Catalyst For Peroxymonosulfate Activation Research Articles

Enhanced degradation of triclosan by cobalt manganese spinel-type oxide activated peroxymonosulfate oxidation process via sulfate radicals and singlet oxygen: Mechanisms and intermediates identification

Spinel is a kind of desirable catalyst to activate peroxymonosulfate (PMS) for chemical oxidation of organic contaminants in wastewater treatment. However, apart from classic sulfate radical based AOPs (SR-AOPs), the generation and oxidative pathways of singlet oxygen (1O2) by Co/Mn spinels have been little explored in PMS catalysis. In this study, spinel-type oxide Co2Mn1O4 was successfully synthesized, and used as highly effective catalyst in PMS activation for heterogeneous degradation of TCS (up to 96.4% within 30 min) at initial pH of 6.8, which was also slightly impacted by coexisting ions. Based on radical scavengers and electron paramagnetic resonance (EPR) experiments, sulfate radicals and singlet oxygen (1O2) were unveiled to be the dominant reactive oxygen species (ROS) in Co2Mn1O4/PMS system. Co2Mn1O4 catalyst exhibited reversible redox properties based on the results of cyclic voltammetry (CV). More importantly, the generation of 1O2 might not only promote the TCS removal rate directly, but also facilitate the metal redox cycle in spinel structure in Co2Mn1O4/PMS system. Finally, degradation pathways of TCS in Co2Mn1O4/PMS system were proposed, which involved the breakage of ether bond and cycloaddition reaction.

Solvent Effect on the Solvothermal Synthesis of Mesoporous NiO Catalysts for Activation of Peroxymonosulfate to Degrade Organic Dyes.

In this work, we successfully prepared three different mesoporous NiO nanostructures with preferential (111) planes using three different solvents–water, a water–ethanol mixture, and a water–ethylene glycol mixture. The NiO nanosheets prepared from the water–ethylene glycol mixture and denoted as NiO-EG showed a nanosheet morphology thinner than 10 nm, whereas the water–ethanol and water samples were 30–40 nm and above 100 nm thick, respectively. The NiO-EG catalyst was found to exhibit a high catalyzing ability to activate peroxymonosulfate (PMS) for decoloring dyes, by which 94.4% of acid orange 7 (AO7) was degraded under the following reaction conditions: AO7 = 50 mg/L, catalyst = 0.2 g/L, PMS = 0.8 g/L, pH = 7, and 30 min reaction time. The dye degradation rate was investigated as a function of the catalyst dosage, pH, and dye concentration. According to quenching experiments, it was found that SO4•–, HO•, and O2•– were the dominant radicals for AO7 degradation, and oxygen vacancies played a significant role in the generation of radicals. High surface area, thin flaky structure, rich oxygen vacancies, fast charge transport, and low diffusion impedance all enhanced the catalytic activity of NiO-EG, which exhibited the highest degradation ability due to its abundant accessible active sites for both adsorption and catalysis.

Direct Electron-Transfer-Based Peroxymonosulfate Activation by Iron-Doped Manganese Oxide (δ-MnO2) and the Development of Galvanic Oxidation Processes (GOPs).

Manganese oxides have been recently investigated as excellent catalysts for peroxymonosulfate (PMS) activation, and the reported mechanisms are mostly forming reactive oxygen species (ROSs). This study investigated the use of iron-doped manganese oxide, synthesized via air oxidation under strong alkaline conditions. The oxidation of three substrates was affected by their adsorption at the catalyst surface, solution pH, and co-solutes. Common ROS scavengers inhibited the oxidation of bisphenol A (BPA), suggesting the possible involvement of ROSs; however, the PMS decomposition tests with and without BPA and the comparison with a 1O2-generation system ruled out the formation of ROSs and pointed to direct electron transfer between the adsorbed BPA and complexed PMS as the mechanism. To prove this mechanism, the catalyst was coated to graphite sheets and a galvanic oxidation process (GOP) was developed to separate BPA and PMS into two half cells. Upon PMS addition into one cell, BPA was quickly oxidized in the other cell, confirming the occurrence of electron transfer. The GOP system successfully degraded BPA in both surface water and hypersaline shale gas-produced water. Overall, this study developed a new catalyst for PMS activation and unveiled the advantages and potential applications of electron shuttling catalysts.

