Ozonation Process Research Articles

Kinetic Modeling of Brilliant Blue Discoloration by Ozonation

This paper presents the results of investigations on the kinetic modeling of Brilliant Blue FCF (BB) discoloration reactions in aqueous solutions with different ozone concentrations and pH conditions. Kinetic studies involve knowledge of the structure and properties of dye and ozone, as well as of the experimental conditions. In general, scientists admit that the predominant oxidation pathway is direct (by free oxygen atoms) or indirect (by free hydroxyl radicals); this will depend on influencing factors such as the physicochemical properties of the dye, the pH of the aqueous solution, ozone concentration, reaction time, and the contact mode with/without stirring. In this experimental research, two pathways were chosen following CBB = f(t)—1. a constant dye concentration and different ozone concentrations, in the concentration range of 100–250 mg/L, in three pH media (acidic, neutral, and basic), with and without stirring; 2. a constant concentration of ozone and different dyes in the concentration range of 2.5–10 mg/L, under the conditions of point 1. With the obtained experimental data, the curves CBB = f(t) were drawn and processed according to the integral method of classical kinetics, based on first- and second-order equations. Unfortunately, this simple procedure did not give any results for the pH values studied. The rate constants were negative, and/or the reaction order depended on the initial conditions. Due to its structure, the BB dye has several chromophore groups, and thus multiple attack centers, resulting in several oxidation by-products, which is why the 1H-NMR spectrum was recorded for the discoloration of BB with ozone. Since the stoichiometry of the overall oxidation reaction, as well as the relationship between the rate constant and the reaction conditions mentioned above, is not known, a kinetic model based on mass transfer coupled with a chain reaction in the bulk liquid phase was proposed and successfully tested at pH = 7. This research approach also involves the consolidation of the theoretical bases of the ozonation process through the kinetic study carried out, as well as the proposal of a kinetic model. These systematics lead to results that are applicable to other aqueous systems that are impure with dyes, allowing for generalizations and the development of the field, ensuring the sustainability of the research.

Decolorization of Acid Yellow 17 by ozonation and peroxone (O3/H2O2) process

Decolorization of Acid Yellow 17 by ozonation and peroxone (O3/H2O2) process

The role of TiO2 and gC3N4 bimetallic catalysts in boosting antibiotic resistance gene removal through photocatalyst assisted peroxone process

Antibiotics are extensively used in human medicine, aquaculture, and animal husbandry, leading to the release of antimicrobial resistance into the environment. This contributes to the rapid spread of antibiotic-resistant genes (ARGs), posing a significant threat to human health and aquatic ecosystems. Conventional wastewater treatment methods often fail to eliminate ARGs, prompting the adoption of advanced oxidation processes (AOPs) to address this growing risk. The study investigates the efficacy of visible light-driven photocatalytic systems utilizing two catalyst types (TiO2-Pd/Cu and g-C3N4-Pd/Cu), with a particular emphasis on their effectiveness in eliminating blaTEM, ermB, qnrS, tetM. intl1, 16 S rDNA and 23 S rDNA through photocatalytic ozonation and peroxone processes. Incorporating O3 into photocatalytic processes significantly enhances target removal efficiency, with the photocatalyst-assisted peroxone process emerging as the most effective AOP. The reemergence of targeted contaminants following treatment highlights the pivotal importance of AOPs and the meticulous selection of catalysts in ensuring sustained treatment efficacy. Furthermore, Polymerase Chain Reaction-Denaturing Gradient Gel Electrophoresis (PCR-DGGE) analysis reveals challenges in eradicating GC-rich bacteria with TiO2 and g-C3N4 processes, while slight differences in Cu/Pd loadings suggest g-C3N4-based ozonation improved antibacterial effectiveness. Terminal Restriction Fragment Length Polymorphism analysis highlights the efficacy of the photocatalyst-assisted peroxone process in treating diverse samples.

