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

Comparative study on CeO2 catalysts with different morphologies and exposed facets for catalytic ozonation: performance, key factor and mechanism insight

Morphology and facet effects of metal oxides in heterogeneous catalytic ozonation (HCO) are attracting increasing interests. In this paper, the different HCO performances for degradation and mineralization of phenol of seven ceria (CeO2) catalysts, including four with different morphologies (nanorod, nanocube, nanooctahedron and nanopolyhedron) and three with the same nanorod morphology but different exposed facets, are comparatively studied. CeO2 nanorods with (110) and (100) facets exposed show the best performance, much better than that of single ozonation, while CeO2 nanocubes and nanooctahedra show performances close to single ozonation. The underlying reason for their different HCO performances is revealed using various experimental and density functional theory (DFT) calculation results and the possible catalytic reaction mechanism is proposed. The oxygen vacancy (OV) is found to be pivotal for the HCO performance of the different CeO2 catalysts regardless of their morphology or exposed facet. A linear correlation is discerned between the rate of catalytic decomposition of dissolved ozone (O3) and the density of Frenkel-type OV. DFT calculations and in-situ spectroscopic studies ascertain that the existence of OV can boost O3 activation on both the hydroxyl (OH) and Ce sites of CeO2. Conversely, various facets without OV exhibit similar O3 adsorption energies. The OH group plays an important role in activating O3 to produce hydroxyl radical (∙OH) for improved mineralization. This work may offer valuable insights for designing Facet- and OV-regulated catalysts in HCO for the abatement of refractory organic pollutants.

High efficiency azo dye removal via a combination of adsorption and photocatalytic processes using heterojunction Titanium dioxide nanoparticles on hierarchical porous carbon

Amidst the rapid development of the textile industry, wastewater problems also arise. High-performance materials for reactive black 5 (RB5) dye treatment by adsorption and photocatalysis were evolved using Titanium dioxide (TiO2) nanoparticles on carbon media. Herein, the synthesis of spherical carbon via the water-in-oil emulsion method alongside a sol-gel process and the production of TiO2 nanoparticles using the precipitation procedure of Titanium isopropoxide and carbonization at 700-900 °C for 2 h are a novel approach in this work. The characterization of these materials indicates that different temperatures result in distinct properties, for instance, raised pores on the surface of the media and changes in the crystal structure of TiO2. The results show that the as-synthesized material carbonized at 900 °C had distinguished dye adsorption, up to 430 ppm in 1 h, due to their high surface area and pore volume. On the contrary, the calcined 700 °C condition had the prominent photocatalytic efficiency on account of the heterojunction band gap between anatase and rutile crystal structure. A mixed phase minimizes the charge recombination, subsequently increasing the photocatalytic capability.

High-efficient M-NC single-atom catalysts for catalytic ozonation in water purification: Performance and mechanisms

Heterogeneous catalytic ozonation (HCO) holds promise in water purification but suffers from limited accessible metal sites, metal leaching, and unclear structure-activity relationships. This work reported M-NC (M=Co, Ni, Fe, and Mn) single-atom catalysts (SACs) with high atomic efficiency and minimal metal release. The new HCO systems, especially the Co-based system, exhibited impressive performance in various refractory contaminant removal, involving various reactive species generation, such as •OHads, •OHfree, *O, and 1O2. For sulfamethoxazole removal, the normalized kobs for Co-NC, Ni-NC, Fe-NC, and Mn-NC were determined as 13.53, 3.94, 3.55, and 4.13 min-1·mMmetal-1·g·m-2 correspondingly, attributed to the abundant acid sites, faster electron transfer, and lower energy required for O3 decomposition and conversion. The metal atoms and hydroxyl groups, individually serving as Lewis and Bronsted acid sites (LAS and BAS), were the primary centers for •OH generation and O3 adsorption. The relationships between active sites and both O3 utilization and •OH generation were found. LAS and BAS were responsible for O3 adsorption, while strong LAS facilitated O3 conversion into •OH. Theoretical calculations revealed the catalytic mechanisms involved O3→ *O→ *OO→ O3•-→ •OH. This work highlights the significance of SAC design for HCO and advances the understanding of atomic-level HCO behavior.

Microalgae-bacterial consortiums for enhanced degradation of nonylphenol: Biodegradability and kinetic analysis

The widespread use of non-ionic surfactant nonylphenol (NP) has led to significant water pollution, posing a threat to both ecological stability and human health. However, the efficient biodegradation method and system of NP-biodegradation remain complex scientific challenges. In this study, we isolated and characterized three Pseudomonas sp. strains SW-1 (Scenedesmus quadricauda-associated), ZL-2 (Ankistrodesmus acicularis-associated), XQ-3 (Chlorella vulgaris-associated), and one NP-degrading Cupriavidus sp. strain EB-4, which exhibited the ability to utilize NP as the sole carbon source. Furthermore, four consortiums of microalgae-bacterial, S. quadricauda and SW-1 (S-SW), A. acicularis and ZL-2 (A-ZL), C. vulgaris and XQ-3 (C-XQ), S. quadricauda and EB-4 (S-EB), were constructed to investigate their biodegradability and kinetic characteristics of NP degradation from water. The consortiums showed higher degradation efficiency compared to individual microalgae or bacteria. The C-XQ consortium exhibited the highest degradation rate, removing over 94% of NP within just seven days. The first-order model with the following order of degradation rate by consortiums was C-XQ (0.3960 d-1) > S-SW (0.3506 d-1) > A-ZL (0.1968 d-1) > S-EB (0.1776 d-1). Compared with the results of our previous study, the interaction between microalgae and bacteria is not a simple additive relationship. Our findings highlight the potential of an algal-bacterial consortium for the remediation of NP-contaminated environments.

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.

Sonoelectrochemical degradation of aspirin in aquatic medium using ozone and peroxymonosulfate activated with FeS2 nanoparticles

The catalytic performance of nano-FeS2 in the sonoelectrochemical activation of peroxymonosulfate (PMS) and ozone to remove aspirin (ASP) was studied for the first time. The crystal structure and Fe bonds in the catalyst were confirmed through XRD and FTIR analysis. Within 30 min, ASP (TOC) was removed by 99.2 % (81.6 %) and 98.6 % (77.4 %) in nano-FeS2/PMS and nano-FeS2/O3 sonoelectrochemical systems, respectively. Water anions, especially (almost 50 %), had an inhibitory effect on ASP removal. The probes confirmed that SO4•-and HO• were the key to ASP degradation in nano-FeS2/PMS and nano-FeS2/O3 systems, respectively. The effective activation of oxidants due to the ideal distribution of Fe2+ by catalyst was the main mechanism of ASP removal, in which electric current (EC) and ultrasound (US) played a crucial role through the recycling of Fe ions, dissolution and cleaning of the catalyst. LC-MS analysis identified thirteen byproducts in the ASP degradation pathways. The energy consumption of the proposed sonoelectrochemical systems was lower than previous similar systems. This study presented economic and sustainable hybrid systems for pharmaceutical wastewater remediation.

Feasibility of intimately coupled CaO-catalytic-ozonation and bio-contact oxidation reactor for heavy metal and color removal and deep mineralization of refractory organics in actual coking wastewater

Considering the challenges for both single and traditional two-stage treatments, advanced oxidation and biodegradation, in the treatment of actual coking wastewater, an intimately coupled catalytic ozonation and biodegradation (ICOB) reactor was developed. In this study, ICOB treatment significantly enhanced the removal of Cu2+, Fe3+, and color by 39 %, 45 %, and 52 %, respectively, outperforming biodegradation. Catalytic ozonation effectively breaking down unsaturated organic substances and high-molecular-weight dissolved organic matter into smaller, more biodegradable molecules. Compared with biodegradation, the ICOB system significantly increased the abundances of Pseudomonas, Sphingopyxis, and Brevundimonas by ∼ 96 %, ∼67 %, and ∼ 85 %, respectively. These microorganisms, possessing genes for degrading phenol, aromatic compounds, polycyclic aromatics, and sulfur metabolism, further enhanced the mineralization of intermediates. Consequently, the ICOB system outperformed biodegradation and catalytic ozonation treatments, exhibiting chemical oxygen demand removal rate of ∼ 58 % and toxicity reduction of ∼ 47 %. Overall, the ICOB treatment showcases promise for practical engineering applications in coking wastewater treatment.

