Catalytic ozonation of ibuprofen with ultrasound and Fe-based catalysts

Integrated ozone-sono-Fenton for the enhanced degradation of acid orange 7: process optimization and kinetic evaluation

The performance of novel hybrid advanced oxidation, ozone-sono-Fenton process in degradation of acid orange 7 (AO7), as a model of azo dyes was modelled and optimized using response surface methodology (RSM) based on central composite design (CCD). Utilizing a bubbling reactor equipped with an ultrasound probe and in the presence of Fenton reagents, a promising hybrid homogeneous AOP, ozone-sono-Fenton, was investigated. According to the experimental results, the variation trend of degradation efficiency (DE%) with pH, reaction time and Fe²⁺/H₂O₂ molar ratio was modelled with the reduced quadratic model. Additionally, the suitability of the model was indicated with close to unity regression coefficient [Formula: see text]. Furthermore, the comparative study of degradation efficiency and COD removal for the individual methods including ozonation, sonication and Fenton reagents as well as their hybrid processes reveals that the novel proposed technique, ozone-sono-Fenton process, is able to rapid and complete degradation of acid orange 7 with initial concentration of 300 mg L^-1, 100% in only 12 min. The complete degradation was obtained under optimum conditions such as pH = 6, reaction time = 12 min and Fe²⁺/H₂O₂ molar ratio = 0.0040. The kinetics evaluation of the acid orange 7 concentration during the processing implied the first-order reaction. Considering the synergetic effect and cost-effectiveness of the hybrid method, the promising ozone-sono-Fenton method could effectively degrade using a wide range of organic contaminants.

Enhancing catalytic ozonation activity of MCM-41 via one-step incorporating fluorine and iron: The interfacial reaction induced by hydrophobic sites and Lewis acid sites

Fe-MCM-41 had been widely used as ozonation catalyst, however, the existence of large amount of hydrophilic silanol hindered its interfacial reaction with O₃ and pollutants. To solve this problem, F-Fe-MCM-41 was synthesized by co-doping F and Fe into the framework of MCM-41 to replace silanol with Si-F groups through a one-step hydrothermal method. F introduced hydrophobic sites which contributed to more ibuprofen (IBP) chemisorption on the surface of F-Fe-MCM-41. Moreover, doping F also enhanced the acidity, which accelerated O₃ decomposition into •OH. F-Fe-MCM-41/O₃ exhibited notably activity with 96.6% IBP removal efficiency within 120 min, while only 78.5% and 80.9% in O₃ alone and Fe-MCM-41/O₃, respectively. Surface Lewis acid sites and metal hydroxyl groups were considered as important factors for O₃ activation and •OH generation. F-Fe-MCM-41 exhibited excellent catalytic performance under acidic and alkaline conditions. Comparative experiments revealed that F doping improved the interfacial reaction, especially the interfacial electron transfer, which resulted in the high catalytic activity of F-Fe-MCM-41. F-Fe-MCM-41 possessed good stability and reusability, with only 5.7% decline for IBP removal in five successive cycles. Furthermore, the possible degradation path of IBP was proposed according to DFT calculation and GC-MS analysis.

Catalyst development for tar reduction in biomass gasification: Recent progress and the way forward

Biomass valorization via catalytic gasification is a potential technology for commercizalization to industrial scale. However, the generated tar during biomass valorization posing numerous problems to the overall reaction process. Thus, catalytic tar removal via reforming, cracking and allied processes was among the priority areas to researchers in the recent decades. This paper reports new updates on the areas of catalyst development for tar reduction. The catalyst survey include metallic and metal-promoted materials, nano-structured systems, mesoporous supports like zeolites and oxides, group IA and IIA compounds and natural catalysts based on dolomite, palygorskite, olivine, ilmenite, goethite and their modified derivatives. The influence of catalyst properties and parameters such as reaction conditions, catalyst preparation procedures and feedstock nature on the overall activity/selectivity/stability properties were simultaneously discussed. This paper not only cover to model compounds, but also explore to real biomass-derived tar for consistency. The area that require further investigation was identified in the last part of this review.

Bimetallic Cu/Fe Catalysts for Ibuprofen Mineralization

At present, the use of conventional wastewater processes is becoming increasingly challenging, mainly due to the presence of biorecalcitrant organic matter. Advanced oxidation processes such as Fenton, Fenton-like and hybrid processes have been successfully employed for the treatment of highly concentrated and toxic non-biodegradable pollutants. Here, a series of bimetallic catalysts, based on Cu/Fe supported over ZrO2, were investigated for the mineralization of ibuprofen with a heterogeneous Fenton-like reaction. The materials were prepared by incipient wetness impregnation and characterized by standard techniques. Temperature-programmed experiments highlighted the promotion of the reduction in CuO due to the synergistic effects of the coupled redox cycles of copper (Cu2+/Cu+) and iron (Fe+3/Fe+2). 5%Cu-5%Fe/ZrO2 not only displays the highest ibuprofen mineralization (83%) under optimum conditions but also exploits its activity in a wider range of pH (3–5) with extremely low metal leaching. The recycling of bimetallic catalysts reveals that only the 5%Cu-5%Fe/ZrO2 system is able to provide sustainable activity in heterogeneous Fenton process.

