Editorial Board Members’ Collection Series: Advanced Oxidation Processes of Organic Contaminants

A special issue of Toxics (ISSN 2305-6304). This special issue belongs to the section "Toxicity Reduction and Environmental Remediation".

Deadline for manuscript submissions: closed (10 February 2024) | Viewed by 11065

Special Issue Editors


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Guest Editor
School of Environment, Nanjing University, Nanjing, China
Interests: advanced oxidation techniques; photocatalysis; ozonation; environmental theoretical chemistry; QSAR
Special Issues, Collections and Topics in MDPI journals

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Guest Editor
College of Natural Resources and Environment, Northwest A&F University, Yangling, China
Interests: wastewater treatment; advanced oxidation techniques; discharge plasma; ozonation; electrochemical oxidation; disinfection by-products; antibiotic resistant bacteria; environmental catalytic materials

Special Issue Information

Dear Colleagues,

Organic pollutants are becoming an increasingly critical threat to ecosystems and human health, resulting in a growing body of research and resources. With the increasing need for environmental measures, such as sustainable development goals and carbon neutrality, efficient and high-purification technologies for wastewater treatment are indispensable.

Therefore, it is important to develop innovative advanced oxidation technologies based on new ideas.

The editors of this Special Issue encourage all interested authors to submit their best manuscripts related to organic pollutant removal by various advanced oxidation techniques. The aim is to improve the knowledge within this field, as well as to open new views and perspectives on this topic.

Prof. Dr. Zunyao Wang
Prof. Dr. Tiecheng Wang
Guest Editors

Manuscript Submission Information

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Keywords

  • wastewater treatment
  • organic contaminants
  • Fenton oxidation
  • persulfate oxidation
  • electrochemical oxidation
  • photocatalytic oxidation
  • ozonation
  • discharge plasma

Published Papers (10 papers)