Carbon-Based Materials in Combined Adsorption/Ozonation for Indigo Dye Decolorization in Constrain Contact Time

This study presents a comprehensive evaluation of catalytic ozonation as an effective strategy for indigo dye bleaching, particularly examining the performance of four carbon-based catalysts, activated carbon (AC), multi-walled carbon nanotubes (MWCNT), graphitic carbon nitride (g-C3N4), and thermally etched nanosheets (C3N4-TE). The study investigates the efficiency of catalytic ozonation in degrading Potassium indigotrisulfonate (ITS) dye within the constraints of short contact times, aiming to simulate real-world industrial wastewater treatment conditions. The results reveal that all catalysts demonstrated remarkable decolorization efficiency, with over 99% of indigo dye removed within just 120 s of mixing time. Besides, the study delves into the mechanisms underlying catalytic ozonation reactions, elucidating the intricate interactions between the catalysts, ozone, and indigo dye molecules with the processes being influenced by factors such as PZC, pKa, and pH. Furthermore, experiments were conducted to analyze the adsorption characteristics of indigo dye on the surfaces of the materials and its impact on the catalytic ozonation process. MWCNT demonstrated the highest adsorption efficiency, effectively removing 43.4% of the indigo dye color over 60 s. Although the efficiency achieved with C3N4-TE was 21.4%, which is approximately half of that achieved with MWCNT and less than half of that with AC, it is noteworthy given the significantly lower surface area of C3N4-TE.

Green Synthesis of Cobalt-Doped CeFe2O5 Nanocomposites Using Waste Gossypium arboreum L. Stalks and Their Application in the Removal of Toxic Water Pollutants

Currently, there is an increasing need to find new ways to purify water by eliminating bacterial biofilms, textile dyes, and toxic water pollutants. These contaminants pose significant risks to both human health and the environment. To address this issue, in this study, we have developed an eco-friendly approach that involves synthesizing a cobalt-doped cerium iron oxide (CCIO) nanocomposite (NC) using an aqueous extract of Gossypium arboreum L. stalks. The resulting nanoparticles can be used to effectively purify water and tackle the challenges associated with these harmful pollutants. Nanoparticles excel in water pollutant removal by providing a high surface area for efficient adsorption, versatile design for the simultaneous removal of multiple contaminants, catalytic properties for organic pollutant degradation, and magnetic features for easy separation, offering cost-effective and sustainable water treatment solutions. A CCIO nanocomposite was synthesized via a green co-precipitation method utilizing biomolecules and co-enzymes extracted from the aqueous solution of Gossypium arboreum L. stalk. This single-step synthesis process was accomplished within a 5-h reaction period. Furthermore, the synthesis of nanocomposites was confirmed by various characterization techniques such as Fourier-transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), thermogravimetric analysis (TGA), dynamic light scattering (DLS), and energy dispersive X-ray (EDX) technology. CCIO NCs were discovered to have a spherical shape and an average size of 40 nm. Based on DLS zeta potential analysis, CCIO NCs were found to be anionic. CCIO NCs also showed significant antimicrobial and antioxidant activity. Overall, considering their physical and chemical properties, the application of CCIO NCs for the adsorption of various dyes (~91%) and water pollutants (chromium = ~60%) has been considered here since they exhibit great adsorption capacity owing to their microporous structure, and represent a step forward in water purification.

Adsorption properties of cellulose-derived hydrogel and magnetic hydrogels from Sophora flavescens on Cu2+ and Congo red

This study synthesized a robust, magnetically responsive hydrogel from Sophora flavescens-modified cellulose and chitosan, employing Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), thermogravimetric analysis (TGA and DTG), and scanning electron microscopy (SEM) to confirm the preservation of cellulose's intrinsic properties and the hydrogel's remarkable elasticity, toughness, and porosity. These hydrogels integrate cellulose's structural backbone with functional moieties from chitosan, enhancing adsorption capabilities for Cu2+ ions and Congo red (CR) dye. Kinetic and thermodynamic analyses reveal that adsorption is spontaneous and endothermic, following a pseudo-second-order model and the Freundlich isotherm. Notably, Cu2+ adsorption capacity increases with pH, while CR adsorption initially decreases before rising, demonstrating the hydrogels' potential as effective, sustainable adsorbents for removing pollutants from water.

Continuous operation of nano-catalytic ozonation using membrane separation coupling system: Influence factors and mechanism

The application of nano-catalysts in improving the ozonation removal efficiency for refractory organic compounds has been extensively investigated. However, cost-effective nano-catalysts separation remains a challenge. In this study, membrane separation processes were employed to separate nano-MgO catalysts from an ozonation system. A continuous nano-catalytic ozonation membrane separation (nCOMS) coupling system was successfully constructed for treating quinoline. The results showed that long hydraulic retention time (HRT) and high nano-MgO dosage could improve the quinolone removal efficiency but shorten operation cycles. At the optimal operation conditions of HRT = 4 h and nano-MgO dosage = 0.2 g/L, the nCOMS system achieved a stable quinoline removal efficiency of 85.2% for 240 min running with a transmembrane pressure lower than 10 kPa. The quinoline removal efficiency contribution for ozonation, catalysis and membrane separation was 57.1%, 24.9% and 18.0%, respectively. Compared to ozonation membrane separation system, the fouling rate index of the nCOMS system increased by 60% under optimal conditions, but the irreversible fouling was reduced to 28%. In addition, the nCOMS system exhibited reduced adverse effects of coexisting natural organic matter (NOM) on quinoline removal and membrane fouling. In conclusion, the nCOMS system demonstrated higher quinoline removal efficiency, lower irreversible fouling, and reduced adverse effect of coexisting NOM, thereby signifying its potential for practical applications in advanced treatment of industrial wastewater.

Efficient degradation of p-nitrophenol from water by enhancing dielectric barrier discharge (DBD) plasma through ozone circulation: Optimization, kinetics and mechanism

Non-thermal dielectric barrier discharge (DBD) plasma has received great attention for degradation of persistent organic pollutants such as p-nitrophenol (PNP). However, the feasibility of the DBD implementation is not clear due to its high energy consumption and relatively low degradation efficiency. In this research, a novel strategy was suggested based on re-circulation of the generated O3 in the DBD system to enhance the PNP degradation efficiency and energy yield. The potential mechanism and possible pathway of PNP degradation were studied by EPR, ESR, DFT and GS-MS analytical tests. According to the results, the PNP degradation efficiency and energy yield increased from 57.4% to 94.4% and from 0.52 to 1.18 g kW-1h-1, respectively through ozone circulation into the DBD reactor. This was due to the more release of long-lived and short-lived reactive species (ROS) in the DBD-O3 system by the O3 circulation. The variations in pH (4-10), initial concentration (50-90 mg L-1), and the presence of co-existing substances in the water matrix had minimal impact on the DBD-O3 system, in comparison to the conventional system. The biological toxicity evaluation revealed that the hybrid DBD-O3 system transform PNP to less toxic intermediates. This study proposes a promising strategy to improve the utilization of DBD for the degradation of PNP.

Valorization of Field-Spent Granular Activated Carbon as Heterogeneous Ozonation Catalyst for Water Treatment

Developing sustainable cost-effective strategies for valorization of field-spent granular activated carbon (s-GAC) from industrial water treatment has gained much interest. Here, we report a cost-effective strategy for the regeneration of s-GAC as an adsorbent in a large-scale drinking water treatment plant and used as an efficient and durable ozonation catalyst in water. To achieve this, a series of samples is prepared by subjecting s-GAC to thermally controlled combustion treatments with and without pyrolysis. The catalytic performance of the optimized sample is evaluated for oxalic acid degradation as the model pollutant under batch (>15 h) and continuous flow operations (>200 h). The partially deactivated catalyst upon reuse is restored by thermal treatment. Electron paramagnetic resonance and selective quenching experiments show the formation of singlet oxygen (1O2) during catalytic ozonation. The GAC-ozonation catalyst is efficient to minimize the formation of chlorinated disinfection by-products like trihalomethanes and haloacetic acids in an urban wastewater effluent.

Synergistic Coassembly of Folic Acid-Based Supramolecular Polymer with a Covalent Polymer Toward Fabricating Functional Antibacterial Biomaterials

Supramolecular biomaterials can recapitulate the structural and functional facets of the native extracellular matrix and react to biochemical cues, leveraging the unique attributes of noncovalent interactions, including reversibility and tunability. However, the low mechanical properties of supramolecular biomaterials can restrict their utilization in specific applications. Combining the advantages of supramolecular polymers with covalent polymers can lead to the fabrication of tailor-made biomaterials with enhanced mechanical properties/degradability. Herein, we demonstrate a synergistic coassembled self-healing gel as a multifunctional supramolecular material. As the supramolecular polymer component, we chose folic acid (vitamin B9), an important biomolecule that forms a gel comprising one-dimensional (1D) supramolecular polymers. Integrating polyvinyl alcohol (PVA) into this supramolecular gel alters its ultrastructure and augments its mechanical properties. A drastic improvement of complex modulus (G*) (∼3674 times) was observed in the folic acid-PVA gel with 15% w/v PVA (33215 Pa) compared with the folic acid gel (9.04 Pa). The coassembled hydrogels possessed self-healing and injectable/thixotropic attributes and could be printed into specific three-dimensional (3D) shapes. Synergistically, the supramolecular polymers of folic acid also improve the toughness, durability, and ductility of the PVA films. A nanocomposite of the gels with silver nanoparticles exhibited excellent catalytic efficiency and antibacterial activity. The folic acid-PVA coassembled gels and films also possessed high cytocompatibility, substantiated by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) and live-dead assays. Taken together, the antibacterial and cell-adhesive attributes suggest potential applications of these coassembled biomaterials for tissue engineering and wound healing.

