Efficient organics heterogeneous degradation by spinel CuFe2O4 supported porous carbon nitride catalyst: Multiple electron transfer pathways for reactive oxygen species generation
Graphical abstract
Introduction
Peroxymonosulfate (PMS) activation has been exploited to achieve prospective application for organic contaminants removal (Shang et al., 2021). The asymmetric structure (HO–O–SO3-) of PMS is believed to be easily dissociated compared to symmetric peroxydisulfate (PDS) and H2O2 (Guo et al., 2021). That, the generated radicals (OH• and SO4•−) or non-radicals (1O2) after PMS cleavage can highly elaborate reactivity for organics degradation (Li et al., 2018; Xu et al., 2020). Notably, the most important of PMS activation is to find an ultra-efficient heterogeneous catalyst, which could be stable enough to consecutively produce reactive oxygen species (ROS) and then to attack pollutants. Normally, the more reactive species generated, the high catalytic efficiency could be achieved (Li et al., 2016). Thus, improvement of ROS generation in activating PMS is an effective way to facilitate the heterogeneous catalysis for organics removal.
Transition-metal-based catalysts have been verified to exhibit superior catalysis in PMS activation for ROS generation (Yu et al., 2018). Especially, spinel CuFe2O4 has attracted considerable attention recently owing to its excellent heterogenous catalytic performance and certain stability (Guan et al., 2013; Zhang et al., 2013). For example, Guan et al. found synthesized magnetic porous CuFe2O4 presented a notable PMS activation, resulting in over 98% of atrazine was degraded within 15 min as 1 mM PMS and 0.1 g/L CuFe2O4 addition (Guan et al., 2013). Zhang et al. prepared magnetically separable CuFe2O4 spinel to activate PMS, which showed an excellent activity for iopromide removal (Zhang et al., 2013). Nevertheless, some effort needs to be required for CuFe2O4-involved catalytic improvement. For one thing, the agglomeration of prepared CuFe2O4 blocked some active sites, and the sluggish reduction rate of surface metal ions restrained the catalysis (Zhang et al., 2016a). For another, the phenomenon of reactive metal ions leaching still occurred during activation. That not only limited the practical prospect and resulted in ambiguous PMS activation mechanism due to both heterogeneous and homogeneous catalytic contribution.
Against this problem, anchoring CuFe2O4 onto a certain non-metallic support is expected to reduce the dissolved metal ions (Lei et al., 2019; Wang et al., 2021a). In the process, PMS decomposition generally occurred on catalyst surface. The carrier could adsorb PMS first to form PMS-catalyst complex, and then the redox loop between PMS and metal sites contribute to ROS generation. However, the number of produced ROS was restrained due to the reduction of active sites when loaded on non-metallic substrate. Therefore, the selection of effective support becomes particularly crucial. It not only requires the carrier can anchor the spinel CuFe2O4 well, meanwhile itself can act as effective mediator for redox cycle.
Among various supporting materials, carbon nitride (g-C3N4) benefits from the superior 2D sheet structure and surface delocalized electrons, which is capable to be used as ideal substrate (Cao et al., 2015). Besides, recent studies proved that the oxygen-doped g-C3N4 (O–CN) could enhance PMS activation for organic pollutants degradation (Gao et al., 2018). The introduction of active oxygen-containing functional groups can enhance the PMS adsorption, and the modification of local electronic structures further promote redox circulation (Qiu et al., 2017). Moreover, the doped oxygen normally leads to pores generation, which can maximize the exposed active sites to some extent (Zhang et al., 2021). Our previous work verified the doped oxygen could act as a linkage to connect g-C3N4 and metal sites for metal-oxo-bridge construction on the surface (Chen et al., 2021b). Based on above consideration, it is acceptable to assume that anchoring CuFe2O4 on O–CN carrier can reduce the aggregation of CuFe2O4 and increase the stability of the catalyst. Importantly, large amounts of ROS might be generated theoretically during PMS activation, ascribe to the regulation of interfacial electrons for both CuFe2O4 and O–CN contribution.
To this end, this study designed a strategy to incorporate small amount of spinel CuFe2O4 on O–CN surface via a one-pot approach. The obtained CuFe2O4@O–CN composite was firstly employed to activate PMS for organics degradation. The morphology and structure of prepared CuFe2O4@O–CN were thoroughly investigated. The catalytic performance of CuFe2O4@O–CN/PMS system was assessed by bisphenol A (BPA) degradation. Several crucial operating conditions (such as catalyst dosage, PMS concentration and initial pH) were explored to optimize reaction conditions. Electron paramagnetic resonance (ESR) technique and quenching tests were conducted to identify the produced ROS. The changes of CuFe2O4@O–CN surface composition before and after reaction were particularly analyzed to reveal the interface mechanism. As a result, we found the developed CuFe2O4@O–CN/PMS system exhibits strong oxidation capability due to large amounts of ROS generation. Three electron transfer routes on CuFe2O4@O–CN surface were figured out to explain the excellent activity. This study provides a reference for metallic oxides-carbon catalyst fabrication, not only significantly improves the heterogeneous catalysis, but also opens a new insight for interfacial electron transfer exploration.
