobalt‐ and/or iron‐doped strontium zirconate and its performance in removal of m‐cresol using ozone as oxidant

AbstractBACKGROUNDWastewater containing m‐cresol has become a global water environmental problem because its degradation is difficult, and it is highly toxic to plants, animals, and humans. The heterogeneous catalytic ozonation process has been widely used in the treatment of environmental pollution, so it is very important to study efficient catalysts. Perovskite catalysts have been widely investigated and applied in catalytic ozonation processes. Among them, strontium zirconate is a promising perovskite catalyst owing to its high oxidation efficiency and environmental friendliness.RESULTSStrontium zirconate was successfully synthesized via the co‐precipitation method. To improve strontium zirconate catalytic performance, some methods such as changing the doping ratio of cobalt and iron, changing the amount of polyethylene glycol added, changing the calcination temperature, and changing the aging time were carried out during the synthesis process. Finally, the optimal conditions were determined. 0.4 g L−1 Sr2Co0.4Fe0.6ZrO6 prepared under the optimal conditions was used for catalytic ozonation of 100 ppm m‐cresol, which achieved the optimum degradation (0.136 min−1), m‐cresol conversion rate (92.2%) and total organic carbon removal rate (12.1%) within 20 min.CONCLUSIONThis work provides the best preparation conditions. The Sr2Co0.4Fe0.6ZrO6 catalyst, as prepared, is the optimal catalyst for catalytic ozonation of m‐cresol among the investigated Sr2CoxFe1−xZrO6 catalysts. © 2024 Society of Chemical Industry (SCI).

Pentachlorophenol degradation in the heterogeneous catalytic ozonation process using Al2O3 as a catalyst agent

Pentachlorophenol degradation in the heterogeneous catalytic ozonation process using Al2O3 as a catalyst agent

Electric field-enhanced heterogeneous catalytic ozonation (EHCO) process for sulfadiazine removal: The role of cathodic reduction

In this work, an electric field-enhanced heterogeneous catalytic ozonation (EHCO) was systematically investigated using a prepared FeOx/PAC catalyst. The EHCO process exhibited high sulfadiazine (SDZ) and TOC removal efficiency compared with electrocatalysis (EC) and heterogeneous catalytic ozonation (HCO) process. Almost 100% of SDZ was removed within 2 min, and the TOC removal reached approximately 85% within 60 min. Quenching experiments and EPR analysis suggested that the prominent SDZ and TOC removal performance is supported by the enhanced ·OH generation ability. Further study proved that H2O2 formed by O2 electrochemical reduction, peroxone reaction and electrochemical reduction of ozone contributed to improving ·OH generation. Furthermore, the EHCO system showed satisfactory stability and recyclability compared to conventional HCO systems, and the SDZ and TOC removal rates were maintained at ≥95% and ≥70% in 16 consecutive recycles, respectively. Meanwhile, XPS analysis and Boehm's titration for the FeOx/PAC catalyst used in HCO and EHCO process confirmed that the external electron supply could restrain the oxidation of surface functional groups of PAC and maintain a balance of the Fe(II)/Fe(III) ratio, which proved the critical role of cathode reduction in catalyst in situ regeneration during long consecutive recycles. In addition, the EHCO system could achieve more than 80% SDZ removal within 2 min in different water matrices. These results confirmed that the EHCO process has a wide application perspective for refractory organics removal in actual wastewater.

Constructed electron-dense Mn sites in nitrogen-doped Mn3O4 for efficient catalytic ozonation of pyrazines: Degradation and odor elimination

In this study, N-doped Mn3O4 catalysts (Mn-nN) with electron-dense Mn sites were synthesized and employed in heterogeneous catalytic ozonation (HCO). These catalysts demonstrated excellent performance in pyrazines degradation and odor elimination. The synthesis of Mn-nN was achieved through a facile urea-assisted heat treatment method. Experimental characterization and theoretical analyses revealed that the MnN structures in Mn-nN, played a crucial role in facilitating the formation of electron-dense Mn sites that served as the primary active sites for ozone activation. In particular, Mn-1N exhibited excellent performance in the HCO system, demonstrating the highest 2,5-dimethylpyrazine (2,5-DMP) degradation efficiency. •OH was confirmed as the primary reactive oxygen species involved in the HCO process. The second-order rate constants for 2,5-DMP degradation with O3 and •OH, were determined to be (3.75 ± 0.018) × 10−1 and (6.29 ± 0.844) × 109 M−1 s−1, respectively. Seventeen intermediates were identified through GC-MS analysis during the degradation of 2,5-DMP via HCO process with Mn-1N. The degradation pathways were subsequently proposed by considering these identified intermediates. This study introduces a novel approach to synthesize N-doped Mn3O4 catalysts and demonstrates their efficacy in HCO for the degradation of pyrazines and the elimination of associated odors. The results show that the catalysts are promising for addressing odor-related environmental issues and provide valuable insights about the broader significance of catalytic ozonation processes.