Mechanisms and Strategies of Advanced Oxidation Processes for Membrane Fouling Control in MBRs: Membrane-Foulant Removal versus Mixed-Liquor Improvement

Membrane bioreactors (MBRs) are well-established and widely utilized technologies with substantial large-scale plants around the world for municipal and industrial wastewater treatment. Despite their widespread adoption, membrane fouling presents a significant impediment to the broader application of MBRs, necessitating ongoing research and development of effective antifouling strategies. As highly promising, efficient, and environmentally friendly chemical methods for water and wastewater treatment, advanced oxidation processes (AOPs) have demonstrated exceptional competence in the degradation of pollutants and inactivation of bacteria in aqueous environments, exhibiting considerable potential in controlling membrane fouling in MBRs through direct membrane foulant removal (MFR) and indirect mixed-liquor improvement (MLI). Recent proliferation of research on AOPs-based antifouling technologies has catalyzed revolutionary advancements in traditional antifouling methods in MBRs, shedding new light on antifouling mechanisms. To keep pace with the rapid evolution of MBRs, there is an urgent need for a comprehensive summary and discussion of the antifouling advances of AOPs in MBRs, particularly with a focus on understanding the realizing pathways of MFR and MLI. In this critical review, we emphasize the superiority and feasibility of implementing AOPs-based antifouling technologies in MBRs. Moreover, we systematically overview antifouling mechanisms and strategies, such as membrane modification and cleaning for MFR, as well as pretreatment and in-situ treatment for MLI, based on specific AOPs including electrochemical oxidation, photocatalysis, Fenton, and ozonation. Furthermore, we provide recommendations for selecting antifouling strategies (MFR or MLI) in MBRs, along with proposed regulatory measures for specific AOPs-based technologies according to the operational conditions and energy consumption of MBRs. Finally, we highlight future research prospects rooted in the existing application challenges of AOPs in MBRs, including low antifouling efficiency, elevated additional costs, production of metal sludge, and potential damage to polymeric membranes. The fundamental insights presented in this review aim to elevate research interest and ignite innovative thinking regarding the design, improvement, and deployment of AOPs-based antifouling approaches in MBRs, thereby advancing the extensive utilization of membrane-separation technology in the field of wastewater treatment.

Holistic insight mechanism of ozone-based oxidation process for wastewater treatment

The world is facing water crises because freshwater scarcity has become a global issue due to rapid population growth, resulting in the need for more industries, agriculture, and domestic sectors. Therefore, it is challenging for scientists and environmental engineers to treat wastewater with cost-effective treatment techniques. As compared to conventional processes (physical, chemical, and biological), advanced oxidation processes (AOP) play an essential role in the removal of wastewater contaminants, with the help of a powerful hydroxyl (OH•) through oxidation reactions. This review study investigates the critical role of O3-based Advanced Oxidation Processes (AOPs) in tackling the complex difficulties of wastewater treatment. Effective treatment methods are critical, with wastewater originating from various sources, including industrial activity, pharmaceutical manufacturing, agriculture, and a wide range of toxins. O3-based AOPs appear to be powerful therapies capable of degrading a wide range of pollutants, including stubborn organics, medicines, and pesticides, reducing environmental and human health risks. This review sheds light on their efficacy in wastewater treatment by explaining the underlying reaction mechanisms and applications of several O3-based AOP processes, such as O3, O3/UV, and O3/H2O2. Ozone, a powerful oxidizing agent, stimulates the breakdown of complex chemical molecules by oxidation processes, which are aided further by synergistic combinations with ultraviolet (UV) radiation or hydrogen peroxide (H2O2). Notably, while ozonation alone may not always produce the best outcomes, it acts as an essential pretreatment step prior to traditional treatments, increasing total treatment efficiency. Furthermore, O3-based AOPs' transformational capacity to convert organic chemicals into simpler, more stable inorganic forms with little sludge creation emphasizes its sustainability and environmental benefits. This study sheds light on the processes, uses, and benefits of O3-based AOPs, presenting practical solutions for sustainable water management and environmental protection. It is a valuable resource for academics, engineers, and politicians looking for new ways to combat wastewater contamination and protect water resources.

MnFe2O4/MoS2 catalyst used for ozonation: optimization and mechanism analysis of phenolic wastewater treatment

The performance of catalytic ability of MFe2O4/MoS2 in the ozonation process was investigated in this work. The synthesized MnFe2O4/MoS2 was optimize prepared and then characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, X-ray photo-electron spectroscopy, and magnetic saturation strength. The results showed that when Cphenol = 200 mg/L, initial pH = 9.0, Q = 0.10 L/min, and CMnFe2O4/MoS2 = 0.10 g/L, MnFe2O4/MoS2 addition improved the degradation efficiency of phenol by 20.0%. The effects of pH, catalyst dosage, and inorganic ions on the phenol removal by the MnFe2O4/MoS2 catalytic ozonation were investigated. Five cycle experiments proved that MnFe2O4/MoS2 had good recyclability and stability. MnFe2O4/MoS2 also showed good catalytic performance in the treatment of coal chemical wastewater pesticide wastewater. The MnFe2O4 doped with MoS2 could provide abundant surface active sites for ozone and promote the stable cycle of Mn2+/Mn3+and Fe2+/Fe3+, thus generating large amounts of •OH and improving the degradation of phenol by ozonation. The MnFe2O4/MoS2/ozonation treatment system provides a technical reference and theoretical basis for industrial wastewater treatment.

The development of multifunctional materials for water pollution remediation using pollen and sporopollenin

Pollen is a promising material for water treatment owing to its renewable nature, abundant sources, and vast reserves. The natural polymer sporopollenin, found within pollen exine, possesses a distinctive layered porous structure, mechanical strength, and stable chemical properties, which can be utilized to prepare sporopollenin exine capsules (SECs). Leveraging these attributes, pollen or SECs can be used to develop water pollution remediation materials. In this review, the structure of pollen is first introduced, followed by the categorization of various methods for extracting SECs. Then, the functional expansion of pollen adsorbents, with an emphasis on their recyclability, reusability, and visual sensing capabilities, as opposed to mere functional group modification, is discussed. Furthermore, the progress made in utilizing pollen as a biological template for synthesizing catalysts is summarized. Intriguingly, pollen can also be engineered into self-propelled micromotors, enhancing its potential application in adsorption and catalysis. Finally, the challenges associated with the application of pollen in water pollution treatment are discussed. These challenges include the selection of environmentally friendly, non-toxic reagents in synthesizing pollen water remediation products and the large-scale application after synthesis. Moreover, the multifunctional synthesis and application of different water remediation products are prospected.

Application of Engineered Nanomaterials as Nanocatalysts in Catalytic Ozonation: A Review

Given the growing scarcity of water and the continuous increase in emerging pollutants detected in water bodies, there is an imperative need to develop new, more effective, and sustainable treatments for wastewater. Advanced oxidation processes (AOPs) are considered a competitive technology for water treatment. Specifically, ozonation has received notable attention as a promising approach for degrading organic pollutants in wastewater. However, different groups of pollutants are hardly degradable via single ozonation. With continuous development, it has been shown that using engineered nanomaterials as nanocatalysts in catalytic ozonation can increase efficiency by turning this process into a low-selective AOP for pollutant degradation. Nanocatalysts promote ozone decomposition and form active free radicals responsible for increasing the degradation and mineralization of pollutants. This work reviews the performances of different nanomaterials as homogeneous and heterogeneous nanocatalysts in catalytic ozonation. This review focuses on applying metal- and carbon-based engineered nanomaterials as nanocatalysts in catalytic ozonation and on identifying the main future directions for using this type of AOP toward wastewater treatment.

Novel cow dung-doped sludge biochar as an efficient ozone catalyst: Synergy between graphitic structure and defects induces free radical pathways

A composite material, cow dung-doped sludge biochar (Zn@SBC-CD), was synthesized by one-step pyrolysis using ZnCl2 as an activating agent and applied to a catalytic ozonation process (COP) for methylene blue (MB) removal. SEM, XRD, FTIR, XPS and BET analyses were performed to characterize the biochar (BC) catalysts. Zn@SBC-CD had high graphitization degree, abundant active sites and uniform distribution of Zn on its surface. Complete removal of MB was achieved within 10 min, with a removal rate much higher than that of ozone alone (32.4%), implying the excellent ozone activation performance of Zn@SBC-CD. The influence of experimental parameters on MB removal efficiency was examined. Under the optimum conditions in terms of ozone dose 0.04 mg/mL, catalyst dose 400 mg/L and pH 6.0, COD was completely removed after 20 min. Electron paramagnetic resonance (EPR) analysis revealed radical and non-radical pathways were involved in MB degradation. The Zn@SBC-CD/O3 system generated superoxide anion radicals (•O2-), which were the main active species for MB removal, through adsorption, transformation, and transfer, Furthermore, Zn@SBC-CD exhibited good reusability and stability in cycling experiments. This study provides a novel approach for the utilization of cow dung and sludge in synthesis of functional biocatalysts and application in organic wastewater treatment.