Changes in physical and chemical properties of microplastics by ozonation

This study evaluated the altered properties of microplastics during the ozonation process in water matrices. The selected polymers include low-density polyethylene, high-density polyethylene, polypropylene, polystyrene, polyethylene terephthalate, and polyvinyl chloride. The morphology, contact angle, and chemical composition of the pristine and altered microplastics were characterized using field-emission scanning electron microscopy-energy dispersive spectrometry, contact angle analysis, Fourier-transform infrared spectroscopy, and X-ray photoelectron spectroscopy (XPS). Microplastic oxidation can lead to surface abrasion, cracking, and fragmentation. XPS analysis indicated that a C=O double bond (carbonyl group) and carboxylic acid/ester bond (O−C=O) were generated in the ozone process. In addition, all the carbonyl index values increased, implying that the number of oxygen functional groups on the surface of the microplastics increased. The contact angle also decreased, indicating that the hydrophilic portion of the microplastics increased due to oxidation. Microplastics, whose surfaces are roughened owing to oxidation or reduced in size owing to fragmentation, pose a fatal threat to aquatic life. In addition, microplastics with increased oxygen functional groups and hydrophilicity due to oxidation treatment have different adsorption properties. Relatively hydrophilic microplastics adsorb heavy metal cations that can adversely affect ecosystems by acting as heavy metal transport mediators.

Kinetic modelling of ozonation and photolytic ozonation of metronidazole removal from water

This work addresses the ozonation, photolysis, and photolytic ozonation of metronidazole (MTZ), a widely used antibiotic frequently detected in urban wastewater. A UVA source emitting radiation between 300 and 400 nm was utilized. The presence of scavengers such as t-butanol and sodium azide confirmed the role of hydroxyl radicals in both ozonation and photolysis processes. Conversely, singlet oxygen did not influence the photolytic processes. The average quantum yields of MTZ and ozone were determined to be 1.2 × 10−3 and 0.72 mol/Einstein, respectively, for the 300–400 nm wavelength range. In direct MTZ photolysis, a stoichiometric ratio of 0.34 mol of hydroxyl radicals formed per mol of photolyzed MTZ was observed. However, the effects of hydroxyl radicals on the MTZ photolytic rate were only significant after 45 min of reaction time. Using rate constant data from literature and quantum yields calculated in this study, a kinetic model for both MTZ ozonation and photolytic ozonation was proposed, enabling the prediction of MTZ conversion and degradation rates. This model includes three intermediate compounds that also consume ozone and hydroxyl radicals. The results show that experimental and calculated concentrations of MTZ are within an error margin of less than 14 % in all cases.

Applying both kinetic and thermodynamic measures to promote solar-driven photocatalytic ozonation on defect-engineered porous tungsten oxide

Mass transfer of ozone within the inner structure of a catalyst and utilization efficiency of the photo-generated electrons are two decisive factors governing the production of hydroxyl radicals (•OH) in photocatalytic ozonation process from kinetic and thermodynamic perspectives, respectively. For achieving precise dual-control, defect-engineered tungsten oxide with a periodic porous architecture (p-WO3-OV) is synthesized. Compared with pristine WO3, p-WO3-OV achieves a 7.6-fold increase in the reaction rate of solar photocatalytic ozonation, accompanied by a 2.3-fold enhancement in the ozone utilization efficiency. The constructed periodic porous structure shortens the migration path of charge carriers and promotes the fluidity of the reactants. The rich oxygen vacancies in WO3 enhance the generation of charge carriers and promote O3 interactions. This work provides mechanistic insights into both the kinetic boost endowed by porous nanoarchitecture, and the thermodynamic modulation enabled by defect engineering to achieve the synergy in solar-driven photocatalytic ozonation.

