Efficiency Of Advanced Oxidation Processes Research Articles

Unraveling Janus-like behavior of copper phosphide for selective production of reactive oxygen species: Singlet oxygen versus hydroxyl radical

The selective control of reactive oxygen species (ROS) and its mechanistic understanding are crucial to effectively abate aquatic organic pollutants in advanced oxidation processes (AOPs). The ROS are generated by single or multiple reaction steps and mainly depend on an electron and/or energy transfer achieved either by an external energy input (e.g., heating, applying electricity, light irradiation, etc.) or a spontaneous process stimulated under certain experimental conditions (△Go < 0). In this study, we demonstrated the Janus-like behavior of copper phosphide (CuxP) for the selective production of ROS under different conditions. The self-dissolution of CuxP at pH 3 in the dark resulted in the formation of hydroxyl radical (∙OH) via a sequential reaction step (i.e., dissolved oxygen (O2) → hydrogen peroxide (H2O2) → ∙OH), while visible light irradiation (λ ≥ 420 nm) at pH 7 led to the production of singlet oxygen (1O2) via an energy transfer from the photo-excited CuxP. CuxP underwent gradual loss of the oxidation activity with the dissolution of Cu and P species during the repetitive reactions at pH 3 in the dark, whereas it maintained the activity without the dissolution at pH 7 under visible light irradiation. The Janus-like behavior of CuxP enables its application not only as a solid oxidative reagent under acidic and dark conditions, but also as a photosensitizer under neutral and light conditions for the treatment of specific organic pollutants vulnerable to the radical and non-radical attacks. The photo-switching control for a selective ROS formation provides a new insight on water treatment by these species and paves the way for the development of highly efficient AOP systems.

Molecularly imprinted catalytic membrane reactor for improved advanced oxidation degradation efficiency of low concentration pollutants

Improving the efficiency of advanced oxidation technology to remove low concentration pollutants is one of the important problems in water treatment. In this study, a molecularly imprinted catalytic membrane (MICM) reactor has been designed and developed to solve this problem. The results showed that the MICM rapidly separated and degrade refractory pollutants in complex aqueous media, while significantly improving oxidation efficiency. Compared to Fe3O4, rate constants on the MICM in three different systems were significantly increased 3.5–33-fold, with kobs in persulfate (PS), hydrogen peroxide (H2O2), and peroxymonosulfate (PMS) oxidation systems reaching 0.093 min−1, 0.073 min−1, and 0.142 min−1, respectively. The results of dynamic experiments showed that sulfamethoxazole (SMX) removal efficiencies in MICM/PMS and H2O2 oxidation systems could exceed 90% within 150 min. Studies have shown that the targeting catalysis process of the MICM benefited from a coupling effect, which endows the MICM with stronger hydrophilicity and superior stability. Based on detection results and kinetic calculations, MICMs could not only selectively identify target pollutants, but also adsorb oxidants to promote non-free radical reactions represented by 1O2 in PMS oxide process. This enabled more efficient contact between the oxidant, the targeted pollutant, and the catalytic core of the MICM, increasing the oxidation efficiency. This study may provide reference for improving the efficiency of advanced oxidation processes and the application of molecularly imprinted catalysts.

Treatment of net washing wastewater by Fenton process

&lt;p&gt;The discharge of wastewater from net washing is one of the most significant problems in the marine ecosystem because of its high organic and saline content. Sea water quality is deteriorated every day due to the high amount of organic matter produced in the aquaculture sector. The aim of this study was to investigate the treatability of net washing wastewater by Fenton process. The efficiency of advanced oxidation processes (AOPs) in the treatability of net washing wastewater was evaluated through chemical oxygen demand (COD) and color removal. The effects of H2O2, and Fe (II) dosages, pH and reaction time were investigated, and the parameters were optimized by 23 full factorial design principles and variance analysis (ANOVA). The results showed that H2O2 dosage was the most effective parameter for Fenton process. The maximum COD removal was found at Fe (II)/H2O2 concentration ratio of 1/5 and the 180 minutes reaction time. The COD removal increased from 77 % to 88 % by increasing the peroxide dose from 80 mM to 400 mM. The total R2 for the three factors was calculated to be 59.67%. According to the experimental results, in the factor analysis between the three variables and COD removal, only the variation in peroxide concentration was statistically significant. Since the efficiency of biological treatment is unstable in treating of high organic matter and saline wastewaters, the Fenton process has great potential in the treatment of net washing wastewater.&lt;/p&gt;

