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In this study, CoCr layered double hydroxide material (CoCr-LDH) was prepared and used as an effective catalyst for peroxymonosulfate (PMS) activation to degrade organics in water. The prepared CoCr-LDH material had a crystalline structure and relatively porous structure, as determined by various surface analyses. In Rhodamine B (RhB) removal, the most outstanding PMS activation ability belongs to the material with a Co:Cr molar ratio of 2:1. The removal of RhB follows pseudo-first-order kinetics (R2 > 0.99) with an activation energy of 38.23 kJ/mol and efficiency of 98% after 7 min of treatment, and the total organic carbon of the solution reduced 47.2% after 10 min. The activation and oxidation mechanisms were proposed and the RhB degradation pathways were suggested with the key contribution of O2•- and 1O2. Notably, CoCr-LDH can activate PMS over a wide pH range of 4 – 9, and apply to a wide range of organic pollutants and aqueous environments. The material has high stability and good recovery, which can be reused for 5 cycles with a stable efficiency of above 88%, suggesting a high potential for practical recalcitrant water treatment via PMS activation by heterogeneous catalysts. [ABSTRACT FROM AUTHOR]

Even though transition metals can activate Oxone to degrade toxic contaminants, bimetallic materials possess higher catalytic activities because of synergistic effects, making them more attractive for Oxone activation. Herein, nanoscale CuCo-bearing N-doped carbon (CuCoNC) can be designed to afford a hollow structure as well as CuCo species by adopting cobaltic metal organic frameworks as a template. In contrast to Co-bearing N-doped carbon (CoNC), which lacks the Cu dopant, CuCo alloy nanoparticles (NPs) are contained by the Cu dopant within the carbonaceous matrix, giving CuCoNC more prominent electrochemical properties and larger porous structures and highly nitrogen moieties. CuCoNC, as a result, has a significantly higher capability compared to CoNC and Co3O4 NPs, for Oxone activation to degrade a toxic contaminant, Rhodamine B (RDMB). Furthermore, CuCoNC+Oxone has a smaller activation energy for RDMB elimination and maintains its superior effectiveness for removing RDMB in various water conditions. The computational chemistry insights have revealed the RDMB degradation mechanism. This study reveals that CuCoNC is a useful activator for Oxone to eliminate RDMB. [ABSTRACT FROM AUTHOR]

As cobalt (Co) has been the most useful element for activating Oxone to generate SO4•−, this study aims to develop a hierarchical catalyst with nanoscale functionality and macroscale convenience by decorating nanoscale Co-based oxides on macroscale supports. Specifically, a facile protocol is proposed by utilizing Cu mesh itself as a Cu source for fabricating CuCo2O4 on Cu mesh. By changing the dosages of the Co precursor and carbamide, various nanostructures of CuCo2O4 grown on a Cu mesh can be afforded, including nanoscale needles, flowers, and sheets. Even though the Cu mesh itself can be also transformed to a Cu-Oxide mesh, the growth of CuCo2O4 on the Cu mesh significantly improves its physical, chemical, and electrochemical properties, making these CuCo2O4@Cu meshes much more superior catalysts for activating Oxone to degrade the Azo toxicant, Acid Red 27. More interestingly, the flower-like CuCo2O4@Cu mesh exhibits a higher specific surface area and more superior electrochemical performance, enabling the flower-like CuCo2O4@Cu mesh to show the highest catalytic activity for Oxone activation to degrade Acid Red 27. The flower-like CuCo2O4@Cu mesh also exhibits a much lower Ea of Acid Red 27 degradation than the reported catalysts. These results demonstrate that CuCo2O4@Cu meshes are advantageous heterogeneous catalysts for Oxone activation, and especially, the flower-like CuCo2O4@Cu mesh appears as the most effective CuCo2O4@Cu mesh to eliminate the toxic Acid Red 27. [ABSTRACT FROM AUTHOR]

Bis(4-hydroxyphenyl)methanone (BHPM), a common ultraviolet stabilizer and filter (USF), is extensively added in sunscreens; however, BHPM is proven as an endocrine disruptor, posing a serious threat to aquatic ecology, and BHPM should be then removed. As sulfate radical (SO4•−) could be useful for eliminating emerging contaminants, oxone appears as a favorable source reagent of SO4•− for degrading BHPM. Even though cobalt is a useful catalyst for activating oxone to generate SO4•−, it would be even more promising to utilize ambient-visible-light irradiation to enhance oxone activation using cobaltic catalysts. Therefore, in contrast to the conventional cobalt oxide, cobalt titanium oxide (CTO) was investigated for chemical and photocatalytic activation of oxone to eliminate BHPM from water. Especially, a special morphology of nanosheet-assembled configuration of CTO was designed to maximize active surfaces and sites of CTO. Thus, CTO outperforms Co3O4 and TiO2 in degrading BHPM via oxone activation. Furthermore, the substituent of Ti enabled CTO to enhance absorption of visible light and possessed a much smaller Eg. These photocatalytic properties intensified CTO's activity for oxone activation. CTO possessed a significantly smaller Ea of degradation of USFs than other catalytic systems. Mechanistic insight for degrading BHPM by CTO + oxone was explicated for identifying contribution of reactive oxygen species to BHPM degradation. The BHPM degradation pathway was also investigated and unveiled in details via the DFT calculation. These results validated that CTO is a superior cobaltic alternative for activating oxone to eliminate BHPM. [ABSTRACT FROM AUTHOR]

• Co 3 O 4 nanofiber (CONF) is facilely fabricated via an electronspinning technique. • CONF, with fibrous shapes, exhibits significantly higher surface area and pore volume. • CONF shows considerably higher catalytic activities than the commercial Co 3 O 4 NPs. • AR decolorization is completed by CONF-activated PMS with a rate constant of 0.21 min−1. • CONF can be re-used for activating PMS to decolorize AR over multiple cycles. Even though Co 3 O 4 is the most conventional heterogeneous catalyst for activating peroxymonosulfate (PMS), Co 3 O 4 nanoparticles (NPs) aggregate severely, especially in water, losing their catalytic activities. In the present study, an electrospinning technique is employed to prepare Co 3 O 4 nanofiber (CONF), in which severe aggregation of Co 3 O 4 NPs can be prevented as Co 3 O 4 NPs are specifically configured into fibers, rendering a much higher surface area and porosity than conventional Co 3 O 4 NPs. When decolorization of Acid Red 27 (AR) is employed as a model test for PMS activation, CONF exhibits considerably higher catalytic activities than the commercial Co 3 O 4 NPs for activating PMS to decolorize AR completely in 15 min with a rate constant of 0.210 min−1. The E a of AR decolorization by CONF-activated PMS is 43.5 kJ/mol, which is also lower than several reported studies. CONF can be also re-used to activate PMS over multiple cycles. AR degradation is confirmed to involve with sulfate radicals via examining effects of radical scavengers and Electron Paramagnetic Resonance analysis. The findings obtained in this study successfully demonstrate that the electrospinning technique can be utilized to prepare nanoscale fibrous Co 3 O 4 with improved physical and chemical properties for catalytic advanced oxidation applications. [ABSTRACT FROM AUTHOR]

Advanced oxidation (AOPs) utilizing peroxymonosulfate (PMS) are efficient processes for the degradation of organic pollutants. This study aimed to synthesize and characterize cobalt ferrite (CoFe 2 O 4), graphene oxide (GO), MIL-101(Fe), and their composite structures. The nanomaterials were applied as catalysts by PMS for triclosan (TCS) decomposition. The maximum removal rates of TCS were 49.29, 66.13, 84.04, 89.73, and 100% for PMS alone, CoFe 2 O 4 , GO, MIL-101(Fe), and CoFe 2 O 4 /MIL-101(Fe)/GO with PMS, respectively. Metal ions leaching declined in CoFe 2 O 4 /MIL-101(Fe)/GO/PMS compared with others. Hence, the composite nanomaterials appear to be effective catalysts for the degradation of organic pollutants by PMS activation. [Display omitted] • Nanomaterials increased PMS activation in TCS removal compared with PMS alone. • The simple and composite forms of nano catalysts for PMS activation were studied. • The composite form was more efficient than simple ones in TCS decomposition. • The composite form decreased metal ions leaching compared with simple forms. [ABSTRACT FROM AUTHOR]