Efficient catalytic activity and bromate minimization over lattice oxygen-rich MnOOH nanorods in catalytic ozonation of bromide-containing organic pollutants: Lattice oxygen-directed redox cycle and bromate reduction

The inhibition of bromate formation is a challenge for the application of ozonation in water treatment due to the carcinogenicity and nephrotoxicity of bromate. In this study, the high-mobility lattice oxygen-rich MnOOH nanorods were synthesized successfully and applied for the bromate inhibition during catalytic ozonation in bromide and organic pollutants-containing wastewater treatment. The catalytic ozonation system using lattice oxygen-rich MnOOH nanorods exhibited an excellent performance in bromate control with an inhibition efficiency of 54.1% compared with the sole ozonation process. Furthermore, with the coexistence of 4-nitrophenol, the catalytic ozonation process using lattice oxygen-rich MnOOH nanorods could inhibit the bromate formation and boost the degradation of 4-nitrophenol simultaneously. Based on the experiments of ozone decomposition, surface manganese inactivation and reactive oxygen species detection, the inhibition of bromate could be attributed to the effective decomposition of ozone with generating more ·O₂^- and the reduction of bromate into bromide by lattice oxygen-rich MnOOH. The existed surface Mn(IV) on lattice oxygen-rich MnOOH can accept electrons from lattice oxygen and ·O₂^- to generate surface transient Mn(II)/Mn(III), in which Mn(II)/Mn(III) can promote the reduction of bromate into bromide during catalytic ozonation. This study provides a promising strategy for the development of bromate-controlling technologies in water treatment.

The enhancement of ozone-liquid mass transfer performance in a PTFE hollow fiber membrane contactor using ultrasound as a catalyzer

A comprehensive assessment of a polytetrafluoroethylene (PTFE) hollow fiber membrane contactor and ultrasound for intensifying ozone-liquid mass transfer was conducted simultaneously. The initial part of the study concentrates on the systematic analysis of the previous literature related to the reinforcement on the ozone-liquid mass transfer. In this paper, the introduction of a membrane contactor and ultrasound as a catalyzer that increased the mass transfer coefficient (K _L a) may be partially attributed to the increase of the net surface area and the decrease of the mass transfer resistance, thus leading to the enhancement of the ozone mass transfer rate and acceleration of the ozone decomposition in solution. Results revealed that the maximum value of the K _L a value was 0.7858 min^-1 in the PTFE hollow fiber membrane contactor in the presence of the ultrasound, while only 0.5154 min^-1 in a single ozone aeration at an intake flow of 300 L h^-1, ozone dosage of 32.38 mg L^-1 and operating temperature of 293.15 K. A 52.46% improvement of the K _L a value was obtained in the presence of the ultrasound. In addition, the dosage of sodium chloride appeared to have a positive correlation with K _L a, but a negative correlation with the concentration of dissolved ozone. The sulfolane destruction by ozonation, ultrasound and the combination between the ozonation and ultrasound were performed to further verify the enhancement of the ozone mass transfer performance. It has been established that the O₃/US combined process was a promising method, giving the maximum degradation of sulfolane (96.5%) with the synergistic index as 2.41.

Coagulation-flocculation followed by catalytic ozonation processes for enhanced primary treatment during wet weather conditions

Combined sewer overflows (CSO), generated during the wet weather flow from the combination of the inflow and stormwater runoff in sewer system, result in an overflow of untreated wastewater from sewer system, which might ultimately contain different micropollutants (MPs). In this study, a coagulation-flocculation-sedimentation (CFS) pretreated CSO spiked with MPs was treated by catalytic ozonation using carbon, iron, and peroxide-based catalysts. The catalysts were characterized and their activity on MPs removal was studied at two different ozone (O₃) doses (5 and 10 mg L^-1). The effect of the treatment on the spiked CSO effluent was also assessed from the acute toxicity of the effluent using Microtox®, Yeast, and Macrophage cell-line toxicity assay tests. All the carbon-based catalysts showed large surface area, which was strongly influenced by the activation technique in the preparation of the catalysts. The CFS treatment strongly reduced the turbidity (≥60%) but had marginal effect on the UV₂₅₄, dissolved organic carbon (DOC), and pH. Sludge Based Carbon (SBC) showed strong adsorption capacity (≥60% removal efficiency) for all MPs studied compared to other carbon and iron-based catalysts. Ozonation alone was effective for the degradation of easily oxidizable MPs (sulfamethoxazole, mecoprop, and 2,4-dichlorophenoxyl acetic acid), achieving more than 80% degradation efficiency at 10 mg L^-1 of ozone, but not effective for atrazine (≤60% degradation efficiency) at similar O₃ dose. Catalytic ozonation (at 10 mg L^-1 O₃ dose) improved the degradation of the MPs at low catalyst dosage but higher dosage strongly inhibited their degradation. In all cases, the effluents showed negligible acute toxicity, indicating the suitability of the process for the treatment of CSO.