Calcined CoAl-layered double hydroxide as a heterogeneous catalyst for the degradation of acetaminophen and rhodamine B: activity, stability, and mechanism.

Peroxymonosulfate (PMS) activated by nanomaterials presents one of the most promising strategies to generate reactive species for remediation of organic pollutant-contaminated water. In this study, CoAl-layered double hydroxide (CoAl-LDH) and calcined CoAl-LDH (CoAl-CLDH) were employed as catalysts for PMS activation towards aqueous organic pollutants degradation. Our experiments showed that the leaching of metal ions from catalyst can be significantly mediated by calcination treatment, which can avoid the secondary contamination. The stable CoAl-CLDH exhibited a high catalytic activity, which is comparable to that of the unstable CoAl-LDH. Importantly, reactive species quenching and electron paramagnetic resonance (EPR) results revealed that singlet oxygen (1O2) is the dominant reactive species and plays a crucial role in the catalytic oxidation process in CoAl-CLDH/PMS system. A possible mechanism was proposed for the activation of PMS on the CoAl-CLDH. We demonstrate that CoAl-CLDH is a highly active and stable heterogeneous catalyst for efficient catalytic oxidation of organic pollutants (such as acetaminophen and rhodamine B (RhB)) via activation of PMS.

Ordered Mesoporous Cobalt Containing Perovskite as a High-Performance Heterogeneous Catalyst in Activation of Peroxymonosulfate.

An ordered mesoporous perovskite, La2CoMnO6-δ (MLCMO), was synthesized for the first time using a facile method of evaporation-induced self-assembly. The N2-sorption, scanning electron microscopy, and transmission electron microscopy measurements indicated that the optimized MLCMO possessed a high specific surface area (58.7 m2/g) and was uniformly mesoporous (11.6 nm). The MLCMO exhibited superior catalytic performance in peroxymonosulfate (PMS) activation for atrazine (ATZ) degradation. From a comparison view, the catalytic activity of the mesoporous MLCMO outperformed that of the bulk La2CoMnO6-δ (LCMO) and other common PMS activators, including α-MnO2, Co3O4, and CoFe2O4. The mechanisms of PMS activation by the MLCMO were investigated by X-ray photoelectron spectroscopy, electron spin resonance, and quenching tests. SO4•-, •OH, 1O2, and O2•- were identified as main reactive oxygen species generated from PMS activation. The Co and Mn in MLCMO were the active sites responsible for active radical generation. The lattice oxygen reversible redox sites (OL-/OL2-), which were involved in the electron transfer of the MnIII/MnIV cycle, were demonstrated as redox partners to the cation active sites. In addition, the SO4•-/•OH radical conversion was promoted at pH 11, which accelerated the consumption of PMS and seriously inhibited the degradation of ATZ.

Zeolitic imidazolate framework-supported Prussian blue analogues as an efficient Fenton-like catalyst for activation of peroxymonosulfate

Prussian blue analogues (PBAs) have gained extensive attention for peroxymonosulfate (PMS) activation. However, the poor recovery ability of PBAs has limited their practical applications. In this work, PBA was firstly immobilized using zeolitic imidazolate framework-8 (ZIF-8) via a facile in-situ growth method. The decoration of PBA onto the surface of ZIF-8 was well confirmed by TEM, XRD, FTIR and XPS. The catalytic efficiency of the PBA-ZIF8 composite was significantly higher than that of pure PBA and ZIF-8 on the activation process of peroxymonosulfate when rhodamine B (RhB) was employed as a target contaminant. RhB degradation efficiency was effectively promoted at relatively high PBA-ZIF8 dosage and PMS concentration, as well as in near-neutral pH medium. Sulphate radicals obviously played a predominant role in attacking RhB during the whole reaction. In addition, PBA-ZIF8 also possessed good stability and reusability with negligible cobalt leaching. Therefore, the PBA-ZIF8 composite was a conveniently prepared and promising catalyst that may be employed to remediate contaminated water due to its excellent catalytic activity and recyclability.