Ozonation of the antiviral oseltamivir in wastewater effluent: Matrix effect, oxidation pathway, and toxicity assessment

The potential environmental impacts of commonly employed antiviral drugs and their byproducts have attracted attention but remain largely unexplored. In this study, ozone (O3) was used to remove the oseltamivir phosphate (OP), a widely used antiviral, from different water matrices, including secondary municipal wastewater effluent (WWE). Over 90 % of OP was removed from a buffer solution using 10 µM of O3 in a short reaction time (30 s), while pseudo-first-order kinetics constants (K) showed a strong linear relationship with the initial O3 dosage. The pH of the solution was found to be an important factor in the ozonation process since the degradation mechanisms and, thereby, the K values are affected by the structural conformations of OP (protonated or deprotonated forms), the generation of hydroxyl radicals (•OH) under mild basic conditions, and the depletion of O3 under extreme basic pH. In addition, common inorganic ions slightly affect the K values, but increasing the ionic strength negatively influences the degradation process. Organic components in WWE also reduced the efficiency; however, over 95 % of OP degradation was achieved using a ratio of O3 dosage to dissolved organic carbon (DOC) of 0.544 g O3 g–1 DOC. Finally, a degradation pathway was proposed based on the detection of byproducts formed by direct ozonation and hydroxylation reactions. Acute toxicity and genotoxicity assessments on ozonated matrices, especially the WWE sample, suggest that these byproducts have no potential toxic effects. All these findings strongly suggest that ozonation can effectively degrade antivirals in municipal effluents.

Manufacture and performance assessment of PVDF-La@TiO2 Photocatalyst implanted membrane for efficient produced water treatment via ozonation-adsorption process under visible-light exposure

This research aims to develop a visible light-activated photocatalytic membranes for produced water treatment system by employing the phase inversion technique for implantation of La@TiO2 photocatalytic nanoparticles into PVDF membrane at concentrations varying from 0 % to 2 % wt. The results demonstrated significant amplification of COD and NH3-N removal efficiency. Implantation of the photocatalyst into PVDF membranes via bulk mixing, coupled with elemental doping and combination with La@TiO2 appreciably reduces band gap energy and increases visible light absorption thereby improves membrane's optical properties. SEM-EDX analysis confirms uniform distribution of La@TiO2 nanoparticles on the membrane surface, which leads to amplify membrane's hydrophilicity and water absorption. The modified membrane facilitated concurrent photocatalytic degradation and filtration processes that lead to remarkable reductions in TDS, COD, and NH3-N pollutants, with the highest flux was achieved when 1.5 % wt. La@TiO2 was incorporated into the membrane matrix. Obviously, adsorption and ozonation processes promote synergistic effect and amplify pollutant flux and efficiency to a greater extent. Furthermore, the modified membrane exhibited extraordinary antifouling properties and stability, providing excellent reusability with a 96.22 % fouling reduction rate after five consecutive cycle tests.

TiO2 nanotubes zeolite nanophotocatalyst performance efficacy toward the photocatalytic degradation of triclocarban in bathroom greywater

Triclocarban (TCC) is persistent in aquatic environments, where it can remain stable for extended periods. It can cause long-term exposure, potentially affecting ecosystems and human health through contaminated fish or water. Therefore, this study aims to investigate the degradation of TCC in bathroom greywater by the application of TiO2 nanotubes coated with zeolite (TNZPC) in photocatalytic degradation. Electrochemical anodization (ECA) and electrophoretic deposition (EPD) were applied to form TNZPC. Field Emission-Scanning Electron Microscopy (FESEM), Energy Dispersive Spectroscopy (EDS), X-ray Diffraction (XRD), and X-ray Fluorescence (XRF) verified the characterization of TNZPC accordingly and the degradation kinetics of TCC followed the pseudo-first-order model of Hinshelwood. The highest degradation rate, reaching 95.2%, was observed at pH 11, while the lowest rate was at pH 3, with a degradation efficiency of only 72.6% after 60 minutes of irradiation with utilization of 0.75 cm2 of TNZPC. The mechanism study has verified eleven intermediate products were produced during TCC degradation by the process of oxidation, ozonation, hydroxyl radical (*OH), and dichlorination. The study suggests that finding the optimum conditions such as photocatalyst modification, cationic material, light sources, TCC initial concentration, pH, and TNZPC size play crucial roles in significant TCC photocatalytic degradation.