Catalytic ozonation of reverse osmosis concentrate from coking wastewater reuse by surface oxidation over Mn-Ce/γ-Al2O3: Effluent organic matter transformation and its catalytic mechanism

Degradation of organics in high-salinity wastewater is beneficial to meeting the requirement of zero liquid discharge for coking wastewater treatment. Creating efficient and stable performance catalysts for high-salinity wastewater treatment is vital in catalytic ozonation process. Compared with ozonation alone, Mn and Ce co-doped γ-Al2O3 could remarkably enhance activities of catalytic ozonation for chemical oxygen demand (COD) removal (38.9%) of brine derived from a two-stage reverse osmosis treatment. Experimental and theoretical calculation results indicate that introducing Mn could increase the active points of catalyst surface, and introducing Ce could optimize d-band electronic structures and promote the electron transport capacity, enhancing HO• bound to the catalyst surface ([HO•]ads) generation. [HO•]ads plays key roles for degrading the intermediates and transfer them into low molecular weight organics, and further decrease COD, molecular weights and number of organics in reverse osmosis concentrate. Under the same reaction conditions, the presence of Mn/γ-Al2O3 catalyst can reduce ΔO3/ΔCOD by at least 37.6% compared to ozonation alone. Furthermore, Mn-Ce/γ-Al2O3 catalytic ozonation can reduce the ΔO3/ΔCOD from 2.6 of Mn/γ-Al2O3 catalytic ozonation to 0.9 in the case of achieving similar COD removal. Catalytic ozonation has the potential to treat reverse osmosis concentrate derived from bio-treated coking wastewater reclamation.

Catalytic ozonation of reverse osmosis membrane concentrates by catalytic ozonation: Properties and mechanisms

Ni-Mn@KL ozone catalyst was prepared for the efficient treatment of reverse osmosis membrane concentrates. The working conditions and reaction mechanism of the ozone-catalyzed oxidation by Ni-Mn@KL were systematically studied. Then, a comprehensive CRITIC weighting-coupling coordination evaluation model was established. Ni-Mn@KL was characterized by scanning electron microscopy, BET, X-ray diffraction, X-ray photoelectron spectroscopy, energy-dispersive spectrometry, and X-ray fluorescence spectrometry and found to have large specific surface area and homogeneous surface dispersion of striped particles. Under the optimum working conditions with an initial pH of 7.9 (raw water), a reaction height-to-diameter ratio of 10:1, an ozone-aeration intensity of 0.3 L/min, and a catalyst filling rate of 10%, the maximum COD removal rate was 60.5%. Free-radical quenching experiments showed that OH oxidation played a dominant role in the Ni-Mn@KL-catalyzed ozone-oxidation system, and the reaction system conformed to the second-order reaction kinetics law. Ni-Mn@KL catalysts were further confirmed to have good catalytic performance and mechanical performance after repeated utilization. PRACTITIONER POINTS: Ni-Mn@KL catalyst can achieve effective treatment of RO film concentrated liquid. High COD removal rate of RO membrane concentrated liquid was obtained at low cost. Ni-Mn@KL catalyst promotes ozone decomposition to produce ·OH and O2 -· oxidized organic matter. The Ni-Mn@KL catalyst can maintain good stability after repeated use. A CRITIC weight-coupling coordination model was established to evaluate the catalytic ozonation.

Understanding Stimulation of Conjugal Gene Transfer by Nonantibiotic Compounds: How Far Are We?

A myriad of nonantibiotic compounds is released into the environment, some of which may contribute to the dissemination of antimicrobial resistance by stimulating conjugation. Here, we analyzed a collection of studies to (i) identify patterns of transfer stimulation across groups and concentrations of chemicals, (ii) evaluate the strength of evidence for the proposed mechanisms behind conjugal stimulation, and (iii) examine the plausibility of alternative mechanisms. We show that stimulatory nonantibiotic compounds act at concentrations from 1/1000 to 1/10 of the minimal inhibitory concentration for the donor strain but that stimulation is always modest (less than 8-fold). The main proposed mechanisms for stimulation via the reactive oxygen species/SOS cascade and/or an increase in cell membrane permeability are not unequivocally supported by the literature. However, we identify the reactive oxygen species/SOS cascade as the most likely mechanism. This remains to be confirmed by firm molecular evidence. Such evidence and more standardized and high-throughput conjugation assays are needed to create technologies and solutions to limit the stimulation of conjugal gene transfer and contribute to mitigating global antibiotic resistance.

Origin of the Activity of Electrochemical Ozone Production Over Rutile PbO2 Surfaces

Ozonation water treatment technology has attracted increasing attention due to its environmental benign and high efficiency. Rutile PbO2 is a promising anode material for electrochemical ozone production (EOP). However, the reaction mechanism underlying ozone production catalyzed by PbO2 was rarely studied and not well-understood, which was in part due to the overlook of the electrochemistry-driven formation of oxygen vacancy (OV) of PbO2. Herein, we unrevealed the origin of the EOP activity of PbO2 starting from the electrochemical surface state analysis using density functional theory (DFT) calculations, activity analysis, and catalytic volcano modeling. Interestingly, we found that under experimental EOP potential (i. e., a potential around 2.2 V vs. reversible hydrogen electrode), OV can still be generated easily on PbO2 surfaces. Our subsequent kinetic and thermodynamic analyses show that these OV sites on PbO2 surfaces are highly active for the EOP reaction through an interesting atomic oxygen (O*)-O2 coupled mechanism. In particular, rutile PbO2(101) with the "in-situ" generated OV exhibited superior EOP activities, outperforming the (111) and (110) surfaces. Finally, by catalytic volcano modeling, we found that PbO2 is close to the theoretical optimum of the reaction, suggesting a superior EOP performance of rutile PbO2. All these analyses are in good agreement with previous experimental observations in terms of EOP overpotentials. This study provides the first volcano model to explain why rutile PbO2 is among the best metal oxide materials for EOP and provides new design guidelines for this rarely studied but industrially promising reaction.

Advanced oxidation processes for water and wastewater treatment - Guidance for systematic future research

Advanced oxidation processes (AOPs) are a growing research field with a large variety of different process variants and materials being tested at laboratory scale. However, despite extensive research in recent years and decades, many variants have not been transitioned to pilot- and full-scale operation. One major concern are the inconsistent experimental approaches applied across different studies that impede identification, comparison, and upscaling of the most promising AOPs. The aim of this tutorial review is to streamline future studies on the development of new solutions and materials for advanced oxidation by providing guidance for comparable and scalable oxidation experiments. We discuss recent developments in catalytic, ozone-based, radiation-driven, and other AOPs, and outline future perspectives and research needs. Since standardized experimental procedures are not available for most AOPs, we propose basic rules and key parameters for lab-scale evaluation of new AOPs including selection of suitable probe compounds and scavengers for the measurement of (major) reactive species. A two-phase approach to assess new AOP concepts is proposed, consisting of (i) basic research and proof-of-concept (technology readiness levels (TRL) 1-3), followed by (ii) process development in the intended water matrix including a cost comparison with an established process, applying comparable and scalable parameters such as UV fluence or ozone consumption (TRL 3-5). Subsequent demonstration of the new process (TRL 6-7) is briefly discussed, too. Finally, we highlight important research tools for a thorough mechanistic process evaluation and risk assessment including screening for transformation products that should be based on chemical logic and combined with complementary tools (mass balance, chemical calculations).

Performance evaluation and optimization of a suspension-type reactor for use in heterogeneous catalytic ozonation

Packed fixed-bed reactors are traditionally used for heterogeneous catalytic ozonation. However, a high solid-to-liquid requirement, poor ozone dissolution, ineffective utilization of catalyst surface area, and production of large amounts of catalyst waste impede application of such reactors. In this study, we designed a suspension catalytic ozonation reactor and compared the performance of this reactor with that of a traditional fixed-bed catalytic ozonation reactor employing oxalic acid (OA) as the target contaminant. Our results showed that total O3 dissolved into the suspension reactor (117-134 mg.L-1) was much higher compared to that measured in the fixed-bed reactor (53 mg.L-1) due to a higher O3(g) interphase mass transfer rate in the suspension reactor. In accordance with the higher O3(g) interphase mass transfer, we observed a much higher proportional OA removal (32 %) compared to that achieved in the fixed-bed reactor (10%) employing an Fe-oxide catalyst supported on Al2O3 (Fe-oxide@Al2O3) in both reactors. Use of a double-layered Cu-Al hydroxide (Cu-Al LDHs) catalyst in the suspension reactor further enhanced the performance with nearly 90 % OA removal observed. Given the superior performance of the suspension reactor, we investigated the impact of operating conditions (catalyst dosage, hydraulic retention time and ozone dosage) employing Cu-Al LDHs as the catalyst. We also developed a mathematical kinetic model to describe the performance of the suspension reactor and, through use of the kinetic model, showed that O3(g) interphase transfer rate was the rate-limiting step in OA removal. Thus, improvement in ozone gas diffuser design is required to improve the performance of the suspension reactor. Overall, the present study demonstrated that suspension reactors were more effective than fixed-bed reactors for oxidation of surface-active organic compounds such as OA due to the higher ozone interphase mass transfer rate and effective utilization of the catalyst surface area that can be achieved. As such, further research on suspension reactor design and development of catalysts suitable for use in suspension reactors should facilitate large-scale application of catalytic ozonation processes by the wastewater treatment industry.