While Prussian Blue (PB) analogues are attractive catalysts for activating peroxymonosulfate (PMS), PB analogues are very small and thus difficult for recovery. Immobilizing PB particles onto graphene is a useful technique which facilitates recovery and also enhances catalytic activities. As doping graphene with sulfur/nitrogen (S/N) increases its electro-conductivity and active sites, the composite of PB and S/N-doped graphene should enhance PMS activation. Thus, this study aims to fabricate such a composite. Unlike conventional S / N-doped graphene prepared via post-modifications, trithiocyanuric acid is used as a precursor, which is converted to S-doped graphitic carbon nitride (SCN). The composite of PB and SCN (PBSCN) is then fabricated by growing a cobalt-based PB analogue on SCN. The resulting PBSCN preserves the crystalline structures, textural properties and catalytic sites of PB and SCN. As degradation of Acid Red 27 (AR) is used as a model reaction, PBSCN exhibits a higher catalytic activity than PB and SCN individually, as well as Co 3 O 4 to activate PMS for AR degradation possibly because SCN may facilitate electron transfer and enhance catalytic activities of PB. PBSCN also remains effective and re-usable over several cycles for AR degradation. These features indicate that PBSCN is a promising catalyst for activating PMS and the fabrication technique demonstrated here can be employed to prepare composites of various PB analogues and carbon nitride to exhibit enhanced catalytic activities. [ABSTRACT FROM AUTHOR]

Cobalt ferrite (CF) nanoparticle (NP) represents a promising alternative to Co3O4 NP for peroxymonosulfate (PMS) activation in view of its strong magnetism for easy recovery. As CF NPs in water are prone to agglomerate, a few attempts have been made to immobilize CF NPs on substrates. While carbonaceous supports are more favorable owing to their earth abundancy, the study of carbon-supported CF for PMS activation is limited to graphene-based CF, which, however, requires complicated protocols to prepare. As carbon-supported CF, by straightforward preparation, is still greatly desired, this study aims to employ electrospinning techniques for preparing carbon-supported CF by carbonizing an electrospun CF-embedded polyacrylonitrile (PAN) fiber. After carbonization, the CF-PAN fiber is converted into CF-embedded carbon nanofiber (CF@CNF), which contains well distributed CF NPs, high magnetism and stable carbon support, making CF@CNF a highly promising catalyst for activating PMS. As amaranth decolorization is used as a model reaction, CF@CNF is able to activate PMS for generating sulfate radicals and then decolorize amaranth in water. Amaranth decolorization by CF@CNF-PMS is also substantially facilitated at elevated temperature, and enhanced under the weakly acidic condition. CF@CNF also remains effective to activate PMS even in the presence of salts and surfactants, and re-usable over multiple cycles. Compared to other reported catalysts, CF@CNF also exhibited a much lower Ea value (35.8 kJ/mol) for amaranth decolorization. These features validate that CF@CNF is an advantageous and convenient catalyst for activating PMS. [ABSTRACT FROM AUTHOR]

This work describes the preparation and characterization of atomically-dispersed V on graphitic carbon nitride (g-C 3 N 4 , CN) via a facile calcination method. The V atoms were found to coordinate with the –N and –O in the triazine units of g-C 3 N 4. The catalytic activity of the as-prepared materials was evaluated in ciprofloxacin (CIP) degradation via peroxymonosulfate (PMS) activation. It was found that the presence of V (0.10 at%) noticeably enhanced the catalytic activity of CN, and the V-CN catalyst showed substantial tolerance towards pH changes, interfering species, various water sources, and different antibiotics. Chemical scavenging and electrochemical methods illustrated that the V-CN/PMS/CIP system encompassed of a nonradical electron-transfer pathway (50.0%), singlet oxygen (1O 2) pathway (30.8%), sulfate radical (SO 4 •-) generation (11.5%), and other reactive species (7.7%), and the activation process was due to the V-redox cycles. Peculiarly, V(IV)/V(III) redox cycles were responsible for the nonradical electron-transfer pathway while V(V)/V(IV) redox cycles were behind the SO 4 •- and 1O 2 generation. Additionally, comprehensive investigation on the catalytic affinity of V-CN towards different antibiotics elucidated that the electrochemical properties of the organic pollutant play a major role in the electron-transfer direction during nonradical activation. Lastly, the CIP degradation pathway was proposed, and the toxicity of its degradation intermediates was estimated. Overall, this work deepens the understanding on the potential of V-based materials in catalytic PMS activation. [Display omitted] • 0.1 at% of V on C 3 N 4 enhanced CIP removal via PMS activation. • V atoms coordinated with N- and O-atoms rather than forming V-oxides. • Nonradical electron-transfer, 1O 2 , and SO 4 •- contributed to PMS activation. • V-CN showed tolerance against interfering species and different pollutants. • Electrochemical properties of pollutants' affect electron-transfer direction. [ABSTRACT FROM AUTHOR]

While heterogeneous cobalt (Co) catalysts are useful peroxymonosulfate (PMS) activators, the development of a heterogeneous Co-based catalyst with intriguing physicochemical properties and outstanding catalytic activities is still of great interest. Herein, a unique cavity-structured grassy-like cobalt oxide (Co 3 O 4) (CGCO) is proposed and fabricated through two-step modifications of partial sculpting and calcination using Co-based metal organic framework (Co-MOF) as an initial precursor. The as-prepared CGCO exhibits a cavity structure covered by grassy-like outer shells, thus possessing special physicochemical properties and enriched oxygen vacancy. These features enable CGCO a much more advantageous activator than commercial Co 3 O 4 for activating PMS, and would efficiently remove 100% of bisphenol A (BA) rapidly. The activation energy (E a) of BA degradation by CGCO+PMS is only 31.2 kJ/mol, which is lower than the recently-reported values. The density function theory calculation is performed to investigate the degradation pathway, and the corresponding eco-toxicity is also studied to realize the environmental implication of BA by CGCO-activated PMS as the toxicities and environmental impact of BA are significantly reduced. This work provides valuable information in term of preparation strategy of cavity structured metal oxide materials, which should be propitious for the degradation of environmental hormones via advanced oxidation reactions. [Display omitted] • Cavity-structured grassy-like cobalt oxide (Co 3 O 4) (CGCO) is proposed • CGCO exhibits a cavity structure covered by grassy-like outer shells • The activation energy (E a) of BA degradation by CGCO+PMS is 31.2 kJ/mol • The DFT calculation is performed to investigate the degradation pathway • The eco-toxicity is also studied to realize the environmental implication of BA [ABSTRACT FROM AUTHOR]

Two-dimensional (2D) planar cobalt-containing materials are promising catalysts for activating peroxymonosulfate (PMS) to degrade contaminants because 2D sheet-like morphology provides large reactive surfaces. However, preparation of these sheet-supported cobaltic materials typically involves multiple steps and complex reagents, making them less practical for PMS activation. In this study, a cobalt-based nanosheet (CoNS) is particularly developed using a one-step hydrothermal process with a single reagent in water. The resulting CoNS can exhibit a thickness as thin as a few nanometers and 2-D morphology. CoNS is also primarily comprised of cobalt species in a coordinated form of Prussian Blue analogue, which consists of both Co 3+ and Co 2+ . These features make CoNS promising for activating PMS in aqueous systems. As degradation of an emerging contaminant, caffeine, is selected as a representative reaction, CoNS not only successfully activates PMS to fully degrade caffeine in 20 min but also exhibits a much higher catalytic activity than the most common PMS activator, Co 3 O 4 . Via studying inhibitive effects of radical scavengers, caffeine degradation by CoNS-activated PMS is primarily attributed to sulfate radicals and hydroxyl radicals to a lesser extent. The degradation products of caffeine by CoNS-activated PMS are also identified and a potential degradation pathway is proposed. Moreover, CoNS could be also re-used to activate PMS for caffeine degradation without activity loss. These results indicate that CoNS is a conveniently prepared and highly effective and stable 2-D catalyst for aqueous chemical oxidation reactions. [ABSTRACT FROM AUTHOR]

As perovskite-type metal oxides are attractive catalysts for activating peroxymonosulfate (PMS), cobalt titanate (CoTiO 3 (CTO)) is particularly promising as CTO consists of earth-abundant Ti and Co is the most effective metal for PMS activation. However, conventional preparation methods of CTO result in large CTO aggregates, leading to very low surface area and porosity, and also limiting its performance. In the present study, an electrospinning technique is employed to prepare CTO nanoscale fiber (CTONF), which can exhibit a consistent nanoscale fibrous morphology, enabling CTO to exhibit a relatively large surface area and porosity, as well as mesoporous structures. Thus, CTONF shows a higher catalytic activity than the bulk CTO for activating PMS to degrade a model toxicant, Amaranth (AR) dye. The PMS activation behaviors are further investigated by examining the effects of temperature, pH, and NaCl on AR degradation by CTONF-activated PMS (CTONF-PMS). Through the effects of probe reagents, the AR degradation mechanism can be attributed primarily to sulfate radicals and hydroxyl radicals to a lesser extent. CTONF was also proven to activate PMS over multiple cycles without regeneration. These results reveal that CTONF is a high effective and recyclable heterogeneous catalyst for PMS activation as it outperforms the conventional bulk CTO. The findings obtained in this study also demonstrate that the electrospinning technique can be utilized to prepare perovskites with enhanced physical and chemical properties for catalytic advanced oxidation applications. [ABSTRACT FROM AUTHOR]

