Perovskite oxides are promising catalysts in peroxymonosulfate (PMS) activation for wastewater treatment, attributed to their flexible structures. In this study, halogen anion (F− or Cl−) was doped ...in La0.6Sr0.4Co0.8Fe0.2O3-δ (LSCF) for PMS activation, showing that appropriate anion doping enhances the catalytic performances. La0.6Sr0.4Co0.8Fe0.2O2.75-δCl0.25 (LSCFCl0.25) exhibits a superior catalytic activity to pristine LSCF and La0.6Sr0.4Co0.8Fe0.2O2.75-δF0.25 (LSCFF0.25), attributed to the strong surface acidity, sufficient oxygen vacancies, and improved B-site metal−oxygen bonding. The rich acidic sites favor PMS adsorption on the catalyst surface. The sufficient hydrated electrons (eaq−) in the oxygen vacancies participated in the generation of free radicals (SO4•− and O2•−) and singlet oxygen (1O2). The enlarged B-site metal−oxygen covalency could boost the electron transfer between PMS and Co(III)/Fe(III), and thus accelerate the redox reaction. SO4•− and 1O2 are the dominating species for the degradation. This study deepens the catalytic mechanism and uncovers the active sites of perovskite catalysts for PMS activation, providing an inspiring modification strategy to improve the catalytic performances.
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•Anion doping improves the catalytic activity of La0.6Sr0.4Co0.8Fe0.2O3-δ.•Electrons in the oxygen vacancy favor the generation of ROS.•Enlarged B-site metal-oxygen covalency improves the redox capability of catalysts.
Inflammatory response mediated by oxidative stress is considered as an important pathogenesis of spinal cord injury (SCI). Advanced oxidation protein products (AOPPs) are novel markers of oxidative ...stress and their role in inflammatory response after SCI remained unclear. This study aimed to investigate the role of AOPPs in SCI pathogenesis and explore the possible underlying mechanisms.
A C5 hemi-contusion injury was induced in Sprague-Dawley rats to confirm the involvement of AOPPs after SCI. For in vivo study, apocynin, the NADPH oxidase inhibitor was used to study the neuroprotective effects after SCI. For in vitro study, the BV2 microglia cell lines were pretreated with or without the inhibitor or transfected with or without small interference RNA (siRNA) and then stimulated with AOPPs. A combination of molecular and histological methods was used to clarify the mechanism and explore the signaling pathway both in vivo and in vitro. One-way analysis of variance (ANOVA) was conducted with Bonferroni post hoc tests to examine the differences between groups.
The levels of AOPPs in plasma and cerebrospinal fluid as well as the contents in the spinal cord showed significant increase after SCI. Meanwhile, apocynin ameliorated tissue damage in the spinal cord after SCI, improving the functional recovery. Immunofluorescence staining and western blot analysis showed activation of microglia after SCI, which was in turn inhibited by apocynin. Pretreated BV2 cells with AOPPs triggered excessive generation of reactive oxygen species (ROS) by activating NADPH oxidase. Increased ROS induced p38 MAPK and JNK phosphorylation, subsequently triggering nuclear translocation of NF-κB p65 to express pro-inflammatory cytokines. Also, treatment of BV2 cells with AOPPs induced NLRP3 inflammasome activation and cleavage of Gasdermin-d (GSDMD), causing pyroptosis. This was confirmed by cleavage of caspase-1, production of downstream mature interleukin (IL)-1β and IL-18 as well as rupture of rapid cell membrane.
Collectively, these data indicated AOPPs as biomarkers of oxidative stress, modulating inflammatory response in SCI by multiple signaling pathways, which also included the induction of NADPH oxidase dependent ROS, and NLRP3-mediated pyroptosis, and activation of MAPKs and NF-κB.