Surface atomic oxygen species mediated the in-situ formation of hydroxyl radicals on Fe3C decorated biochar for enhancing catalytic ozonation

Developing highly efficient and anti-interference catalysts was still a challenge for the practical application of heterogeneous catalytic ozonation (HCO) in water decontamination. Herein, a magnetic Fe3C decorated biochar (Fe3C/BC) was prepared for HCO to achieve efficient degradation of 2,4-dichlorophenoxyacetic acid (2,4-D). The Fe3C/BC catalytic ozonation system promoted the degradation ratio of 2,4-D from 58.7% (ozonation alone) to 90.0% within 10 mins when the ozone dosage was 1.0 mg/L. And the observed degradation rate constant (kobs) of 2,4-D under catalytic ozonation system was 2.58 times that of ozonation alone. Fe3C/BC exhibited negligible adsorption on 2,4-D but with a significant enrichment to ozone, which realized the cooperating process of “adsorption-catalysis” at the solid–liquid interface, thus avoiding the ineffective decomposition of ozone. The dissociative adsorption of ozone molecules on the surface Fe3C generated surface atomic oxygen species (O* and O2*), which mediated the in-situ formation of hydroxyl radicals (·OH). ATR-FTIR, in-situ Raman, isotope tracing tests, and theoretical calculations were used to disclose the interface reaction processes and reveal the ·OH formation mechanism. Free radical reactions at the interface efficiently avoid the interference of coexisting ions dissolved in water. The presence of 3 mM (183 mg/L) bicarbonate had essentially little effect on the degradation of 2,4-D. The consecutive use of Fe3C/BC did not influence its catalytic performance and stable structure. This study provided new insight into the ·OH-dominated interfacial reaction in the HCO process.

Revisit the Role of Salinity in Heterogeneous Catalytic Ozonation: The Trade-Off between Reaction Inhibition and Mass Transfer Enhancement.

Heterogeneous catalytic ozonation (HCO) is an effective technology for advanced wastewater treatment, while the influence of coexisting salts remains unclear and controversial. Here, we systematically explored the influence of NaCl salinity on the reaction and mass transfer of HCO through lab experiments, kinetic simulation, and computational fluid dynamics modeling, and proposed that the trade-off between reaction inhibition and mass transfer enhancement would affect the pollutants degradation pattern under varying salinity. The increase of NaCl salinity decreased ozone solubility and accelerated the futile consumption of ozone and hydroxyl radicals (•OH), and the maximum •OH concentration under 50 g/L salinity was only 23% of that without salinity. However, the increase of NaCl salinity also significantly reduced the ozone bubble size and enhanced the interphase and intraliquid mass transfer, with the volumetric mass transfer coefficient being 130% higher than that without salinity. The trade-off between reaction inhibition and mass transfer enhancement shifted under different pH values and aerator pore sizes, and the oxalate degradation pattern would change correspondingly. Besides, the trade-off was also identified for Na2SO4 salinity. These results emphasized the dual influence of salinity and offered a new theoretical perspective on the role of salinity in the HCO process.

