Advanced Oxidation Process System Research Articles

Immobilization of Erythrosine Dye in Polysiloxane to Fabricate a Cost-effective Renewable Antibiotic Film through Visible Light-induced Singlet Oxygen Generation

The advanced oxidation process (AOP) is the most effective strategy to remove volatile organic compounds that are considered to be one of the main pollutants adversely affecting the environment and human health. While metal-based semiconductors are widely considered as promising photocatalysts to remove pollutants through AOP systems, their low light absorption efficiency and poor processibility remain major issues to be utilized for a sustainable AOP system with low energy consumption. However, the organic dye, erythrosine, which can generate singlet oxygens by absorbing visible light, is considered an excellent substitute for metal-based photocatalysts for cheap renewable AOP systems. Accordingly, we here demonstrate a new hybrid membrane, wherein erythrosine molecules are embedded into films of polydimethylsiloxane. The polymeric networks therefore play an important role in enhancing the thermal stability and light absorption efficiency of dye molecules upon hybridization. In addition, the foamed structures of films to enhance their porosity and oxygen permeability are introduced via the fast evaporation of ethanol. As a result, the photocatalytic performance of dyes is significantly reinforced as the porosity of the membrane increases, which is proven by analyzing the degradation efficiency of 1,3–diphenylisobenzofuran with the presence of foamed and hybridized films. The photocatalytic ability of the formed hybrid films was well regenerated in three repeated recycles. Moreover, an optical parametric oscillator (OPO) laser system was used to successfully demonstrate that the singlet oxygen generated from the optimized hybrid film was well diffused into the surface of polymer matrix. Accordingly, the film could effectively sterilize S. aureus and E. coli in an aqueous solution. Therefore, this study suggests that the hybridization of polymer and dye without chemical modification can be an effective strategy to fabricate cheap and reusable porous membranes for a practical environment purification system.

Modulating electronic structure of NiFe layered double hydroxide membrane by interlayer-confinement for enhanced water decontamination

Herein, the role of nanoconfinement on modulating the electronic structure of the catalyst that influences the efficiency of advanced oxidation processes (AOPs) was investigated. Peroxymonosulfate (PMS)-based AOP was conducted within the nanoconfined sub-nanometer interlayer channels of a 2D NiFe layered double hydroxide membrane (NiFeM). The interlayer-confined NiFeM exhibited complete removal of sulfamethoxazole, with a degradation rate constant of 211.67 s−1 that was 2.6–946.2 times higher than previously reported nanoconfined AOPs systems, and also demonstrated broad pH working range and anti-interference ability with excellent catalytic stability in 25 h. Theoretical calculations suggested such interlayer confinement upshifted the catalyst metal d-band center, accounting for strengthened PMS adsorption and electron transfer from catalyst to PMS molecules. This work embodies the interlayer confinement effect on modulating the electronic structure of catalyst and provides insights for designing catalysts with excellent capability for environmental remediation, energy conversion and chemical synthesis.

Constructing Tandem Fenton-like Reaction Systems Based on Structure Adaption to Boost Water Contaminant Mineralization Efficiency.

Mineralization of emerging contaminants by using advanced oxidation processes (AOPs) is a desirable option to ensure water safety, but still challenged by the excessive chemical and/or energy input. Here, we conceptually proposed the tandem reaction system (TRS) of different reactive oxygen species (ROS) based on structure adaption of target contaminants. To construct a model TRS, we first realized highly selective generation of three classical ROS (1O2, HO⋅ and SO4⋅-) by peroxymonosulfate activation in an electrochemical Fenton-like system, where three replaceable Fe-centered cathodes were rationally designed as electronic mediator. The 1O2+SO4⋅--TRS exhibited nearly 100 % mineralization of sulfamethoxazole (SMX), whereas only 34.2 %, 56.2 % and 60.8 % for each of the single 1O2/HO⋅/SO4⋅--AOP systems. Mechanism exploration of SMX degradation in TRS evidenced that the initial reaction with 1O2 selectively destructed the sulfonamide bridge of SMX to form p-aminobenzenesulfonic acid, which will be vulnerable to sequent SO4⋅- attack to facilitate mineralization. Successful extendibility of 1O2+SO4⋅--TRS to other sulfonamide antibiotics and 1O2+HO⋅-TRS to phenolic and arylcarboxylic compounds, as well as the demonstration of 1O2+SO4⋅--TRS in treatment of three actual pharmaceutical wastewaters strongly support that TRS is a powerful and sustainable strategy to enhance the mineralization of emerging contaminants in water.