Sulfidized state and formation: Enhancement of nanoscale zero-valent iron on biochar（S-nZVI/BC） in activating peroxymonosulfate for Acid Red 73 degradation

To improve the performance of the nanoscale zero-valent iron (nZVI)-based advanced oxidation process (AOPs), a sulfidation pre-modification endowed nZVI with stable reduction nature mechanism was proposed, and a coupled system of activating PMS with sulfidized nanoscale zero-valent iron supported by biochar(S-nZVI/BC@PMS) was constructed in this study. It could be found that sulfidation state and formation, largely dependent on the sulfidized modification method, had a great impact on the enhancement for nZVI/BC in activating PMS for Acid Red 73 degradation. Compared with original nZVI/BC, the formed FeS shell blocked the external air to protect the internal Fe0, and S-nZVI/BC became relatively hydrophobic, which could slow down the material corrosion by water and dissolved oxygen to enhance the reaction durability. Appropriate sulfidation reduced the electrochemical impedance and enhanced the electrical conductivity of the catalyst, which facilitated the electron transfer in the system, and the participation of reducing sulfur species enabled the reaction to form a positive cycle and ensure a prolonged duration. Excessive sulfidation caused the material to become unstable and thus susceptible to air erosion, reducing the efficiency of contaminant removal. Due to the FeS protective shell, hydrophobicity of S-nZVI/BC and the promoted electron transfer in the system, S-nZVI/BC@PMS system secured more free radicals and had longer reaction time under the same conditions. In addition, S-nZVI/BC had good antioxidant properties, universality, and reusability for practical applications. These findings not only elucidated the superiority of S-nZVI/BC@PMS system but also provided new insights into cost-saving and efficient advanced oxidation processes.

Efficient sonocatalytic degradation of orange II dye and real textile wastewater using peroxymonosulfate activated with a novel heterogeneous TiO2–FeZn bimetallic nanocatalyst

TiO2–FeZn nanocatalyst combined with sonolysis were used to activate peroxymonosulfate (PMS) as a highly efficient advanced oxidation process (US/TiO2–FeZn/PMS) for the decoloration of orange II dye (OII) and real textile wastewater. The characterization of the as-synthesized NPs was performed by SEM, FTIR, EDX and XRD analyses. Optimal experimental conditions of operational parameters were obtained: pH = 3, 15 mg/L initial OII concentration, 0.2 g/L PMS, 0.7 g/L nanocatalyst dosing, and 300 W ultrasonic power. The decolorization was observed to increase with increasing the dose of nanocatalyst and the ultrasonic power, and with decreasing pH (under acidic conditions). Under optimal experimental conditions, decolorization and COD removal of textile wastewater were 99.9% and 74.6%, respectively, at 40 min. The TiO2–FeZn/PMS/US as a novel process exhibited a higher removal of OII (95%) than TiO2 NPs/PMS/US process (54%). The OII removal efficiency by the different processes decreased in the following order: TiO2–FeZn/US/PMS > TiO2–FeZn/PMS > TiO2–FeZn/US > TiO2 /US/PMS > US/PMS > TiO2–FeZn > PMS > US. The recyclability study revealed that the process could be reused up to three consecutive cycles. The current US/nanocatalyst/PMS system was concluded to be an efficient, reusable and stable nanocatalyst for the oxidation of textile dyes.