While sulfate radical-generating Advanced Oxidation Processes (AOPs) are promising techniques to degrade Bisphenol A (BPA), transition metals are typically required as catalysts to activate peroxymonosulfate (PMS) to generate sulfate radicals for BPA degradation. To reduce environmental impact and associated costs from metallic catalysts, metal-free catalysts for activating PMS are more attractive and should be further developed. Here, we propose to employ a one-step prepared sulfur-doped carbon nitride (CNS) as a non-metal and easy-to-prepare catalyst to activate PMS for BPA degradation. The as-prepared CNS exhibited a significantly higher surface area and catalytic activity for activating PMS than undoped carbon nitride (CN). Under visible light irradiation, BPA degradation extent and kinetics by CNS-activated PMS were also much higher than CN-activated PMS. The more effectiveness of CNS-activated PMS can be attributed to the synergy of sulfur and nitrogen co-doping, which might enable CNS to exhibit higher catalytic and photo-catalytic activities. Factors influencing BPA degradation were also examined, including temperature, pH, and co-existing ions. CNS-activated PMS was much more favorable to degrade BPA at elevated temperatures and under neutral conditions. The effect of concentrated NaCl did not significantly inhibit PMS activation by CNS for BPA degradation. The mechanism and pathway of BPA degradation by CNS-activated PMS were also proposed by evaluating effects of radical scavengers and degradation intermediates. CNS was also reusable to activate PMS for BPA degradation over multiple cycles without significant efficiency loss. These features demonstrate that CNS is a conveniently-prepared and promisingly effective non-metal catalyst to activate PMS for BPA degradation. [ABSTRACT FROM AUTHOR]

• Hollow-architected fluffy cubic Co 3 O 4 (HFCC) is derived from carving cubic CoMOF. • HFCC shows more superior electrochemistry than the solid cubic Co 3 O 4 (SCC). • HFCC exhibits more active surfaces than SCC for activating oxone to degrade BZC. • DFT calculation is performed to elucidate degradation process of BZC by HFCC. • Eco-toxicity of BZC degradation intermediates is evaluated to study implication. As the most widely-used oral anesthetic, benzocaine (BZC), is increasingly detected in municipal wastewater and regarded as an emerging contaminant. Thus, it would be highly imperative to develop useful methods to eliminate BZC from water. However, very few studies have been ever reported, and only photocatalysis of BZC was attempted. Therefore, this present study aims to be the first study of developing the sulfate-radical-based chemical oxidation technology (SR-COT) for degrading BZC. For establishing a useful SR-COT, the oxidant, Oxone, is then adopted and a facile nanostructured Co 3 O 4 is then developed for maximizing catalytic activities of Oxone activation by creating a hollow fluffy Co 3 O 4 nanostructure using CoMOF as a template, followed by a carving-architected treatment to afford the hollow fluffy Co 3 O 4 (HFCC). In comparison to the solid (non-hollow) Co 3 O 4 (SCC), HFCC possesses not only the excellent textural properties, but also superior electrochemical properties and highly reactive surfaces, making HFCC exhibit the significantly higher catalytic activity than SCC as well as traditional Co 3 O 4 nanoparticle in activating Oxone to degrade BZC. The density function theory calculation is performed to investigate the degradation pathway, and the corresponding eco-toxicity is also studied to realize the degradation implication of BZC by HFCC-activated Oxone. [Display omitted] [ABSTRACT FROM AUTHOR]

Although perovskites are extensively investigated in many areas, studies using perovskites as catalysts to activate oxidants for chemical oxidations are still quite limited. While various transition metals can be inserted into perovskites to form different perovskites, it is critical to investigate the effects of various transition metallic substituents on the activation of oxidants in chemical oxidation reactions. In this study, we propose to evaluate various metallic substituents in Lanthanum (La)-based perovskites (LaMO 3 (M: Co, Cu, Fe and Ni)) for activating a strong oxidant, peroxymonosulfate (POMS), in order to degrade organic contaminants. Rhodamine B (RB) decolorization is used as a model test to evaluate generation of sulfate radicals from activation of POMS by LaMO 3 . LaCoO 3 was found to exhibit the highest catalytic activity, followed by LaNiO 3 , LaCuO 3 and then LaFeO 3 . LaCoO 3 was then selected as a representative LaMO 3 to be further investigated for the behavior of POMS activation under various conditions. LaCoO 3 -activated POMS was favorable under neutral conditions and at high temperatures, but less effective in the presence of NaCl. The mechanism of RB decolorization by LaCoO 3 -activated POMS was elucidated by examining the effects of radical inhibitors and attributed primarily to sulfate radicals and hydroxyl radicals to a lesser extent. We also found that both La 3+ and Co 3+ /Co 2+ ions contribute to catalytic decomposition of POMS for yielding sulfate radicals. LaCoO 3 was also shown to activate POMS for RB decolorization over multiple trials without losing efficiency. These results reveal that LaCoO 3 is a recyclable and effective La-based perovskite for POMS activation, which can be used for degradation of organic contaminants. [ABSTRACT FROM AUTHOR]

While Oxone can be activated by catalysts for efficient generation of sulfate radicals, most of catalysts are transition metals, which could lead to secondary pollution and relatively high costs. Thus, non-metal catalysts consisting of earth-abundant elements are promising metal-free alternatives for activating Oxone. As graphitic carbon nitride (CN) has been demonstrated to activate Oxone under visible light irradiation, sulfur-doping CN (SCN) is expected to exhibit a relatively high catalytic activity for activating Oxone. However, few studies have been conducted to investigate SCN for activating Oxone. Additionally, SCN should be prepared conveniently to reduce usage of associated reagents during the doping. To this end, a one-step preparation method is adopted in this study to convert trithiocyanuric acid to SCN. The as-prepared SCN shows the morphology of crumpled micro-bags with porous surfaces, enabling it to exhibit a much higher surface area (86.8 m 2 g −1 ) than typical CN (ca. 10 m 2 g −1 ). As Rhodamine B (RB) decolorization was employed as a model test to evaluate sulfate radicals generated from activation of Oxone, SCN also exhibited a much higher catalytic activity (rate constant ( k 1 ) = 0.107 min −1 ) to activate Oxone than CN ( k 1 = 0.037 min −1 ). SCN-activated Oxone for RB decolorization was relatively favorable at elevated temperatures as well as neutral conditions; it also remained quite effective even in the presence of NaCl. Through examining effects of radical scavengers, the RB mechanism can be primarily attributed to sulfate radicals. SCN was also reusable to activate Oxone for RB decolorization over 6 cycles. These features indicate that SCN is an easy-to-prepare and promisingly effective non-metal catalyst to activate Oxone. [ABSTRACT FROM AUTHOR]

Extensive usage of caffeine (CAF) as a medicine and additives in beverages has led to increasing presence of CAF in wastewater and even drinking water. To remove CAF, peroxymonosulfate (PMS), is adopted to generate sulfate radical to degrade CAF in water. To facilitate PMS activation, a magnetic carbon-supported cobalt (MC/Co) hybrid material is prepared via carbonization of a cobalt-containing Prussian blue analogue framework (Co 3 [Co(CN) 6 ] 2 ). The resultant MC/Co contains Co and Co 3 O 4 nanoparticles supported on a carbon matrix, making it an attractive magnetic catalyst to activate PMS for degrading CAF. MC/Co-activated PMS was shown to degrade CAF much more effectively than PMS and Co 3 O 4 -activated PMS. Parameters affecting CAF degradation by MC/Co-activated PMS were also examined, including MC/Co and PMS concentrations, temperature, pH, and salt. Effects of radical quenchers were also examined to provide insights into the CAF degradation mechanism. MC/Co-activated PMS was much more favorable at higher temperatures than ambient temperature, and under neutral conditions. Nevertheless, the presence of concentrated NaCl noticeably hindered CAF degradation. Through examining effects of radical quenchers, the mechanism of CAF degradation by MC/Co-activated PMS was attributed primarily to sulfate radicals and hydroxyl radicals to a lesser extent. The degradation products of CAF by MC/Co-activated PMS were also identified and a possible degradation pathway is proposed. MC/Co can activate PMS over multiple cycles without loss of catalytic activity. These findings demonstrate that MC/Co, simply prepared from simple carbonization of Co 3 [Co(CN) 6 ] 2 can be a promising heterogeneous catalyst for activating PMS to degrade CAF. [ABSTRACT FROM AUTHOR]