Adsorption, degradation, and mineralization of emerging pollutants (pharmaceuticals and agrochemicals) by nanostructures: a comprehensive review

This review discusses a fresh pool of research findings reported on the multiple roles played by metal-based, magnetic, graphene-type, chitosan-derived, and sonicated nanoparticles in the treatment of pharmaceutical- and agrochemical-contaminated waters. Some main points from this review are as follows: (i) there is an extensive number of nanoparticles with diverse physicochemical and morphological properties which have been synthesized and then assessed in their respective roles in the degradation and mineralization of many pharmaceuticals and agrochemicals, (ii) the exceptional removal efficiencies of graphene-based nanomaterials for different pharmaceuticals and agrochemicals molecules support arguably well a high potential of these nanomaterials for futuristic applications in remediating water pollution issues, (iii) the need for specific surface modifications and functionalization of parent nanostructures and the design of economically feasible production methods of such tunable nanomaterials tend to hinder their widespread applicability at this stage, (iv) supplementary research is also required to comprehensively elucidate the life cycle ecotoxicity characteristics and behaviors of each type of engineered nanostructures seeded for remediation of pharmaceuticals and agrochemicals in real contaminated media, and last but not the least, (v) real wastewaters are extremely complex in composition due to the mix of inorganic and organic species in different concentrations, and the presence of such mixed species have different radical scavenging effects on the sonocatalytic degradation and mineralization of pharmaceuticals and agrochemicals. Moreover, the formulation of viable full-scale implementation strategies and reactor configurations which can use multifunctional nanostructures for the effective remediation of pharmaceuticals and agrochemicals remains a major area of further research.

Bioavailability of dissolved organic matter in biogas slurry enhanced by catalytic ozonation combined with membrane separation

Large molecular weight pig biogas slurry (L-PBS) and small molecular weight pig biogas slurry (S-PBS) were separated from original pig biogas slurry (O-PBS) using a 100 kDa membrane. The original bioavailability and biosafety of L-PBS was very low. In order to enhance the total bioavailable dissolved organic nitrogen (TB-DON) and total bioavailable dissolved organic phosphorus (TB-DOP), optimum catalytic ozonation of L-PBS conditions were determined using Box-behnken design models (P < 0.0001) and intersection tests. The optimal values for ozone concentration, pH value, active catalyst concentration and reaction time were 2.63 mg·L^-1, 6.48, 1.43 g·L^-1 and 40 min, respectively. Catalytic ozonation can effectively decompose and transform 68.07% of L-PBS into S-PBS to improve content organic bioavailability, with a molecular weight distribution of 0-1 kDa (13.53%), 1-5 kDa (16.62%), 5-10 kDa (11.16%), 10-30 kDa (11.73%), 30-100 kDa (15.04%). Catalytic ozonation of L-PBS can reduce protein levels from 85.28% to 47.18%, but increases the proportion of fulvic and humic components from 10.22% to 32.67% and 4.51%-20.15%, respectively. Because catalytic ozonation changes the internal components and molecular weights of L-PBS, both saw increases in TB-DON and TB-DOP from 3.33% to 41.12% and 2.43%-37.88%, respectively, with a large number of TB-DON and TB-DOP derived from hydrophilic organic components during catalytic ozonation. These important internal mechanisms changed by catalytic ozonation can effectively reduce the ecotoxicity (IR, from 76.5% to 33.1%) and phytotoxicity (GI, enhanced from 35.4% to 70.3%) of L-PBS. Therefore, catalytic ozonation combined with membrane separation is a choice technology in improving the nutrition of biogas slurry and reduce its ecological risk.

Comparison of the behavior of ZVI/carbon composites from both commercial origin and from spent Li-ion batteries and mill scale for the removal of ibuprofen in water

Zero valent iron/carbon composites were successfully synthesized from commercial iron oxide and graphite (ZVI/C) and also by using graphite obtained from spent Li-ion batteries and iron oxide from mill scale (ZVI/C-X) as a new approach for the valorization of these waste. The composites were synthesized through carbothermic reactions and tested as catalysts for the degradation of ibuprofen from water by Fenton reaction. The optimal conditions for synthesizing ZVI/C composites were a temperature of 1000 °C maintained for 2 h. The structural, and textural features of ZVI/C with different ZVI mass ratios were characterized by different techniques. ZVI/C composites with higher ZVI mass ratios showed higher degradation rates for the removal of ibuprofen both in presence and absence of H₂O₂. Moreover, ZVI/C-X composite, obtained from industrial waste, showed activity even after four consecutive cycles of use with very low concentration of iron ions in solution after reaction (4.8 mg L^-1 after 4 h), which supports the high stability and low Fe-lixiviation of ZVI/C-X composite. The results of this study prove the possibility of synthesizing composites using graphite from spent Li-ion batteries and iron oxide from mill scale, and their potential for the degradation of ibuprofen in water, with comparable activities to those obtained from commercial feedstocks.

Catalytic ozonation for water and wastewater treatment: Recent advances and perspective

Ozonation process has been widely applied in water and wastewater treatment, such as for disinfection, for degradation of toxic organic pollutants. However, the utilization efficiency of ozone is low and the mineralization of organic pollutants by ozone oxidation is ineffective, and some toxic disinfection byproducts (DBPs) may be formed during ozonation process. Catalytic ozonation process can overcome these problems to some extent, which has received increasing attention in recent years. During catalytic ozonation, catalysts can promote O₃ decomposition and generate active free radicals, which can enhance the degradation and mineralization of organic pollutants. In this paper, the history of ozonation application in water treatment was briefly reviewed. The properties of the ozone molecule, the ozonation types and several ozone-based water treatment processes were briefly introduced. Various catalysts for catalytic ozonation, including homogeneous and heterogeneous catalysts, such as metal ions, metal oxidizes, carbon-based materials and their possible catalytic mechanisms were analyzed and summarized in detail. Furthermore, some inconsistent results of previous research on catalytic ozonation were analyzed and discussed. The application of catalytic oxidation for the degradation of toxic organic pollutants, including phenols, pesticides, dyes, pharmaceuticals and others, was summarized. Finally, several key aspects of catalytic ozonation, such as pH effect, the catalyst performance, the catalytic mechanism were proposed, to which more attention should be paid in future study.