Evaluation of Heterogeneous Catalytic Ozonation Process for the Removal of Micropollutants from Water/Wastewater: Application of a Novel Pilot-Scale Continuous Flow System

The present study evaluates the removal of micropollutants from water/wastewater contaminated sources through the application of a heterogeneous catalytic ozonation process, using a pilot-scale continuous operation unit, composed of a membrane module for the diffusion and effective dilution of ozone into the liquid phase to be treated and a plug flow reactor/continuous stirred tank reactor (PFR/CSTR) contact reactor system in series, where the catalyst is recirculated in dispersion mode. The solid materials tested as catalysts are natural and calcined zeolite, Bayoxide and alumina, whereas the examined micropollutants, used in this case as probe compounds, are p-chlorobenzoic acid (p-CBA), atrazine, benzotriazole and carbamazepine. A high-performance liquid chromatography system was used to determine the removal of micropollutants. In the case of p-CBA, an ozone-resistant compound, the addition of catalyst was found to significantly enhance its degradation rate, leading to >99% removal under the optimum defined conditions, i.e., in terms of catalyst concentration, pH, temperature, and process time. On the other hand, in the case of atrazine, a different ozone-resistant compound, the introduction of examined catalysts in the ozonation process was found to reduce the degradation of micropollutant, when compared with the application of single ozonation, indicating the importance of specific affinity between the pollutant and the solid material used as catalyst. Benzotriazole, a moderately ozone-reactive compound was degraded by more than 95% under all experimental conditions and catalysts tested in the pilot unit, while carbamazepine, a highly ozone-reactive compound, was completely removed even during the first stage of treatment process (i.e., at the membrane contactor). When increasing the pH value (in the range 6–8) and the contact time, the performance of catalytic ozonation process also improved.

Exploration of surface hydroxyl on goethite during heterogeneous catalytic ozonation process: Generation, category, charged property, and contribution

The surface hydroxyl of a catalyst is believed to play a crucial role in O3 decomposition during heterogeneous catalytic ozonation. However, studies related to the generation, category, charged properties and the respective contributions of surface hydroxyl are inadequate. In this study, a hydroxyl-rich goethite (α-FeOOH) was selected as the catalyst for the ozonation of ibuprofen (IBP). By heating the catalyst and changing the reaction pH, the state of the hydroxyl groups on the catalyst surface was successfully adjusted, and the main functional hydroxyl group for ozone catalysis was identified. The results indicated that the addition of α-FeOOH during ozonation effectively degraded and mineralized IBP, and the main action was to promote the decomposition of O3 into •OH. Thermogravimetry and X-ray photoelectron spectroscopy (XPS) analyses showed that four types of hydroxyl groups coexisted on the surface of the catalyst. While adsorbed hydroxyl presented the least, the vacancy, metal, and basic site hydroxyls were dominant. Fourier transform infrared spectroscopy (FTIR) and XPS analyses revealed that heating the catalyst to 350 °C could eliminate the vacancy hydroxyl, whereas the metal and basic site hydroxyls recovered to their before-heating levels, which is related to the crystal transformation of the catalyst from goethite to hematite. Changing the solution pH from 3.0 to 9.0 adjusted the surface hydroxyl charge from positive to negative, and the neutral vacancy hydroxyl was judged as the main functional hydroxyl for ozone catalysis. Finally, a route involving the decomposition of O3 into •OH on the surface hydroxyl is proposed.

Hierarchical nano-reactor with core-shell structure for efficient removal of atrazine via heterogeneous catalytic ozonation: Experimental parameters, kinetics and performance analysis

The engineering application of the heterogeneous catalytic ozonation process (HCOP) is severely hampered by inefficient heterogeneous catalysts. Herein, a novel hierarchical core-shell MnO2@mSiO2 nano-reactor was prepared using hydrothermal and sol-gel methods. Its catalytic performance was systematically evaluated through the degradation and mineralization of atrazine (ATZ) in HCOP under various reaction parameters. At optimal parameters (O3/7.5 mg/L, ATZ/15 uM, catalyst/30 mg/L, pH = 7), 96.5 % and 36.1 % of ATZ and total organic carbon (TOC) removal efficiencies could be obtained after 30 min, respectively. After five cycles, the ATZ removal efficiency of MnO2@mSiO2 only decreased by approximately 10 %. The synergy effects between the core and mesoporous shell played a vital role in its efficient catalytic activity. The large specific surface area and confined environment favored ozone adsorption, mass transfer and enhanced the enrichment of ATZ, intermediate products, and oxidants. Quenching experiments and the chemical kinetic model indicated that hydroxyl radical (·OH) was the primary oxidant. The Mn3+/ Mn4+ and oxygen vacancies (OVs) acted as active sites to promote ozone decomposition via electron transfer facilitated by the shell. This work provides new advancements for the development of high-efficiency catalysts for the engineering application of HCOP.