Catalytic Ozonation Treatment of Coal Chemical Reverse Osmosis Concentrate: Water Quality Analysis, Parameter Optimization, and Catalyst Deactivation Investigation.

Catalytic ozone oxidation, which is characterized by strong oxidizing properties and environmental friendliness, has been widely used in organic wastewater treatments. However, problems such as a low organic pollutant removal efficiency and unstable operation during the catalytic ozone treatment process for wastewater remain. To address these disadvantages, in this study, the treatment efficacy of catalytic ozone oxidation on a coal chemical reverse osmosis concentrate was investigated. The basic water quality indicators of the chemical reverse osmosis concentrate were analyzed. The effects of initial pollutant concentration, pH, ozone concentration, and catalyst concentration on the COD removal rate from the coal chemical reverse osmosis concentrate were explored. Water quality indicators of the chemical reverse osmosis concentrate before and after the catalytic ozone treatment were studied using spectroscopic analysis methods. The RO concentrate demonstrated large water quality fluctuations, and the catalytic ozonation process removed most of the pollutants from the treated wastewater. A possible deactivation mechanism of the ozone catalyst was also proposed. This study provides a theoretical reference and technical support for the long-term, efficient, and stable removal of organic pollutants from coal chemical reverse osmosis concentrate using a catalytic ozone oxidation process in practical engineering applications.

Assessment of Blast Furnace Slags as a Potential Catalyst in Ozonation to Degrade Bezafibrate: Degradation Study and Kinetic Study via Non-Parametric Modeling

This study investigates the effectiveness of blast furnace slags (BFSs) as catalysts in the ozonation process to degrade complex contaminants such as bezafibrate (BFZ) at different pH levels. The findings reveal that the presence of BFS enhances degradation efficiency, achieving a 10% improvement at pH 10 and a 30% improvement at pH 5.5 compared to simple ozonation. The highest degradation efficiency was observed in the Ozonation–BFS system at pH 10, with 90% decomposition of BFZ. These results were corroborated through ozone consumption analysis, BOD5 measurements, and the identification of oxalic acid as the final decomposition product. Due to the complexity of the reaction system, kinetic characterization was performed using non-parametric modeling based on differential neural networks. The model indicated that the observed reaction rate for BFZ degradation in the presence of ozone and BFS was 4.12 times higher at pH 5.0 and 1.08 times higher at pH 10.0 compared to simple ozonation. These results underscore the potential of using BFS in catalytic ozonation processes for the effective treatment of recalcitrant contaminants in wastewater.

Effective methods for the decontamination of healthcare waste: Ozone and UV-C radiation process

ABSTRACT Human-generated waste, including infectious healthcare waste, poses significant risks to public health and the environment. The COVID-19 pandemic has increased the global production of infectious waste, emphasizing the need for safe and sustainable waste management practices. While autoclaves are commonly used for on-site disposal, alternative methods like ozone gas and UV-C radiation offer environmentally friendly options that effectively eliminate pathogens without leaving toxic residues. Inadequate waste management can contribute to disease transmission, while open burning releases harmful pollutants. This study investigated the effectiveness of different disinfection agents – ozone gas and UV-C radiation – on infectious solid waste contaminated with bacteria. The bacterial indicators examined were Staphylococcus aureus, Bacillus subtilis, and Pseudomonas aeruginosa. The experimental methods included operating each ozone and UV-C radiation individually and simultaneously using ozone gas and UV-C radiation. The study also investigated exposure times and various concentrations of ozone gas. The findings demonstrated that the simultaneous application of ozone gas and UV-C radiation was the most effective method for decontaminating infectious solid waste and targeting the selected bacteria. The concentration of ozone gas ranged from 165 to 5000 ppm, depending on generation time and treatment chamber volume, while exposure times varied from 1 to 180 minutes. In applying UV-C rays, complete elimination of S. aureus was observed after 60 minutes up to 6-log, while the reduction of B. subtilis and P. aeruginosa were 2-log and 3-log, respectively. Ozone gas had the ability to inactivate all strains, but when ozone gas and UV-C rays were used simultaneously, this process was accelerated and improved. The total reduction in the bacterial load was 8-log. Considering the increase in population and the subsequent increase in waste generation, adopting an environmentally friendly waste management method can be very advantageous. Implications: This study highlights the effectiveness of simultaneously applying ozone gas and UV-C radiation for decontaminating infectious solid waste, offering an environmentally friendly alternative to traditional thermal treatments like autoclave and incineration. By optimizing ozone concentrations and exposure times, this method reduces disease transmission risks and minimizes environmental impact. These findings are crucial, especially during outbreaks such as the COVID-19 pandemic, providing scalable, sustainable waste management solutions for healthcare facilities. Implementing these techniques can protect public health and the environment, setting a new standard for safe infectious waste disposal worldwide, mitigating hazardous pollutants, and reduce the exposure risk of bio-hazardous residues.