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Research

15 pages, 1150 KiB  
Article
Transformation and Degradation of PAH Mixture in Contaminated Sites: Clarifying Their Interactions with Native Soil Organisms
by Xiaoyu Li, Shengnan Zhang, Ruixue Guo, Xuejing Xiao, Boying Liu, Rehab Khaled Mahmoud, Mostafa R. Abukhadra, Ruijuan Qu and Zunyao Wang
Toxics 2024, 12(5), 361; https://doi.org/10.3390/toxics12050361 - 13 May 2024
Viewed by 494
Abstract
Soil contamination of polycyclic aromatic hydrocarbons (PAHs), especially caused by the mixture of two or more PAHs, raised great environmental concerns. However, research on the migration and transformation processes of PAHs in soils and their interactions with native communities is limited. In this [...] Read more.
Soil contamination of polycyclic aromatic hydrocarbons (PAHs), especially caused by the mixture of two or more PAHs, raised great environmental concerns. However, research on the migration and transformation processes of PAHs in soils and their interactions with native communities is limited. In this work, soil samples from uncontaminated sites around the industrial parks in Handan, Hengshui, and Shanghai were artificially supplemented with three concentrations of anthracene (Ant), 9-chloroanthracene (9-ClAnt), benzopyrene (BaP), and chrysene (Chr). Ryegrass was planted to investigate the degradation of PAHs and its interaction with native soil organisms in the constructed ryegrass–microbe–soil microcosmic system. The bacterial and fungal communities in soil were affected by PAHs; their species diversity and relative abundance changed after exposure to different concentrations of PAHs, among which Lysobacter, Bacillus, Pseudomonas, and Massilia bacteria were correlated to the degradation of PAHs. On the 56th day, the contents of BaP, Chr, and Ant decreased with the degradation process, while the degradation of 9-ClAnt was limited. Nineteen intermediates, including hydroxylation and carboxylated compounds, were identified. The present research would help clarify the potential interactions between PAHs and native organisms in contaminated sites, providing fundamental information for evaluating the transformation risks of PAHs in the natural environment. Full article
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23 pages, 3719 KiB  
Article
Identification and Mechanistic Analysis of Toxic Degradation Products in the Advanced Oxidation Pathways of Fluoroquinolone Antibiotics
by Shuhai Sun, Zhonghe Wang, Qikun Pu, Xinao Li, Yuhan Cui, Hao Yang and Yu Li
Toxics 2024, 12(3), 203; https://doi.org/10.3390/toxics12030203 - 6 Mar 2024
Viewed by 870
Abstract
The degradation of fluoroquinolones (FQs) via advanced oxidation processes (AOPs) is a promising avenue, yet the complete mineralization of certain FQ molecules remains elusive, raising concerns about the formation of toxic by-products. This study delineates five primary AOP degradation pathways for 16 commercially [...] Read more.
The degradation of fluoroquinolones (FQs) via advanced oxidation processes (AOPs) is a promising avenue, yet the complete mineralization of certain FQ molecules remains elusive, raising concerns about the formation of toxic by-products. This study delineates five primary AOP degradation pathways for 16 commercially available FQ molecules, inferred from existing literature. Density functional theory (DFT) was employed to calculate the bond dissociation energies within these pathways to elucidate the correlation between bond strength and molecular architecture. Subsequently, Comparative Molecular Similarity Index Analysis (CoMSIA) models were constructed for various degradation reactions, including piperazine ring cleavage, defluorination, hydroxylation, and piperazine ring hydroxylation. Three-dimensional contour maps generated from these models provide a deeper understanding of the interplay between FQ molecular structure and bond dissociation energy. Furthermore, toxicity predictions for 16 FQ molecules and their advanced oxidation intermediates, conducted using VEGA 1.2.3 software, indicate that degradation products from pathways P2 and P5 pose a heightened health risk relative to their parent compounds. Furthermore, the application of the Multwfn program to compute the Fukui function for FQ molecules discerns the disparity in degradation propensities, highlighting that N atoms with higher f0 values can augment the likelihood of piperazine ring cleavage. HOMO-LUMO distribution diagrams further confirm that methoxy substitution at