Efficient degradation of atrazine with porous sulfurized Fe2O3 as catalyst for peroxymonosulfate activation

In this study, magnetic porous sulfurized Fe2O3 (PS-Fe2O3) composites were prepared through the co-precipitation method and were applied to activate peroxymonosulfate (PMS) for the degradation of emerging contaminants. Characterization results indicated that PS-Fe2O3 catalyst with uniform elemental distribution possessed a large number of micro- and meso- pores. When the molar ratio of FeSO4:S2O32− was 2:1 during the synthesis process, the PS-Fe2O3-2 exhibited the best performance on PMS activation for atrazine (ATZ) removal. The catalytic activity of PS-Fe2O3 catalysts was enhanced with increased sulfurization extent. The effects of catalyst dosage, PMS concentration, pH, and water impurities (i.e. Cl−, HCO3−, NO3− and humic acid) on ATZ degradation were investigated. Both sulfate radicals and hydroxyl radicals were detected in the PS-Fe2O3-2/PMS system, and sulfate radicals played the predominant role for the degradation of ATZ. The cycle of Fe(II)/Fe(III) and surface-bonded hydroxyl group both contributed to the PMS activation, and the reduction of Fe3+ to Fe2+ was significantly accelerated by the low-valent sulfur species (such as sulfite) on the catalyst surface. The transformation products of ATZ in PS-Fe2O3-2/PMS system were monitored on LC/MS, which were probably generated through lateral chain oxidation and dechlorination-hydroxylation. Overall, PS-Fe2O3 has potential to be a feasible catalyst for the removal of organic pollutants from water.

Metal-Organic Frameworks and Their Derived Materials: Emerging Catalysts for a Sulfate Radicals-Based Advanced Oxidation Process in Water Purification.

With the ever-growing environmental issues, sulfate radical (SO4•- )-based advanced oxidation processes (SR-AOPs) have been attracting widespread attention due to their high selectivity and oxidative potential in water purification. Among various methods generating SO4•- , employing heterogeneous catalysts for activation of peroxymonosulfate or persulfate has been demonstrated as an effective strategy. Therefore, the future advances of SR-AOPs depend on the development of adequate catalysts with high activity and stability. Metal-organic frameworks (MOFs) with large surface area, ultrahigh porosity, and diversity of material design have been extensively used in heterogeneous catalysts, and more recently, enormous effort has been made to utilize MOFs-based materials for SR-AOPs applications. In this work, the state-of-the-art research on pristine MOFs, MOFs composites, and their derivatives, such as oxides, metal/carbon hybrids, and carbon materials for SR-AOPs, is summarized. The mechanisms, including radical and nonradical pathways, are also detailed in the discussion. This work will hopefully promote the future development of MOFs-based materials toward SR-AOPs applications.