Phenolic Compounds, Fatty Acid Contents, and Antibacterial Properties of Ozonated and Non-Ozonated Tobacco Seed Oils

ABSTRACT In this study, the fatty acid content, phenolic compounds, and antimicrobial activity of seed oils from Ege Özbaş (EO), Sarıbağlar 407 (S407) and Akhisar 98 (A98) tobacco plants grown in the Aegean region were investigated. The ozonation process altered fatty acid and phenolic compound compositions and affected antimicrobial activities against Gram-positive and Gram-negative bacteria in the oils. Tobacco seed oils (TSOs) were extracted via cold pressing (CP) and Soxhlet extraction (SE). Fatty acids and phenolic compounds were analyzed using GC-FID and LC-MS/MS, respectively. Non-ozonated oils averaged 73% linoleic acid, 13% oleic acid, 9% palmitic acid, and 3% stearic acid, while ozonated oils contained 41% linoleic acid, 18% oleic acid, 22% palmitic acid, and 11% stearic acid. The presence of 33 phenolic compounds was investigated and 22 common phenolic compounds were detected in both ozonated and non-ozonated TSOs, including gallic acid, protocatechuic acid, chlorogenic acid, 3-hydroxybenzoic acid, (-)-epicatechin, 2,5-dihydroxybenzoic acid, caffeic acid, verbascoside, luteolin-7-glucoside, hesperidin, and rosmarinic acid. The increased antimicrobial activity of fatty acids and phenolic compounds following ozonation suggests the potential for developing creams to treat skin diseases and wounds caused by antibiotic-resistant pathogens, and to reduce the effects of aging skin wrinkles.

Effect of Ozonation on Physicochemical Properties of Olive Oil Based Sunscreen Product

ABSTRACT Ozone serves as a potent oxidizing agent and a universal antiseptic, extensively employed in industries such as food, pharmaceuticals, and cosmetics due to its ability to dissolve in water and decompose into oxygen. This study aimed to treat virgin olive oil (VOO) with the ozonation process prior to its incorporation into a sunscreen product, and to discover any new potentially useful properties by comparing it with a sunscreen containing non-ozonated olive oil. The comparison was based on physicochemical properties, physical appearance, and sun protection factor (SPF) value. VOO treated with 0.017 mole/L ozone was tested for various physicochemical properties such as color, viscosity, refractive index, acid value, iodine value, peroxide value, saponification value, and oxidative stability. The composition was analyzed using gas chromatography (GC) and gas chromatography – mass spectrometry (GC-MS). The properties of ozonated olive oil (OOO) differed from VOO in terms of viscosity and flow behavior. An increase in shear rate significantly reduced the viscosity of OOO, while VOO maintained a constant viscosity and exhibited Newtonian flow behavior. When OOO was incorporated into sunscreen products, it enhanced the spreadability of the product on the skin, resulting in a significantly higher SPF value. The ability of a sunscreen to spread evenly on the skin and form a continuous thin film is crucial for effective protection against the sun’s rays. These findings highlight the potential of OOO in enhancing the photoprotection efficacy of sunscreen products by providing valuable data for its incorporation into formulations aiming to improve sun protection. Future research could focus on long-term stability and potential side effects of OOO in cosmetic formulations.