Nano catalytic ozonation of biomethanated distillery wastewater for biodegradability enhancement, color and toxicity reduction with biofuel production

The effectiveness of O₃, O₃/Fe²⁺, and O₃/nZVI processes on biomethanated distillery wastewater (BMDWW) was evaluated in terms of biodegradability index (BI) enhancement, biofuel production, COD, color & toxicity reduction. A significant increase in biodegradability, COD, color and toxicity reduction was observed in O₃/nZVI compared with O₃, O₃/Fe²⁺ due to more hydroxyl radical production. The O₃/nZVI pretreated wastewater with enhanced BI (up to 0.71) showed 60% COD removal with additional biogas generation (64% methane content). From the Gas Chromatography Mass Spectrometry (GC-MS) analysis, 18 foremost organic compounds were predominantly detected in the raw distillery wastewater. The disappearance of the corresponding FTIR (Fourier Transform Infrared Spectroscopy) & GC-MS spectra during pretreatment processes signified the degradation or transformation of the recalcitrant present in the distillery wastewater. Subsequent (AnO + AO, AO) of pretreated BMDWW resulted in biodegradation rate enhancement by (1.83, 1.67), (3.5, 2.4) and (4.7, 2.9) times for O₃, O₃/Fe²⁺ and O₃/nZVI processes respectively.

Treatment of pharmaceutical industrial wastewater by nano-catalyzed ozonation in a semi-batch reactor for improved biodegradability

The study reports the biodegradability enhancement of pharmaceutical wastewater along with COD (Chemical Oxygen Demand) color and toxicity removal via O₃, O₃/Fe²⁺, O₃/nZVI (nano zero valent iron) processes. Nano catalytic ozonation process (O₃/nZVI) showed the highest biodegradability (BI = BOD₅/COD) enhancement of pharmaceutical wastewater up to 0.63 from 0.18 of control with a COD, color and toxicity removal of 62.3%, 93% and 82% respectively. The disappearance of the corresponding Fourier transform infrared (FTIR) and gas chromatography-mass spectrometry (GC-MS) peaks after pretreatment indicated the degradation or transformation of the refractory organic compounds to more biodegradable organic compounds. The subsequent aerobic degradation study of pretreated pharmaceutical wastewater resulted in biodegradation rate enhancement of 5.31, 2.97, and 1.22 times for O₃/nZVI O₃/Fe²⁺ and O₃ processes respectively. Seed germination test using spinach (Spinacia oleracea) seeds established the toxicity removal of pretreated pharmaceutical wastewater.

Ultrasound-Enhanced Catalytic Ozonation Oxidation of Ammonia in Aqueous Solution

Excessive ammonia is a common pollutant in the wastewater, which can cause eutrophication, poison aquatic life, reduce water quality and even threaten human health. Ammonia in aqueous solution was converted using various systems, i.e., ozonation (O₃), ultrasound (US), catalyst (SrO-Al₂O₃), ultrasonic ozonation (US/O₃), ultrasound-enhanced SrO-Al₂O₃ (SrO-Al₂O₃/US), SrO-Al₂O₃ ozonation (SrO-Al₂O₃/O₃) and ultrasound-enhanced SrO-Al₂O₃ ozonation (SrO-Al₂O₃/US/O₃) under the same experimental conditions. The results indicated that the combined SrO-Al₂O₃/US/O₃ process achieved the highest NH₄⁺ conversion rate due to the synergistic effect between US, SrO-Al₂O₃ and O₃. Additionally, the effect of different operational parameters on ammonia oxidation in SrO-Al₂O₃/O₃ and SrO-Al₂O₃/US/O₃ systems was evaluated. It was found that the ammonia conversion increased with the increase of pH value in both systems. The NH₃(aq) is oxidized by both O₃ and ·OH at high pH, whereas the NH₄⁺ oxidation is only carried out through ·OH at low pH. Compared with the SrO-Al₂O₃/O₃ system, the ammonia conversion was significantly increased, the reaction time was shortened, and the consumption of catalyst dosage and ozone were reduced in the SrO-Al₂O₃/US/O₃ system. Moreover, reasonable control of ultrasonic power and duty cycle can further improve the ammonia conversion rate. Under the optimal conditions, the ammonia conversion and gaseous nitrogen yield reached 83.2% and 51.8%, respectively. The presence of tert-butanol, CO₃²⁻, HCO₃⁻, and SO₄²⁻ inhibited the ammonia oxidation in the SrO-Al₂O₃/US/O₃ system. During ammonia conversion, SrO-Al₂O₃ catalyst not only has a certain adsorption effect on NH₄⁺ but accelerates the O₃ decomposition to ·OH.