the 1-position leads to a dilution of HOMOs on the piperazine ring and an increased energy gap for free radical reactions, diminishing the reactivity with hydroxyl radicals. This study elucidates the pivotal role of structural characteristics in FQ antibiotics for their degradation efficiency within AOPs and unveils the underlying mechanisms of bond dissociation energy disparities. The toxicity parameter predictions for FQ molecules and their intermediates offer unique perspectives and theoretical underpinnings for mitigating the use of high-risk FQs and for devising targeted degradation strategies to circumvent the generation of toxic intermediates in AOPs through molecular structure optimization. Full article
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18 pages, 1487 KiB  
Article
Sequential Treatment by Ozonation and Biodegradation of Pulp and Paper Industry Wastewater to Eliminate Organic Contaminants
by Jessica Amacosta, Tatyana Poznyak, Sergio Siles and Isaac Chairez
Toxics 2024, 12(2), 138; https://doi.org/10.3390/toxics12020138 - 8 Feb 2024
Viewed by 1120
Abstract
In this research, the decomposition of toxic organics from pulp and paper mill effluent by the sequential application of ozonation and biodegradation was studied. Ozonation, as a pre-treatment, was executed to transform the initial pollutants into less toxic compounds (such as organic acids [...] Read more.
In this research, the decomposition of toxic organics from pulp and paper mill effluent by the sequential application of ozonation and biodegradation was studied. Ozonation, as a pre-treatment, was executed to transform the initial pollutants into less toxic compounds (such as organic acids of low molecular weights). Biodegradation was executed during three days with acclimated microorganisms that were able to complete the decomposition of the initial organic mixture (raw wastewater) and to achieve a higher degree of mineralization (85–90%). Experiments were performed under three different conditions: (a) only ozonation of the initial contaminants, (b) only biodegradation of residual water without previous treatment by ozone and (c) ozonation followed by biodegradation performed by acclimated microorganisms. In the case of 72 h of biodegradation, the mineralization efficiency reached 85% and 89% after 30 and 60 min of ozonation, respectively. The no significant difference in this parameter coincided with the calculated generalized microorganisms’ consortia specific growing rate μmax that was reduced from 2.08 × 10−3 h−1 to 6.05 × 10−4 h−1 when the ozonation time was longer. The identification of the organics composition by gas chromatography with mass detector (GC-MS) before and after treatments confirmed that the proposed combined process served as a more efficient alternative to secondary and tertiary treatments (mineralization degree between 60 and 80% in average) of the paper industry wastewater. Full article
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13 pages, 1717 KiB  
Article
Study on the Direct and Indirect Photolysis of Antibacterial Florfenicol in Water Using DFT/TDDFT Method and Comparison of Its Reactivity with Hydroxyl Radical under the Effect of Metal Ions
by Yue Kang, Ying Lu and Se Wang
Toxics 2024, 12(2), 127; https://doi.org/10.3390/toxics12020127 - 3 Feb 2024
Viewed by 1227
Abstract
Florfenicol (FLO) is a widely used antibacterial drug, which is often detected in the environment. In this paper, the photolysis mechanism of FLO in water was investigated using density functional theory (DFT) and time-dependent density functional theory (TDDFT). The focus of the study [...] Read more.
Florfenicol (FLO) is a widely used antibacterial drug, which is often detected in the environment. In this paper, the photolysis mechanism of FLO in water was investigated using density functional theory (DFT) and time-dependent density functional theory (TDDFT). The focus of the study is to elucidate the direct photolysis mechanism of FLO in the water environment and the indirect photolysis of free radicals (·OH, ·NO3, and ·SO4) as active species. The effect of metal ions Ca2+/Mg2+/Zn2+ on the indirect photolysis was also investigated. The results show that the direct photolysis of FLO involves C–C/C–N/C–S bond cleavage, the C5–S7 bond cleavage is most likely to occur, and the C17–C18 cleavage reaction is not easy to occur during the direct photodegradation of FLO. The indirect photolysis of FLO is more likely to occur in the environment than direct photolysis. The main indirect photolysis involves OH-addition, NO3-addition, and SO4-addition on benzene ring. The order of difficulty in the indirect photolysis with ·OH is C2 > C3 > C4 > C5 > C6 > C1, Ca2+ can promote the indirect photolysis with ·OH, and Mg2+/Zn2+ has a dual effect on the indirect photolysis with ·OH. In other words, Mg2+ and Zn2+ can inhibit or promote the indirect photolysis with ·OH. These studies provide important information for theoretical research on the environmental behavior and degradation mechanism of drug molecules. Full article