Synthesis and characterization of Bi2S3@NH2-MIL125(Ti) and survey the sono-catalytic ozonation process’s efficiency in the degradation of tocilizumab from aqueous

A Bi2S3@NH2-MIL125(Ti) core–shell nanocomposite was synthesized using a solvothermal method for the degradation of tocilizumab through a sono-catalytic ozonation process. The physicochemical properties of the catalyst were characterized using FESEM, EDS, TEM, XRD, FT-IR, DRS, BET, and XPS techniques. The optimum conditions were found to be as 0.75 g/L nanocatalyst, 10 mg/L tocilizumab, 5 L/hr ozone flow, 240 W ultrasonic power, and pH 9.0 over 15 min. Under these conditions, the process achieved approximately 100 % removal of tocilizumab, 86 % reduction in COD, and 76 % reduction in TOC, with only slight decreases in efficiency after five consecutive cycles. The degradation of tocilizumab was attributed to 38 % ozonation, 20 % sorption, and 15 % sonolysis. Methanol had the most significant impact on the process, while sodium azide had the least. The primary reactive species were identified as α-Hydrogen/OH radicals, with e−-h+ pairs playing a minor role. PO43− had the greatest impact on process efficiency, while SO42− had the least. The reaction followed a first-order kinetic model with an R2 value of 0.94. The synergistic effect coefficient of 1.88 indicated a significant synergistic impact from the combined ozonation and sonolysis processes. The energy efficiency (EE/O) of the sono-catalytic ozonation process was calculated to be 66.67 kW/h-m3-order.

Ozone processing of milk and milk products: a review of applications, quality effect and implementation challenges

Abstract The impact on the natural characteristics of dairy products during thermal processing warrants the investigation of non-thermal techniques. Ozone has proved to be an effective and sustainable processing technology for the dairy processing sector. This review delves into the effect of ozone processing on the microbiological, physiochemical, nutri-functional, and sensory quality of milk and milk products. Alongside this, the other ozone applications in the dairy processing sector (storage room disinfection, wastewater treatment, benefits in Clean-in-Place (CIP) system, toxin reduction) have been discussed. Current regulatory and industrial status, and safety requirements in the facility have also been highlighted. Overall, ozone treatment has lower microbial inactivation efficiency in milk and milk products than thermal treatment. Further, safety precautions are needed in the processing areas due to its potential health hazard concerns.

Degradation and mineralization of atrazine by ozonation: A toxicological prediction by QSAR toolbox

This work aims to investigate the atrazine (ATZ) mitigation by an advanced oxidative process. Atrazine is one an effective herbicide which has been detected in water sources, causing contamination problems. To address the persistent issue of contamination, ATZ degradation and mineralization were studied by ozonation. In addition, the eco-toxicity of the possible degradation byproducts was also evaluated by the Quantitative Structure-Activity Relationship (QSAR) OECD toolbox. To evaluate the influence and predict the optimum conditions of the ozonation process and the reaction time on the degradation of ATZ, as well as, the percentage of mineralization, an experimental design was performed based on factorial design 23 methodology with center-point analysis. Total organic carbon (TOC) analyses and High-Performance Liquid Chromatography (HPLC) were employed to evaluate the efficiency of ATZ mitigation. The optimal conditions were achieved at an ozone flow rate of 0.4 mL/min, oxidation time = 30 min, and pH=8 where 100 % of ATZ was degraded and the highest percentage of mineralization was obtained (25.61 %). The potential toxicity of the residual concentration of ATZ was obtained by comparing with the values predicted by the QSAR tool, by comparing the outcomes. It was possible to come to the conclusion that the approach had positive implications for environmental safety. The values obtained are below the values considered toxic in aquatic environments, in almost all experiments. Low-concentration byproduct formation suggests that the degradation routes lead to low-hazardous concentrations of compounds for the environment. This implies the ozone treatment strategy might offer a long-term remedy for the ATZ.