Constructing Tandem Fenton‐like Reaction Systems Based on Structure Adaption to Boost Water Contaminant Mineralization Efficiency

AbstractMineralization of emerging contaminants by using advanced oxidation processes (AOPs) is a desirable option to ensure water safety, but still challenged by the excessive chemical and/or energy input. Here, we conceptually proposed the tandem reaction system (TRS) of different reactive oxygen species (ROS) based on structure adaption of target contaminants. To construct a model TRS, we first realized highly selective generation of three classical ROS (1O2, HO⋅ and SO4⋅−) by peroxymonosulfate activation in an electrochemical Fenton‐like system, where three replaceable Fe‐centered cathodes were rationally designed as electronic mediator. The 1O2+SO4⋅−‐TRS exhibited nearly 100 % mineralization of sulfamethoxazole (SMX), whereas only 34.2 %, 56.2 % and 60.8 % for each of the single 1O2/HO⋅/SO4⋅−‐AOP systems. Mechanism exploration of SMX degradation in TRS evidenced that the initial reaction with 1O2 selectively destructed the sulfonamide bridge of SMX to form p‐aminobenzenesulfonic acid, which will be vulnerable to sequent SO4⋅− attack to facilitate mineralization. Successful extendibility of 1O2+SO4⋅−‐TRS to other sulfonamide antibiotics and 1O2+HO⋅‐TRS to phenolic and arylcarboxylic compounds, as well as the demonstration of 1O2+SO4⋅−‐TRS in treatment of three actual pharmaceutical wastewaters strongly support that TRS is a powerful and sustainable strategy to enhance the mineralization of emerging contaminants in water.

Curvature strain tunes electron transfer accelerates peroxymonosulfate activation to achieve high-efficiency advanced oxidation

The development of high performance and stable heterogeneous catalysts is conducive to promoting the advanced oxidation process (AOPs) to promote the degradation of organic pollutants efficiently, low-cost and environmentally friendly. Here nitrogen-doped hollow carbon spheres (NHCSs) and rigid organic molecule were used to create space confinement and complexation confinement conditions, respectively, and an advanced single-atom catalyst capable of strongly activating peroxymonosulfate (PMS) to degrade organic pollutants was finally constructed. The AOPs system driven by CoNC/NHCSs (20 mg) combined with PMS (20 mg) can degrade nearly 100 % of 20 mg/L (100 mL) bisphenol A (BPA, a microplastic) pollutant within 30 min, and the mineralization rate is up to 70.5 %. Face the complex water environment, such as sewage containing coexisting anions and cations, or acidic or alkaline sewage, the CoNC/NHCSs/PMS system still has high catalytic stability, and universality for other organic pollutants. The filter column with CoNC/NHCSs as the core also realizes the continuous purification of organic pollutants, which shortens the distance between laboratory research and practical application. Radical quenching and electron paramagnetic resonance techniques confirmed that CoNC/NHCSs activated PMS to SO4·−, ·OH, and 1O2, and these reactive oxygen species combined to eliminate organic pollutants. Density functional theory (DFT) calculations jointly confirm that the strong activation of PMS by CoNC/NHCSs is the key to achieving efficient degradation of organic pollutants, and the activity of CoNC/NHCSs is derived from high exposure rate of active sites and curvature effect caused by structural bending.

Catalytic micro-structured ceramic beads and efficacy evaluation through SMX degradation in PMS-activated systems