Novel activation of peroxymonosulfate by an easily recyclable VC@Fe3O4 nanoparticles for enhanced degradation of sulfadiazine

An easily recyclable nanocomposite ascorbic acid-modified Fe3O4 (VC@Fe3O4) was synthesized, characterized, and evaluated as a green heterogeneous catalyst for activation of peroxymonosulfate (PMS). The structures of fresh and used VC@Fe3O4 were well characterized by TEM, XRD, FTIR, and XPS. The catalytic activity comparison between Fe3O4 and VC@Fe3O4 was performed under different parameters for depletion of sulfadiazine (SD). Additionally, scavenging tests and in-situ electron paramagnetic resonance (EPR) tests were applied to discern the primary radicals generated in the VC@Fe3O4/PMS system. The results indicate that the VC@Fe3O4 possesses a higher catalytic activity towards PMS compared with Fe3O4 for SD removal, and the observed pseudo first rate constant (kobs) were 7.24 × 10−2 min−1 for the VC@Fe3O4/PMS system and 1.05 × 10−2 min−1 for the Fe3O4/PMS system, correspondingly. 56.6% SD removal efficiency was obtained with 0.3 mM PMS and 0.8 g/L VC@Fe3O4 under pH 7.0. A large amount of hydroxyl radicals (OH) and a few number of sulfate radicals (SO4−) were discerned by the hyperfine splitting constant values and scavenging results. Mechanisms on the peroxymonosulfate activation and radical generation in the VC@Fe3O4/PMS system were supposed. Results indicate that VC would obviously boost the cycle of Fe2+-Fe3+ on surface of VC@Fe3O4 nanoparticles and newly generated Fe2+ can continuously be consumed to activate PMS, which is answer for the rapid generation of reactive radicals (OH, SO4−). At last, mineralization and degradation pathway were also investigated. The findings of this study suggest that VC@Fe3O4 is a novel effective catalyst in activation of peroxymonosulfate under neutral pHs.

Enhanced degradation of sulfadiazine by novel β-alaninediacetic acid-modified Fe3O4 nanocomposite coupled with peroxymonosulfate

Magnetic nanocomposite β-alaninediacetic acid-modified Fe3O4 (β-ADA@Fe3O4) was prepared, characterized and evaluated to activate peroxymonosulfate (PMS) for improved degradation of sulfadiazine (SD). The results reveal that β-ADA@Fe3O4 express more efficient catalytic activity in PMS inducement compared with Fe3O4, and the observed pseudo first rate constant (kobs) of SD degradation is enhanced from 1.05 × 10−2 to 7.02 × 10−2 min−1 when Fe3O4 is replaced by β-ADA@Fe3O4. The highest removal rate 54.0% occurs when [PMS]0 and m(β-ADA@Fe3O4)0 was 0.3 mM and 0.8 g/L at neutral pH. High intensity of hydroxyl radicals (OH) and relatively low intensity of sulfate radicals (SO4−) are distinguished in system by scavenging experiments and electron paramagnetic resonance (EPR) tests. Results point that β-ADA would significantly promote the circulation of Fe2+-Fe3+ on the surface of β-ADA@Fe3O4, producing more radicals (OH, SO4−). The findings herein imply that β-ADA@Fe3O4 is an efficient and green catalyst in activation of peroxymonosulfate under neutral environment.

Origins of boron catalysis in peroxymonosulfate activation and advanced oxidation

Amorphous boron is employed as a novel and high-performance metal-free catalyst for activation of peroxymonosulfate for degrading various organic contaminants in water.

Novel magnetic MnO2/MnFe2O4 nanocomposite as a heterogeneous catalyst for activation of peroxymonosulfate (PMS) toward oxidation of organic pollutants

Novel magnetic MnO2/MnFe2O4 nanocomposite was successfully fabricated by hydrothermal method. Subsequently, this nanocomposite was characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microcopy (TEM), X-ray photoelectron spectra (XPS), vibrating sample magnetometer (VSM) and Brunauer-Emmett-Teller (BET) measurements. Then the material was applied to activate PMS for Rhodamine B (Rh B) degradation. The results displayed that the decomposition efficiency of the MnO2/MnFe2O4 nanocomposite with a mole ratio of 7:1 was 90% for Rh B within 5 min in the presence of PMS, higher than other MnO2/MnFe2O4 ratio, homogeneous catalysts (Fe3+ and Mn2+), pure MnO2 and pure MnFe2O4. In addition, influences of pivotal factors (PMS concentration, catalyst dosage and initial pH value), performance of different processes and reusability of MnO2/MnFe2O4 nanocomposite were also evaluated. Radical scavenging experiments were conducted and SO4− was indicated as the primary radical. What’s more, the MnO2/MnFe2O4 nanocomposite could be convenient to recycle in practical application benefited from its magnetism. Finally, according to the results and previous studies, the believable mechanism of activating PMS by MnO2/MnFe2O4 nanocomposite was put forward, which could occupy an important position as a fast treatment option in sewage disposal.