Synergistic oxidation induced by underwater bubbling plasma and diatomite-CoFe2O4 activated peroxymonosulfate for the degradation of ciprofloxacin hydrochloride

Underwater bubbling plasma (UBP) coupled with diatomite-CoFe2O4 (Dt-CFO) activated peroxymonosulfate (PMS) was proposed for the degradation of ciprofloxacin hydrochloride (CIP) in this work. The catalyst sample of Dt-CFO with large specific surface area, rich active sites and excellent magnetic property was prepared by the hydrothermal method and systematically characterized to investigate its material properties. The combination of UBP and Dt-CFO activated PMS (UBP/Dt-CFO/PMS) showed excellent synergy with the synergistic factor of 1.98, and reached the CIP degradation percentage of 94.7%, which corresponded to the kinetic constant of 0.097 min-1. Dt-CFO with the diatomite content of 30 wt% achieved the best catalytic activity in the reaction system. Higher catalyst and PMS dose, peak voltage, pulse frequency and lower initial CIP concentration were beneficial for CIP removal. The addition of Cl-, HCO3-, SO42- and humic acid suppressed CIP degradation, while NO3- had no effect on CIP removal. The Dt-CFO composite exhibited excellent reusability and low leaching metal amount, demonstrating its good stability. SO4-·, ·OH, ·O2-, 1O2, eaq, O3 and H2O2 were the active species confirmed to be involved in CIP degradation. The redox circles of ≡ Co(Ⅱ)/≡Co(Ⅲ) and ≡ Fe(Ⅱ)/≡Fe(Ⅲ) on Dt-CFO surface and the plasma-induced physicochemical effects dominated PMS activation. The decomposition process of CIP was explored through fluorescence spectra. Three degradation pathways were inferred, and the toxicity analysis showed the toxicity of CIP solution weakened after discharge treatment.

Degradation of pharmaceuticals and other emerging pollutants employing bi-metal catalysts/magnesium and/or (green) hydrogen in aqueous solution

Contaminations by pharmaceuticals, personal care products, and other emerging pollutants in water resources have become a seriously burgeoning issue of global concern in the first third of the twenty-first century. As societal reliance on pharmaceuticals continues to escalate, the inadvertent introduction of these substances into water reservoirs poses a consequential environmental threat. Therefore, the aim of this study was to investigate reductive degradation, particularly, catalytic hydrogenation regarding model pollutants such as diclofenac (DCF), ibuprofen (IBP), 17α-ethinylestradiol (EE2), or bisphenol-A (BPA), respectively,  in aqueous solutions at lab scale. Iron bimetals (zero valent iron, ZVI, and copper, Cu, or nickel, Ni) as well as zero valent magnesium (Mg, ZVM) in combination with  rhodium, Rh, or palladium, Pd, as hydrogenation catalysts (HK), were investigated. Studies were executed through various short-term batch experiments, with multiple sample collections, over a total range of 120 min. The results indicated that DCF was attenuated at over 90 % when exposed to Fe-Cu or a Fe-Ni bimetal (applied as a single model pollutant). However, when DCF was part of a mixture alongside with IBP, EE2, and BPA, the attenuation efficacy decreased to 79 % with Fe-Cu and 23 % with Fe-Ni. Conversely, both IBP and BPA exhibit notably low attenuation levels with both bimetals, less than 50 %, both deployed as single substances or in mixtures. No reaction (degradation) products could be identified employing LC-MS, but sometimes a release of the parent pollutant when applying an acetic acid buffer could be noted to a certain extent, suggesting adsorption processes on corrosion products such as iron hydroxide and/or oxides. Surprisingly, Mg in combination with Rh (Rh-HK) or Pd (Pd-HK) showed a significantly rapid decrease in the concentrations of DCF, EE2, and BPA, in part up to approximately 100 %, that is, within a few minutes only in part due to hydrogenation degradation reactions (related reaction products could actually be identified by LC-MS; adsorption processes were not observed here). Moreover, kinetic modeling of the DCF degradation with Mg-Rh-HK was conducted at different temperatures (15 °C, 20 °C, 25 °C, 35 °C) and varied initial concentrations (2.5 mg/L, 5.0 mg/L, 7.5 mg/L, 10.0 mg/L). The outcomes prove that the degradation of DCF at the Rh-HK's surface followed a modified first-order kinetics, most probably by catalytic hydrodehalogenation and subsequent hydrogenation of the aromatic moieties (molecular hydrogen was provided by the corrosion of Mg). From the determined reaction rate constants at four different temperatures, the activation energy was estimated to be 59.6 kJ/mol by means of the Arrhenius equation what is in good agreement with similar results reported in the literature. This coupled hydrodehalogenation and hydrogenation approach may be upscaled into a new promising technical process for comprehensively removing such pharmaceuticals and similar pollutants in sewage plants in a single step, furthermore, even in combination with adsorption by activated carbon and/or ozonation which have already been established at some sewage plants in Switzerland and Germany recently.

TiO2-MoS2-PMMA Nanocomposites for an Efficient Water Remediation

An improvement of water supply and sanitation and better management of water resources, especially in terms of water reuse, is one of the priorities of the European Green Deal. In this context, it is crucial to find new strategies to recycle wastewater efficiently in a low-cost and eco-friendly manner. The immobilization of inorganic nanomaterials on polymeric matrices has been drawing a lot of attention in recent years due to the extraordinary properties characterizing the as-obtained nanocomposites. The hybrid materials, indeed, combine the properties of the polymers, such as flexibility, low cost, mechanical stability, high durability, and ease of availability, with the properties of the inorganic counterpart. In particular, if the inorganic fillers are nanostructured photocatalysts, the materials will be able to utilize the energy delivered by light to catalyze chemical reactions for efficient wastewater treatment. Additionally, with the anchoring of the nanomaterials to the polymers, the dispersion of the nanomaterials in the environment is prevented, thus overcoming one of the main limits that impede the application of nanostructured photocatalysts on a large scale. In this work, we will present nanocomposites made of polymers, i.e., polymethyl methacrylate (PMMA), and photocatalytic semiconductors, i.e., TiO2 nanoparticles (Evonik). MoS2 nanoflakes were also added as co-catalysts to improve the photocatalytic performance of the TiO2. The hybrid materials were prepared using the sonication and solution casting method. The nanocomposites were deeply characterized, and their remarkable photocatalytic abilities were evaluated by the degradation of two common water pollutants: methyl orange and diclofenac. The relevance of the obtained results will be discussed, opening the route for the application of these materials in photocatalysis and especially for novel wastewater remediation.

Three-Dimensional Printed Filters Based on Poly(ethylene glycol) Diacrylate Hydrogels Doped with Silver Nanoparticles for Removing Hg(II) Ions from Water

Nowadays, due to water pollution, more and more living beings are exposed to dangerous compounds, which can lead to them contracting diseases. The removal of contaminants (including heavy metals) from water is, therefore, a necessary aspect to guarantee the well-being of living beings. Among the most used techniques, the employment of adsorbent materials is certainly advantageous, as they are easy to synthesize and are cheap. In this work, poly(ethylene glycol) diacrylate (PEGDA) hydrogels doped with silver nanoparticles (AgNPs) for removing Hg(II) ions from water are presented. AgNPs were embedded in PEGDA-based matrices by using a photo-polymerizable solution. By exploiting a custom-made 3D printer, the filters were synthesized. The kinetics of interaction was studied, revealing that the adsorption equilibrium is achieved in 8 h. Subsequently, the adsorption isotherms of PEGDA doped with AgNPs towards Hg(II) ions were studied at different temperatures (4 °C, 25 °C, and 50 °C). In all cases, the best isotherm model was the Langmuir one (revealing that the chemisorption is the driving process and the most favorable one), with maximum adsorption capacities equal to 0.55, 0.57, and 0.61 mg/g, respectively. Finally, the removal efficiency was evaluated for the three temperatures, obtaining for 4 °C, 25 °C, and 50 °C the values 94%, 94%, and 86%, respectively.