A Prussian blue analogue, cobalt hexacyanoferrate Co 3 [Fe(CN) 6 ] 2 , was used for the first time to prepare a magnetic carbon/cobalt/iron (MCCI) nanocomposite via one-step carbonization of Co 3 [Fe(CN) 6 ] 2 . The resulting MCCI consisted of evenly-distributed cobalt and cobalt ferrite in a porous carbonaceous matrix, making it an attractive magnetic heterogeneous catalyst for activating peroxymonosulfate (PMS). As Rhodamine B (RhB) degradation was adopted as a model test for evaluating activation capability of MCCI, factors influencing RhB degradation were thoroughly examined, including MCCI and PMS dosages, temperature, pH, salt and radical scavengers. A higher MCCI dosage noticeably facilitated the degradation kinetics, whereas insufficient PMS dosage led to ineffective degradation. RhB degradation by MCCI-activated PMS was much more favorable at high temperatures and under neutral conditions. The presence of high concentration of salt slightly interfered with RhB degradation by MCCI-activated PMS. Through examining effects of radical scavengers, RhB degradation by MCCI-activated PMS can be primarily attributed to sulfate radicals instead of a combination of sulfate and hydroxyl radicals. Compared to Co 3 O 4 , a typical catalyst for PMS activation, MCCI also exhibited a higher catalytic activity for activating PMS. In addition, MCCI was proven as a durable and recyclable catalyst for activating PMS over multiple cycles without efficiency loss and significant changes of chemical characteristics. These features demonstrate that MCCI, simply prepared from a one-step carbonization of Co 3 [Fe(CN) 6 ] 2 is a promising heterogeneous catalyst for activating PMS to degrade organic pollutants. [ABSTRACT FROM AUTHOR]

Background Readily-available and efficient catalysts are preferable for activating oxidants such as persulfate ( PSF) and peroxymonosulfate ( PMS) for environmental remediation. Ferrocene (Fc), a stable and non-toxic Fe2+-bearing compound, is a promising heterogeneous catalyst for activation of PSF/ PMS, that has not been previously investigated. In this study, the activation of PSF/ PMS by Fc is evaluated using the oxidation of toxic amaranth dye as a model reaction. Results While an insignificant amount of amaranth dye was removed by Fc or PSF/ PMS separately, the combination of Fc and the oxidants completely decolorized amaranth dye, indicating that Fc activated PSF/ PMS. Fc-activated PMS was found to be much more effective than Fc-activated PSF for degrading amaranth. Elevated temperatures improved the degradation efficiency and kinetics, while the activation of PSF/ PMS remained consistent under acidic conditions. Through examining the effects of inhibitors and electron paramagnetic resonance analyses, Fc was proven to activate PSF/ PMS to generate sulfate radicals. Fc could also be re-used for multiple cycles to activate PSF and PMS. Conclusion Fc remained intact after the activation according to X-ray diffraction, FT-IR and X-ray photoelectron spectroscopy analyses. These features make Fc an effective and readily-available heterogeneous catalyst to activate PSF and PMS for advanced oxidation processes ( AOPs). © 2016 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

Metal organic frameworks (MOFs) can exhibit chemical, photo and biomimetic catalytic activities. While MOFs have been intensively investigated as photo-catalysts to degrade pollutants in water, studies of wet chemical oxidation catalyzed by MOFs are still quite limited. Particularly, the activation of peroxymonosulfate (PMS) represents a widely-used chemical oxidation reaction for chemical synthesis and environmental remediation. Yet little effort has been made to evaluate MOFs as a catalyst for the PMS activation. In this study, it is proposed to use a cobalt-based MOF, ZIF-67, as a heterogeneous catalyst to activate PMS to degrade Rhodamine B (RB) dye. Through the RB degradation, ZIF-67 as the PMS activation catalyst was evaluated and its underlying mechanism was proposed. Additionally, factors affecting the PMS activation were also examined, including ZIF-67 loading, temperature, pH, UV irradiation and ultrasonication. A ratio of 1/3/1 (RB/PMS/ZIF-67) is the most effective ratio to degrade RB in water. The higher temperature, UV irradiation and ultrasonication also enhanced the RB degradation using PMS activated by ZIF-67. The recyclability test revealed that ZIF-67 can be used continuously with stable and effective catalytic activity. These features reveal that ZIF-67 can be an interesting and promising heterogeneous catalyst to activate PMS for the degradation of organic pollutants in water. [ABSTRACT FROM AUTHOR]

• Cobalt sulfide-doped Co 3 O 4 (CSCO) is prepared via a facile sulfidization process. • CSCO exhibits more superior electrochemical and textural properties than pristine CO. • CSCO shows much higher catalytic activities for activating Oxone to degrade PSA. • CSCO exhibits a lower activation energy of PSA degradation than the reported values. • PSA degradation pathway is elucidated through the theoretical (DFT) calculation. As 2-phenylbenzimidazole-5-sulfonic acid (PSA) is increasingly consumed as a sunscreen agent, release of PSA to water bodies has caused threats to aquatic ecology, such as endocrine disruption, and reproductive inhibition. While Oxone-derived sulfate radicals are useful for treating such emerging contaminants, and cobalt is the most capable metal for activating Oxone, Co 3 O 4 (CO) nanoparticles (NPs) suffer from serious agglomeration, exhibiting low surface areas and catalytic activities even though CO NPs are commercially available. For utilizing accessibility of commercial CO NPs and improving their catalytic activities, a facile technique is proposed here to modify CO NPs through a straightforward sulfidization process for doping CO with cobalt sulfide (CS). The sulfidization process changes surficial properties of CO chemically, and transforms the morphology of CO NPs to a composite of inter-penetrated nanosheet and NP, making this CS-doped CO (CSCO) possess more superior properties of electron transfer and textural characteristics than CO. Thus, CSCO shows a higher catalytic activity for activating Oxone to degrade PSA. E a of PSA degradation by CSCO+Oxone (i.e., 38.1 kJ/mol) is also much lower than the reported values. The activation mechanism and degradation pathway of PSA degradation by CSCO+Oxone is investigated here through theoretical calculation and experimental evidences to provide valuable insights into degradation behaviors of PSA. [Display omitted] [ABSTRACT FROM AUTHOR]

While bis(4-hydroxyphenyl) ketone (BHK) represents one of the most typical UV filters, which, however, exhibits xenohormone toxicities, very few studies exist for investigating elimination of BHK from water. As sulfate radical-based oxidation processes are validated for degrading emerging contaminants, this current work attempts developing advantageous sulfate radical-based processes through activating monopersulfate (MPS) for eliminating BHK in water. Since cobalt (Co)-containing catalysts are effective catalysts for MPS activation, this study proposes to develop a Co NP-containing catalyst, in which Co NPs are confined in hollow N-containing carbon nanocube (HCoNC) derived from a cobaltic metal-organic framework (Co-MOF). The cubic Co-MOF would be firstly afforded through a surfactant-assisted method. The resultant cubic Co-MOF would be then modified with tannic acid (TAA) to etch its interior for affording the cubic Co-MOF with the hollow structure, which is subsequently converted into Co NP-containing hollow N- containing carbon nanocube (HCoNC) through carbonization. HCoNC can exhibit significantly superior catalytic activities than the non-hollow CoNC and Co 3 O 4 nanoparticles for MPS activation to BHK degradation. The activation energy (E a) for degrading BHK by MPS is 45.3 kJ/mol, which is much lower than reported values. HCoNC could be reusable over 5 consecutive BHK degradation cycles without decreasing catalytic activities. The MPS activation and plausible BHK degradation route by HCoNC+MPS is elucidated by experimental investigations as well as density functional theory (DFT) calculation to provide insightful mechanism of BHK degradation process. [Display omitted] • Co NP-embedded hollow N-carbon nanocube (HCoNC) is derived from cubic ZIF-67. • HCoNC activates MPS to fully eliminate bis(4-hydroxyphenyl) ketone (BHK). • HCoNC surpassingly outperforms the benchmark Co 3 O 4 NP for degrading BHK. • HCoNC can be reused to effectively activate MPS for degrading BHK completely. • DFT calculation is performed to elucidate degradation behaviors of BHK. [ABSTRACT FROM AUTHOR]