Activated carbon‐supported cobalt molybdate as a heterogeneous catalyst to activate peroxymonosulfate for removal of organic dyes

Activated carbon‐supported cobalt molybdate (CoMoO4/AC) composite was conveniently fabricated using a simple hydrothermal route and high‐temperature calcination, aiming to create a novel heterogeneous catalyst for activation of peroxymonosulfate (PMS) to degrade organic dyes. The CoMoO4/AC catalyst was characterized using scanning electron microscopy, powder X‐ray diffraction, energy‐dispersive spectroscopy, Fourier transform infrared spectroscopy, Raman spectroscopy, elemental mapping analysis and X‐ray photoelectron spectroscopy. Efficient catalytic activity, high stability and superior reusability were observed. Additionally, the catalytic performance of CoMoO4/AC was systematically assessed through numerous controlled experiments and several operational factors, such as catalyst dosage, oxidant dosage, reaction temperature, initial pH and catalyst stability. Under the condition of CoMoO4/AC = 0.1 g l−1, oxidant = 2.0 mM, dye = 100 mg l−1, T = 25°C, the removal of methylene blue reached 90% within 60 min without pH adjustment. Batch experiment results showed that the degradation of organic dye relied upon the dosage of catalyst and oxidant and reaction temperature. Further, high catalyst and oxidant dosage, as well as high reaction temperature, were favorable for dye removal. Moreover, quenching experiments suggested that the CoMoO4/AC catalyst successfully activated PMS to generate sulfate and hydroxyl radicals. A rational mechanism is proposed based on a non‐radical process and a free radical process. The result revealed that the enhanced active sites were mainly ascribed to the synergistic effects between Co species and oxygen‐containing functional groups (especially ketone groups) on the catalyst surface. The findings of this study demonstrated the as‐prepared CoMoO4/AC composite has potential superiority for refractory organic contaminant removal from water.

Optimization of the catalytic activity of a ZnCo2O4 catalyst in peroxymonosulfate activation for bisphenol A removal using response surface methodology

An effective peroxymonosulfate activator, ZnCo2O4, was synthesized through a microwave-assisted method. According to response surface methodology (RSM) using Box-Behnken design (BBD), the effects of four parameters, microwave temperature, microwave time, calcination time and calcination temperature, were investigated, and the results show that both the microwave temperature and calcination temperature have a great influence on the catalytic activity during the preparation process. In addition, a quadratic model is valid for computing and predicting the observed responses. The characteristics of the synthesized ZnCo2O4 catalyst were analyzed with various equipments. The results show that the ZnCo2O4 nanosheets are cubic crystals with a spinel structure and a high surface area of 105.90 m2‧g−1. Under the conditions of [ZnCo2O4] = 0.2 g‧L−1 and [PMS]/[BPA]molar = 2.0, the bisphenol A degradation efficiency reaches 99.28% within 5 min in the ZnCo2O4/PMS system. ZnCo2O4 possesses great stability and reusability according to recycling experiments. In addition, the possible active radical species were confirmed through quenching experiments and EPR detection, indicating that surface-bound SO4- and OH play vital roles during the degradation process.