Metal-organic frameworks (MOFs) as efficient catalysts for electro-Fenton (EF) reactions: Current progress and prospects

As a type of coordination polymer, metal–organic frameworks (MOFs) have attracted extensive attention due to their large specific surface area, adjustable pore size and high porosity. Electro-Fenton (EF) technology is an environmentally-friendly and efficient advanced oxidation process (AOPs) degradation technology, which has also received extensive attention. Therefore, the paper systematically reviews the applications of MOFs in EF systems. Firstly, the advantages and disadvantages of homogeneous and heterogeneous EF were generalized, and the influencing factors of EF system (i.e., electrode, pH, current density, conductivity) were summarized. Secondly, different series of MOFs (i.e., zeolite imidazole framework (ZIF), materials of institute lavoisier frameworks (MIL) and universitetet i oslo (UIO)) were introduced. Then, the methods to improve the catalytic activity and water stability of MOFs were also described. Finally, the future application of MOFs in EF systems is prospected, which provides a detailed summary and foreshadowing for future research in this direction.

Fibrous cellulose nanoarchitectonics on N-doped Carbon-based Metal-Free catalytic nanofilter for highly efficient advanced oxidation process

N-doped carbon materials have been considered as promising efficient and environment-friendly catalysts for sulfate radical-based advanced oxidation processes (SR-AOPs). Herein, we first report a facile strategy to prepare nanoporous N-doped carbon nanofilters (NCNFs) using cellulose nanofibers (CNFs) and metal–organic framework (MOF) as the superior metal-free catalytic for SR-AOPs. In this work, CNFs are employed as nanoporous templates and binders to fix ZIF-8 for fabricating ZIF-8@CNF membrane, and the as-prepared membrane was converted into NCNFs by a simple pyrolysis process. To evaluate the catalytic degradation performance of the NCNFs, methylene blue (MB) was chosen as a model contaminant. It is found that the NCNFs demonstrate a remarkable efficiency for MB removal by peroxymonosulfate (PMS) activation, and 96 % of MB (10 mg/L) was degraded in 15 min. The catalytic reaction and process including removal and washing are very simple and easy because the nanoporous N-doped carbons are fixed on CNF-derived networks. Furthermore, the reaction parameters including reaction temperature, pH, and catalyst/PMS dosage are also investigated. In addition, a series of radical quenching experiments reveal that non-radical mechanism is responsible for the degradation of MB. Importantly, the NCNFs membrane showed a good reusability by the annealing process and it can serve as a catalytic filter in practical organic dye remediation application. This present work shows that MOF derived metal-free carbon membranes have a promising avenue as catalysts for organic dye degradation and water remediation.

Electro-Fenton process in combination with other advanced oxidation processes: Challenges and opportunities

Combination of electro-Fenton (EF) process with other advanced oxidation processes (AOPs) is found very much effective for water and wastewater treatment. The combined processes including sono-EF (SEF), photo-EF (PEF), electro-peroxone, ferrate-EF and EF combined with persulfate oxidation allow enhancing the mineralization efficiency of treatment as well as reducing operational cost and toxicity of treated wastewater. Even though, there are several advantages in combined processes, they also present some disadvantages such as increased side reactions, increased energy requirement etc., which are challenges to overcome. • Electro-Fenton (EF) is an efficient advanced electrochemical advanced oxidation process. • However, it presents some disadvantages. • Combination of EF with other AOPs allows to enhance its performance. • Combinations such as sono-EF, (solar)photo-EF, Ferrate-EF, EF-persulfate were presented.