Fe
O
magnetic nanoparticles (MNPs) are attractive heterogeneous Fenton-like catalysts for oxidative degradation of organic pollutants with H
O
. Herein highly efficient and stable Fe
O
MNPs (Fe
O
...-op-DES, ca. 10nm) were successfully prepared via a novel oxidative precipitation-combined ionothermal synthesis, which comprised oxidative precipitation of FeSO
·7H
O in choline chloride:2urea deep eutectic solvent. Among five different Fe
O
particles tested, Fe
O
-op-DES MNPs exhibited the highest catalytic activity with the activation energy of 47.6kJmol
for degradation of Rhodamine B (RhB) with H
O
under the same conditions (Fe
O
dosage of 0.50gL
, H
O
concentration of 40mmolL
, pH 6.4, 55°C, 2h). Fe
O
-op-DES MNPs were magnetically recoverable, and had good catalytic stability and recyclability without the need of regeneration (>98% degradation efficiency of RhB in 2h and pseudo-first-order rate constant of 0.0376min
after having been continuously running for 12h). The superior catalytic performance of Fe
O
-op-DES MNPs was attributed to the combination of multiple technologically important features, including the nanometer size, high Fe
content, large surface area, high density of surface active sites and stable crystal structure (no phase transformation, negligible iron leaching and particle aggregation after reaction). The wide applicability of Fe
O
-op-DES MNPs was also demonstrated by the degradation of four other organic pollutants.
•Wastewater treatment plants effluents constitute the major source of PhACs in aquatic environment.•Nano-filtration is an effective technique for PhACs removal from wastewater.•Coupling of AOPs with ...membrane filtration as pre/post-treatment or hybrid process.•Hybrid process is only possible with photocatalysis or EAOPs.•EAOPs–membrane filtration is an efficient hybrid wastewater treatment technique.
Pharmaceuticals as emerging pollutants have become a major concern not only because of the threat posed to health and safety of the aquatic life but also due to their continuous accumulation in aquatic environment and development of antibiotic-resistant microbial strains. Single classical water treatment techniques have been generally inadequate for the removal of these hazardous substances. Combined treatment techniques such as membrane separation and advanced oxidation processes (AOPs) is an exciting technology for complete removal of these pollutants because each technique complements the advantages and overcomes the challenges of the other. Technical flexibility of membrane separation technology has allowed possible integration/coupling with several AOPs as: pretreatment stage for removal of organics (which may cause membrane fouling) from membrane feed stream; post-treatment stage for oxidation of organics in both membrane permeate and concentrate streams or one pot/hybrid process for concurrent separation and oxidation of pollutants in the feed stream. AOPs such as ozonation, peroxone (O3/H2O2), UV/H2O2, photo-Fenton, photocatalysis and electrochemical advanced oxidation processes (EAOPs) have been successfully integrated with membrane separation for removal of pharmaceuticals from water and they are critically examined in this review.
•Some •OH probes were over-degraded by unknown reactive species in UV/H2O2 system.•Unknown reactive species was not found in dark •OH production systems.•Unknown reactive species seems related to ...unidentified transitional state H2O2.••OHss can be overestimated depending on the type of •OH probe.
The UV/H2O2 process is a benchmark advanced oxidation process (AOP) that in situ generates highly reactive and nonselective hydroxyl radical (•OH) to oxidatively destroy a wide range of organic compounds. Accurately quantifying the concentration of short-lived •OH is essential to predict process performance, optimize the operation parameters, and compare with other process options. The •OH concentration is typically measured using organic probe molecules that react with •OH but not with other oxidants. In the extremely well-characterized UV/H2O2 system in which •OH is proven to be the dominant oxidant, using photolysis-resistant probes such as benzoic acid and its derivatives is a widely agreed and practiced norm. We herein report that certain •OH probe compounds can be degraded in UV/H2O2 system by unknown reactive species that has not been reported in the past. Several common organic probes, particularly p-substituted benzoic acid compounds (i.e., p-hydroxybenzoic acid, p-chlorobenzoic acid, and p-phthalic acid), were found to be vulnerable to attack by the unknown reactive species, leading to false quantification of •OH concentration under high radical scavenging conditions. Lines of evidence obtained from a series of •OH scavenging experiments performed under various conditions (i.e., different concentrations of H2O2, •OH probe compounds, and dissolved oxygen) point toward excited state H2O2. The results from this study suggest the importance of using appropriate •OH probe compounds in mechanistic studies and needs for considering the unidentified role of excited state of H2O2 on the UV/H2O2 process and related AOPs.