A multipath peroxymonosulfate activation process over supported by magnetic CuO-Fe3O4 nanoparticles for efficient degradation of 4-chlorophenol

Heterogeneous catalysts with low cost, environmentally friendly, highly effective and ready separation from aqueous solution are highly desirable. Magnetic CuO-Fe3O4 nanoparticles, a type of non-toxic bimetallic transition metal oxide, is a promising heterogeneous catalyst for activation of peroxymonosulfate (PMS) to generate reactive oxygen species (ROS) that has not been previously investigated. In this study, the activation of PMS by CuO-Fe3O4 nanoparticles was evaluated using the degradation of 4-chlorophenol as a model reaction. Several critical factors such as pH, catalyst dosage and PMS concentration were investigated. CuO-Fe3O4/PMS system demonstrated a wide effective pH range to degrade 4-chlorophenol, namely 5.5 to 9.5. With the increase of the catalyst dosage, the degradation efficiency of 4-chlorophenol appeared to increase first and then decrease, that the inflection point was 0.5 g/L. Elevated PMS concentration obviously improved the decomposition of 4-chlorophenol; however, the plateau was reached when the PMS concentration was 8 mM. Further increase in PMS concentration would not significantly improve the removal efficiency. Through examining the effects of scavengers and electron spin resonance (ESR) analyses, CuO-Fe3O4 nanoparticles were proven to activate PMS through a non-radical and radical pathway to generate singlet oxygen, sulfate radicals and hydroxyl radicals. Based on results, CuO-Fe3O4 nanoparticles were effective, environmentally friendly and low cost catalysts for efficient activation of PMS. These features make CuO-Fe3O4 nanoparticles a readily available heterogeneous catalyst to activate PMS for refractory organic pollutants degradation in advanced oxidation processes (AOPs).

Enhanced degradation of Bisphenol A (BPA) by peroxymonosulfate with Co3O4-Bi2O3 catalyst activation: Effects of pH, inorganic anions, and water matrix

In this study, a novel Co3O4-Bi2O3 catalyst was synthesized using a microwave-assistant method, and the corresponding characteristics were studied through XRD, SEM, and N2 adsorption. As a peroxymonosulfate (PMS) activator, the catalytic activity of the synthesized catalyst was evaluated on Bisphenol A (BPA) removal, and the result showed that Co3O4-Bi2O3 catalyst promoted BPA degradation, where 100% BPA was degraded within 15 min under the condition of [catalyst] = 0.1 g·L−1 and [PMS]/[BPA]molar = 5. The Co3O4-Bi2O3/PMS system presented a good catalytic activity when the solution pH varied from 3.0 to 11.0. Under the different concentrations of various inorganic anions in the Co3O4-Bi2O3/PMS system, Cl− showed an inhibited effect at low concentration and a promoted effect at high concentration. CO32− showed a slight inhibited effect, while H2PO4− showed a considerable inhibited effect. Additionally, both NO3− and SO42− showed a negligible effect on BPA removal. For the real water bodies, both the drinking water and tap water showed a slight decrease in degradation efficiency of BPA but a distinctly negative effect on BPA mineralization, which might be contributed to the competition between BPA and indigenous organic matters in the two water matrices for their oxidation by radical species. The quenching experiment was enforced and it was found that both SO4− and OH on the surface-bound of catalyst were the main active radicals in this system. Overall, the Co3O4-Bi2O3 catalyst as a PMS activator is a promising catalyst in PMS activation for sulfate radical-based wastewater treatment.

Template synthesis of nitrogen-doped carbon nanocages–encapsulated carbon nanobubbles as catalyst for activation of peroxymonosulfate

Nitrogen-doped carbon nanocages–encapsulated carbon nanobubbles were employed as high-performance peroxymonosulfate activators for the degradation of organic pollutants.

Magnetic EDTA functionalized CoFe2O4 nanoparticles (EDTA-CoFe2O4) as a novel catalyst for peroxymonosulfate activation and degradation of Orange G.