This study tackles the challenge of applying fine and nano-catalyst particles in Advanced Oxidation Processes (AOPs), primarily due to the complexities of nanoparticle removal from treated water to prevent secondary nano-hazards. We propose an innovative solution: micro-structured ceramic beads (MSCBs, approximately 3 mm in diameter) with a unique anisotropic pore structure. For the first time, we prepared MSCBs impregnated with cobalt oxide (Co/MSCBs) using a phase-inversion and sintering-assisted process. The Co/MSCBs were investigated for the degradation of sulfamethoxazole (SMX) in the peroxymonosulfate (PMS) induced AOPs system under mild reaction conditions. The effects of operating parameters (e.g., SMX concentration, reaction temperature, and catalyst dosage) in the Co/MSCBs|PMS system were studied on three different types of catalytic ceramic beads: 2Co/MSCB0 (beads with a common isotropic pore structure), 2Co/MSCB1 (beads with radial finger-like microstructures and a denser outer skin-layer), and 2Co/MSCB2 (beads with finger-like microstructures and no outer skin layer). At 20 °C, 2Co/MSCB2 (59.1 %) demonstrated a higher degradation efficiency for 40 mg/L SMX in comparison to 2Co/MSCB1 (54.9 %) and 2Co/MSCB0 (49.6 %). Additionally, it is noteworthy that the sample 2Co/MSCB2, after being used and regenerated, exhibited significantly a higher catalytic performance (70.83 % removal in 20 min during the 16th run) than the fresh one (70.47 % removal in 120 min). After reactions, Co/MSCBs can be readily separated from the bulk solution and used for the next run, making them ideal for practical applications. Furthermore, a radical quenching experiment was conducted, and a plausible catalytic mechanism was proposed. This research presents a new approach for the fabrication of micro-structured ceramic beads that are capable of effectively overcoming the diffusion limitations encountered in both heterogeneous reactions and adsorption processes.

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

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

Unraveling Different Reaction Characteristics of Alkoxy Radicals in a Co(II)-Activated Peracetic Acid System Based on Dynamic Analysis of Electron Distribution.

Peracetic acid (PAA)-based advanced oxidation processes (AOPs) have shown broad application prospects in organic wastewater treatment. Alkoxy radicals including CH3COO• and CH3COOO• are primary reactive species in PAA-AOP systems; however, their reaction mechanism on attacking organic pollutants still remains controversial. In this study, a Co(II)/PAA homogeneous AOP system at neutral pH was constructed to generate these two alkoxy radicals, and their different reaction mechanisms with a typical emerging contaminant (sulfacetamide) were explored. Dynamic electron distribution analysis was applied to deeply reveal the radical-meditated reaction mechanism based on molecular orbital analysis. Results indicate that hydrogen atom abstraction is the most favorable route for both CH3COO• and CH3COOO• attacking sulfacetamide. However, both radicals cannot react with sulfacetamide via the radical adduct formation route. Interestingly, the single-electron transfer reaction is only favorable for CH3COO• due to its lower ESUMO. In comparison, CH3COOO• can react with sulfacetamide via a similar radical self-sacrificing bimolecular nucleophilic substitution (SN2) route owing to its high ESOMO and easy escape of unpaired electrons from n orbitals of O atoms in the peroxy bond. These findings can significantly improve the knowledge of reactivity of CH3COO• and CH3COOO• on attacking organic pollutants at the molecular orbital level.

Nanoconfined catalytic membrane assembled by nitrogen-doped carbon encapsulating Fe-based nanoparticles for rapid removal of 2,4-dichlorophenol in wastewater by peroxymonosulfate activation

Surface-dependent non-radical oxidation of carbon materials-based persulfate systems show a better application prospect in the removal of pollutants in complex wastewater. However, their potential is severely limited by the restricted liquid-to-solid mass transfer efficiency of conventional suspension systems. In this paper, a nitrogen-doped carbon encapsulating iron-based nanoparticles (Fe@NC) was prepared, and loaded onto a polyvinylidene fluoride (PVDF) membrane to construct a novel catalytic membrane Fe@NC/PVDF. The Fe@NC/PVDF/PMS system could achieve 99.74% of 2,4-dicholophenol (2,4-DCP) removal within a retention time of 0.867 s, the kinetic constant is 840 times higher than that of Fe@NC/PMS system, and 2–5 orders of magnitude higher than that of various reported advanced oxidation processes systems. The system exhibits strong anti-interference to various water matrices, long-time operational stability at high flux (306 L·m−2·h−1), universality to pollutants that do not contain strong electron-withdrawing groups and mitigation of membrane fouling. Mechanism studies indicate that the electron transfer pathway dominates the 2,4-DCP removal, and singlet oxygen (1O2) plays an auxiliary role. The higher mass transfer efficiency of the filtration mode releases the full potential of the non-radical pathway. This paper provides theoretical and technical support for the development and efficient utilization of carbon-based materials with excellent persulfate catalytic properties.