Sonochemical and sonocatalytic destruction of methylparaben using raw, modified and SDS-intercalated particles of a natural clay mineral

The first part of the study is about the degradation of a common PPCP-methylparaben by high-frequency ultrasound to highlight the operation parameters, the reaction sites, the oxidation byproducts and the role of OH radicals. The second part covers the catalytic effect of a highly abundant and cost-effective clay mineral-sepiolite, and investigates the role of surface modification and SDS-composites of the clay in improving the efficiency of the degradation reactions. It was found that the compound (C₀ = 10 mg L^-1) was readily and totally decomposed by 30-min sonication at neutral pH, producing phenolic and aliphatic intermediates, but with insignificant mineralization. The major reaction site was the bubble-liquid interface, where the reactions were governed by OH radical attack. Modification of the sepiolite surface by pre-sonication in an ultrasonic bath improved the rate of reaction and the degree of TOC decay. Further modification by the synthesis of 20-min sonicated (200 kHz bath) SDS-intercalates of the clay was found to yield significant enhancement in the rate of target compound decomposition and the fraction of TOC decay, provided that the reaction was operated at acidic pH.

Insights into Heteroatom-Doped Graphene for Catalytic Ozonation: Active Centers, Reactive Oxygen Species Evolution, and Catalytic Mechanism

To guide the design of novel graphene-based catalysts in catalytic ozonation for micropollutant degradation, the mechanism of catalytic ozonation with heteroatom-doped graphene was clarified. Reduced graphene oxide doped with nitrogen, phosphorus, boron, and sulfur atoms (N-, P-, B-, and S-rGO) were synthesized, and their catalytic ozonation performances were evaluated in the degradation of refractory organics and bromate elimination simultaneously. Doping with heteroatoms, except sulfur, significantly improved the catalytic ozonation activity of graphene. Introducing sulfur atoms destroyed the stability of graphene during ozonation, with the observed partial performance improvement caused by surface adsorption. Degradation pathways for selected refractory organics were proposed based on the intermediates identified using high-resolution Orbitrap mass spectroscopy and gas chromatographic-mass spectroscopy. Three and six new unopened intermediates were identified in benzotriazole and p-chlorobenzoic acid degradation, respectively. Roles of chemical functional groups, doped atoms, free electron, and delocalized π electron of heteroatom-doped graphene in catalytic ozonation were identified, and contributions of these active centers to the formation of reactive oxygen species (ROS), including hydroxyl radicals, superoxide radicals, singlet oxygen, and H₂O₂, were evaluated. A mechanism for catalytic ozonation by heteroatom-doped graphene was proposed for the first time.

Degradation of atrazine by catalytic ozonation in the presence of iron scraps: performance, transformation pathway, and acute toxicity

Degradation of atrazine by catalytic ozonation in the presence of iron scraps (ZVI/O₃) was carried out. The key operational parameters (i.e., initial pH, ZVI dosage, and ozone dosage) were optimized by the batch experiments, respectively. This ZVI/O₃ system exhibited much higher degradation efficiency of atrazine than the single ozonation, ZVI, and traditional ZVI/O₂ systems. The result shows that the pseudo-first-order constant (0.0927 min^-1) and TOC removal rate (86.6%) obtained by the ZVI/O₃ process were much higher than those of the three control experiments. In addition, X-ray diffraction (XRD) analysis indicates that slight of γ-FeOOH and Fe₂O₃ were formed on the surface of iron scrap after ZVI/O₃ treatment. These corrosion products exhibit high catalytic ability for ozone decomposition, which could generate more hydroxyl radical (HO^•) to degrade atrazine. Six transformation intermediates were identified by liquid chromatography-mass spectrometry (LC-MS) analysis in ZVI/O₃ system, and the degradation pathway of atrazine was proposed. Toxicity tests based on the inhibition of the luminescence emitted by Photobacterium phosphoreum and Vibrio fischeri indicate the detoxification of atrazine by ZVI/O₃ system. Finally, reused experiments indicate the approving recyclability of iron scraps. Consequently, the ZVI/O₃ system could be as an effective and promising technology for pesticide wastewater treatment.

General and Prospective Views on Oxidation Reactions in Heterogeneous Catalysis

In this review paper, we have assembled the main characteristics of partial oxidation reactions (oxidative dehydrogenation and selective oxidation to olefins or oxygenates, as aldehydes and carboxylic acids and nitriles), as well as total oxidation, particularly for depollution, environmental issues and wastewater treatments. Both gas–solid and liquid–solid media have been considered with recent and representative examples within these fields. We have also discussed about their potential and prospective industrial applications. Particular attention has been brought to new raw materials stemming from biomass, as well as to liquid–solid catalysts cases. This review paper also summarizes the progresses made in the use of unconventional activation methods for performing oxidation reactions, highlighting the synergy of these technologies with heterogeneous catalysis. Focus has been centered on both usual catalysts activation methods and less usual ones, such as the use of ultrasounds, microwaves, grinding (mechanochemistry) and photo-activated processes, as well as their combined use.