EDTA functionalized CoFe2O4 nanoparticles (EDTA-CoFe2O4) synthesized using a facile one-pot solvothermal method were employed as catalysts to activate peroxymonosulfate (PMS) with Orange G (OG) as the target pollutant. Effects of operating parameters including initial solution pH, catalyst dosage, PMS dosage, and water matrix components such as Cl-, NO3-, CO32-, and humic acid were evaluated. A degradation efficiency of 93% was achieved in 15min with 1mM PMS and 0.2g/L EDTA-CoFe2O4 catalyst, while only 57% of OG was degraded within 15min in CoFe2O4/PMS system. The degradation of OG followed pseudo-first-order kinetics, and the apparent first-order date constant (k obs) for OG in EDTA-CoFe2O4/PMS and CoFe2O4/PMS system was determined to be 0.152 and 0.077min-1, respectively. OG degradation by EDTA-CoFe2O4/PMS was enhanced with the increase of catalyst and PMS doses at respective range of 0.1-2.0g/L and 0.5-10.0mM. Higher efficiency of OG oxidation was observed within a wide pH range (3.0-9.0), implying the possibility of applying EDTA-CoFe2O4/PMS process under environmental realistic conditions. Humic acid (HA) at low concentration accelerated the removal of OG; however, a less apparent inhibitive effect was observed at HA addition of 10mg/L. The k obs value was found to decrease slightly from 0.1601 to 0.1274, 0.1248, and 0.1152min-1 with the addition of NO3-, CO32-, and Cl-, respectively, but near-complete removal of OG could still be obtained after 15min. Both of the sulfate radicals and hydroxyl radicals were produced in the reaction, and sulfate radicals were the dominant according to the scavenging tests and electron paramagnetic resonance (EPR) tests. Finally, a degradation mechanism was proposed, and the stability and reusability of the EDTA-CoFe2O4 were evaluated.

Prussian blue analogue derived magnetic carbon/cobalt/iron nanocomposite as an efficient and recyclable catalyst for activation of peroxymonosulfate

A Prussian blue analogue, cobalt hexacyanoferrate Co3[Fe(CN)6]2, was used for the first time to prepare a magnetic carbon/cobalt/iron (MCCI) nanocomposite via one-step carbonization of Co3[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 Co3O4, 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 Co3[Fe(CN)6]2 is a promising heterogeneous catalyst for activating PMS to degrade organic pollutants.

Hierarchically-structured Co–CuBi2O4 and Cu–CuBi2O4 for sulfanilamide removal via peroxymonosulfate activation

Herein, we report the syntheses of Co–CuBi2O4 and Cu–CuBi2O4 composites using a facile hydrothermal synthesis method for sulfanilamide (SA) removal via peroxymonosulfate (PMS) activation. The composites were characterized using FESEM, XRD and porosimeter and the results indicated that they were hierarchically-structured with several phases. The performance of the composites as catalysts for PMS activation was evaluated with respect to different initial pHs (4.5–9.5), catalyst loadings (L, 0.10–0.60gL−1) and Oxone® dosages (D, 0.03–0.30gL−1) and the empirical relationship between the kapp, L and D were obtained. The results also indicated that Cl− and humic acid exerted negative effect on SA degradation due to the intrinsic competition between Cl− and humic acid with SA for SO4− oxidation. The principal reactive radical in the Co–CuBi2O4/PMS and Cu–CuBi2O4/PMS systems was identified to be SO4−. A simple method to calculate the normalized steady-state concentrations of SO4− ([SO4−]Nss) and OH ([OH]Nss) in the heterogeneous catalyst/PMS system is proposed. The results indicated that the generated SO4− and OH in the Co–CuBi2O4/PMS system were utilized at least five times more efficiently than the Cu–CuBi2O4/PMS system. The proposed method for calculating [SO4−]Nss and [OH]Nss can be potentially employed to characterize and compare the intrinsic catalytic activity of various heterogeneous catalyst/PMS systems in future studies.