Strengthened ozone adsorption through positive electric field-induced charge migration on various TiO2 crystal surfaces: A mechanistic and theoretical study

This study investigates the enhancement of ozone adsorption on diverse TiO2 crystal interfaces through an innovative electrochemical modulation approach. The research focuses on the effects of applied electric field strength and reaction sites on ozone interfacial adsorption energies for Ti/Anatase TiO2 (0 0 1) and Ti/Rutile TiO2 (1 1 0) interfaces. The findings reveal that positive electric fields significantly enhance ozone adsorption on both interfaces, with adsorption energies increasing by up to 18% for Ti/Anatase TiO2 (0 0 1) and 15% for Ti/Rutile TiO2 (1 1 0). Notably, double water molecule sites (≡(H2O)2) play a crucial role in this enhancement process. The study demonstrates that the applied electric field alters the charge distribution at the TiO2 catalytic interface, thereby increasing interfacial charge density and promoting charge migration to ozone. Furthermore, this process leads to enhanced overlap and hybridization between ≡(H2O)2 sites and the s and p orbitals of ozone molecules, resulting in the formation of chemical bonds with lower Fermi levels. These comprehensive results demonstrate the broad applicability of the electrochemical interfacial ozone adsorption enhancement method across different crystal types and surfaces. Consequently, this study provides essential data to support the advancement of greener and more energy-efficient heterogeneous catalytic ozonation processes, potentially contributing to significant improvements in ozone-based water treatment technologies.

Bleaching Scutched Flax Tow (SFT) With Ozone Process in Low Water Environment: Evaluation of Fiber Physicochemical Properties and Bleaching Performance

Bleaching Scutched Flax Tow (SFT) With Ozone Process in Low Water Environment: Evaluation of Fiber Physicochemical Properties and Bleaching Performance

The effect of autochthonous metal ions and humic substances on landfill leachate ozonation: Reactive oxygen species and 3D fluorescence analysis

This study investigated the ozonation process for landfill leachate treatment, focusing on the impact of autochthonous metal ions (Fe3+, Cu2+, Mn2+, Mg2+) and humic substances on the degradation of pollutants. Our findings revealed that the presence of these metal ions significantly enhanced the generation of hydroxyl radicals (OH), especially for Fe3+, demonstrating the highest catalytic activity. However, the humic substance attenuated the signals of reactive oxygen species (ROS), particularly the superoxide radical (O2−) in the presence of Cu2+ and Mn2+. These suggested that metal ions could complex with humic substances and further inhibit ROS production. Despite this inhibition, Fe3+ maintained its ROS-generating capacity even in the presence of humic substances, indicating its potential as a robust catalyst in landfill leachate. Batch tests further demonstrated that Fe3+ had the most positive effect on the degradation of sodium humate, as evidenced by a significant reduction in fluorescence regional integration (FRI) values. An integrated membrane bioreactor (MBR) and ozonation system were conducted, which firstly processed activated sludge treatment in the MBR and then pumped into the ozonation system via a peristaltic pump. After ozonation, the leachate overflowed back into the MBR for further treatment, creating a closed-loop system. It was observed that there was a significant reduction in humic substances, with a decrease of 96.31% in the FRI. Parallel factor analysis (PARAFAC) results corroborated these findings, which indicated a marked reduction in the abundance of humic-like substances C-BO-1 and C-BO-4 during the 17 days treatment period. This study revealed the pivotal role of microorganisms, ROS, metal ions, and humic substances in the treatment of landfill leachate. The metal ions presented in the leachate were confirmed to produce ROS during the ozonation process. However, a significant quantity of humic-like substances reduced the reactive ROS through complexation and consumption reactions. Simultaneously, microorganisms in the MBR system consumed humic substances such as C-BO-1 and C-BO-4, which promoted the degradation of contaminants in the landfill leachate. These insights provided implications for optimizing ozonation processes in leachate management, potentially leading to more efficient and environmentally sustainable waste disposal practices.