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•Activation of SO4− precursor salts by nanomaterials (NMs) was reviewed.•NMs effectively activate peroxymonosulfate (PMS) and persulfate (PS) to SO4−.•NMs exhibit high catalytic ...activity, large surface area and controllable structure.•Improving SO4− based oxidation necessitates novel design of functional NMs.
Sulfate radical anion (SO4−) based advanced oxidation technologies (AOTs) have received a great deal of attention due to their high reactivity with the organic contaminants and high selectivity in complex environmental matrices. Among all SO4− activation techniques, the heterogeneous activation of precursor peroxides such as peroxymonosulfate (PMS) and persulfate (PS) by nanostructured materials has demonstrated to be an effective method to generate SO4−. This paper reviews SO4− chemistry and the nanostructured materials that can effectively activate PMS/PS, namely, transition metal-based nano-catalysts, carbon nanomaterials, and nano-composites. In addition, we also discuss the activation mechanisms of PMS/PS initiated by heterogeneous nanostructured materials, emphasizing their catalytic activity, stability, and reusability for the removal of organic contaminants. This review shows that nanostructured materials have promising potential in environmental remediation based on their excellent catalytic efficiency, large specific surface area, and controllable structure. It also provides perspective on potential future studies on the design of novel nanostructured materials and process development in the field of SO4− based AOTs.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Emerging contaminants such as pharmaceuticals that cannot be completely removed by traditional biological treatments are ubiquitously present in water bodies with detected concentrations ranging from ...ng L−1 to mg L−1. Advanced oxidation technologies (AOTs) are promising, efficient, and environmentally friendly for the removal of these pharmaceuticals. In this study, we investigated the degradation kinetics of a model pharmaceutical, clonidine (CLD), via hydroxyl radical (OH) in UV/H2O2 and sulfate radical (SO4•−) in UV/peroxydisulfate (PS) systems for the first time. The second−order rate constants (k) of protonated cationic CLD with OH and SO4•− were measured to be (2.15 ± 0.07) × 109 M−1 s−1 and (1.12 ± 0.03) × 109 M−1 s−1, respectively. We also calculated the pKa value of CLD and thermodynamic behaviors for reactions of CLD/HCLD+ with OH and SO4•− at M05–2X/6–311++G**//M05–2X/6–31+G** level with SMD solvation model. The pKa value was calculated to be 8.14, confirming the literature value. H atom abstraction pathway was the most favorable pathway for both OH and SO4•−, while single electron transfer pathway was thermodynamically feasible only for SO4•− for CLD but not for HCLD+. In addition, the reactivities of both tautomeric forms of CLD (i.e., amino and imino CLD) with both radicals were also investigated. This study contributed to a better understanding on the degradation mechanisms of CLD and proposed the possibilities of the elimination of pharmaceuticals by applying AOTs during wastewater treatment processes.
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•The degradation kinetics and mechanisms of CLD by OH and SO4•− were investigated.•The k values of OH and SO4•− with CLD were 2.15 × 109 and 1.12 × 109 M−1 s−1.•H atom abstraction is dominant pathway for both OH and SO4•− reacting with CLD.•Imino tautomer is more stable than amino form but high conversion energy barrier.•We proposed the possibilities of the elimination of CLD by applying AOTs.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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•We investigated kinetics ofO2·-–mediated transformation of phenol and nitrobenzene.•The reaction mechanisms were elucidated by experimental and theoretical approaches.•Our results ...indicated that O2·- exhibits limited effects on their transformations.•Nitrobenzene exhibited a higher reactivity towards O2·- than that with phenol.
In this study, the kinetics and mechanisms of superoxide radical (O2·-)-mediated transformation of two monosubstituted aromatic contaminants with diametrically opposed electronic effect, namely phenol (PhOH) and nitrobenzene (NB), were investigated through combined experimental and theoretical approaches. The reaction rate constant between O2·- and PhOH was determined to be 269 M−1 s−1via competition kinetic method. Such weak role of O2·- was confirmed by density functional theory (DFT) calculations at SMD/CAM-B3LYP/6-311++G(2d,2p)//CAM-B3LYP/6-31+G(d,p) level of theory. However, NB exhibited a higher reactivity towards O2·- than PhOH, demonstrating the selectivity of O2·- to electron withdrawing group. Despite the difference in reactivity, O2·- shows very limited removal capacity for PhOH and NB. These results were also in reasonably good agreement with an indication from a quantitative structure–property relationship model. With these quantitative and mechanistic results, we provided a more comprehensive understanding on the O2·--mediated transformation of organic pollutants bearing different electron donating/withdrawing groups.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Carbamazepine (CBZ), a widely detected pharmaceutical in wastewaters, cannot currently be treated by conventional activated sludge technologies, as it is highly resistant to biodegradation. In this ...study, the degradation kinetics and reaction mechanisms of CBZ by hydroxyl radical (OH) and sulfate radical (▪)–based advanced oxidation processes (AOPs) were investigated with a combined experimental/theoretical approach. We first measured the UV absorption spectrum of CBZ and compared it to the theoretical spectrum. The agreement of two spectra reveals an extended π–conjugation system on CBZ molecular structure. The second–order rate constants of OH and ▪ with CBZ, measured by competition kinetics method, were (4.63 ± 0.01) × 109 M−1 s−1 and (8.27 ± 0.01) × 108 M−1 s−1, respectively at pH 3. The energetics of the initial steps of CBZ reaction with OH and ▪ were also calculated by density functional theory (DFT) at SMD/M05–2X/6–311++G**//M05–2X/6–31 + G**level. Our results reveal that radical addition is the dominant pathway for both OH and ▪. Further, compared to the positive ΔGR0 value for the single electron transfer (SET) reaction pathway between CBZ and OH, the ΔGR0 value for SET reaction between CBZ and ▪ is negative, showing that this reaction route is thermodynamically favorable. Our results demonstrated the remarkable advantages of AOPs for the removal of refractory organic contaminants during wastewater treatment processes. The elucidation of the pathways for the reaction of OH and ▪ with CBZ are beneficial to predict byproducts formation and assess associated ecotoxicity, providing an evaluation mean for the feasibility of AOPs application.