Efficient removal of sulfamethazine by a magnetic recoverable CeO2/Fe3O4/natural zeolite catalyst in catalytic ozonation process

In order to realize the efficient removal of sulfamethazine (SMZ) and overcome the recycling difficulty of catalysts in a heterogeneous catalytic ozonation process, low-cost natural zeolite loaded with CeO2 and Fe3O4 (FC/HZ) was synthesized by the co-precipitation method. The FC/HZ catalyst could completely degrade SMZ and realize 39.6% removal of TOC through catalytic ozonation. Moreover, the FC/HZ catalyst exhibited high catalytic ozonation activity under a wide pH range and possessed excellent recyclability (>90%) and stability with a magnet. Based on experiment and material characterization, the possible catalytic mechanism and degradation pathway of SMZ was revealed. In brief, this study offered an effective strategy for preparing recyclable catalysts and eliminating SMZ in aqueous solution.

Synergistic effect of Fe and Ce on Fe doped CeO2 for catalytic ozonation of amoxicillin: Efficiency evaluation and mechanism study

A Fe-doped CeO2 was fabricated for catalytic ozonation of Amoxicillin (AMX), and the catalytic mechanisms were explored in this study. Under optimal conditions (the initial solution pH of 7.0, FC-0.3 dosage of 0.5 g/L, O3 dosage of 4 mg/min), the AMX and TOC removal by the optimal material (FC-0.3, at Fe/Ce atomic ratio of 0.3) reached 98.1 % at 24 min and 55.2 % at 36 min, respectively. Improved the AMX mineralization efficiency by 3.7 times. The experiments and theoretical calculation reveal the mechanisms of promoted catalytic ozonation by FC-0.3: 1) Highly abundant surface-active sites (i.e., –OH) enabled the adsorption of H2O and O3, which was favorable to the generation of reactive oxygen species (ROS) and improved the reaction probability for ROS and contaminants. 2) The synergistic effect between Ce4+/Ce3+ and Fe3+/Fe2+ redox couples accelerated the electron transfer and formation of ROS. More than 42 % of •OH was generated in the presence of FC-0.3, and the •OH, •O2− and 1O2 were the main ROS that contributed to AMX degradation. The surface OH groups played a key role in the catalytic ozonation. The oxygen vacancies (OVs) played an important role in electron transfer, Ce and Fe were the active sites of electrons transfer following the sequence of (Ce3+ + Fe2+) → (Ce4+ + Fe3+) → (Ce3+ + Fe2+) redox reaction. The degradation pathway investigation and toxicity evaluation revealed that some more toxic intermediates were generated during the ozonation process, and sufficient mineralization is required to meet safe discharge. This study provides reference for the synthesis of new catalysts and insight into the reaction mechanisms in the heterogeneous catalytic ozonation process.

Application of Heterogeneous Catalytic Ozonation in Wastewater Treatment: An Overview

Catalytic ozonation is a non-selective mineralization technology of organic matter in water by using active free radicals generated by ozone degradation. Catalytic ozonation technology can be divided into homogeneous catalytic reactions using metal ions as catalysts and heterogeneous catalytic reactions using solid catalysts. Homogeneous catalytic ozonation technology has many problems, such as low mineralization rate, secondary pollution caused by the introduction of metal ions and low utilization efficiency of oxidants, which limit its practical application. Compared with homogeneous catalytic ozonation technology, heterogeneous catalytic ozonation technology has the advantages of easy recovery, lower cost of water treatment, higher activity and improved mineralization rate of organic matter. This overview classifies and describes catalysts for heterogeneous catalytic ozonation technology, including the different types of metal oxides, metal-free catalysts, and substrates used to immobilize catalysts. In addition, the heterogeneous catalytic ozonation process involved in the multiphase complex reaction process is discussed. The effects of different parameters on the performance of heterogeneous catalytic ozonation are also discussed.

A comprehensive review on metal based active sites and their interaction with O3 during heterogeneous catalytic ozonation process: Types, regulation and authentication.