Catalytic activation of peroxymonosulfate (PMS) and peroxydisulfate (PDS) (or collectively known as persulfate, PS) using carbocatalyst is increasingly gaining attention as a promising technology for sustainable recalcitrant pollutant removal in water. Single heteroatom doping using either N, S, B or P is widely used to enhance the performance of the carbocatalyst for PS activation. However, the performance enhancement from single heteroatom doping is limited by the type of heteroatom used. To further enhance the performance of the carbocatalyst beyond the limit of single heteroatom doping, multi-heteroatom doping can be conducted. This review aims to provide a state-of-the-art overview on the development of multi-heteroatom-doped carbocatalyst for PS activation. The potential synergistic and antagonistic interactions of various heteroatoms including N and B, N and S, N and P, and N and halogen for PS activation are evaluated. Thereafter, the preparation strategies to develop multi-heteroatom-doped carbocatalyst including one-step and multi-step preparation approaches along with the characterization techniques are discussed. Evidence and summary of the performance of multi-heteroatom-doped carbocatalyst for various recalcitrant pollutants removal via PS activation are also provided. Finally, the prospects of employing multi-heteroatom-doped carbocatalyst including the need to study the correlation between different heteroatom combination, surface moiety type, and amount of dopant with the PS activation mechanism, identifying the best heteroatom combination, improving the durability of the carbocatalyst, evaluating the feasibility for full-scale application, developing low-cost multi-heteroatom-doped carbocatalyst, and assessing the environmental impact are also briefly discussed. [Display omitted] • Recent development in multi-heteroatom-doped carbocatalyst (MHDC) is reviewed. • Heteroatom interactions in MHDC are critically discussed. • Synthesis strategies and characterization techniques for MHDC are evaluated. • Performance of MHDC as persulfate activator is examined. • Prospects of developing MHDC as persulfate activator are proposed. [ABSTRACT FROM AUTHOR]

• Copper ferrite anchored on h -BN (CuFeBN) was prepared using a hydrothermal method. • CuFeBN with 1:2 copper ferrite: h -BN has the best performance as PMS activator. • Cu(II)/Cu(I) and Fe(III)/Fe(II) redox cycling formed SO 4 − (main ROS) from PMS. • Excellent mineralization and good recyclability can be achieved. In this study, CuFe 2 O 4 anchored on h -BN (CuFeBN) at various %w/w ratios was prepared via a hydrothermal method and characterized. The CuFeBN catalyst consists of irregular microparticle-like morphology with uniform CuFe 2 O 4 distribution and magnetic property. It was employed as peroxymonosulfate (PMS) activator for ciprofloxacin (CIP) removal. The results indicated that CuFeBN with CuFe 2 O 4 : h -BN w/w ratio of 1:2 (or CuFeBN-12) performed the best with CIP removal efficiency exceeding 91% in 60 min (apparent rate constant, k app = 0.0901 min−1). Higher CuFe 2 O 4 : h -BN w/w ratio resulted in increased CuFe 2 O 4 agglomeration. Additionally, increasing the CuFeBN-12 loading and initial pH leads to gradual increase in k app due to the increased catalytic sites and catalyst-to-PMS interaction, respectively. The redox cycling between Cu(II)/Cu(I) and Fe(III)/Fe(II) resulted in the formation of SO 4 −, acting as the main radical for CIP degradation and mineralization. Overall, the CuFeBN-12 shows remarkable potential as PMS activator for treating antibiotics in water. [ABSTRACT FROM AUTHOR]

[Display omitted] Azo compounds, particularly azo dyes, are widely used but pose significant environmental risks due to their persistence and potential to form carcinogenic by-products. Advanced oxidation processes (AOPs) are effective in degrading these stubborn compounds, with Oxone activation being a particularly promising method. In this study, a unique nanohybrid material, raspberry-like CuCo alloy embedded carbon (RCCC), is facilely fabricated using CuCo-glycerate (Gly) as a template. With the incorporation of Cu into Co, RCCC is essentially different from its analogue derived from Co-Gly in the absence of Cu, affording a popcorn-like Co embedded on carbon (PCoC). RCCC exhibits a unique morphology, featuring a hollow spherical layer covered by nanoscale beads composed of CuCo alloy distributed over carbon. Therefore, RCCC significantly outperforms PCoC and Co 3 O 4 for activating Oxone to degrade the toxic azo contaminant, Azorubin S (AS), in terms of efficiency and kinetics. Furthermore, RCCC remains highly effective in environments with high NaCl concentrations and can be efficiently reused across multiple cycles. Besides, RCCC also leads to the considerably lower E a of AS degradation than the reported E a values by other catalysts. More importantly, the contribution of incorporating Cu with Co as CuCo alloy in RCCC is also elucidated using the Density-Function-Theory (DFT) calculation and synergetic effect of Cu and Co in CuCo contributes to enhance Oxone activation, and boosts generation of SO 4 •−and •OH. The decomposition pathway of AS by RCCC + Oxone is also comprehensively investigated by studying the Fukui indices of AS and a series of its degradation by-products using the DFT calculation. In accordance to the toxicity assessment, RCCC + Oxone also considerably reduces acute and chronic toxicities to lower potential environmental impact. These results ensure that RCCC would be an advantageous catalyst for Oxone activation to degrade AS in water. [ABSTRACT FROM AUTHOR]

The escalation of global water pollution due to emerging pollutants has gained significant attention. To address this issue, catalytic peroxymonosulfate (PMS) activation technology has emerged as a promising treatment approach for effectively decontaminating a wide range of pollutants. Recently, modified biochar has become an increasingly attractive as PMS activator. Metal-heteroatom-co-doped biochar (MH-BC) has emerged as a promising catalyst that can provide enhanced performance over heteroatom-doped and metal-doped biochar due to the synergism between metal and heteroatom in promoting PMS activation. Therefore, this review aims to discuss the fabrication pathways (i.e., internal vs external doping and pre-vs post-modification) and key parameters (i.e., source of precursors, synthesis methods, and synthesis conditions) affecting the performance of MH-BC as PMS activator. Subsequently, an overview of all the possible PMS activation pathways by MH-BC is provided. Subsequently, Also, the detection, identification, and quantification of several reactive species (such as, •OH, SO 4 •−, O 2 •−, 1O 2 , and high valent oxo species) generated in the catalytic PMS system by MH-BC are also evaluated. Lastly, the underlying challenges associated with poor stability, the lack of understanding regarding the interaction between metal and heteroatom during PMS activation and quantification of radicals in multi-ROS system are also deliberated. [Display omitted] [ABSTRACT FROM AUTHOR]

While Prussia Blue analogues (PBs) are promising catalysts, PBs are typically prepared to be nanoscale, making them less practical especially for solution-based reactions. Although a few attempts have developed substrate-supported PBs, many of them are still very small and PB is not grown homogeneously. However, there is still an urgent demand for developing substrate-supported PB which is catalytically effective, convenient-to-prepare, simple-to-use and easy-to-recover. To this end, a macrosphere-supported nanoscale PB is proposed using ion exchange resins as readily available, robust and functionalized macrospheres. Through layer-by-layer impregnating resins in cobalt and hexacyanoferrate solutions, PB is grown on the surface of resins via self-assembling. Both cation and anion exchange resins (CR and AR) can be successfully employed to grown PB through the same self-assembling technique. The resulting PB@R can preserve porous structures and metal coordination of PB, and easy-to-handle features of resins, making them promising catalysts for aqueous catalytic reactions. As 4-NP reduction is selected as a model reductive reaction, PB@R quickly reduces 4-NP to 4-AP in the presence of NaBH4 and exhibits a much lower E a compared to other reported precious metal catalysts. PB@R can also activate PMS to generate sulfate radicals to degrade organic pollutants. PB@R can be also packed in a column for continuous flow-through reductive and oxidative reactions. These results indicate that PB@R is a conveniently prepared and highly effective and stable macro-spherical catalyst for aqueous environmental catalysis. The preparation scheme here can be also applied to fabricate other versatile macrosphere-supported metal complex catalysts. [ABSTRACT FROM AUTHOR]

Direct carbonization of cobalt complexes represents as a convenient approach to prepare magnetic carbon/cobalt nanocomposites (MCCNs) as heterogeneous environmental catalysts. However, most of MCCNs derived from consist of sheet-like carbon matrices with very sparse cobaltic nanoparticles (NPs), making them exhibit relatively low catalytic activities, porosity and magnetism. In this study, dipicolinic acid (DPA) is selected to prepare a 3-dimensional cobalt coordination polymer (CoDPA). MCCN derived from CoDPA can consist of a porous carbon matrix embedded with highly-dense Co 0 and Co 3 O 4 NPs. This magnetic Co 0 /Co 3 O 4 NP-anchored carbon composite (MCNC) appears as a promising heterogeneous catalyst for oxidative and reductive environmental catalytic reactions. As peroxymonosulfate (PMS) activation is selected as a model catalytic oxidative reaction, MCNC exhibits a much higher catalytic activity than Co 3 O 4 , a benchmark catalyst for PMS activation. The reductive catalytic activity of MCNC is demonstrated through 4-nitrophenol (4-NP) reduction in the presence of NaBH 4 . MCNC could rapidly react with NaBH 4 to generate H 2 for hydrogenation of 4-NP to 4-aminophenol (4-AP). In comparison with other precious metallic catalysts, MCNC also shows a relatively high catalytic activity. These results indicate that MCNC is a conveniently prepared and highly effective and stable carbon-supported cobaltic heterogeneous catalyst for versatile environmental catalytic applications. [ABSTRACT FROM AUTHOR]