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•The k values of OH and ▪ with CBZ were 4.63 × 109 and 8.27 × 108 M−1 s−1.•DFT result showed energy barriers of ▪ reacting with CBZ was higher than OH.•Radical addition was the dominant pathway for both OH and ▪ reacting with CBZ.•Remarkable advantages of AOPs for removal of organic contaminants were exhibited.
The k values of OH and ▪ reacting with CBZ were measured to be 4.63 × 109 and 8.27 × 108 M−1 s−1, respectively. Radical addition is dominant reaction pathway.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The benchmark advanced oxidation technology (AOT) that uses UV/H2O2 integrated with hypochlorous species exhibits great potential in removing micropollutants and enhancing wastewater treatability for ...reclamation purposes. Although efforts have been made to study the reactions of H2O2 with hypochlorous species, there exist great discrepancies in the order of reaction kinetics, the rate constants, and the molecule-level mechanisms. This results in an excessive use of hypochlorous reagents and system underperformance during treatment processes. Herein, the titled reaction was investigated systematically through complementary experimental and theoretical approaches. Stopped-flow spectroscopic measurements revealed a combination of bi- and trimolecular reaction kinetics. The bimolecular pathway dominates at low H2O2 concentrations, while the trimolecular pathway dominates at high H2O2 concentrations. Both reactions were simulated using direct dynamics trajectories, and the pathways identified in the trajectories were further validated by high-level quantum chemistry calculations. The theoretical results not only supported the spectroscopic data but also elucidated the molecule-level mechanisms and helped to address the origin of the discrepancies. In addition, the impact of the environmental matrix was evaluated by using two waters with discrete characteristics, namely municipal wastewater and ammonium-rich wastewater. Municipal wastewater had a negligible matrix effect on the reaction kinetics of H2O2 and the hypochlorous species, making it a highly suitable candidate for this integration technique. The obtained in-depth reaction mechanistic insights will enable the development of a viable and economical technology for safe water reuse.
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IJS, KILJ, NUK, PNG, UL, UM
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•We developed a method to generate micromolar level O2∙- in aqueous solution.•O2∙- was confirmed by the UV spectra under pulse radiolysis and NBT.•We constructed an in situ ...spectroscopy to study the reaction of O2∙- and CCl4.•CCl4 reacts slowly with O2∙- than with ·OH/SO4∙-.•Nucleophilic substitution is the major pathway for the reaction of O2∙- and CCl4.
Contemporary studies emphasize that superoxide radical (O2∙-) exhibits the potential to degrade organic contaminants, but practical application of this radical in engineered waters require an in-depth understanding of its kinetic profiles in a quantitative way. Here, we developed, for the first time, a convenient and reliable approach to generate micromolar level O2∙- in aqueous solution by photolysis of formate and H2O2. The presence of O2∙- was confirmed by comparing the UV spectra under pulse radiolysis and chromogenic reaction. We then constructed an in situ long-path spectroscopy to investigate the kinetics and mechanisms of O2∙--mediated degradation of carbon tetrachloride (CCl4), a halogenated model contaminant. The rate constant for the reaction of O2∙- and CCl4 was determined to be 478 M−1 s−1. In addition, we employed the transition state theory to model the reaction rate constants. Both results show that O2∙- exhibited low reactivity towards CCl4 with bimolecular rate constant lower by at least one order of magnitude than those radicals generated in typical advanced oxidation processes such as hydroxyl and sulfate radicals. Our results also indicate that nucleophilic substitution is the major pathway, and the solvation effect plays an important role in the reaction. The complementary experimental and theoretical approaches provide a mechanistic basis for better understanding aqueous–phase O2∙- chemistry and a holistic evaluation on the application of O2∙- for the degradation of organic contaminants of emerging concern.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The benchmark advanced oxidation technology (AOT) that uses UV/H
O
integrated with hypochlorous species exhibits great potential in removing micropollutants and enhancing wastewater treatability for ...reclamation purposes. Although efforts have been made to study the reactions of H
O
with hypochlorous species, there exist great discrepancies in the order of reaction kinetics, the rate constants, and the molecule-level mechanisms. This results in an excessive use of hypochlorous reagents and system underperformance during treatment processes. Herein, the titled reaction was investigated systematically through complementary experimental and theoretical approaches. Stopped-flow spectroscopic measurements revealed a combination of bi- and trimolecular reaction kinetics. The bimolecular pathway dominates at low H
O
concentrations, while the trimolecular pathway dominates at high H
O
concentrations. Both reactions were simulated using direct dynamics trajectories, and the pathways identified in the trajectories were further validated by high-level quantum chemistry calculations. The theoretical results not only supported the spectroscopic data but also elucidated the molecule-level mechanisms and helped to address the origin of the discrepancies. In addition, the impact of the environmental matrix was evaluated by using two waters with discrete characteristics, namely municipal wastewater and ammonium-rich wastewater. Municipal wastewater had a negligible matrix effect on the reaction kinetics of H
O
and the hypochlorous species, making it a highly suitable candidate for this integration technique. The obtained in-depth reaction mechanistic insights will enable the development of a viable and economical technology for safe water reuse.