Uma revisão das abordagens de tratamento da atrazina empregando tecnologias de processos oxidativos avançados

ABSTRACT Atrazine is a synthetic pesticide widely used in many crops. It is considered a contaminant to soil and water, and due to its leaching and recalcitrant capacities, new treatment technologies have been developed for its removal, with an emphasis on advanced oxidation processes (AOPs), since conventional wastewater treatments show reduced capacity to remove persistent organic pollutants. This article provides a literature review of the main AOP approaches, such as photolysis, ozonation, photoperoxidation, fenton and photo-fenton, photocatalysis, and electrochemical processes, for the atrazine treatment and the fundamentals behind each process. In addition, the innovations and applications of hybrid AOP systems were documented. It is worth mentioning that despite the high efficiency obtained by AOPs in the degradation of ATZ, it is important to evaluate the resulting toxicity and by-products formed, as well as the costs associated with the application of these processes.

Analysis of scientific and technological trends in the incorporation of activated carbon in advanced oxidation processes-a bibliometric study.

There is high interest in the development of water pollution remediation technologies. Advanced oxidation processes (AOPs) are a promising alternative for the degradation of organic compounds; however, these technologies have been limited mainly by high operating costs and, in some cases, by forming byproducts, which can be more hazardous than the original pollutants. Activated carbon (AC) is a porous material that can be combined with AOP systems in various ways, given its adsorbent and catalytic characteristics. In addition, AC is a flexible, adaptable, and low-cost material. This article presents a bibliometric analysis of AOPs incorporating CA in scientific research and patents; the Scopus database was used to obtain patents and Orbit Express for patents. The most investigated AOPs incorporating AC are photocatalysis processes, Fenton processes, persulfate-based AOP, electrochemical processes, and ozonation. However, it is the persulfate-based AOP that has seen the greatest growth in scientific publications in recent years; this great interest can be related to the synergy that the process has with AC, allowing the degradation of contaminants via radical and non-radical. According to the maturity analysis of scientific publications, photocatalysis, Fenton, electrochemistry, ozonation, and persulfate technologies are in a growth stage and will reach maturity in 2034, 2042, 2040, 2034, and 2035, respectively; these technologies coupled with AC are expected to generate a greater number of patents when they reach maturity.

Highly graphitized biochar as nonmetallic catalyst to activate peroxymonosulfate for persistent quinclorac removal in soil through both free and non-free radical pathways

To explore highly effective and nonmetallic advanced oxidation process system to alleviate the persistent herbicides contamination in agricultural soils is of great importance. In this study, a significantly graphitized biochar with abundant C = O structure is prepared as non-metallic catalyst (WCGBC800). Different from other traditional amorphous pristine biochar, WCGBC800 can accelerate the electron transfer in the system and then effectively activate peroxymonosulfate (PMS) to produce free (OH, O2–, SO4−, etc.) and non-free radicals (1O2, electron transfer, etc.). Consequently, WCGBC800 can degrade 100 % the persistent organic herbicide quinclorac (QNC, with a content of 50 mg·kg−1) in soil within 20 min after PMS addition. The T.E.S.T-QSAR software simulation evidence that the toxicity of degradation intermediates is much lower than QNC. The stress of QNC on rice seedlings was directly described through rice cultivation experiment. The stress of rice seedlings was relieved after WCGBC800 + PMS treatment. The growth experiment of rice seedlings also shows that with an original QNC concentration of 7 mg·kg−1 in soil, the root length, root surface area, leaf length, leaf area, and leaves perimeter of rice increase of 255.30 %, 148.38 %, 207.64 %, 204.19 %, and 63.69 % respectively after detoxification by WCGBC800 + PMS system. This functional material and the WCGBC800 + PMS system provide new solutions for solving the problem of herbicide residues in soil with promising safety.