The research investigated the pulse potential effect on Electrochemical Advanced Oxidation Processes (EAOPs) for benzoic acid oxidation. The current efficiency of the electrooxidation is enhanced by ...changing the pulse frequency and potential on electrodes. The experiments showed that there are opposing phenomena affecting energy efficiency. On the one hand, pulse potential accelerates the mass transfer of benzoic acid in an electric field. On the other hand, pulse potential increases the non-faradic current that uses energy without causing oxidation. Using the Sand equation and the electric double-layer theory, we optimized the pulse frequency and voltage amplitude to achieve the highest energy efficiency for the pulse potential EAOPs. Compared with DC (Direct current) EAOPs, the pulse potential EAOPs save 50% EE/O and have a 41 % CE for the 4_2 V cycle at 50 Hz. Therefore, pulse potential EAOPs can achieve both high pollutant degradation efficiency and low energy consumption at the same time.The research investigated the pulse potential effect on Electrochemical Advanced Oxidation Processes (EAOPs) for benzoic acid oxidation. The current efficiency of the electrooxidation is enhanced by changing the pulse frequency and potential on electrodes. The experiments showed that there are opposing phenomena affecting energy efficiency. On the one hand, pulse potential accelerates the mass transfer of benzoic acid in an electric field. On the other hand, pulse potential increases the non-faradic current that uses energy without causing oxidation. Using the Sand equation and the electric double-layer theory, we optimized the pulse frequency and voltage amplitude to achieve the highest energy efficiency for the pulse potential EAOPs. Compared with DC (Direct current) EAOPs, the pulse potential EAOPs save 50% EE/O and have a 41 % CE for the 4_2 V cycle at 50 Hz. Therefore, pulse potential EAOPs can achieve both high pollutant degradation efficiency and low energy consumption at the same time.
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•Possible reactive species formed in various AOPs were summarized.•Formation mechanisms and influencing factors of reactive species were analyzed.•Various methods for identifying ...reactive species formed in AOPs were introduced.•Reaction mechanisms of different reactive species with pollutants were discussed.
The formation, identification and reaction mechanism of reactive species in various advanced oxidation processes (AOPs) are crucial for understanding the principles of AOPs and the degradation mechanism of recalcitrant organic contaminants because reactive species are responsible for the degradation of organic contaminants in AOPs. In this review, the possible reactive species generated in various AOPs (such as Fenton oxidation, photochemical oxidation, electrochemical oxidation, ozonation, gamma ray/electron beam radiation, persulfate-based oxidation, wet air oxidation and ultrasonic oxidation), were systematically analyzed and summarized, including hydroxyl radicals (HO), hydrogen radical (H), hydrated electron (eaq−), sulfate radicals (SO4−), peroxymonosulfate radicals (SO5−), superoxide radicals (O2−), singlet oxygen (1O2) and hydroperoxy radicals (HO2). The factors that influence the formation of reactive species were discussed, mainly including pH, inorganic anions and dissolved organic matter. The main identification methods, such as electron spin resonance (ESR), electron paramagnetic electron (EPR), high performance liquid chromatography (HPLC), transient absorption spectrum, quenching experiments and kinetic analysis, were introduced, and the reaction mechanism of reactive species with organic contaminants were discussed. Finally, concluding remarks and perspectives were proposed. This review paper will provide an insight into the formation, identification and reaction mechanism of reactive species in AOPs, which is helpful for reader to better understand the degradation mechanism of recalcitrant organic contaminants in various AOPs.
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•Effect of inorganic anions (IA) on the performance of AOPs was summarized.•Effect of IA on the formation and transformation of reactive species was discussed.•Effect of IA on the ...stability of oxidants (H2O2 and persulfate) was evaluated.•Effect of IA on the catalytic activity of catalysts was analyzed.•Inorganic anions have influence on comprehensive performance on AOPs.