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18 pages, 3937 KiB  
Article
Z-Type Heterojunction MnO2@g-C3N4 Photocatalyst-Activated Peroxymonosulfate for the Removal of Tetracycline Hydrochloride in Water
by Guanglu Lu, Xinjuan Li, Peng Lu, He Guo, Zimo Wang, Qian Zhang, Yuchao Li, Wenbo Sun, Jiutao An and Zijian Zhang
Toxics 2024, 12(1), 70; https://doi.org/10.3390/toxics12010070 - 14 Jan 2024
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Abstract
A Z-type heterojunction MnO2@g-C3N4 photocatalyst with excellent performance was synthesized by an easy high-temperature thermal polymerization approach and combined with peroxymonosulfate (PMS) oxidation technology for highly efficient degrading of tetracycline hydrochloride (TC). Analysis of the morphological structural and [...] Read more.
A Z-type heterojunction MnO2@g-C3N4 photocatalyst with excellent performance was synthesized by an easy high-temperature thermal polymerization approach and combined with peroxymonosulfate (PMS) oxidation technology for highly efficient degrading of tetracycline hydrochloride (TC). Analysis of the morphological structural and photoelectric properties of the catalysts was achieved through different characterization approaches, showing that the addition of MnO2 heightened visible light absorption by g-C3N4. The Mn1-CN1/PMS system showed the best degradation of TC wastewater, with a TC degradation efficiency of 96.97% following 180 min of treatment. This was an approximate 38.65% increase over the g-C3N4/PMS system. Additionally, the Mn1-CN1 catalyst exhibited excellent stability and reusability. The active species trapping experiment indicated •OH and SO4•− remained the primary active species to degrade TC in the combined system. TC degradation pathways and intermediate products were determined. The Three-Dimensional Excitation-Emission Matrix (3DEEM) was employed for analyzing changes in the molecular structure in TC photocatalytic degradation. The biological toxicity of TC and its degradation intermediates were investigated via the Toxicity Estimation Software Test (T.E.S.T.). The research offers fresh thinking for water environment pollution treatment. Full article
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13 pages, 2364 KiB  
Article
Degradation of Butylated Hydroxyanisole by the Combined Use of Peroxymonosulfate and Ferrate(VI): Reaction Kinetics, Mechanism and Toxicity Evaluation
by Peiduan Shi, Xin Yue, Xiaolei Teng, Ruijuan Qu, Ahmed Rady, Saleh Maodaa, Ahmed A. Allam, Zunyao Wang and Zongli Huo
Toxics 2024, 12(1), 54; https://doi.org/10.3390/toxics12010054 - 10 Jan 2024
Cited by 1 | Viewed by 1127
Abstract
Butylated hydroxyanisole (BHA), a synthetic phenolic antioxidant (SPA), is now widely present in natural waters. To improve the degradation efficiency of BHA and reduce product toxicity, a combination of peroxymonosulfate (PMS) and Ferrate(VI) (Fe(VI)) was used in this study. We systematically investigated the [...] Read more.
Butylated hydroxyanisole (BHA), a synthetic phenolic antioxidant (SPA), is now widely present in natural waters. To improve the degradation efficiency of BHA and reduce product toxicity, a combination of peroxymonosulfate (PMS) and Ferrate(VI) (Fe(VI)) was used in this study. We systematically investigated the reaction kinetics, mechanism and product toxicity in the degradation of BHA through the combined use of PMS and Fe(VI). The results showed that PMS and Fe(VI) have synergistic effects on the degradation of BHA. The effects of operational factors, including PMS dosage, pH and coexisting ions (Cl, SO42−, HCO3, K+, NH4+ and Mg2+), and different water matrices were investigated through a series of kinetic experiments. When T = 25 °C, the initial pH was 8.0, the initial BHA concentration was 100 μM, the initial concentration ratio of [PMS]0:[Fe(VI)]0:[BHA]0 was 100:1:1 and the degradation rate could reach 92.4% within 30 min. Through liquid chromatography time-of-flight mass spectrometry (LC-TOF-MS) identification, it was determined that the oxidation pathway of BHA caused by PMS/Fe(VI) mainly includes hydroxylation, ring-opening and coupling reactions. Density functional theory (DFT) calculations indicated that OH was most likely to attack BHA and generate hydroxylated products. The comprehensive comparison of product toxicity results showed that the PMS/Fe(VI) system can effectively reduce the environmental risk of a reaction. This study contributes to the development of PMS/Fe(VI) for water treatment applications. Full article