Intensified degradation of reactive blue 222 (RB222) textile dye by a hybrid AOP system of hydrodynamic cavitation coupled with inline UV and PMS oxidant

Treatment of textile wastewater poses a significant problem due to the recalcitrant nature of dyes. The present work aims to evaluate a hybrid advanced oxidation process (AOP) comprising hydrodynamic cavitation (HC), ultraviolet irradiation (UV) and different oxidants. Synthetic wastewater (SW) was prepared by dissolving 50 ppm of reactive blue 222 dye, salt, sodium carbonate and detergent. A venturi, a single-hole orifice plate and multiple-hole orifice plates were compared as cavitating devices for HC. Multiple-hole orifice plate 3 proved to be the most efficient cavitation device. Three different oxidants, namely Fenton, potassium peroxymonosulfate (PMS), and potassium persulfate (KPS), were compared in combination with HC + UV. PMS turned out to be the most effective oxidant at pH 6.5, and HC + UV + PMS was the most effective treatment process as compared to standalone methods. NaCl (salt) in wastewater promotes the degradation of RB222 dye, and sodium carbonate suppresses the degradation of RB222 by scavenging radicals. After 120 min, the TOC reduction for the HC-only, UV-only, HC + UV, UV + PMS (2 g/L), and HC + UV + PMS (2 g/L) process was 3.23 %, 4.17 %, 9.64 %, 32.48 %, 38.51 %, and 75.96 %, respectively. After 180 min of treatment with HC + UV + PMS (2 g/L), the maximum 85.66 % TOC reduction of SW was reached, and the complex intermediates formed are also reported.

FeS and Fe3O4 Co-modified biochar to build a highly resistant advanced oxidation process system for quinclorac degradation in irrigation water

Advanced oxidation processes (AOPs), based on sulfate radical (SO4·-) produced by peroxymonosulfate (PMS), can effectively mineralize refractory organic pollutants. However, the coexistence of anions and natural organic matters in actual wastewater prevents the application of AOPs. A simple one-step method was used to prepare FeS/Fe3O4 co-modified biochar materials (FFB) that could activate PMS to degrade quinclorac (QNC) with a removal rate of 100%, even exhibiting optimum degradation of QNC reached 99.31% in irrigation water, demonstrating excellent anti-interference performance for co-existing anions and natural organic matter. Meanwhile, ecotoxicity analysis showed that the toxicity of degradation intermediates was lower than that of QNC. Characterization results demonstrated the even distribution of FeS and Fe3O4 onto biochar, supplying abundant Fe2+ to activate PMS producing reactive oxygen species (ROS), while the generated Fe3+ after reactive continue to be reduced with sulfur species to promote the cycle of Fe2+/Fe3+. The coexistence of ·OH, SO4·-, 1O2, and O2·- in the FFB/PMS-QNC system suggest the possession of two pathway with free radical and non-free radical pathways to degrade QNC. The density functional theory (DFT) was used to analyze the adsorption sites and adsorption energy of PMS, as well as the differential charge density, which further proved the generation of SO4·-, O2·- and 1O2. In addition, the electrochemical test results showed that electron transfer also played an important role in the degradation of QNC. This study provides a feasible approach for the removal of organic pollutants in actual water.

Reduced TiO2 nanotube arrays as environmental catalysts that enable advanced oxidation processes: A mini review

Advanced oxidation processes (AOPs) that utilize heterogeneous catalysts are an engaging and compelling technology for treating emerging contaminants in water and wastewater. Substantial efforts have been devoted to developing cost-effective and environmentally benign materials for application in AOPs. Reduced TiO2 nanotube arrays (r-TNAs) have recently emerged as promising environmental materials for efficiently mitigating persistent organic pollutants (POPs) resistant to conventional biological treatment. r-TNAs possess distinct electrical, optical, and catalytic features, including superior conductivity and solar light absorption due to structural defects involving oxygen vacancies and Ti3+ states. Moreover, their well-organized open channel structures provide a substantial surface area, facilitating the efficient mass transfer of reactants and products. Notably, r-TNAs can be grown directly on the substrate without using organic adhesives or binders, which improves their mechanical and chemical durability and facilitates their repeated use. This article represents the pioneering comprehensive review of r-TNAs in AOP applications. We introduce an electrochemical anodization technique to fabricate TNAs and summarizes the reduction methods employed in r-TNA synthesis. We also elucidate the appealing attributes of r-TNAs and explore their applications in emerging AOPs, including persulfate activation, electrocatalysis, and photo(electro)catalysis. Finally, we outline critical challenges and provide insights into future prospects for the development of AOP systems based on r-TNAs.