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IJS, KILJ, NUK, PNG, UL, UM
•A new structural influence surfaces calculation method is proposed by innovatively combining the three-dimensional boundary element method with the bivariate polynomial function.•A structural damage ...localization method based on deflection influence surfaces calculated by the three-dimensional boundary element method is proposed.•The proposed method is verified by the numerical and experimental cases.
A structural damage localization method based on deflection influence surfaces (DIS) calculated by the three-dimensional (3D) boundary element method (BEM) is proposed. By combining the 3D BEM with Structural Properties Intelligent Analysis Programs (SPIAP), the static equilibrium method (SEM) is performed on a square plate. Then, all the deflection values are automatically extracted by the SPIAP for the purpose of using the optimized bivariate polynomial function (BPF) to fit the DIS. The accuracy of the SPIAP-fitted DIS is proved by the optimized BPF program. Finally, a structural damage localization module is developed and verified through an experimental example. The numerical and experimental results indicate that compared to the analytical solution, the deflection calculation error of the square plate is no more than 1.8‰. Moreover, the damage localization accuracy of the simply supported beam under single-damage and double-damage cases has been improved by 28.6% and 16.7%, respectively.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
•The generation pathways and detection of O2•- were discussed.•Reactivities of O2•- with various contaminants (n = 111) were analyzed.•O2•- exhibits weak reactivity towards most of aquatic ...contaminants.•We critically evaluated reaction mechanisms of contaminants with O2•-.•Environmental implications for O2•- in aquatic systems were highlighted.
The roles of superoxide radical (O2•−) in the domains of physiological, physical, and material chemistry are becoming increasingly recognized. Although extensive efforts have been directed to understand O2•− functions in diverse aquatic systems, there is a lack of systematic and in-depth review for its kinetics and mechanisms in various environmental scenarios. This review aims to bridge this gap through discussion of O2•− generation pathways under both natural and controlled conditions. The merits and limitations of the generation and detection methods under various conditions are compared, with emphasis on different approaches for the determination of O2•−-triggered reaction kinetics. We summarize the reaction rate constants of O2•− with organic contaminants covering a wide diversity of structures and reactivity. The comparison indicates that O2•− exhibits weak reactivity with most contaminants and lacks selectivity towards compounds with different functional groups, except with quinones which exhibit higher reactivity compared to non-quinones. Further, the reaction mechanisms, namely single electron transfer, nucleophilic substitution, hydrogen atom abstraction, and radical-adduct formation, are critically evaluated. Various environmental implications of O2•− are highlighted including maintenance of biogeochemical iron cycle, synthesis of nanoparticles for antibacterial purposes, desorption of contaminants from heterogeneous interfaces, and synergetic degradation of contaminants.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
When the production of reactive oxygen species (ROS) is overloaded surpassing the capacity of the reductive rheostat, mammalian cells undergo a series of oxidative damage termed oxidative stress ...(OS). This phenomenon is ubiquitously detected in many human pathological conditions. Wound healing program implicates continuous neovascularization, cell proliferation, and wound remodeling. Increasing evidence indicates that reactive oxygen species (ROS) have profound impacts on the wound healing process through regulating a series of the physiological and pathological program including inflammatory response, cell proliferation, angiogenesis, granulation as well as extracellular matrix formation. In most pathological wound healing processes, excessive ROS exerts a negative role on the wound healing process. Interestingly, the moderate increase of ROS levels is beneficial in killing bacteria at the wound site, which creates a sterile niche for revascularization. In this review, we discussed the physiological rhythms of wound healing and the role of ROS in this progress, aim to explore the potential manipulation of OS as a promising therapeutic avenue.
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•ROS regulates the wound healing process by affecting inflammation, cell proliferation, angiogenesis, granulation formation, and extracellular matrix formation.•Excess ROS negatively affects the healing process in most pathological wounds.•Moderate elevation of ROS facilitates the re-establishment of a sterile ecological niche at the wound site.•Targeting oxidative stress therapy prompts clinical wound healing treatment.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