Inorganic anions, such as chloridion, carbonate, phosphate, sulfate and nitrate are ubiquitous in water, they will react with hydroxyl radical and sulfate radical produced during advanced oxidation processes (AOPs), to form chlorine radical, carbonate radical nitrate radical, phosphate radical and sulfate radical, which have a significant influence on the transformation of organic pollutants. It is generally believed that the quenching effect of inorganic anions on reactive species produced in AOPs was the main reason to influence the performance of AOPs. While this reason cannot explain all the results. In addition, at present most of studies only focused on the effect of inorganic anions on the removal efficiency of targeted organic pollutant by AOPs. For better understanding the effect of inorganic anions on the performance of AOPs, it is crucial to comprehensively evaluate the effect of inorganic anions on AOPs. In this review paper, the effect of inorganic anions (such as chloridion, carbonate, phosphate, sulfate and nitrate) on the performance of AOPs, including the transformation of reactive species, stability of oxidants, catalytic activity of catalysts and degradation products, was systematically summarized and reviewed. Firstly, their effect on the formation and transformation of reactive species was discussed, then the effect on the stability of oxidants (H2O2 and persulfate) and catalysts was introduced. Furthermore, the effect on the catalytic activity of catalysts was analyzed. Finally, the effect on the degradation intermediate products of organic pollutants was summarized. This review will provide an insight into the underlying influence mechanism of inorganic anions on AOPs, which is conducive to comprehensively evaluate the effect of inorganic anions on the performance of AOPs.
•The traditional mineralization path of CN− was overturned in a novel Electro-Fenton system.•CN− could be converted into NO3− but not CNO− by the synergy of •OH and •O2−.•The Electro-Fenton system ...shows the feasibility of practical application for the actual cyanide residue eluent.
Traditional methods of cyanides’ (CN−) mineralization cannot overcome the contradiction between the high alkalinity required for the inhibition of hydrogen cyanide evolution and the low alkalinity required for the efficient hydrolysis of cyanate (CNO−) intermediates. Thus, in this study, a novel Electro-Fenton system was constructed, in which the free cyanides released from ferricyanide photolysis can be efficiently mineralized by the synergy of •OH and •O2−. The complex bonds in ferricyanide (100 mL, 0.25 mM) were completely broken within 80 min under ultraviolet radiation, releasing free cyanides. Subsequently, in combination with the heterogeneous Electro-Fenton process, •OH and •O2− were simultaneously generated and 92.9% of free cyanides were transformed into NO3- within 120 min. No low-toxic CNO− intermediates were accumulated during the Electro-Fenton process. A new conversion mechanism was proposed that CN− was activated into electron-deficient cyanide radical (•CN) by •OH, and then the •CN intermediates reacted with •O2− via nucleophilic addition to quickly form NO3-, preventing the formation of CNO− and promoting the mineralization of cyanide. Furthermore, this new strategy was used to treat the actual cyanide residue eluent, achieving rapid recovery of irons and efficient mineralization of cyanides. In conclusion, this study proposes a new approach for the mineralization treatment of cyanide-containing wastewater.
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•Structural defects and certain O-groups on surface of C material cause activation.•Synergistic effect takes place for heteroatomic C materials to activate persulfates.•Both radical ...and non-radical pathways are responsible for the activation.•Application of C materials for the activation is limited but have great potential.
In recent years, persulfate-based advanced oxidation processes (PS-AOPs) for removal of organic contaminants from water have gained wide attention. Ever-emerging carbonaceous materials, including pristine carbon materials and their derivatives, heteroatom-doped carbon materials, and carbon materials with metal particles, are demonstrated to be effective in the activation of persulfates (peroxymonosulfate (PMS) and peroxydisulfate (PDS)) to generate free radicals or non-radical active species for degradation of the contaminants. In this paper, mechanisms for the activation of persulfates by carbonaceous materials and their composites are analyzed and summarized. In particular, the synergistic effect for activation improvement in the composites or in the hybrid activation systems is explored. Then the influence of the environmental conditions, such as pH, temperature, inorganic anions and dissolved organic matter, on the activation processes are discussed. Deactivation and regeneration of the carbonaceous materials are discussed as well. Finally, the application of these carbonaceous materials in activating persulfates for remediation of contaminated groundwater and treatment of wastewater are reviewed and the challenges for such applications are proposed.
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