Pilot-scale study on catalytic ozonation of bio-treated dyeing and finishing wastewater using recycled waste iron shavings as a catalyst

A pilot scale reactor with an effective volume of 2.93 m³ was built in-situ and run in both batch and continuous modes to investigate the removal for organic pollutants in bio-treated dyeing and finishing wastewater by heterogeneous catalytic ozonation under neutral pH with waste iron shavings as a catalyst. Experimental results showed that both running modes were able to reduce the chemical oxygen demand (COD) from 132–148 mg/L to a level below the discharge criteria (<80 mg/L) within 15–30 mins under several conditions. Specifically, significantly organic removal was observed with COD, soluble COD (sCOD) and dissolved organic carbon (DOC) decreased from the initial 165, 93 and 76 mg/L to 54, 28 and 16 mg/L respectively, when treated by 10.2 g-O₃/min of ozone dosage at a hydraulic retention time of 30 mins under continuous mode. 80% proteins and 85% polysaccharides were removed with a decrease in their contribution to sCOD from 69% to 43%. Mineralization as well as conversion of high molecular organic compounds was observed through Gas Chromatography-Mass Spectrometer (GC-MS) & Liquid Chromatography-Mass Spectrometer (LC-MS) analysis, which led to a decrease of inhibitory effect from 29% to 25%, suggesting a reduction in the acute toxicity.

Mechanism insight of pollutant degradation and bromate inhibition by Fe-Cu-MCM-41 catalyzed ozonation

A flexible catalyst, Fe-Cu-MCM-41, was employed to enhance diclofenac (DCF) mineralization and inhibit bromate formation in catalytic ozonation process. Greater TOC removal was achieved in Fe-Cu-MCM-41/O₃ process (78%) than those in Fe-MCM-41/O₃ (65%), Cu-MCM-41/O₃ (73%) and sole ozonation (42%). But it was interesting that both Cu-MCM-41/O₃ and Fe-MCM-41/O₃ achieved 93% bromate inhibition efficiency, only 71% inhibition efficiency was observed in Fe-Cu-MCM-41/O₃. Influence of pH, TBA/NaHSO₃ and detection of by-products were conducted to explore the mechanism. By Pyridine adsorption-IR and XPS, a relationship was found among activity of catalysts, Lewis acid sites and electron transfer effect between Fe (II/III) and Cu (I/II). Fe-Cu-MCM-41 promoted ozone decomposition to generate OH, which accounted for enhanced DCF mineralization. The consumption of aqueous O₃ also suppressed the oxidative of Br^- and HBrO/Br^-. More HBrO/BrO^- accumulated in catalytic ozonation process and less bromate generated. Bromate formation in Fe-Cu-MCM-41/O₃ process was sensitive with pH value, the acidic condition was not favor for bromate formation. Both DCF mineralization and bromate inhibition were influenced by surface reaction. Moreover, Fe-Cu-MCM-41 showed excellent catalytic performance in suppressing the accumulation of carboxylic acid, especially for oxalic acid. Nearly no oxalic acid was detected during Fe-Cu-MCM-41/O₃ process.

A novel catalytic ceramic membrane fabricated with CuMn2O4 particles for emerging UV absorbers degradation from aqueous and membrane fouling elimination

A novel catalytic ceramic membrane (CM) for improving ozonation and filtration performance was fabricated by surface coating CuMn₂O₄ particles on a tubular CM. The degradation of ultraviolet (UV) absorbers, reduction of toxicity, elimination of membrane fouling and catalytic mechanism were investigated. The characterization results suggested the particles were well-fixed on membrane surface. The modified membrane showed improved benzophenone-3 removal performance (from 28% to 34%), detoxification (EC₅₀ as 12.77%) and the stability of catalytic activity. In the degradation performance of model UV absorbers, the developed membrane significantly decreased the UV254 and DOC values in effluent. Compared with a virgin CM, this CM ozonation increased water flux as 29.9% by in-situ degrade effluent organic matters. The CuMn₂O₄ modified membrane enhanced the ozone self-decompose to generate O₂^- and initiated the chain reaction of ozone decomposition, and subsequently reacted with molecule ozone to produce OH. Additionally, CM was able to promote the interaction between ozone and catalyst/organic chemicals to form H₂O₂ that promoted the formation of OH. This catalytic ceramic membrane combining with ozonation showed potential applications in emerging pollutant degradation and membrane fouling elimination, and acted as a novel ternary technology for wastewater treatment and water reuse.

Iron Based Catalysts Used in Water Treatment Assisted by Ultrasound: A Mini Review

The characteristics and performances of catalyst are the key in catalytic ultrasonic treatment of wastewater, and iron based catalysts are known for low cost, high accessibility and safety. This paper reviewed the current research status of iron-based catalysts in water treatment assisted by ultrasound. Zero valent iron, Fe₃O₄ and iron composited with other metals were analyzed, their behaviors in catalytic sonochemistry were summarized, and the potential catalytic mechanisms were discussed in details. Finally, the future development in this field was proposed.