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13 pages, 5428 KiB  
Article
Safe Disposal of Accident Wastewater in Chemical Industrial Parks Using Non-Thermal Plasma with ZnO-Fe3O4 Composites
by Aihua Li, Chaofei Wang, Chengjiang Qian, Jinfeng Wen and He Guo
Toxics 2024, 12(1), 40; https://doi.org/10.3390/toxics12010040 - 4 Jan 2024
Cited by 1 | Viewed by 1105
Abstract
Chemical wastewater has a high concentration of toxic and hazardous antibiotic pollutants, which not only devastates the ecological environment and disrupts the ecological balance, but also endangers human health. This research proposed a non-thermal plasma (NTP) combined with a ZnO-Fe3O4 [...] Read more.
Chemical wastewater has a high concentration of toxic and hazardous antibiotic pollutants, which not only devastates the ecological environment and disrupts the ecological balance, but also endangers human health. This research proposed a non-thermal plasma (NTP) combined with a ZnO-Fe3O4 nano-catalyst system to achieve the efficient degradation of ciprofloxacin (CIP) in chemical wastewater. Firstly, ZnO-Fe3O4 composite materials were prepared using hydrothermal method and characterized with scanning electron microscopy (SEM), transmission electron microscope (TEM), X-ray diffractometer (XRD), X-ray photoelectron spectroscopy (XPS), etc. With the sole NTP, NTP/ZnO, and NTP/ZnO-Fe3O4 systems, the removal efficiency of CIP can reach 80.1%, 88.2%, and 99.6%, respectively. The optimal doping amount of Fe3O4 is 14%. Secondly, the capture agent experiment verified that ·OH, ·O2, and 1O2 all have a certain effect on CIP degradation. Then, liquid chromatography–mass spectrometry (LC-MS) was used to detect the intermediate and speculate its degradation pathway, which mainly included hydroxyl addition, hydroxyl substitution, and piperazine ring destruction. After treatment with the NTP/ZnO-Fe3O4 system, the overall toxicity of the product was reduced. Finally, a cyclic experiment was conducted, and it was found that the prepared ZnO-Fe3O4 catalyst has good reusability. The NTP/ZnO-Fe3O4 was also applied in practical pharmaceutical wastewater treatment and has practical applicability. Full article
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17 pages, 6113 KiB  
Article
Degradation of Ciprofloxacin in Water by Magnetic-Graphene-Oxide-Activated Peroxymonosulfate
by Xiaoping Wang, Yulan Li, Jiayuan Qin, Ping Pan, Tianqing Shao, Xue Long and Debin Jiang
Toxics 2023, 11(12), 1016; https://doi.org/10.3390/toxics11121016 - 13 Dec 2023
Viewed by 1044
Abstract
Antibiotics are extensively applied in the pharmaceutical industry, while posing a tremendous hazard to the ecosystem and human health. In this study, the degradation performance of ciprofloxacin (CIP), one of the typical contaminants of antibiotics, in an oxidation system of peroxymonosulfate (PMS) activated [...] Read more.
Antibiotics are extensively applied in the pharmaceutical industry, while posing a tremendous hazard to the ecosystem and human health. In this study, the degradation performance of ciprofloxacin (CIP), one of the typical contaminants of antibiotics, in an oxidation system of peroxymonosulfate (PMS) activated by magnetic graphene oxide (MGO) was investigated. The effects of the MGO dosage, PMS concentration and pH on the degradation of CIP were evaluated, and under the optimal treatment conditions, the CIP degradation rate was up to 96.5% with a TOC removal rate of 63.4%. A kinetic model of pseudo-secondary adsorption indicated that it involves an adsorption process with progressively intensified chemical reactions. Furthermore, the MGO exhibited excellent recyclability and stability, maintaining strong catalytic activity after three regenerative cycles, with a CIP removal rate of 87.0%. EPR and LC-MS experiments suggested that •OH and SO4• generated in the MGO/PMS system served as the main reactants contributing to the decomposition of the CIP, whereby the CIP molecule was effectively destroyed to produce other organic intermediates. Results of this study indicate that organic pollutants in the aqueous environment can be effectively removed in the MGO/PMS system, in which MGO has excellent catalytic activity and stabilization for being recycled to avoid secondary pollution, with definite research value and application prospects in the field of water treatment. Full article