Electron beam degradation of the cardiovascular drug salbutamol: Mechanisms and degradation pathways

With the increasing incidence and mortality of cardiovascular diseases, high consumption of the cardiovascular drug salbutamol (SAL) has made this compound an emerging pollutant in natural water and a challenge for traditional wastewater treatment. In this paper, an efficient advanced oxidation process was used to degrade SAL by electron beam (EB) irradiation. The results revealed that 100 mg L−1 of SAL could be nearly completely removed (95.1%) at 10 kGy and the degradation kinetic well followed pseudo first-order kinetic model. Different factors, including pH, inorganic ions and water matrix, had varying effects on the degradation of SAL owing to their important influence on the formation of reactive species in the aqueous solution. And it was found that eaq− played a major role in the degradation of SAL parent. Moreover, the addition of K2S2O8 (20 mM) increased the SAL mineralization rate from 2.9% to 64.2%, suggesting that oxidation free radicals could greatly improve the mineralization rate of SAL. Combining with the theoretical calculations and determined degradation by-products, four possible degradation pathways of SAL by EB irradiation were proposed, including H•, •OH and eaq− all participated in the degradation of SAL. Finally, toxicity evaluation suggested that the toxicity of SAL aqueous solution reduced after EB irradiation, indicating that it is an effective method to degrade SAL.

Photocatalytic reduction of methylene blue induced by a commercial titanium precursor in homogeneous phase

This work evaluates the photocatalytic activity of titanium(IV) bis(ammonium lactate) dihydroxide (TiBALDH), an inexpensive commercial precursor and potential alternative to TiO2 nanostructures in heterogeneous photocatalysis, to reduce methylene blue in an aqueous medium. Results show that the titanium precursor without further preparation (other than dilution) shows a high activity for degrading the dye within a few seconds, even at 0.5 mM. The photocatalytic activity is dependent on the concentration, type of radiation, and pH, suggesting the presence of two main concentration-dependent photoreactive species, most likely oxoclusters. Additionally, the homogeneous system is not limited by adsorption processes, as is the case in heterogeneous systems with TiO2 nanoparticles, and it offers greater reusability while avoiding catalyst poisoning. This approach shows the potential for efficient advanced oxidation processes in homogeneous solutions by exploiting the chemical equilibrium of titanium lactate complexes in aqueous solution.

Detailed mechanism of organic pollutant oxidation via the heterogeneous Fenton reaction requires using at least two substrates, e.g.: DMSO and EtOH

Heterogeneous catalysts hold immense potential applicability in batch-advanced oxidation technologies. The present study examined LaFeO3 Fenton-like catalyzed oxidation of EtOH and DMSO. LaFeO3 is used to catalyze many processes, including an advanced oxidation process (AOP). Less is known about its role in Fenton-like reactions for AOPs. The results point out that two short-lived oxidizing intermediates are formed. Based on oxidation products analysis, it is tentatively proposed that the two short-lived oxidizing intermediates are [((LaFeIIIO3)n)n((LaFeIIIO2(OH)m-2)(LaFeIV(O)O2)2] and [(LaFeIVO3)2(LaFeIIIO3)n-2]2+. Both substrates are oxidized by [((LaFeIIIO3)n)n((LaFeIIIO2(OH)m-2)(LaFeIV(O)O2)2], the oxidation of DMSO by this intermediate is considerably faster than that of ethanol. [(LaFeIVO3)2(LaFeIIIO3)n-2]2+ oxidizes only EtOH. The yield of [((LaFeIIIO3)n)n((LaFeIIIO2(OH)m-2)(LaFeIV(O)O2)2] is larger than that of [(LaFeIVO3)2(LaFeIIIO3)n-2]2+. The knowledge gained in this study will help elucidate the detailed mechanisms of perovskite catalyzed Fenton-like processes and thus facilitate the development of efficient AOPs. The involvement of two short-lived intermediates was shown only by studying the oxidation of two very different substrates, a novel approach whose groundbreaking results are important for catalytic processes that will advance environmental strategies.