Heterogeneous catalytic ozonation (HCO) was a promising water purification technology. Designing novel metal-based catalysts and exploring their structural-activity relationship continued to be a hot topic in HCO. Herein, we reviewed the recent development of metal-based catalysts (including monometallic and polymetallic catalysts) in HCO. Regulation of metal based active sites (surface hydroxyl groups, Lewis acid sites, metal redox cycle and surface defect) and their key roles in activating O3 were explored. Advantage and disadvantage of conventional characterization techniques on monitoring metal active sites were claimed. In situ electrochemical characterization and DFT simulation were recommended as supplement to reveal the metal active species. Though the ambiguous interfacial behaviors of O3 at these active sites, the existence of interfacial electron migration was beyond doubt. The reported metal-based catalysts mainly served as electron donator for O3, which resulted in the accumulation of oxidized metal and reduced their activity. Design of polymetallic catalysts could accelerate the interfacial electron migration, but they still faced with the dilemma of sluggish Me(n+m)+/Men+ redox cycle. Alternative strategies like coupling active metal species with mesoporous silicon materials, regulating surface hydrophobic/hydrophilic properties, polaring surface electron distribution, coupling HCO process with photocatalysis and H2O2 were proposed for future research.

Byproduct formation in heterogeneous catalytic ozonation processes

Heterogeneous catalytic ozonation (HCO) is a promising advanced oxidation process (AOP) that can effectively degrade recalcitrant organic pollutants; but formation of harmful byproducts should be carefully evaluated.

Heterogeneous Catalytic Ozonation: Solution pH and Initial Concentration of Pollutants as Two Important Factors for the Removal of Micropollutants from Water

There are several publications on heterogeneous catalytic ozonation; however, their conclusions and the comparisons between them are not always consistent due to the variety of applied experimental conditions and the different solid materials used as catalysts. This review attempts to limit the major influencing factors in order to reach more vigorous conclusions. Particularly, it highlights two specific factors/parameters as the most important for the evaluation and comparison of heterogeneous catalytic ozonation processes, i.e., (1) the pH value of the solution and (2) the initial concentration of the (micro-)pollutants. Based on these, the role of Point of Zero Charge (PZC), which concerns the respective solid materials/catalysts in the decomposition of ozone towards the production of oxidative radicals, is highlighted. The discussed observations indicate that for the pH range 6–8 and when the initial organic pollutants’ concentrations are around 1 mg/L (or even lower, i.e., micropollutant), then heterogeneous catalytic ozonation follows a radical mechanism, whereas the applied solid materials show their highest catalytic activity under their neutral charge. Furthermore, carbons are considered as a rather controversial group of catalysts for this process due to their possible instability under intense ozone oxidizing conditions.

Catalytic ozonation for imazapic degradation over kelp-derived biochar: Promotional role of N- and S-based active sites

It is a feasible strategy to prepare reliable biochar catalysts for heterogeneous catalytic ozonation (HCO) processes by using inexpensive, high quality, and easily available raw materials. Here, an environmentally friendly, simple, and green biochar catalyst rich in nitrogen (N) and sulfur (S) has been prepared by the pyrolysis of kelp. Compared with directly carbonized kelp biomass (KB), acid-activated KB (KBA) and base-activated KB (KBB) have higher specific surface areas and more extensive porous structures, although only KBB displays effective ozone activation. Imazapic (IMZC), a refractory organic herbicide, was chosen as the target pollutant, which has apparently not hitherto been investigated in the HCO process. Second-order rate constants (k) for the reactions of IMZC with three different reactive oxygen species (ROS), specifically kO3, IMZC, kOH, IMZC, and k1O2, IMZC, have been determined as 0.974, 2.48 × 109, and 6.23 × 105 M−1 s−1, respectively. The amounts of graphitic N and thiophene S derived from the intrinsic N and S showed good correlations with the IMZC degradation rate, implicating them as the main active sites. OH and O2− and 1O2 were identified as main ROS in heterogeneous catalytic ozonation system for IMZC degradation. This study exemplified the utilization of endogenous N and S in biological carbon, and provided more options for the application of advanced oxidation processes and the development of marine resources.