Oxidative Dissolution Process of Sphalerite in Fe2(SO4)3-O3 System: Implications for Heavy Metals Removal and Recovery

Metal sulfides in waste rocks and tailings are susceptible to serious soil and water contamination due to the generation of acid mine drainage (AMD) during stockpiling. The hydrometallurgical process is one of the most essential heavy metal remediation technologies through harmless disposal and resource utilization of the waste sulfides. However, atmospheric hydrometallurgy of sulfides still faces great challenges due to low leaching efficiency and high cost. In this work, we proposed a cooperative leaching system (Fe2(SO4)3-O3) and investigated the oxidative dissolution process of sphalerite (ZnS). Under the optimal conditions, the extracted zinc reached 97.8%. Reactive oxygen species (ROS) (·OH, 1O2 and ·O2-) were identified in the radical quenching experiments. The dissolution of sphalerite did not show passivation due to the ozone's capability to oxidize the sulfur in sphalerite to sulfate. In addition, stirring rate, O3 inlet concentration, and Fe2(SO4)3 concentration had a significant effect on the dissolution of sphalerite. Meanwhile, the apparent activation energy was 24.11 kJ/mol based on kinetic fitting, which indicated that the controlling step of the reaction was mainly a diffusion process. This work demonstrated the cooperative effect of sphalerite leaching in the O3-Fe2(SO4)3 system and provided a theoretical reference for efficient and atmospheric dissolution of sphalerite.

Influence of ozonation and UV/H2O2 on the genotoxicity of secondary wastewater effluents

The implementation of novel wastewater treatment technologies, including Advanced Oxidation Processes (AOPs) such as ozonation and ultraviolet radiation (UV) combined with hydrogen peroxide (H2O2), can be a promising strategy for enhancing the quality of these effluents. However, during effluent oxidation AOPs may produce toxic compounds that can compromise the water reuse and the receiving water body. Given this possibility, the aim of this study was to evaluate the genotoxic potential of secondary effluents from two different Wastewater Treatment Plants (WWTP) that were subjected to ozonation or UV/H2O2 for periods of 20 (T1) and 40 (T2) minutes. The genotoxic potential was carried out with the Comet assay (for clastogenic damage) and the Micronucleus assay (for clastogenic and aneugenic damage) in HepG2/C3A cell culture (metabolizing cell line). The results of the comet assay revealed a significant increase in tail intensity in the Municipal WWTP (dry period) effluents treated with UV/H2O2 (T1 and T2). MN occurrence was noted across all treatments in both Pilot and Municipal WWTP (dry period) effluents, whereas nuclear buds (NBs) were noted for all Pilot WWTP treatments and UV/H2O2 treatments of Municipal WWTP (dry period). Moreover, the UV/H2O2 (T1) treatment of Municipal WWTP (dry period) exhibited a noteworthy incidence of multiple alterations per cell (MN + NBs). These findings imply that UV/H2O2 treatment demonstrates higher genotoxic potential compared to ozonation. Furthermore, seasonal variations can have an impact on the genotoxicity of the samples. Results of the study emphasize the importance of conducting genotoxicological tests using human cell cultures, such as HepG2/C3A, to assess the final effluent quality from WWTP before its discharge or reuse. This precaution is essential to safeguard the integrity of the receiving water body and, by extension, the biotic components it contains.

Integrated model of ozone mass transfer and oxidation kinetic: Construction, solving and analysis

Ozone-based advanced oxidation process (O3-AOPs) is rapidly evolving, but the surge of emerging pollutants brings new challenges for ozone oxidation research. Herein, we proposed a state-of-the-art model for simultaneously analyzing both ozone mass transfer and oxidation kinetics during ozone oxidation of emerging organic contaminants. The numerical solution and graphical representations of the integrated model were utilized to analyze the dynamics of ozone and pollutant concentration. An in-depth analysis of the integrated model revealed that the reaction rate constants in this present study were higher than previously reported apparent reaction rate constants, and catalysts were not always necessary. Finally, we developed an installable mobile application (APP) that allowed the simulation of the dynamic process for ozone oxidizing organic pollutants in the laboratory, which offered theoretical support for the selection of experimental conditions. The results of model simulation not only provide scientific explanations for counter-intuitive experimental phenomena, but also optimized experimental conditions to enhance ozone utilization.

Cobalt doping amount determines dominant reactive species in peroxymonosulfate activation via porous carbon catalysts co-doped by cobalt and nitrogen

Switching the reaction routes in peroxymonosulfate (PMS)-based advanced oxidation processes have attracted much attention but remain challenging. Herein, a series of Co-N/C catalysts with different compositions and structures were prepared by using bimetallic zeolitic imidazolate frameworks based on ZIF-8 and ZIF-67 (xZn/Co-ZIFs). Results show that Co doping amount could mediate the transformation of the activation pathway of PMS over Co-N/C. When Co doping amount was less than 10%, the constructed xCo-N/C/PMS system (x ≤ 10%) was singlet oxygen-dominated reaction; however further increasing Co doping amount would lead to the generation and coexistence of sulfate radicals and high-valent cobalt, besides singlet oxygen. Furthermore, the nitrogen-coordinated Co (Co-NX) sites could serve as main catalytically active sites to generate singlet oxygen. While excess Co doping amount caused the formation of Co nanoparticles from which leached Co ions were responsible for the generation of sulfate radicals and high-valent cobalt. Compared to undoped N/C, Co doping could significantly enhance the catalytic performance. The 0.5% Co-N/C could achieve the optimum degradation (0.488 min-1) and mineralization abilities (78.4%) of sulfamethoxazole among the investigated Co-N/C catalysts, which was superior to most of previously reported catalysts. In addition, the application prospects of the two systems in different environmental scenarios (pH, inorganic anions and natural organic matter) were assessed and showed different degradation behaviors. This study provides a strategy to regulate the reactive species in PMS-based advanced oxidation process.

An insight into the role of experimental parameters in advanced oxidation process applied for pharmaceutical degradation

The advanced oxidation process (AOP) is an efficient method to treat recalcitrance pollutants such as pharmaceutical compounds. The essential physicochemical factors in AOP experiments significantly influence the efficiency, speed, cost, and safety of byproducts of the treatment process. In this review, we collected recent articles that investigated the elimination of pharmaceutical compounds by various AOP systems in a water medium, and then we provide an overview of AOP systems, the formation mechanisms of active radicals or reactive oxygen species (ROS), and their detection methods. Then, we discussed the role of the main physicochemical parameters (pH, chemical interference, temperature, catalyst, pollutant concentration, and oxidant concentration) in a critical way. We gained insight into the most frequent scenarios for the proper and improper physicochemical parameters for the degradation of pharmaceutical compounds. Also, we mentioned the main factors that restrict the application of AOP systems in a commercial way. We demonstrated that a proper adjustment of AOP experimental parameters resulted in promoting the treatment performance, decreasing the treatment cost and the treatment operation time, increasing the safeness of the system products, and improving the reaction stoichiometric efficiency. The outcomes of this review will be beneficial for future AOP applicants to improve the pharmaceutical compound treatment by providing a deeper understanding of the role of the parameters. In addition, the proper application of physicochemical parameters in AOP systems acts to track the sustainable development goals (SDGs).

Defluorination of perfluorooctanoic acid and perfluorooctane sulfonic acid by heterogeneous catalytic system of Fe-Al2O3/O3: Synergistic oxidation effects and defluorination mechanism

In this study, catalytic ozonation by Fe-Al2O3 was used to investigate the defluorination of PFOA and PFOS, assessing the effects of different experimental conditions on the defluorination efficiency of the system. The oxidation mechanism of the Fe-Al2O3/O3 system and the specific degradation and defluorination mechanisms for PFOA and PFOS were determined. Results showed that compared to the single O3 system, the defluorination rates of PFOA and PFOS increased by 2.32- and 5.92-fold using the Fe-Al2O3/O3 system under optimal experimental conditions. Mechanistic analysis indicated that in Fe-Al2O3, the variable valence iron (Fe) and functional groups containing C and O served as important reaction sites during the catalytic process. The co-existence of 1O2, OH, O2- and high-valence Fe(IV) constituted a synergistic oxidation system consisting of free radicals and non-radicals, promoting the degradation and defluorination of PFOA and PFOS. DFT theoretical calculations and the analysis of intermediate degradation products suggested that the degradation pathways of PFOA and PFOS involved Kolbe decarboxylation, desulfonation, alcoholization and intramolecular cyclization reactions. The degradation and defluorination pathways of PFOA and PFOS consisted of the stepwise removal of -CF2-, with PFOS exhibiting a higher defluorination rate than PFOA due to its susceptibility to electrophilic attack. This study provides a theoretical basis for the development of heterogeneous catalytic ozonation systems for PFOA and PFOS treatment.

The critical role of microplastics in the fate and transformation of sulfamethoxazole and antibiotic resistance genes within vertical subsurface-flow constructed wetlands

Constructed wetlands (CWs) are reservoirs of microplastics (MPs) in the environment. However, knowledge about the impact of MPs on antibiotic removal and the fate of antibiotic resistance genes (ARGs) is limited. We focused on sulfamethoxazole (SMX) as a representative compound to examine the effects of MPs on SMX removal and the proliferation and dissemination of two SMX-related ARGs (sul1 and sul2) in vertical subsurface-flow CW (VFCW) microcosm. The presence of MPs in the substrate was found to enhance the proliferation of microorganisms owing to the large specific surface area of the MPs and the release of dissolved organic carbon (DOC) on MP surfaces, which resulted in a high SMX removal ranging from 97.80 % to 99.80 %. However, the presence of MPs promoted microbial interactions and the horizontal gene transfer (HGT) of ARGs, which led to a significant increase in the abundances of sul1 and sul2 of 68.47 % and 17.20 %, respectively. It is thus imperative to implement rigorous monitoring strategies for MPs to mitigate their potential ecological hazards.