[Display omitted] • N, S-codoped biochar (BSN) was prepared and BSN formation mechanism was studied. • BSN can effectively activate PMS for gatifloxacin (GAT) removal at various conditions. • A kinetic model incorporating PMS consumption and GAT removal is proposed. • Synergism between graphitic N and thiophenic S promoted the nonradical pathways. • GAT degradation intermediates are identified, and the degradation pathways are proposed. Multi-heteroatom doping is a promising approach to increase the affinity of biochar for catalysis. Herein, a series of N, S-codoped biochar (BSN) were synthesized at different temperatures using a one-pot calcination protocol. Investigation on the physiochemical characteristics of these BSNs revealed that g-C 3 N 4 was first formed from the precursors at lower temperature, engulfing the biochar. At higher synthesis temperature, the g-C 3 N 4 decomposed and coalesce with the biochar to form BSN. The performance of BSN as peroxymonosulfate (PMS) activator for gatifloxacin (GAT) removal was evaluated. The results indicated that BSN prepared at 800 °C (BSN-800) exhibited the greatest performance due to its relatively high specific surface area and synergism between heteroatoms. A kinetic model based on the second-order PMS consumption and first-order GAT removal was developed to describe GAT removal and PMS consumption simultaneously at various operating conditions including BSN-800 loading, PMS dosage and pH. The proposed kinetic model has better fit compared to the conventional pseudo first-order kinetics. The major PMS activation mechanism was identified using chemical scavenger and electrochemical studies indicating that the nonradical pathway involving 1O 2 generation and electron mediator mechanisms are dominant with graphitic N and thiophenic S acting as the active sites. Despite its restricted reusability, BSN-800 can be used effectively to remove GAT in various water matrixes including river water, secondary water and tap water. The GAT degradation intermediates were identified, and the degradation pathway was also proposed. Overall, this study provides a better understanding on the development of multi-heteroatom-doped biochar as promising catalyst for antibiotics removal. [ABSTRACT FROM AUTHOR]

• The first study of Cobalt Sulfide-activated Oxone to degrade C4mim. • Yolk-shell cobalt sulfide (Co 4 S 3) (YSCS) is fabricated from Metal-alkoxide. • YSCS outperforms its precursor and Co 3 O 4 for activating Oxone to degrade C4M. • The DFT calculation is performed to investigate the degradation pathway. • The toxicity is also studied to realize the environmental implication of C4M. The low bio-degradability of room-temperature ionic liquids (RTILs) makes RTILs a new class of persistent contaminants. It is urgent to develop useful technology to eliminate RTILs to prevent their presence in the environment. Sulfate-radical advanced oxidation processes (SR-AOPs) are particularly suitable for degrading such low-biodegradability pollutants. This study introduces a novel SR-AOP aimed at eliminating the representative RTIL, 1-butyl-3-methylimidazolium chloride (C4M), using an enhanced catalyst to activate Oxone. Traditionally, cobalt (Co) has been used for Oxone activation, but homogeneous catalysis with Co ions poses recovery challenges and secondary pollution risks. Recent studies suggest that cobalt sulfides (CSs) are more promising due to their superior redox properties, which are critical for effective Oxone activation. In this work, we developed a catalyst composed of cobalt sulfide (CS) with a unique yolk-shell (YS) structure, termed YSCS, to maximize catalytic activity. YSCS was easily fabricated from Co-Glycerate (CoG) precursors through a self-destruction/reconstruction process during sulfidization, resulting in a YS structure covered by self-assembled Co 4 S 3 nanoplates. This morphology provides a highly mesoporous structure, enhanced electrochemical properties, and expanded active sites. Consequently, YSCS demonstrated significantly higher catalytic activity for Oxone activation compared to its precursor CoG and the benchmark Co 3 O 4 , with a reaction rate constant (k) of 0.108 min-1, surpassing those of Co 3 O 4 NP + Oxone (0.007 min-1) and CoG + Oxone (0.023 min-1). Additionally, YSCS + Oxone exhibited a lower activation energy (E a) of 17.8 kJ/mol for C4M degradation. The degradation pathway of C4M by YSCS + Oxone was thoroughly investigated using Fukui indices and analyzing the degradation by-products. Toxicity assessments showed that YSCS + Oxone significantly reduces the acute toxicity and bioconcentration factor of C4M, as well as potential mutagenicity and developmental toxicity risks. These findings confirm that YSCS is a highly effective catalyst for Oxone activation and RTIL degradation in water. [ABSTRACT FROM AUTHOR]

[Display omitted] • Boosted PMS activation is achieved by N, S co-doped durian peel-derived biochars (N,S-BCD-X) • N and S raise the ESP and redistribute the electron density in the doping sites of BCD. • Electron-donating capability is enhanced by N&S doping-induced decrease of work function. • 1O 2 is generated via different ways, enhanced by •OH and SO 4 •− due to elongated O-O bond of PMS. • S site in N,S-BCD-800 exhibits the strongest PMS adsorption with the most electron transferred. Biochar is an environmentally friendly material with various potential applications in water treatment. Herein, nitrogen and sulfur co-doped biochars (N,S-BCD-X) were fabricated from durian peel as an agricultural waste by coupling with thiourea via thermal treatment to activate peroxymonosulfate (PMS) for degradation of ofloxacin (OFX) in water. The OFX removal using PMS activated by N,S-BCD-800 was over 85 % after 120 min of reaction, which was 17.78 times higher than that by pure BCD. The OFX degradation was not inhibited over a wide pH range of 3 to 9. Through radical quenching tests, electron paramagnetic resonance, and DFT calculations, 1O 2 was revealed as the key reactive species in the N,S-BCD-800/PMS system because of PMS's elongated O-O bond-induced promoted generation of •OH and SO 4 •- with an insignificant contribution and the generation of 1O 2 via various reactions associated with •OH, SO 4 •-, and PMS. The boosted catalytic activity of N,S-BCD-800 mainly came from synergetic effect of N and S co-doping due to the enhanced electron-donating capability caused by decrease in the work function. Furthermore, the increase in electrostatic potential and the difference in electron density and atomic charge could also account for stronger adsorption and activation of PMS on N,S-BCD-800 to generate more 1O 2 besides the N,S-BCD-800/PMS complex as a minor species responsible for the degradation of OFX via electron transfer. Finally, the attainment of high efficiency of N,S-BCD/PMS for OFX degradation in various water matrices as well as after 5 cycles proved that N,S-BCD had high stability and applicability. [ABSTRACT FROM AUTHOR]

[Display omitted] • Waste-derived MCM-41 was employed as dual functional support for CoFe 2 O 4 (CFMCM) • MCM-41 improve catalyst dispersion and can adsorb leached metal. • CFMCM with 11 wt% CoFe 2 O 4 was the best peroxymonosulfate (PMS) activator for ciprofloxacin (CIP) removal. • SO 4 •− contributed dominantly (67 %) to PMS activation while •OH played a minor role. • CIP degradation proceeds via piperazine ring oxidation, and decarboxylation reactions. Herein, a series of CoFe 2 O 4 decorated on waste-derived Mobil Composition of Matter No. 41 (MCM-41) was developed. Incorporation of MCM-41 as a support for CoFe 2 O 4 (CFMCM) provides dual functionality to disperse the catalyst and adsorb leached metal, leading to remarkable performance and stability. The CFMCM was used as a peroxymonosulfate (PMS) activator for ciprofloxacin (CIP) removal indicating that CFMCM with 11 wt% CoFe 2 O 4 (CFMCM-11) had the highest performance (k app = 0.17 min−1). Increasing the catalyst loading and PMS dosage contributed positively to the CIP degradation. The catalyst can be reused at least 3 times without significant metal leaching (<35 µg/L) showing that it is stable. Analysis of the dominant reactive species using scavengers revealed that SO 4 •− was the major reactive species while HO• played a minor role. The SO 4 •− and HO• were generated from the redox transition between Co2+/Co3+ and Fe2+/Fe3+. Based on the intermediates identified, the CIP degradation pathways consisting of piperazine ring oxidation, and decarboxylation reactions were proposed. Overall, this study shows that the waste-derived materials can be integrated as part of the strategy to develop catalysts for environmental applications. [ABSTRACT FROM AUTHOR]

