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•Excellent MPS activation is explored in various CoFe2O4 (NCFs): CFNB, CFNS, CFNP.•Dual-pathway under neutral conditions shifts to non-radical pathway at low and high pH.•Intrinsic ...electron transfer from DBP enhances ROS generation in CFNB/MPS system.•OV and defects in CFNS accelerate electron cycling of metal species for SO4•− generation.•DBP degradation pathway is elucidated through the theoretical (DFT) calculation.
Differences in the structural morphology of heterogeneous catalysts, oxygen vacancy (OV), and lattice defect degree could induce different catalytic performances due to the possession of different active sites and abundance of unpaired electrons. Despite this, few studies on in-depth discussion and detailed comparison of the influence of these factors for activating monopersulfate (MPS) have been made so far. Here, we proposed three types of nanostructured cobalt ferrites (NCFs), consisting of CoFe2O4 nanobundle (CFNB), CoFe2O4 nanosheet (CFNS), and CoFe2O4 nanoplate (CFNP). The catalytic performance of these NCFs was evaluated through MPS activation for degradation of 4,4′-dihydroxybenzophenone (DBP), an extensively used UV filter. As a result, pH-dependent generation of reactive oxygen species (ROS) showed that the catalytic mechanism tended to shift from radical and non-radial pathways under neutral conditions to 1O2-induced non-radical at low and high pH with increased generation of SO4•− and •OH. Given the abundance of OV, lattice defects, and highest specific area, CFNS possessed the most superior performance driven by high reactivity of ≡CoII/≡CoIII and ≡FeII/≡FeIII redox cycles, while DBP-induced electron transfer accounted for enhanced activity of CFNB. CFNP with relatively high OV and electrochemically active surface area, on the other hand, showed its efficiency in generation of ROS. Intermediates from the reaction were also verified through LCQ-LC/MS spectra and DFT calculation for elucidating the DBP degradation over NCFs-activated MPS.
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 Co3O4 nanoparticles for MPS activation to BHK degradation. The activation energy (Ea) 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.
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•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 Co3O4 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.
•Co@NC exhibits a higher catalytic activity for reducing bromate than Co3O4 NP.•The Ea of bromate reduction by Co@NC is also much lower than the reported Ea.•Co@NC completely reduces bromate to ...bromide under alkaline conditions.•Co@NC exhibit a high selectivity for bromate reduction in the presence of other anions.•Co@NC is also reused for multiple-cycles to continuously reduce bromate to bromide.
While catalytic hydrogenation of bromate represents a useful technique for eliminating carcinogenic bromate, expensive noble-metal catalysts and excessive H2 gas are usually required, impeding large-scale implementation of this technique. As borohydride is an alternative source for releasing H2 in a more controllable way and non-noble metal catalysts (e.g., Co) can catalyze hydrolysis of borohydride to generate H2, it is promising to employ Co and borohydride for hydrogenation of bromate. Moreover, it is even more practical to develop heterogeneous catalysts with magnetism for easier handle and recovery of catalysts. Therefore, the aim of this study is to develop such a magnetic heterogeneous catalyst for bromate reduction by using borohydride. Herein, a special Co-based catalyst is fabricated by transforming Co-substituted prussian blue analogue into Co-embedded N-doped carbon (Co@NC) composite through carbonization. Co@NC also exhibits a higher catalytic activity for reducing bromate than the commercial Co3O4 as Co@NC could accelerate hydrolysis of NaBH4 to generate H2 gas much faster. The activation energy (Ea) of bromate reduction by Co@NC is also much lower than the reported Ea. Co@NC could still completely remove bromate and reduce it to bromide under alkaline conditions, and Co@NC also exhibit a very high selectivity towards bromate reduction in the presence of other anions. Moreover, Co@NC could be also reused for multiple-cycles to continuously reduce bromate to bromide. These features demonstrate that Co@NC is certainly an advantageous and convenient heterogeneous catalyst for reducing bromate in water.
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•Cu/CoS@nickel foam (CCSNF) is fabricated by sulfurizing CuCo-LDH on NF.•CCSNF possesses more surface area, current density, and lower charge transfer resistance.•CCSNF ourperforms ...CuCo-LDH@NF & CuCo2O4@NF for activating MPS to degrade RB.•RB degradation by CCSNF-activated MPS leads to the significantly lower Ea of 26.8 kJ/mol.•CCSNF can be reused to activate MPS for RB degradation over 5 cycles and remains effective.
While metal oxides are conventionally proposed for activating monopersulfate (MPS) to degrade refractory contaminants, metal sulfides have recently gained increased attention for MPS activation because these sulfides exhibit more reactive redox characteristics to enhance the catalytic activation of MPS. The present study attempts to develop a novel material comprised of metal sulfides with 3D hierarchical nanostructures to activate MPS. Specifically, a 3D hierarchically structured catalyst was fabricated by growing CuCo-layered double hydroxide (LDH) on nickel foam (NF), followed by direct sulfurization, affording Cu/CoS@NF (CCSNF). CCSNF could exhibit a unique morphology of floral bunches comprised of nano-needles, residing on the NF surfaces. Compared with its precursor, CuCo-LDH@NF, oxide analogue, and CuCo2O4@NF, CCSNF possessed superior physical and chemical properties, including larger surface area and pore volume, higher current density, and lower charge transfer resistance. These features render CCSNF a much more effective catalyst than CuCo-LDH@NF and CuCo2O4@NF for activating MPS to degrade Rhodamine B (RB). In particular, RB degradation by CCSNF-activated MPS required an activation energy only 26.8 kJ/mol, which is much lower than the reported values. The activation mechanism and degradation pathway of RB degradation by CCSNF-activated MPS were investigated and validated through experimental evidences and density function theory calculations.