Single, simultaneous and sequential applications of ultrasonic frequencies for the elimination of ibuprofen in water

The study is about the assessment of single and multi-frequency operations for the overall degradation of a widely consumed analgesic pharmaceutical-ibuprofen (IBP). The selected frequencies were in the range of 20-1130kHz emissions coming from probes, baths and piezo-electric transducers attached to plate-type devices. Multi-frequency operations were applied either simultaneously as "duals", or sequentially at fixed time intervals; and the total reaction time in all operations was 30-min. The work also covers evaluation of the effect of zero-valent iron (ZVI) on the efficiency of the degradation process and the performance of the reaction systems. It was found that low-frequency probe type devices especially at 20kHz were ineffective when applied singly and without ZVI, and relatively more effective in combined-frequency operations in the presence of ZVI. The power efficiencies of the reactors and/or reaction systems showed that 20-kHz probe was considerably more energy intensive than all others, and was therefore not used in multi-frequency operations. The most efficient reactor in terms of power consumption was the bath (200kHz), which however provided insufficient mineralization of the test chemical. The highest percentage of TOC decay (37%) was obtained in a dual-frequency operation (40/572kHz) with ZVI, in which the energy consumption was neither low nor exceptionally too high. A sequential operation (40+200kHz) in that respect was more efficient, because it required much less energy for a similar TOC decay performance (30%). In general, the degradation of IBP increased with increased power consumption, which in turn reduced the sonochemical yield. The study also showed that advanced Fenton reactions with ZVI were faster in the presence of ultrasound, and the metal was very effective in improving the performance of low-frequency operations.

Mechanistic investigations in sono-hybrid (ultrasound/Fe2+/UVC) techniques of persulfate activation for degradation of Azorubine

Persulfate-based oxidation of recalcitrant pollutants has been investigated as an alternative to OH radical based advanced oxidation processes due to distinct merits such as greater stability and non-selective persistent reactivity of SO₄^- oxidant species. The present study has attempted to highlight mechanistic features of persulfate-based decolorization of textile dye (Azorubine) using sono-hybrid techniques of activation. Three activation techniques, viz. sonolysis, Fe²⁺ ions and UVC light and combinations thereof, have been examined. UVC is revealed to be the most efficient decolorization technique. The mechanism of sonolysis (i.e. thermal activation of persulfate in the bubble-bulk interfacial region) is revealed to be almost independent of the mechanism of UVC. Fe²⁺ activation is revealed to have an adverse interaction with UVC due to scavenging of sulfate radicals by Fe²⁺ ions. The best hybrid activation technique for persulfate-based degradation and mineralization of Azorubine is UVC+ultrasound. Due to independent mechanisms, degradation and mineralization of the dye obtained with simultaneous application of UVC and ultrasound is nearly equal to the sum of degradation and mineralization obtained using individual techniques.

Catalytic ozonation of dimethyl phthalate using Fe3O4/multi-wall carbon nanotubes

In this paper, Fe₃O₄/multi-wall carbon nanotubes composites were prepared, characterized and used as a catalyst for enhancing the ozonation of dimethyl phthalate (DMP) in aqueous solution. The experimental results showed that DMP degradation and mineralization increased by 26% and 20%, respectively, in catalytic ozonation compared with single ozonation, and more H₂O₂ and organic acids were produced during catalytic ozonation process than single ozonation. The effect of pH, ozone concentration and catalyst dosage on DMP degradation was determined. The addition of tert-butanol and phosphates showed a negative effect on DMP degradation, suggesting that the acidic sites on the catalyst is favorable to ozone decomposition to produce hydroxyl radicals. The possible mechanism for catalytic ozonation of DMP was tentatively proposed. The adsorption of ozone and organics onto the surface of catalyst could improve the DMP degradation.

Application of ozonation for pharmaceuticals and personal care products removal from water

Due to the shortening on natural water resources, reclaimed wastewater will be an important water supply source. However, suitable technologies must be available to guaranty its proper detoxification with special concern for the emerging pharmaceutical and personal care products that are continuously reaching municipal wastewater treatment plants. While conventional biological systems are not suitable to remove these compounds, ozone, due to its interesting features involving molecular ozone oxidation and the possibility of generating unselective hydroxyl radicals, has a wider range of action on micropollutants removal and water disinfection. This paper aims to review the studies dealing with ozone based processes for water reuse by considering municipal wastewater reclamation as well as natural and drinking water treatment. A comparison with alternative technologies is given. The main drawback of ozonation is related with the low mineralization achieved that may lead to the production of reaction intermediates with toxic features. The use of hydrogen peroxide and light aided systems enhance ozone action over pollutants. Moreover, scientific community is focused on the development of solid catalysts able to improve the mineralization level achieved by ozone. Special interest is now being given to solar light catalytic ozonation systems with interesting results both for chemical and biological contaminants abatement. Nowadays the integration between ozonation and sand biofiltration seems to be the most interesting cost effective methodology for water treatment. However, further studies must be performed to optimize this system by understanding the biofiltration mechanisms.

Coagulation-flocculation as pre-treatment for micro-scale Fe/Cu/O3 process (CF-mFe/Cu/O3) treatment of the coating wastewater from automobile manufacturing

A coagulation-flocculation as pre-treatment combined with mFe/Cu/O₃ (CF-mFe/Cu/O₃) process was developed to degrade the pollutants in automobile coating wastewater (ACW). In coagulation-flocculation (CF) process, high turbidity removal efficiency (97.1%) and low COD removal efficiency (10.5%) were obtained under the optimal conditions using Al₂(SO₄)₃·18H₂O and CaO. The effluent of CF process (ECF) was further disposed by mFe/Cu/O₃ process, and its key operating parameters were optimized by batch experiments. Optimally, COD removal efficiency of ECF obtained by the mFe/Cu/O₃ process (i.e., 87.6% after 30 min treatment) was much higher than those of mFe/Cu alone (8.3%), ozone alone (46.6%), and mFe/Cu/air (6.1%), which confirms the superiority of the mFe/Cu/O₃ process. In addition, the analysis results of UV-vis, excitation-emission matrix (EEM) fluorescence spectra and GC/MS further confirm that the phenol pollutants of ECF had been effectively decomposed or transformed after CF-mFe/Cu/O₃ process treatment. Meanwhile, B/C ratio of ACW increased from 0.19 to 0.56, which suggests the biodegradability was improved significantly. Finally, the operating cost of CF-mFe/Cu/O₃ process was about 1.83 USD t^-1 for ACW treatment. Therefore, the combined process is a promising treatment technology for the coating wastewater from automobile manufacturing.