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15 pages, 3772 KiB  
Article
A Theoretical Study on the Degradation Mechanism, Kinetics, and Ecotoxicity of Metronidazole (MNZ) in •OH- and SO4•−-Assisted Advanced Oxidation Processes
by Jingyu Sun, Ruijun Chu and Zia Ul Haq Khan
Toxics 2023, 11(9), 796; https://doi.org/10.3390/toxics11090796 - 20 Sep 2023
Cited by 4 | Viewed by 1427
Abstract
Metronidazole (MNZ), a typical example of nitroimidazole antibiotics, is widely used in the treatment of infectious diseases caused by anaerobic bacteria. The degradation mechanism and kinetics of MNZ in the presence of HO• and SO4•− were studied using density functional theory [...] Read more.
Metronidazole (MNZ), a typical example of nitroimidazole antibiotics, is widely used in the treatment of infectious diseases caused by anaerobic bacteria. The degradation mechanism and kinetics of MNZ in the presence of HO• and SO4•− were studied using density functional theory (DFT). It was confirmed that both HO• and SO4•− easily added to the carbon atom bonded to the NO2 group in the MNZ molecule as the most feasible reaction channel. This study shows that subsequent reactions of the most important product (M-P) include the O2 addition, hydrogen abstraction and bond breakage mechanisms. The rate constants of HO• and SO4•−-initiated MNZ in the aqueous phase were calculated in the temperature range of 278–318 K. The total rate constants of MNZ with HO• and SO4•− were determined to be 8.52 × 109 and 1.69 × 109 M−1s−1 at 298 K, which were consistent with experimental values of (3.54 ± 0.42) × 109 and (2.74 ± 0.13) × 109 M−1s−1, respectively. The toxicity of MNZ and its degradation products to aquatic organisms has been predicted. The results proposed that the toxicity of the initial degradation product (M-P) was higher than that of MNZ. However, further degradation products of MNZ induced by HO• were not harmful to three aquatic organisms (fish, daphnia, and green algae). This study provides a comprehensive theoretical basis for understanding the degradation behavior of MNZ. Full article
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12 pages, 2442 KiB  
Article
Dielectric Barrier Discharge Plasma Coupled with Cobalt Oxyhydroxide for Methylene Blue Degradation
by Xiaomei Yao, Yingbo Fang, Xiaochen Cui, Xian Cheng and Zixia Cheng
Toxics 2023, 11(9), 763; https://doi.org/10.3390/toxics11090763 - 8 Sep 2023
Viewed by 799
Abstract
In this study, the coupled use of a double dielectric barrier discharge (DDBD) and CoOOH catalyst was investigated for the degradation of methylene blue (MB). The results indicated that the addition of CoOOH significantly promoted MB degradation performance compared to the DDBD system [...] Read more.
In this study, the coupled use of a double dielectric barrier discharge (DDBD) and CoOOH catalyst was investigated for the degradation of methylene blue (MB). The results indicated that the addition of CoOOH significantly promoted MB degradation performance compared to the DDBD system alone. In addition, both the removal rate and energy efficiency increased with an increase in CoOOH dosage and discharge voltage. After 30 min of discharge treatment in the coupled system (with CoOOH of 150 mg), the removal rate reached 97.10% when the discharge voltage was 12 kV, which was 1.92 times that in the single DDBD system. And when the discharge time was 10 min, the energy efficiency could reach 0.10 g (k·Wh)−1, which was 3.19 times better than the one in the single DDBD system. Furthermore, the addition of CoOOH could also significantly enhance the TOC and COD removal rates of MB. In the DDBD-coupled-with-CoOOH system, TOC and COD were 1.97 times and 1.99 times those of the single DDBD system after 20 min of discharge treatment with a discharge voltage of 12 kV and 100 mg of CoOOH. The main active substances detected in the coupled system indicated the conversion of the active species H2O2 and O3 into a more oxidizing ·OH was enhanced through the addition of a CoOOH catalyst, resulting in the more effective decomposition of MB and intermediate molecules. Full article
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