Site Engineering of Covalent Organic Frameworks for Regulating Peroxymonosulfate Activation to Generate Singlet Oxygen with 100 % Selectivity

AbstractSinglet oxygen (1O2) is an excellent reactive oxygen species (ROSs) for the selective conversion of organic matter, especially in advanced oxidation processes (AOPs). However, due to the huge dilemma in synthesizing single‐site type catalysts, the control and regulation of 1O2 generation in AOPs is still challenging and the underlying mechanism remains largely obscure. Here, taking advantage of the well‐defined and flexibly tunable sites of covalent organic frameworks (COFs), we report the first achievement in precisely regulating ROSs generation in peroxymonosulfate (PMS)‐based AOPs by site engineering of COFs. Remarkably, COFs with bipyridine units (BPY‐COFs) facilitate PMS activation via a nonradical pathway with 100 % 1O2, whereas biphenyl‐based COFs (BPD‐COFs) with almost identical structures activate PMS to produce radicals (⋅OH and SO4⋅−). The BPY‐COFs/PMS system delivers boosted performance for selective degradation of target pollutants from water, which is ca. 9.4 times that of its BPD‐COFs counterpart, surpassing most reported PMS‐based AOPs systems. Mechanism analysis indicated that highly electronegative pyridine‐N atoms on BPY‐COFs provide extra sites to adsorb the terminal H atoms of PMS, resulting in simultaneous adsorption of O and H atoms of PMS on one pyridine ring, which facilitates the cleavage of its S−O bond to generate 1O2.

Prussian blue analogues derived magnetic FeCo@GC material as high-performance metallic peroxymonosulfate activators to degrade tetrabromobisphenol A over a wide pH range.

Metal-organic frame (MOF) materials can effectively degrade organic pollutants, whereas the MOF is rapidly hydrolysed in water and has poor stability and low reusability. However, in the current advanced oxidation process (AOP) system, the removal effect of pollutants under alkaline condition is not ideal. In this study, a magnetic composite material derived from MOF was synthesised and used as a new catalyst for rapid degradation of tetrabromobisphenol A (TBBPA). Compared to precarbonisation, FeCo@GC formed a conductive graphite carbon skeleton, retained the complete rhombododecahedron structure, had a larger specific surface area and provided more active sites for peroxymonosulfate (PMS) activation. The target pollutant TBBPA (20 mg/L) was completely degraded within 30 min, and the mineralisation rate reached 40.98% in the FeCo@GC (150 mg/L) and PMS (1 mM) systems, owing to the synergistic interaction between Fe, Co and graphite carbon. The reactive oxygen species (ROS) involved in the reaction were determined to be SO4•-, ·OH, 1O2 and O2•- by electron paramagnetic resonance and free radical scavenging experiments, and the 1O2 played a dominant role. Based on the results of LC-MS analysis results, the main degradation pathways of TBBPA involve three mechanisms: the debromination reaction, hydroxylation and cleavage of the benzene ring. In addition, compared with previous AOP systems, FeCo@GC/PMS overcomes the disadvantage of poor degradation effect of TBPPA under alkaline conditions, has a wide range pH (3-11) application and has the best effect on TBBPA degradation under alkaline conditions. FeCo@GC has an excellent cycle performance, with a removal rate of re-calcined material of 88.52% after five cycles. Therefore, FeCo@GC can be used as a promising and efficient catalyst for removing environmental organic pollutants.

Site Engineering of Covalent Organic Frameworks for Regulating Peroxymonosulfate Activation to Generate Singlet Oxygen with 100% Selectivity.

Singlet oxygen (1O2) is an excellent reactive oxygen species (ROSs) for the selective conversion of organic matter, especially in advanced oxidation processes (AOPs). However, due to the huge dilemma in synthesizing single-site type catalysts, the control and regulation of 1O2 generation in AOPs is still challenging and the underlying mechanism remains largely obscure. Here, taking advantage of the well-defined and flexibly tunable sites of covalent organic frameworks (COFs), we report the first achievement in precisely regulating ROSs generation in peroxymonosulfate (PMS)-based AOPs by site engineering of COFs. Remarkably, COFs with bipyridine units (BPY-COFs) facilitate PMS activation via a nonradical pathway with 100% 1O2, whereas biphenyl-based COFs (BPD-COFs) with almost identical structures activate PMS to produce radicals (•OH and SO4•-). The BPY-COFs/PMS system delivers boosted performance for selective degradation of target pollutants from water, which is ca. 9.4 times that of its BPD-COFs counterpart, surpassing most reported PMS-based AOPs systems. Mechanism analysis indicated that highly electronegative pyridine-N atoms on BPY-COFs provide extra sites to adsorb the terminal H atom of PMS, resulting in simultaneous adsorption of O and H atoms of PMS on one pyridine ring, which facilitates the cleavage of its S-O bond to generate 1O2.