Removal of a Contaminant of Emerging Concern by Heterogeneous Catalytic Ozonation Process with a Novel Nano Bimetallic Catalyst Embedded on Activated Carbon

ABSTRACT Organic contaminants such as Bisphenol A are classified as Contaminants of Emerging Concern (CECs). The inability of conventional water and wastewater treatments to remove CECs has made Advanced Oxidation Processes (AOPs) attractive for their removal from water sources. Oxidation species such as hydroxyl radicals are produced by AOPs that degrades and mineralize CECs found in water and wastewater. The present study focuses on using heterogeneous nano-metallic oxide embedded activated carbon (AC) for degrading Bisphenol-A (BPA) present in the water. The catalytic ozonation process was carried out using AC/Cu2O/ZnO as the catalyst. The bimetallic catalyst was characterized using BET, XRD, FESEM, Raman Spectra, and DLS. Total organic carbon (TOC) removal was 19% higher for catalytic ozonation when compared with non-catalytic ozonation. HPLC studies found that BPA was removed by 98%. The optimal conditions for degradation were 650 µg/L, pH 8 and 60 minutes. LC-MS/LC-Q-TOF was utilized to find the degradation pathway.

Application of Fe-RGO for the removal of dyes by catalytic ozonation process.

Due to continuous industrialization, the discharge of hazardous dyes has enormously disrupted the ecosystem causing environmental problems. Due to the stable recalcitrant nature of dyes, advanced catalytic ozonation processes with the latest catalyst are under investigation. Fe-RGO is an effective oxidation catalyst, and the metal loaded platform provides enhanced catalytic performance. This study aims to investigate the effectiveness of Fe-RGO/O3 process for the removal of dyes. In the current research, the application of iron-coated reduced graphene oxide (Fe-RGO) was studied as a catalyst in the heterogeneous catalytic ozonation process to remove dyes. Methylene blue (MB) was selected as a model pollutant. RGO was prepared using the improved Hummers method and was coated with iron (Fe) implying the impregnation method. The FTIR, SEM-EDX, XRD, and BET analyses of RG and Fe-RGO were performed to characterize the catalyst. The effect of various parameters such as pH (3-10), catalyst dose (0.01-0.04g), and radical scavengers (NaHCO3, NaCl) on removal efficiency was elucidated. The result revealed an excellent catalytic efficiency of Fe-RGO in the ozonation process. At optimum conditions, 96% removal efficiency was achieved in catalytic ozonation at pH 7 with a catalyst dose of 0.02g and ozone dose 0.5mg/min, after 10min. Interestingly, a slight decrease in removal efficiency was observed in the catalytic ozonation process in hydroxyl radical scavengers (NaCl and NaHCO3), which makes the proposed catalyst more applicable in real conditions. Therefore, it is concluded that Fe-RGO can be used as an excellent catalyst for the removal of dyes in real conditions where radical scavengers may be present in a significant amount.

Comparative study of ozonation and ozonation catalyzed by Fe-loaded biochar as catalyst to remove methylene blue from aqueous solution

Ozone-based processes gained much attention in recent years. However, due to low oxidative stability and utilization rate, single ozonation process (SOP) is insufficient for complete mineralization of pollutants. As a result, the single ozonation process is performed in the presence of a catalyst, a process known as catalytic ozonation process (COP). A promising catalyst (Fe/BC) was prepared by impregnating iron on biochar surface to remove methylene blue from aqueous solution via heterogeneous catalytic ozonation process (HCOP). The prepared Fe/BC features were characterized using Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM) and Brunauer–Emmett–Teller method (BET) before and after HCOP. Furthermore, the effect of various operating parameters such as ozone dose, catalyst dose, initial dye concentration, initial pH on the efficiency of SOP and HCOP were compared. In comparison to single ozonation process, the experimental study found that heterogeneous catalytic ozonation process has the highest efficiency. At pH 7.0, approximately 76% of methylene blue is removed during single ozonation process in 60 min. Heterogeneous catalytic ozonation process showed 95% methylene blue elimination from aqueous solution. The efficiency of heterogeneous catalytic ozonation process was decreased by 52% in the presence of hydroxyl radical (●OH) scavenger, indicating that hydroxyl is the major oxidant during heterogeneous catalytic ozonation process for the removal of methylene blue from aqueous solution. Fe/BC catalyst appears to have a lot of industrial promise, as well as the ability to remove methylene blue from aqueous solution via heterogeneous catalytic ozonation process.