Application of artificial intelligence for the optimization of advanced oxidation processes to improve the water quality polluted with pharmaceutical compounds

Sulfamethoxazole and metronidazole are emerging pollutants commonly found in surface water and wastewater. These compounds have a significant environmental impact, being necessary in the design of technologies for their removal. Recently, the advanced oxidation process has been proven successful in the elimination of this kind of compounds. In this sense, the present work discusses the application of UV/H2O2 and ozonation for the degradation of both molecules in single and binary systems. Experimental kinetic data from O3 and UV/H2O2 process were adequately described by a first and second kinetic model, respectively. From the ANOVA analysis, it was determined that the most statistically significant variables were the initial concentration of the drugs (0.03 mmol L-1) and the pH = 8 for UV/H2O2 system, and only the pH (optimal value of 6) was significant for degradation with O3. Results showed that both molecules were eliminated with high degradation efficiencies (88-94% for UV/H2O2 and 79-98% for O3) in short reaction times (around 30-90 min). The modeling was performed using a quadratic regression model through response surface methodology representing adequately 90 % of the experimental data. On the other hand, an artificial neural network was used to evaluate a non-linear multi-variable system, a 98% of fit between the model and experimental data was obtained. The identification of degradation byproducts was performed by high-performance liquid chromatography coupled to a time mass detector. After each process, at least four to five stable byproducts were found in the treated water, reducing the mineralization percentage to 20% for both molecules.

Current trends in textile wastewater treatment-bibliometric review

A bibliometric study using 1992 to 2021 database of the Science Citation Index Expanded was carried out to identify which are the current trends in textile wastewater treatment research. The study aimed to analyze the performance of scholarly scientific communications in terms of yearly publications/citations, total citations, scientific journals, and their categories in the Web of Sciences, top institutions/countries and research trends. The annual publication of scientific articles fluctuated in the first ten years, with a steady decrease for the last twenty years. An analysis of the most common terms used in the authors' keywords, publications' titles, and KeyWords Plus was carried out to predict future trends and current research priorities. Adsorbent nanomaterials would be the future of wastewater treatment for decoloration of the residual dyes in the wastewater. Membranes and electrolysis are important to demineralize textile effluent for reusing wastewater. Modern filtration techniques such as ultrafiltration and nanofiltration are advanced membrane filtration applications.

Oxidative treatment of micropollutants present in wastewater: A special emphasis on transformation products, their toxicity, detection, and field-scale investigations

Micropollutants have become ubiquitous in aqueous environments due to the increased use of pharmaceuticals, personal care products, pesticides, and other compounds. In this review, the removal of micropollutants from aqueous matrices using various advanced oxidation processes (AOPs), such as photocatalysis, electrocatalysis, sulfate radical-based AOPs, ozonation, and Fenton-based processes has been comprehensively discussed. Most of the compounds were successfully degraded with an efficiency of more than 90%, resulting in the formation of transformation products (TPs). In this respect, degradation pathways with multiple mechanisms, including decarboxylation, hydroxylation, and halogenation, have been illustrated. Various techniques for the analysis of micropollutants and their TPs have been discussed. Additionally, the ecotoxicity posed by these TPs was determined using the toxicity estimation software tool (T.E.S.T.). Finally, the performance and cost-effectiveness of the AOPs at the pilot scale have been reviewed. The current review will help in understanding the treatment efficacy of different AOPs, degradation pathways, and ecotoxicity of TPs so formed.

Innovative technologies for removal of micro plastic: A review of recent advances

Plastics are becoming a pervasive pollutant in every environmental matrix, particularly in the aquatic environment. Due to increased plastic usage and its impact on human and aquatic life, microplastic (MP) pollution has been studied extensively as a global issue. The production of MP has been linked to both consumer and commercial practices. There is a significant amount of MP's that must be removed by wastewater treatment plants before they can be bioaccumulated. Many researchers have recently become interested in the possibility of eliminating MPs in wastewater treatment plants (WWTP). Many studies have analyzed MP's environmental effects, including its emission sources, distribution, and impact on the surrounding environment. The effectiveness of their removal by various wastewater treatment technologies requires a critical review that accounts for all these methods. In this review, we have covered the most useful technologies for the removal of MP during WWTP. The findings of this review should help scientists and policymakers move forward with studies, prototypes, and proposals for significant remediation impact on water quality.

Insights into enhanced oxidation of benzophenone-type UV filters (BPs) by ferrate(VI)/ferrihydrite: Increased conversion of Fe(VI) to Fe(V)/Fe(IV)

In this work, the oxidation performance of a new ferrate(VI)/ferrihydrite (Fe(VI)/Fh) system was systematically explored to degrade efficiently six kinds of benzophenone-type UV filters (BPs). Fe(VI)/Fh system not only had a superior degradation capacity towards different BPs, but also exhibited higher reactivity over a pH range of 6.0-9.0. The second-order kinetic model successfully described the process of BP-4 degradation by heterogeneous Fh catalyzed Fe(VI) system (R2 = 0.93), and the presence of Fh could increase the BP-4 degradation rate by Fe(VI) by an order of magnitude (198 M-1·s-1 v.s. 14.2 M-1·s-1). Remarkably, there are higher utilization efficiency and potential of Fe(VI) in Fe(VI)/Fh system than in Fe(VI) alone system. Moreover, characterization and recycling experiments demonstrated that Fh achieved certain long-term running performance, and the residual Fe content of solution after clarifying process meet World Health Organization (WHO) guidelines for drinking water. The contributions of reactive species could be ranked as Fe(V)/Fe(IV) > Fe(VI) > •OH. Fe(IV)/Fe(V) were the dominant species for the enhanced removal in the Fe(VI)/Fh system, whose percentage contribution (72 %-36 %) were much higher than those in Fe(VI) alone system (5 %-17 %). However, the contribution of Fe(VI) in oxidizing BP-4 should not be underestimated (20 %-56 %). These findings reasonably exploit available Fh resources to reduce the relatively high cost of Fe(VI), which offers a proper strategies for efficient utilization of high-valent iron species and may be used as a highly-efficient and cost-effective BPs purification method.

Catalytic Ozonation of Reactive Black 5 in Aqueous Solution Using Iron-Loaded Dead Leaf Ash for Wastewater Remediation

In the current study, iron-loaded dead leaf ash (Fe-DLA) was used as a novel catalyst in the heterogeneous catalytic ozonation process (HCOP) for textile wastewater containing Reactive Black 5 (RB-5). The research demonstrates a significant boost in removal efficiency, reaching 98.76% with 1.0 g/min O3 and 0.5 g/L catalyst dose, by investigating key variables such as pH, ozone and catalyst doses, initial concentration, and the presence of scavengers in 1 L wastewater. The addition of tert-butyl alcohol (TBA) reduced RB-5 elimination, indicating the involvement of OH radicals. Catalyst reusability decreased slightly (2.05% in the second run; 4.35% in the third), which was attributed to iron leaching. A comparison of single ozonation (Fe-DLA) adsorption and catalytic ozonation processes (Fe-DLA/O3) revealed that the combined process improved dye degradation by 25%, with removal rates ranking as Fe-DLA adsorption O3 Fe-DLA/O3, with an impressive 76.44% COD removal. These results strongly support RB-5 removal using Fe-DLA and HCOP at a basic pH, highlighting the catalyst's utility in practical wastewater treatment.

Abatement of antibiotics and resistance genes during catalytic ozonation enhanced sludge dewatering process: Synchronized in volume and hazardousness reduction

Based on the efficiency of the catalytic ozonation techniques (HDWS+O3 and MnFe2O4 @SBC+O3) in enhancing the sludge dewaterability, the effectiveness in synchronized abatement antibiotics and antibiotic resistance genes (ARGs) was conducted to determine. The results revealed that catalytic ozonation conditioning altered the distribution of target antibiotics (tetracycline (TC), oxytetracycline (OTC), norfloxacin (NOR), ofloxacin (OFL)) in the dewatered filtrate, the dewatered sludge cake and the extra-microcolony/cellular polymers (EMPS/ECPS) layers, achieving the redistribution from solid-phase adsorption to liquid-phase dissolution. The total degradation rate was over 90% for TC and OTC, 72-78% for NOR and OFL; the abatement efficiency of eleven ARGs reached 1.47-3.01 log and 1.64-3.59 log, respectively, and more than four eARGs were eliminated. The effective abatement of the absolute abundance of Mobile genetic elements (MGEs) (0.91-1.89 log) demonstrated that catalytic ozonation conditioning could also significantly inhibit horizontal gene transfer (HGT). The abundance of resistant bacteria was greatly reduced and the signal transduction of the typical ARGs host bacteria was inhibited. The highly reactive oxidation species (ROS) generated were responsible for the abatement of antibiotics and ARGs. These findings provided new insights into the sludge conditioning for ideal and synchronized reduction in volume and hazardousness by catalytic ozonation processes in sludge treatment.