Optimizing Co site electron structure by construction of heterogeneous interface for efficient sulfite activation on paracetamol removal

Sulfite(S(IV))-induced advanced oxidation processes (AOPs) have great prospect in the field of removing organic pollutants, yet developing highly efficient sulfite activation systems and optimizing active sites for favorable catalytic processes are important but still challenging. Herein, we have achieved a composite catalyst with modulated Co electron structure for efficient AOPs by decorating Co(OH)2 on ultrathin graphitic carbon nitride (g-C3N4) nanosheet through an adjustable strategy, which exhibits high catalytic performance in S(IV) activation system. At optimal pH 9, 92% of paracetamol (APAP) (0.005 mM) is removed with the degradation rate constant of k1 = 0.193 min−1 within 30 min in presence of the composite material. The in-situ synthesis mode introduces strong heterogeneous interface interaction, resulting in directional electron transfer from cobalt hydroxide layer to g-C3N4 sheet revealed by X-ray photoelectron spectroscopy and density functional theory (DFT) calculations. The underlying activity enhanced mechanisms for APAP in S(IV) activation system using Co(OH)2/g-C3N4 are proposed: (i) The ultrathin g-C3N4 nanosheets provide more anchoring centers for generating small Co(OH)2 nanoparticles with abundant active sites which benefit to form metastable intermediates of Co(II)-SO3; (ii) The strong interface interaction induces charge redistribution between Co(OH)2 and g-C3N4 conformed by DFT calculation, which modulates the d-band center of Co site and strengthens the bind of Co(II)-SO3, thereby giving rise to radicals (•OH, SO4• and O2•) and nonradicals (1O2 and electron transfer) oxidation for highly-efficient removal APAP. Our work will pave the way to build an environmentally friendly strategy for emerging organic pollutant degradation in water through building efficient catalysts in sulfite activation system.

Advanced oxidation processes for treating raw leachate: an experimental study (Barka landfill, Oman)

Management of municipal solid waste leachate has become an urgent environmental problem in many countries due to the high growth of population and consumption trends. Advanced oxidation processes (AOPs) are efficient methods to treat leachate because of their high ability to reduce unpleasant parameters. Although the simultaneous application of different AOP methods is more effective than a single process, the simultaneous application of AOPs for the treatment of municipal solid waste leachate has received little attention. To fill this knowledge gap, this study presents the simultaneous application of AOP methods to treat municipal solid waste leachate. The efficiency of AOPs was studied in terms of organic compounds such as chemical oxygen demand (COD) and total organic carbon (TOC). Leachate samples were collected from the Barka landfill, which is located in the north-east of Oman. Four combinations of applied AOP methods (e.g. ozone (O3), hydrogen peroxide (H2O2) and ultraviolet (UV)) in this study resulted in the order of hydrogen peroxide/ozone/UV &gt; hydrogen peroxide/ozone &gt; ozone/UV &gt; hydrogen peroxide/UV according to the COD removal efficiency. Combining these AOP methods resulted in an about 1.5 times increase in COD removal (56.62%) and a 1.9 times increase in TOC removal (39.34%) compared with the individual applications.

Trace Mn(II)-catalyzed periodate oxidation of organic contaminants not relying on any transient reactive species: The substrate-dependent dual roles of in-situ formed colloidal MnO2

Traditional advanced oxidation processes (AOPs) generally suffer from the inevitable deactivation of catalysts and the ineffective consumption of transient reactive species (TRSs) that compromise the efficiency in destructing aqueous contaminants. Herein, it was interestingly found that trace Mn(II) could robustly catalyze the oxidation of organic contaminants by periodate (PI), with the performance was much better than the representative TRSs-dominated AOPs (i.e., the Fe(II)-activated hydrogen peroxide, peroxymonosulfate (PMS), peroxydisulfate and PI processes). Multiple lines of evidence excluded the oxidative contributions of TRSs, instead the stoichiometric formation of colloidal MnO2 via the condensation of di-μ-oxo-bridged Mn(IV) cluster was confirmed by UV-vis, X-ray absorption near edge structure spectroscopy and density functional theory calculation. Dependent on the structure of substrate, MnO2 colloids solely or simultaneously served as oxidant and catalyst for the enhanced treatment performance. Benefiting from the non-TRSs-involved oxidation strategy and the catalytic effects of Mn species, the trace-Mn(II)/PI process even outperformed the Co(II)-activated PMS counterpart (i.e., one of the most efficient AOPs known at present) on oxidant utilization efficiency. This study not only elucidated the roles of Mn(II) and colloidal MnO2 in PI-mediated contaminant degradation, but also signified the superiority of trace catalyst-assisted process without TRSs involvement in avoiding undesired side reactions and maximizing oxidation efficiency.