Catalytic ozonation of organic pollutants from bio-treated dyeing and finishing wastewater using recycled waste iron shavings as a catalyst: Removal and pathways

Catalytic ozonation of organic pollutants from actual bio-treated dyeing and finishing wastewater (BDFW) with iron shavings was investigated. Catalytic ozonation effectively removed organic pollutants at initial pH values of 7.18-7.52, and the chemical oxygen demand (COD) level decreased from 142 to 70 mg·L(-1) with a discharge limitation of 80 mg·L(-1). A total of 100% and 42% of the proteins and polysaccharides, respectively, were removed with a decrease in their contribution to the soluble COD from 76% to 41%. Among the 218 organic species detected by liquid chromatography-mass spectrometry, 58, 77, 79 and 4 species were completely removed, partially removed, increased and newly generated, respectively. Species including textile auxiliaries and dye intermediates were detected by gas chromatography-mass spectrometry. The inhibitory effect decreased from 51% to 33%, suggesting a reduction in the acute toxicity. The enhanced effect was due to hydroxyl radical (OH) oxidation, co-precipitation and oxidation by other oxidants. The proteins were removed by OH oxidation (6%), by direct ozonation, co-precipitation and oxidation by other oxidants (94%). The corresponding values for polysaccharides were 21% and 21%, respectively. In addition, the iron shavings behaved well in successive runs. These results indicated that the process was favorable for engineering applications for removal of organic pollutants from BDFW.

Cerium doped red mud catalytic ozonation for bezafibrate degradation in wastewater: Efficiency, intermediates, and toxicity

In this study, the performance of bezafibrate (BZF) degradation and detoxification in the aqueous phase using cerium-modified red mud (RM) catalysts prepared using different cerium sources and synthesis methods were evaluated. Experimental results showed that the surface cerium modification was responsible for the development of the catalytic activity of RM and this was influenced by the cerium source and the synthesis method. Catalyst prepared from cerium (IV) by precipitation was found to show the best catalytic activity in BZF degradation and detoxification. Reactive oxygen species including peroxides, hydroxyl radicals, and super oxide ions were identified in all reactions and we proposed the corresponding catalytic reaction mechanism for each catalyst that prepared from different cerium source and method. This was supported by the intermediates profiles that were generated upon BZF degradation. The surface and the structural properties of cerium-modified RM were characterized in detail by several analytical methods. Two interesting findings were made: (1) the surface texture (specific surface area and mesoporous volume) influenced the catalytic reaction pathway; and (2) Ce(III) species and oxygen vacancies were generated on the surface of the catalyst after cerium modification. This plays an important role in the development of the catalytic activity.

Investigations in sono-enzymatic degradation of ibuprofen

The drug ibuprofen (IBP) appears frequently in the wastewater discharge from pharmaceutical industries. This paper reports studies in degradation of IBP employing hybrid technique of sono-enzymatic treatment. This paper also establishes synergy between individual mechanisms of enzyme and sonolysis for IBP degradation by identification of degradation intermediates, and Arrhenius & thermodynamic analysis of the experimental data. Positive synergy between sonolysis and enzyme treatment is attributed to formation of hydrophilic intermediates during degradation. These intermediates form due to hydroxylation and oxidation reactions induced by radicals formed during transient cavitation. Activation energy and enthalpy change in sono-enzymatic treatment are lower as compared to enzyme treatment, while frequency factor and entropy change are higher as compared to sonolysis. Degradation of IBP in sono-enzymatic treatment is revealed to be comparable with other hybrid techniques like photo-Fenton, sono-photocatalysis, and sono-Fenton.

Treatment of wastewater derived from dinitrodiazophenol (DDNP) manufacturing by the Fe/Cu/O3 process

In this paper, the Fe/Cu bimetallic particles and ozone were combined to decompose or transform the toxic and refractory pollutants in dinitrodiazophenol (DDNP) wastewater.

Mineralization of ammunition wastewater by a micron-size Fe0/O3 process (mFe0/O3)

A micron-size Fe⁰/O₃ process (mFe⁰/O₃) was set up to mineralize the pollutants in ammunition wastewater, and its key operational parameters (e.g., initial pH, ozone flow rate, and mFe⁰ dosage) were optimized by the batch experiments, respectively.

Electrocatalytic degradation of ibuprofen in aqueous solution by a cobalt-doped modified lead dioxide electrode: influencing factors and energy demand

PbO₂ electrode modified with Co exhibited higher electrochemical oxidation. The effects of HA, FA, OA and CA were investigated.