[Display omitted] • Co 3 O 4-x -0.20 with the yolk-shell structure is constructed via tailoring oxygen vacancy (OV) • OV reduces charge transfer resistance and increases the conductivity for enhancing catalytic activities. • Phenol degradation is accelerated by single-electron transfer and Co(IV) = O generation. • Single-electron transfer of phenol is induced by electron-deficient OV due to electron donation to O 2. • Relationship between Co(IV) = O and OV is unraveled by elongated S-O and shortened Co O bonds. As Co 3 O 4 represents a promising material for peroxymonosulfate (PMS) activation, a yolk-shell-structured nanosphere, Co 3 O 4-x -0.20, is developed here for maximizing its catalytic activity by governing electronic structures via tailoring oxygen vacancies (OV) of Co 3 O 4. This OV-tailored Co 3 O 4 enables single-electron transfer and generates high-valent cobalt-oxo species (Co(IV) = O) to achieve the fastest phenol degradation. The single-electron transfer is unraveled by an electron donation of Co atoms near OV to O 2 to form O 2 − followed by O 2 evolution after 1O 2 and the charge balance maintained by an electron acquisition from phenol by the electron-deficient Co atoms. Meanwhile, the generation of Co(IV) = O by the cleavage of the S O bond in the Co(II)-O-SO 3 -OH complex accepts electrons from phenol to turn back to Co(II) and Co(III), causing phenol oxidation. These results demonstrate the pre-eminence of Co 3 O 4-x -0.20 over the reported catalysts for phenol degradation and also offer insights into the mechanism of OV triggering electron donation and enhancing Co(IV) = O generation. [ABSTRACT FROM AUTHOR]

As the extensively-employed UV stabilizer, 2,4-dihydroxybenzophenone (benzophenone-1 (BP1)) has been proven an endocrine disruptor, developing of useful technologies for eliminating BP1 is highly desired. Because SO 4 •−-based oxidation technologies are promising for eliminating emerging pollutants, cobalt (Co) is an extremely useful catalyst for peroxymonosulfate (PMS) activation, and it is critical to developing an advantageous cobaltic catalyst for PMS activation. Herein, an exceptional catalyst is developed for the first time from a Hofmann-type MOF ([CoFe]pyrazine[Ni(CN) 4 ]), which is then pyrolyzed to afford CoFeNi alloy nanoparticles (NPs) confined in carbon nanotubes (CNTs), resulting in CoFeNi@CNT (CFNC). This CFNC would exhibit numerous promising features: (1) as Co represents the most efficient metal for activating PMS, CoFeNi alloy would offer superior activities for PMS activation; (2) the strong magnetism of CoFeNi alloy enables CFNC to be magnetically controllable; (3) CoFeNi alloy NPs confined within CNT would be guarded to increase its durability; (4) the interlaced structures of CFNC make it exhibit much more reactive surface areas for activating PMS. Thus, CFNC exhibits a significantly stronger activating capability than Co 3 O 4 , which is the benchmark heterogeneous catalyst for PMS. Furthermore, CFNC could also be reusable and remain highly effective, stable, and robust for multiple cycles of BP1 degradation with minimal leaching of CoFeNi alloy. Mechanisms of PMS activation and elimination path of BP1 by CFNC are also elucidated via the theoretical DFT calculation and experimental data to supply valuable information about behaviors of BP1 degraded by Hofmann MOF-derived magnetic catalysts. [Display omitted] • Hofmann MOF-derived CoFeNi@C (CFNC) is used for the 1st time to activate PMS. • CFNC consists of a unique nanosphere comprised of CoFeNi alloy NPs confined in CNT. • CFNC shows much higher catalytic activities than Co 3 O 4 for PMS activation. • CNC is recyclable for activating PMS to degrade BP-1 with minimal metal leaching. • BP-1 degradation pathway is elucidated through the theoretical (DFT) calculation. [ABSTRACT FROM AUTHOR]

• Single-step sulfidation allows hollow rhombic cobalt sulfide (HRCS) to possess defects and SV. • HRCS exhibits excellent Oxone activation for Novantisol (NVT) degradation dominated by SO 4 •−. • SV-induced highly active CoII accounts for high SO 4 •− generation enhanced by S species. • O 2 •−-mediated 1O 2 generation is fully explored. • Pathways for NVT degradation is unraveled elaborately via DFT calculation. This study aimed to design hollow rhombic cobalt sulfide (HRCS) via a single-step sulfidation of cobaltic metal organic framework (CoMOF) as a template. The obtained HRCS with abundance of defects and sulfur vacancy (SV) was then employed for degradation of Novantisol (NVT), a sunscreen agent, through Oxone activation. The superior catalytic performance of HRCS was attributed to its more electroactive sites and low charge transfer resistance that were enhanced by highly active CoII due to the existence of SV for increased generation of SO 4 •− as a predominant species. Although •OH and 1O 2 were proved to be generated obviously from activation of Oxone over HRCS, their contribution to NVT degradation was marginal. While •OH and SO 4 •− were generated mainly by CoII-activated Oxone, the formation of SO 4 •− was accelerated by sulfur species and the disproportionation of SO 5 •−. The limited conversion of SO 4 •− by reacting with −OH and undirect self-hydrolysis of Oxone, on the other hand, contributed to enhanced •OH generation. Further experiments on furfuryl alcohol (FFA) consumption showed that 1O 2 generated from O 2 •− as an intermediate species did not account for the NVT degradation but rather from self-decomposition of Oxone, dissociation and self-combination of SO 5 •−, and disproportionation of •OH. The degradation pathway was also investigated and unveiled in details via DFT calculation, which further validated that HRCS appeared to be a superior catalyst for NVT degradation through Oxone activation. [ABSTRACT FROM AUTHOR]

[Display omitted] • UVA-LED/CFO-rGO/PMS system was highly effective for BPA degradation. • The effect of reaction parameters for BPA degradation was completely studied. • Degradation intermediates were determined and degradation pathway was proposed. • CFO-rGO had high stability and low metal leaching. • Ecotoxicity of BPA and intermediates were evaluated by ECOSAR. In this work, CoFe 2 O 4 -reduced graphene oxide (CFO-rGO) nanocomposite was synthesized to activate peroxymonosulfate (PMS) under UVA-LED irradiation. Bisphenol A (BPA) was selected as an emerging pollutant to evaluate the performance of the UVA-LED/CFO-rGO/PMS system. CFO-rGO was characterized by several advanced methods including XRD, FTIR, FESEM, EDX-mapping, TEM, XPS, BET-BJH, Raman spectrometry, VSM, PL, and EIS analyses. The operating factors, the determination of reactive species, and the mechanism were studied and discussed. During 30 min reaction time, more than 99% of BPA was removed by 150 mg/L PMS and 400 mg/L CFO-rGO under mild conditions (pH = 3–9). Bicarbonate ions could inhibit the BPA degradation by scavenging the free radicals. The trapping experiments exhibited that sulfate ( SO 4 • - ) and hydroxyl (•OH) radicals were prevailing agents for BPA degradation. Humic acid (HA) and sodium dodecyl sulfate (SDS) had a hindering effect on BPA degradation. CFO-rGO showed a high potential for recyclability up to six cycles. Moreover, the leaching of metals was approximately null for CFO-rGO, indicating that the current nanocomposite is highly stable. We also examined UVA-LED/CFO-rGO/PMS system on other pollutants, as well as real conditions. The results showed high efficiency for all conditions. The UVA-LED/CFO-rGO/PMS process could mineralize 67% of BPA during 80 min reaction time. Intermediates of BPA degradation were identified and their toxicity was also estimated. This work enlightened the ferrite catalysts' importance in activating PMS under UVA-LED irradiation for emerging pollutants wastewater remediation. [ABSTRACT FROM AUTHOR]