Metal-free ultrathin C3N5 photocatalyst coupling sodium percarbonate for efficient sulfamethoxazole degradation

Traditional Fenton reaction takes place at a low pH and generates waste. Additionally, the storage and transportation of liquid H2O2 may pose safety risks. To overcome these disadvantages, an eco-friendly, efficient advanced oxidation process was established with ultrathin-C3N5 photocatalyst coupling sodium percarbonate (SPC). Under visible light irradiation, up to 93.97% of SMZ was removed within 120 min. Such efficient removal was attributed to the high carriers separation efficiency of U-C3N5, which was certified by DFT calculations and characterization methods. All the factors (various anions, pH values, fulvic acid, light sources, and water matrices) had a slight influence on SMZ degradation. Moreover, the toxicities of SMZ and its intermediates were reduced after degradation. Finally, a gelatin aerogel/U-C3N5 composite was obtained to facilitate the recycling of U-C3N5. This work highlights the combination of metal-free photocatalysis with SPC to degrade sulfonamide antibiotics and furthers the development of advanced oxidation process for micropollutant removal.

A general and programmable preparation of α-MnO2/GO/CS aerogels used for efficient degradation of MB in wastewater

Heterogeneous Fenton reaction, as an efficient advanced oxidation process (AOP), has been proved as a promising method to treat organic wastewater. In this study, combining the outstanding adsorption capacity of aerogels and the excellent catalytic ability of α-MnO2, various composite aerogels functionalized by α-MnO2 through double cross-linking structures were developed to degrade methylene blue (MB) in a heterogeneous Fenton process. Herein, a series of α-MnO2/GO/CS composite aerogels with different amount of graphene oxide (GO) were prepared, and detailed characterizations were made to evaluate the structures of aerogels. Finally, aerogel-5 with the most amount of GO was proved to be the optimal catalyst, which could degrade 99.7 % MB in 50 min under an optimal condition (50 mL 30 mg/L MB, 0.05 g aerogels, 2 mL 30 % H2O2, pH = 10). Especially, aerogel-5 also displayed excellent degradation efficiency (D%) when used in higher concentration MB solution in 15 min (98.4 % for 100 mg/L MB, 98.1 % for 150 mg/L MB, 97.4 % for 200 mg/L MB). In addition, the D% still reached 92.7 % after the 5th reuse. Therefore, this work developed a high active composite catalyst, which would be promising for highly efficient treatment of dye wastewater.

Synergistic effect of novel Co-modified micro/nano geopolymers in a photo-PDS system

Persulfate activation is an efficient advanced oxidation process for water treatment. However, many catalyst materials make their preparation methods and raw materials very complicated and expensive while pursuing high-efficiency catalytic effects. In this research, a novel Co-modified micro/nano geopolymer (Co-MNG) material was prepared from solid waste using a mechanochemical method. The whole preparation process of Co-MNG is simple and time-saving, and most of its raw materials are solid waste. In addition, it has few adverse effects on the environment during preparation and use and has a good effect on PDS activation. Under dark conditions, 1 mg L−1 of unloaded Co metal MNG material could degrade 20 mg L−1 Rhodamine B solution by 79% in 60 min with 15 mM PDS, but the application of visible light could not enhance its effect. However, after adding 4 wt% of different Co-containing compounds, the prepared Co-MNG materials could improve their degradation effect under the same conditions, and it is more obvious under the condition of applying visible light. Among them, MNG-Co(NO3)2 could completely degrade RhB within 40 min under the application of visible light. ESR (electron spin resonance) tests showed that the MNG-Co(NO3)2 material could generate a variety of active radicals in a photo-PDS system, such as h+, ·OH, ·O2− and SO4−. Mechanistic research experiments showed that both visible light and Co-MNG materials can activate PDS to a certain extent, but when both exist at the same time, the material could effectively couple visible light and Co activation of PDS in a photo-PDS activation system to achieve synergistic degradation of pollutants in water.