Advanced treatment of coking wastewater: Recent advances and prospects

Advanced treatment of refractory industrial wastewater is still a challenge. Coking wastewater is one of coal chemical wastewater, which contains various refractory organic pollutants. To meet the more and more rigorous discharge standard and increase the reuse ratio of coking wastewater, advanced treatment process must be set for treating the biologically treated coking wastewater. To date, several advanced oxidation processes (AOPs), including Fenton, ozone, persulfate-based oxidation, and iron-carbon micro-electrolysis, have been applied for the advanced treatment of coking wastewater. However, the performance of different advanced treatment processes changed greatly, depending on the components of coking wastewater and the unique characteristics of advanced treatment processes. In this review article, the state-of-the-art advanced treatment process of coking wastewater was systematically summarized and analyzed. Firstly, the major organic pollutants in the secondary effluents of coking wastewater was briefly introduced, to better understand the characteristics of the biologically treated coking wastewater. Then, the performance of various advanced treatment processes, including physiochemical methods, biological methods, advanced oxidation methods and combined methods were discussed for the advanced treatment of coking wastewater in detail. Finally, the conclusions and remarks were provided. This review will be helpful for the proper selection of advanced treatment processes and promote the development of advanced treatment processes for coking wastewater.

Aluminum-based ozone catalysts prepared by mixing method: Characteristics, performance and carbon emissions

Green and low carbon is an essential direction for the development of water treatment technology. Ozone catalysts prepared by the mixing method have advantages in terms of energy consumption and CO2 emissions, but are considered to be insufficient in catalytic efficiency and stability. In this paper, an Mn-Cu-Ce/Al2O3 (MCCA) catalyst was prepared by optimizing the preparation conditions of the mixing method and the types and ratios of active components. Taking petrochemical secondary effluent (PCSE) as the treatment object, the performance of the catalyst and the carbon emission in the preparation process were studied; and compared with the impregnation method. Results showed that compared with catalysts loaded with other components, the MCCA had a higher removal efficiency for TOC (43.04%) and COD (53.18%), which was basically equivalent to the impregnation method, and the treated effluent reached the expected concentration. MCCA promoted the decomposition rate of O3 by ten times, and the main active species generated were found to be •OH and 1O. Similar to the catalytic ozonation by the catalyst prepared by the impregnation method, the adsorption sites and surface hydroxyl groups on the MCCA surface play a significant role in the degradation of pollutants. However, the carbon emission in the catalyst preparation process of the mixing method was 418.68 kg/ton, which was only 44% of the impregnation method (949.67 kg/ton). Under the global low-carbon transition, this study shows that the mixing method aligns more with the concept of green, clean, and efficient ozone catalyst preparation.

3D Carbon Microspheres with a Maze-Like Structure and Large Mesopore Tunnels Built From Rapid Aerosol-Confined Coherent Salt/Surfactant Templating

Hierarchically porous carbons with tailor-made properties are essential for applications wherein rich active sites and fast mass transfer are required. Herein, a rapid aerosol-confined salt/surfactant templating approach is proposed for synthesizing hierarchically porous carbon microspheres (HPCMs) with a maze-like structure and large mesopore tunnels for high-performance tri-phase catalytic ozonation. The confined assembly in drying microdroplets is crucial for coherent salt (NaCl) and surfactant (F127) dual templating without macroscopic phase separation. The HPCMs possess tunable sizes, a maze-like structure with highly open macropores (0.3-30 µm) templated from NaCl crystal arrays, large intrawall mesopore tunnels (10-45 nm) templated from F127, and rich micropores (surface area >1000 m2 g-1 ) and oxygen heteroatoms originated from NaCl-confined carbonization of phenolic resin. The structure formation mechanism of the HPCMs and several influencing factors on properties are elaborated. The HPCMs exhibit superior performance in gas-liquid-solid tri-phase catalytic ozonation for oxalate degradation, owing to their hierarchical pore structure for fast mass transfer and rich defects and oxygen-containing groups (especially carbonyl) for efficient O3 activation. The reactive oxygen species responsible for oxalate degradation and the influences of several structure parameters on performance are discussed. This work may provide a platform for producing hierarchically porous materials for various applications.

Integrated Fenton-like and ozonation based advanced oxidation processes for treatment of real-time textile effluent containing azo reactive dyes

The treatment of real-time textile effluent, collected from the Common Effluent Treatment Plant (CETP) of Kerala Industrial Infrastructure Development Corporation (KINFRA) at Kannur (District), Kerala (State), India, have been studied by utilizing the Fenton-like and ozone (O3) based advanced oxidation processes (AOPs). The Fenton-like AOP has been conducted as the pre-treatment of textile effluent involving the activation of persulfate (PS) and hydrogen peroxide (H2O2) as a single and the mixed oxidants by using the Flyash (FA)-Pd composite particles as the activator. The maximum chemical oxygen demand (COD) removal of 84% has been observed for a stand-alone O3 based treatment at an O3 flow rate of 5-6 g h-1. By conducting the pre-treatment of textile effluent with the PS, H2O2, and mixed oxidants (PS and H2O2) based Fenton-like AOPs, the COD removal after an O3 based post-treatment has been observed to be 83, 87, and 93% respectively at an O3 flow rate of 2, 3, and 5 g h-1. Hence, the Fenton-like pre-treatment involving the activation of mixed oxidants has been determined to be the best method for the highest COD removal of real-time textile effluent. The optimum values of initial oxidant-ratio (initial [H2O2]:initial [PS]), initial oxidant-dosage, and ozonation time, for the mixed oxidants based Fenton-like pre-treatment, have been determined to be 3 wt% mM-1, 6:2 wt% mM-1, and 60 min respectively. Under the most optimum conditions, the COD removal has been attributed to the combination of O2•- (for the pre-treatment) and •OOH (for the post-treatment) which possess relatively lower oxidation potential values.

The synergistic effect of oxidant-peroxide coupling systems for water and wastewater treatments

With the growing complexity and severity of water pollution, it has become increasingly challenging to effectively remove contaminants or inactivate microorganisms just by traditional chemical oxidants such as O3, chlorine, Fe(VI) and Mn(VII). Up till now, numerous studies have indicated that these oxidants in combination with peroxides (i.e., hydrogen peroxide (H2O2), peroxymonosulfate (PMS), peracetic acid (PAA) and periodate (PI)) exhibited excellent synergistic oxidation. This paper provided a comprehensive review on the combination of aforementioned oxidant-peroxide applied in water and wastewater treatments. From one aspect, the paper thoroughly elucidated the synergy mechanism of each oxidant-peroxide combination in turn. Among these combinations, H2O2 or PMS generally performed as the activator of four traditional oxidants above to accelerate reactive species generation and therein various reaction mechanisms, including electron transfer, O atom abstraction and oxo ligand substitution, were involved. In addition, although neither PAA nor PI was able to directly activate Fe(VI) and Mn(VII), they could act as the stabilizer of intermediate reactive iron/manganese species to improve the latter utilization efficiency. From another aspect, this paper summarized the influence of water quality parameters, such as pH, inorganic ions and natural organic matter (NOM), on the oxidation performance of most combined systems. Finally, this paper highlighted knowledge gaps and identified areas that require further research.

Catalytic Ozonation of Air toward Direct Nitric Acid Production Using Hierarchical Co3O4 with a Tunable Microstructure

The nitrogen oxidation reaction (NOR) to form nitric acid by applying natural air and H2O under ambient conditions is a sustainable approach to achieving efficient and selective N2 fixation for industrial applications. In this study, four kinds of Co3O4 catalysts with a controllable microstructure were prepared to catalyze the direct NOR of N2 in the air. At the same time, the reaction mechanism of the conversion of N2 to nitric acid under catalytic ozonation was explored through experimental research and density functional theory (DFT) calculation. The results showed that the prepared porous nanosheets self-assembled into microflower-structured samples. The HCOF showed extraordinary catalytic performance for direct NOR to produce a high concentration of nitric acid. The maximum rate of nitric acid formation could be as high as 6.67 mmol/(h·gcat), which was higher than those of most reported photocatalytic or electrocatalytic N2 fixation processes for direct NOR to produce NO3-. Furthermore, the 15N isotopic-labeling experiment confirmed that the produced NO3- originated from N2 in the air by the direct NOR process. In the direct NOR mechanism, inert N2 molecules were captured at the Co3+ active sites by the acceptance-donation electron conduction mode, and the oxygen vacancies boosted the chemical adsorption of N2 molecules and greatly reduced the activation energy barrier of N2 molecules. The active free radicals •OH and •O2- generated by the decomposition of O3 molecules oxidized N2 to the intermediate *NO, which was the rate-determining step, and it was then absorbed by water to form nitric acid. The air catalytic ozonation method in this study was proposed as a facile pathway for efficient nitrogen fixation. This research provides a new method for environmental protection and efficient production of nitric acid at distributed sources.