As UV-light stabilizers, Bis(4-hydroxy)benzophenone (BBP), are extensively consumed to quench radicals from photooxidation, continuous release of BPs into the environment poses serious threats to the ecology in view of their xenohormone toxicities, and BBP shall be eliminated from water to avoid its adverse effect. Since sulfate radical (SR)-based chemical oxidation techniques have been proven as effective procedures for eliminating organic emerging contaminants, this study aims to develop useful SR-based procedures through activating Oxone for degrading BBP in water. In contrast to the conventional Co 3 O 4 , cobalt sulfide (CoS) is particularly proposed as an alternative heterogeneous catalyst for activating Oxone to degrade BBP because CoS exhibits more reactive redox characteristics. As structures of catalysts predominantly control their catalytic activities, in this study, a unique nanoplate-assembled CoS (NPCS) 3D cluster is fabricated via a convenient one-step process to serve as a promising heterogeneous catalyst for activating Oxone to degrade BBP. With NPCS = 100 mg/L and Oxone = 200 mg/L, 5 mg/L of BBP can be completely eliminated in 60 min. The catalytic activity of NPCS towards Oxone activation also significantly surpasses the reference material, Co 3 O 4 , to enhance degradation of BBP. E a of BBP degradation by NPCS-activated Oxone is also determined as a relatively low value of 42.7 kJ/mol. The activation mechanism as well as degradation pathway of BBP degradation by NPCS-activated Oxone was investigated and validated through experimental evidences and density functional theory (DFT) calculation to offer valuable insights into degradation behaviors for developing SR-based processes of BBP degradation using CoS catalysts. [Display omitted] • Nanoplate-assembled CoS (NPCS) is prepared via a one-step hydrothermal process. • NPCS activates Oxone to fully eliminate 5 mg/L of Bis(4-hydroxy)benzophenone (BBP). • NPCS outperforms the benchmark Co 3 O 4 NP for degrading BBP with E a = 42.7 kJ/mol. • NPCS can be reused up to 5 cycles to activate Oxone for degrading BBP completely. • DFT calculation is performed to elucidate degradation behaviors of BBP with Fukui index. [ABSTRACT FROM AUTHOR]

Over the past decade, there has been a surge of interest in using char (hydrochar or biochar) derived from biomass as persulfate (PS, either peroxymonosulfate or peroxydisulfate) activator for anthropogenic pollutants removal. While extensive investigation showed that char could be used as a PS activator, its sustainability over prolonged application is equivocal. This review provides an assessment of the knowledge gap related to the sustainability of char as a PS activator. The desirable char properties for PS activation are identified, include the high specific surface area and favorable surface chemistry. Various synthesis strategies to obtain the desirable properties during biomass pre-treatment, hydrochar and biochar synthesis, and char post-treatment are discussed. Thereafter, factors related to the sustainability of employing char as a PS activator for anthropogenic pollutants removal are critically evaluated. Among the critical factors include performance uncertainty, competing adsorption process, char stability during PS activation, biomass precursor variation, scalability, and toxic components in char. Finally, some potential research directions are provided. Fulfilling the sustainability factors will provide opportunity to employ char as an economical and efficient catalyst for sustainable environmental remediation. [Display omitted] • The desirable char properties as persulfate activator for pollutant removal are identified. • Various strategies to obtain the desirable properties are discussed. • Factors affecting sustainability of char as persulfate activator are critically evaluated. • Prospects of developing sustainable char as persulfate activation are proposed. [ABSTRACT FROM AUTHOR]

Contaminated water with landfill leachate (CWLL) with high salinity and high organic content (total organic carbon (TOC) = 649 mg/L and Chemical Oxygen Demand (COD) = 1175 mg/L) is a toxic and non-biodegradable effluent. The present research aimed to assess the treatment effectiveness of CWLL by electrocoagulation (EC)/oxidant process. The ferrous ions generated during the process were employed as coagulant and catalyst for the activation of different oxidants such as peroxymonosulfate (PMS), peroxydisulfate (PDS), hydrogen peroxide (HP), and percarbonate (PC) to decrease TOC in CWLL. Removal of ammonia, color, phosphorous, and chemical oxygen demand (COD) from CWLL effluent was explored at various processes. EC/HP had the best performance (∼73%) in mineralization of organic pollutants compared to others under the condition of pH 6.8, applied current of 200 mA, oxidant dosage of 6 mM, and time of 80 min. The oxidation priority was to follow this order: EC/HP > EC/PMS > EC/PDS > EC/PC. These processes enhanced the biodegradability of CWLL based on the average oxidation state and biochemical oxygen demand (BOD)/COD ratio. SUVA 254 and E 2 /E 3 indices were also investigated on obtained effluents. The phytotoxicity evaluation was carried out based on the germination index, indicating that the electro-activated oxidant was an effective system to reduce the toxicity of polluted waters. EC/HP showed supremacy compared to others in terms of efficiency, cost, and detoxification. Therefore, the electro-activated oxidant system is a good means for removing organic pollutants from real wastewater. [Display omitted] • PC, HP, PDS, and PMS were used in EC to treat CWLL. • COD, ammonia, TOC, color, and phosphorous were monitored in different processes. • Phytotoxicity, biodegradability, and humification of each effluent were evaluated. • Economic analysis showed that EC/HP is the best option for the treatment. [ABSTRACT FROM AUTHOR]

Engineered biochar is increasingly regarded as a cost-effective and eco-friendly peroxymonosulfate (PMS) activator. Herein, biochar doped with nitrogen and sulfur moieties was prepared by pyrolysis of wood shavings and doping precursor. The doping precursor consists of either urea, thiourea or 1:1 w/w mixture of urea and thiourea (denoted as NSB-U, NSB-T and NSB-UT, respectively). The physicochemical properties of the NSBs were extensively characterized, revealing that they are of noncrystalline carbon with porous structure. The NSBs were employed as PMS activator to degrade organic pollutants particularly methylene blue (MB). It was found that NSB-UT exhibited higher MB removal rate with k app = 0.202 min−1 due to its relatively high surface area and favorable intrinsic surface moieties (combination of graphitic N and thiophenic S). The effects of catalyst loading, PMS dosage and initial pH were evaluated. Positive enhancement of the MB removal rate can be obtained by carefully increasing the catalyst loading or PMS dosage. Meanwhile, the MB removal rate is greatly influenced by pH due to electrostatic interactions and pH dependent reactions. The NSB-UT can be reused for several cycles to some extent and its catalytic activity can be restored by thermal treatment. Based on the radical scavenger study and XPS analysis, the nonradical pathway facilitated by the graphitic N and thiophenic S active sites are revealed to be the dominant reaction pathway. Overall, the results of this study show that engineered biochar derived from locally available biowaste can be transformed into PMS activator for environmental applications. [Display omitted] • Biochar co-doped with nitrogen and sulfur was prepared using wood shavings. • Physicochemical properties of the doped biochar were comprehensively studied. • Graphitic N and thiophenic S were endowed into the biochar for efficient PMS activation. • Doped biochar prepared with 1:1 w/w% urea and thiourea has the best catalytic activity. • Mechanism of PMS activation involving MB is dominated by the nonradical pathway. [ABSTRACT FROM AUTHOR]

• OPS-confined Co 3 O 4 is facilely fabricated by a solvent-free confined space strategy. • Template-retained OPS (TS) contains silanol to facilitate insertion of Co into pores. • CoTS exhibits a higher catalytic activity than Co-loaded template-free OPS (CoFS) • CoTS outperforms Co 3 O 4 for degrading SSA and exhibits lower E a than other catalysts. • Degradation pathway of SSA is also proposed based on degradation intermediates. As 5-sulfosalicylic acid (SSA) is extensively consumed as a medical intermediate, SSA is continuously released into the environment. Due to its poor bio-degradability, SSA in water has posed threats to aquatic organisms. Therefore, advanced oxidation processes (AOPs) should be adopted for eliminating SSA. In view of many advantages of SO 4 −-based AOPs, it is necessary to develop SO 4 −-based AOPs for treating SSA. As peroxymonosulfate (PMS) is selected as a source of SO 4 −, a Co-based heterogeneous catalyst is fabricated by a confined space strategy (CSS) to load Co 3 O 4 into pores of ordered porous silica (OPS). Unlike the conventionally-prepared Co-loaded OPS, which loads Co onto the template-free OPS (FS) to form CoFS, the proposed OPS-confined Co 3 O 4 was fabricated through grinding Co into the template-retained OPS (TS), which consists of silanol groups. The OH groups of these silanol groups attract Co precursors and facilitate insertion of Co into pores of TS, resulting in CoTS. These morphologic differences between CoTS and CoFS leads to significantly different catalytic activities for PMS activation to degrade SSA. When CoFS is incapable of activating PMS effectively to degrade SSA, CoTS-activated PMS completely degrades SSA within 60 min. CoTS also exhibits much higher catalytic activities than commercial Co 3 O 4 NPs for activating PMS to degrade SSA. In addition, CoTS-activated PMS shows a lower E a than other catalysts for activating PMS to degrade pollutants. Degradation pathway of SSA is also proposed based on degradation intermediates. These results and findings validate that CoTS can be a promising and advantageous heterogeneous catalyst, which could be conveniently prepared, for activating PMS to degrade the emerging contaminant, SSA. [ABSTRACT FROM AUTHOR]