Current Trends in the Utilization of Photolysis and Photocatalysis Treatment Processes for the Remediation of Dye Wastewater: A Short Review

Development in the textile industry leads to an increased demand for the use of various dyes. Moreover, there is the use of some dyes in the food industry as well as medical diagnostics. Thereby, increased demand for dyes in various fields has resulted in dye-containing wastewater. Only a small portion of the generated wastewater is adequately treated. The rest is usually dumped or otherwise directly discharged into the sewage system, which ultimately enters rivers, lakes, and streams. The handling and disposal of such concentrated wastewater, especially the dye-containing wastewater, is considered to be a major environmental issue from the moment of its generation to its ultimate disposal. Conventional water treatment methods such as flotation, filtration, adsorption, etc., are non-destructive physical separation processes. They only transfer the pollutants to other phases, thereby generating concentrated deposits. The advanced oxidation process (AOP) is one of the most effective emerging methods for the treatment of wastewater containing chemical pollutants. The method involves the formation and interaction of highly reactive hydroxyl radicals under suitable activation conditions. These radicals are non-selective and efficient for the destruction and eventual mineralization of recalcitrant organic pollutants. This review aims at the pros and cons of using photocatalysis as an efficient AOP to degrade dye-containing wastewater.

Electronic Metal-Support Interaction Directing the Design of Fe(III)-Based Catalysts for Efficient Advanced Oxidation Processes by Dual Reaction Paths.

Persistent organic pollutants (POPs) have a huge impact on human health due to their high toxicity and non-degradability. It is still of great difficulty to develop highly efficient catalysts toward the degradation of POPs. Herein, it is reported that regulating electronic structure of quasi-single atomic ferric iron (Fe(III)) in the VO2 support through the electronic metal-support interaction (EMSI) is a versatile strategy to enhance the catalytic activity. Activated Fe(III) can react with peroxydisulfate (PDS) to produce both radicals and high-valent iron (HVFe) simultaneously for the efficient and fast degradation of POPs. Density functional theory (DFT) calculations prove that the influence of EMSI promotes the electrons on Fe(III) 3d-bond center moving close to the Fermi level, facilitating the charge transfer from Fe(III) to the adsorbate. Through the control experiments, both the radical path by PDS and the HVFe path aroused by the EMSI are confirmed in the POP degradation process. Consequently, the Fe/VO2 catalyst exhibits record-breaking catalytic activity with the k-value as high as 56.7, 43.3µmol s-1 g-1 for p-chlorophenol and 2,4-dichlorophenol degradation, respectively.

Cobalt (II)‐catalyzed oxidation of 2‐aryl benzoic acids to access biaryl lactones

Cobalt/peroxymonosulfate (Co/PMS) system is an efficient advanced oxidation process (AOP) for degradation of organic pollutants in wastewater, however, has limitations in organic synthesis. Herein, we employ a Co/PMS system to the preparation of biaryl lactones by the valorization of 2‐aryl aromatic acids via intramolecular O‐H/C‐X oxidative coupling. This system exhibits intriguing advantages, such as non‐noble metal catalyst, common oxidant, mild condition, easy workup and product isolation. Mechanism studies, including the radical quenching experiments and multiple probe substrates, suggest that a high‐valent cobalt‐oxo intermediate should be one major active species. Meanwhile, both persulfate radical anion (SO4•−) and hydroxyl radical (•OH) are present in the process and contribute to the organic reaction. This work not only expands the synthetic application of Co/Oxone system beyond environmental fields, but also provides more active intermediates than generally‐accepted SO4•− in the known metal‐based AOPs.