Synergy between UV light and trichloroisocyanuric acid on methylisothiazolinone degradation: Performance, kinetics and degradation pathway.

Methylisothiazolinone (MIT) is widely used in daily chemicals, fungicides, and other fields and its toxicity has posed a threat to water system and human health. In this study, ultraviolet (UV)/trichloroisocyanuric acid (TCCA), which belongs to advanced oxidation processes (AOP), was adopted to degrade MIT. Total chlorine attenuation detection proved that TCCA has medium UV absorption and a strong quantum yield (0.49 mol E−1). At a pH of 7.0, 93.5% of MIT had been decontaminated after 60 min in UV/TCCA system (kobs = 4.4 × 10−2 min−1, R2 = 0.978), which was much higher than that in the UV alone system and TCCA alone system, at 65% (1.7 × 10−2 min−1, R2 = 0.995) and 10% (1.8 × 10−3 s−1, R2 = 0.915), respectively. This system also behaved well in degrading other five kinds of contaminants. Tert-butanol (TBA) and carbonate (CO32−) were separately used in quenching experiments, and the degradation efficiency of MIT decreased by 39.5% and 46.5% respectively, which confirmed that HO• and reactive chlorine species (RCS) were dominant oxidants in UV/TCCA system. With TCCA dosage increasing in a relatively low concentration range (0.02–0.2 mM) and pH decreasing, the effectiveness of this AOP system would be strengthened. The influences of coexisting substances (Cl−, SO42−, CO32−, NO2− and NO3−) were explored. MIT degradation pathways were proposed and sulfur atom oxidation and carboxylation were considered as the dominant removal mechanisms of MIT. Frontier orbital theory and Fukui indexes of MIT were employed to further explore the degradation mechanism.

Kinetic study on the degradation of organic pollutants in UV/persulfate and in other advanced oxidation processes: Role of radicals and improvement of the degradation rates

Kinetic degradation of five typical pollutants including clothianidin (CLO), levofloxacin (LEV), p-nitrosodimethylaniline (RNO), paracetamol (PCM), and basic fuchsin (BF) by UV/persulfate (UV/PS) and other advanced oxidation processes (AOPs) (i.e., UV/H2O2, Fe2+/H2O2, electrochemical process, UV/PS/heat, UV/PS/Fe2+, UV/PS/Fe2O3, and UV/PS/rGO) were studied. The result showed that all pollutants were effectively degraded by UV/PS with different degradation rates. The oxidizing factors contributing to the pollutant degradation in UV/PS were studied, showing that UV is the predominant contributor to CLO degradation, while its contribution is negligible in the degradation of other compounds. •OH and SO4•- were the main radicals contributing to the degradation of all pollutants in UV/PS, except CLO. The second-order rate constant of •OH and SO4•- towards pollutants was determined according to the competition kinetic model, to be in the range of 109-1010 M−1 s−1. The degradation rate of pollutants in different AOPs were varied, because the oxidizing factors and their role in AOP systems directly affect the degradation efficiency of pollutants. In all AOPs, •OH radical played a major role in their degradation. The presence of water matrices has different influences on the degradation rates of pollutants. For example, 10 mM NO2- inhibited the degradation of pollutants to 99.1%, whereas Br-, SO42-, and F- had a lower inhibitory effect on their degradation. HPO42- can improve the degradation rate of BF, but it also significantly inhibited the degradation of PCM. The results also revealed that UV/PS/Fe2+ and UV/PS/rGO can remarkably increase the degradation efficiency of all pollutants, while using α-Fe2O3 and heat were less efficient. In addition, other parameters including COD removal, energy consumption, and toxicity assessment were also investigated to evaluate the potential application of UV/PS in practice.