In this study, Osaka daigakuestuary model (ODEM) was applied for hydrodynamic simulation of suspended solids (SS) concentration in the Isahaya regulating reservoir. Water samples were collected every ...hourfrom 9:00 to 15:00 at nine sampling points inside the observation area of the reservoir.Parameters used for the model included initial conditions (i.e., SS concentration, water depth, temperature, and salinity) and boundary conditions (i.e., wind speed and direction, atmospheric temperature, solar irradiation, and cloud cover). The calculated results of SS in the reservoir and its concentration fluctuation from the model were compared with those estimated from the image analysis of unmanned aerial vehicle (UAV) and observed results. The SS simulated from ODEM distributed in high concentration, whereas that estimated from UAV distributed in low concentration although in both data they spread across a wide range at most investigated times. Although there was a big difference between the accuracy of ODEM and UAV, the SS concentration values described by them were closed to the observed values. Between them, the ODEM model showed its advantages in simulating the SS concentration and achieved more accuracy than UAV, showing a potential for using ODEM model in monitoring of SS in water.
As bromate removal and reduction can be also achieved using metals, aluminum (Al) appears as the most promising one for reduction of bromate because Al is abundant element and exhibits a high ...reduction power. Reactions between bromate and Al shall be even enhanced through ultrasound (US) process because US can facilitate mass transfer on liquid/solid interfaces and clean surfaces via generating microscale turbulence to facilitate reactions. Therefore, the aim of this study is for the first time to investigate the effect of US on bromate removal by Al metal. Specifically, Al particle would be treated by HCl to afford HCl‐treated Al (HCTAL), which is capable of removing bromate and even reducing it to bromide. Such a mechanism is also validated by density function theory calculation through determining adsorption energy as −152.8 kJ/mole, and oxygen atoms of bromate would be extracted and reacted with Al atoms, releasing bromide ion. US not only facilitated bromate removal by further increasing removal capacity under the acidic condition but also suppressed the inhibitive effect from basicity at relatively high pH. The spent HCTAL could still remove bromate and convert it to bromide after regeneration. These features indicate that US considerably enhances bromate removal by Al.
Practitioner points
Bromate removed by Al is elucidated by DFT calculation with Eabsorption = −152.8 kJ/mole.
Oxygen atoms of bromate are extracted and reacted with Al atoms, releasing bromide ion.
A higher power of ultrasound would substantially enhance bromate removal efficiency.
Ultrasound also suppresses the inhibitive effect from basicity at relatively high pH.
With ultrasound, the interference of co‐existing anions on bromate removal is lessened.
Ultrasonication enhances aqueous reduction of bromate to bromide by zero‐valent aluminum.
Abstract
Azorubin S (ARS) represents one of the most common and frequently-utilized toxic azo dyes produced from industrial activities. While various conventional treatment techniques could not ...effectively eliminate ARS from water, heterogeneous metal-based catalyst coupled with monopersulfate (MPS) is a highly-efficient process for eliminating ARS, in which tricobalt tetroxide (Co
3
O
4
) has been attracted increasing attention as a preeminent MPS activator due to its outstanding physicochemical properties. However, the nanoscale Co
3
O
4
particles usually pose a limitation of serious agglomeration in the aqueous environment, thus lowering their efficiency. Thus, developing an easy-synthesized and exceptionally efficient Co
3
O
4
-based catalyst is crucially paramount. Therefore, in this work, a special hollow-structured oval-like cobalt oxide (abbreviated as HOCO) was successfully constructed using Co-metal organic framework as a precursor, which was then utilized for catalyzing activation of MPS to degrade ARS. This as-obtained HOCO exhibited distinct physicochemical characteristics from commercially-available Co
3
O
4
, which subsequently resulted in superior activities for MPS activation in ARS degradation. Specifically, 100% of ARS could be degraded in 30 min with a corresponding reaction kinetic of 0.22 min
− 1
by HOCO + MPS system. SO
4
•–
radicals were validated to be primary reactive species for ARS degradation while the degradation pathway of ARS was also elucidated. This study further provides insightful information about the development of novel hollow-structured Co
3
O
4
-based catalyst for catalyzing activation of MPS to remove toxic dyes from water.
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In this study, we reported on the concept and practical use of cation exchange resin (CER) for removing anions in water via pretreating the CER with metal salts. The cation exchange ...resin-supported iron and magnesium oxides/hydroxides composite (Fe-Mg/CER) was synthesized and introduced as a new and potential adsorbent for selective removal of nitrate ion in the water environment. Characteristics of Fe-Mg/CER were determined by techniques such as Fourier-transform infrared spectroscopy, scanning electron microscopy, and X-ray diffraction. The results showed that Fe-Mg/CER material had a high nitrate adsorption capacity of 200 mg NO3−·g−1 with a fast equilibrium adsorption time of 30 min at pH 5. In addition, it had good durability of at least 10 times of regeneration, which could be applied to practical water and wastewater treatment.
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.
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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 Co3O4 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 Ea of AS degradation than the reported Ea 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 SO4•−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.