Section snippets
Chemicals
PMS (Oxone, 2KHSO5·KHSO4·K2SO4) purchased from Sigma-Aldrich (St. Louis, USA). Urea (AR), oxalic acid dihydrate (AR), Cu(NO3)2·3H2O (AR), Fe(NO3)3·9H2O (AR), Na2S2O3 (AR), HNO3 (AR) and NaOH (AR) were obtained from Sinopharm Chemical Reagent Co., Ltd (China). l-histidine (≥99.5%), 5,5-dimethyl-1-pyrroline N-oxide (DMPO, 97%), 2,2,6,6-tetramethyl-4-piperidinol (TEMP, >98%), and bisphenol A (BPA, >99%) were purchased from Aladdin Industrial Corporation (China). D2O was supplied by ANPEL
Morphology of CuFe2O4@O–CN composite
The surface morphology and microstructural details of the prepared CuFe2O4@O–CN was observed by SEM, TEM and HR-TEM investigations. As depicted in Fig. 1b, the SEM image shows that CuFe2O4@O–CN exhibits lamellar structure accompanied with intensive reticular intertwined, and no evident metal oxide particles are accumulated on the surface. This could be originated from the relatively less amounts of raw metal salts during calcination process. Meanwhile, the TEM image (Fig. 1c) presents the
Conclusions
In summary, this study successfully prepared a CuFe2O4@O–CN catalyst by one-pot calcination route, which can act as effective PMS activation material to degrade diverse organics in water. The results found that the developed CuFe2O4@O–CN/PMS system exhibits strong oxidation ability, which was ascribed to the efficient multi-electrons transfer routes on CuFe2O4@O–CN surface. The surface Cu(II)/Cu(I), Fe(III)/Fe(II) and their synergistic effect are responsible for the facilitated redox cycle. The
Author contribution statement
Ting Chen: Conceptualization, Formal analysis, Methodology, Visualization, Writing – original draft. Zhiliang Zhu: Project administration, Resources, Supervision, Writing – review & editing. Yue Wang: Methodology, Data curation. Hua Zhang: Characterization. Yanling Qiu: Methodology, Investigation. Daqiang Yin: Conceptualization, Resources.
Declaration of competing interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
Acknowledgements
This work was supported by the National Key Research and Development Project of China (No. 2021YFC3200805) and the Chinese Scholarship Council (Grant No. 202006260273). The authors thank the facilities and scientific technical assistance from the State Key Laboratory of Pollution Control and Resource Reuse in Tongji University and FACTS Lab in Nanyang Technological University.
References (44)
- et al.
Efficient degradation of atrazine by magnetic porous copper ferrite catalyzed peroxymonosulfate oxidation via the formation of hydroxyl and sulfate radicals
Water Res.
(2013) - et al.
Bisphenol A (BPA) in China: a review of sources, environmental levels, and potential human health impacts
Environ. Int.
(2012) - et al.
Co-selection of multi-antibiotic resistance in bacterial pathogens in metal and microplastic contaminated environments: an emerging health threat
Chemosphere
(2019) - et al.
CuFe2O4@GO nanocomposite as an effective and recoverable catalyst of peroxymonosulfate activation for degradation of aqueous dye pollutants
Chin. Chem. Lett.
(2019) - et al.
One step synthesis of oxygen doped porous graphitic carbon nitride with remarkable improvement of photo-oxidation activity: role of oxygen on visible light photocatalytic activity
Appl. Catal., B
(2017) - et al.
Simultaneous hydrogen production with the selective oxidation of benzyl alcohol to benzaldehyde by a noble-metal-free photocatalyst VC/CdS nanowires
Chin. J. Catal.
(2022) - et al.
Catalytic degradation of sulfamethoxazole through peroxymonosulfate activated with expanded graphite loaded CoFe2O4 particles
Chem. Eng. J.
(2019) - et al.
Catalytic removal NO by CO over LaNi0.5M0.5O3 (M = Co, Mn, Cu) perovskite oxide catalysts: tune surface chemical composition to improve N2 selectivity
Chem. Eng. J.
(2019) - et al.
A review on Fenton process for organic wastewater treatment based on optimization perspective
Sci. Total Environ.
(2019) - et al.
Catalytic degradation of diethyl phthalate in aqueous solution by persulfate activated with nano-scaled magnetic CuFe2O4/MWCNTs
Chem. Eng. J.
(2016)
Degradation of haloacetonitriles with UV/peroxymonosulfate process: degradation pathway and the role of hydroxyl radicals
Chem. Eng. J.
Catalytic degradation of diethyl phthalate in aqueous solution by persulfate activated with nano-scaled magnetic CuFe2O4/MWCNTs
Chem. Eng. J.
Degradation of benzotriazole by a novel Fenton-like reaction with mesoporous Cu/MnO2: combination of adsorption and catalysis oxidation
Appl. Catal., B
Efficient degradation of 2,4-dichlorophenol in aqueous solution by peroxymonosulfate activated with magnetic spinel FeCo2O4 nanoparticles
Chemosphere
Polymeric photocatalysts based on graphitic carbon nitride
Adv. Mater.
Well-dispersed iron and nitrogen co-doped hollow carbon microsphere anchoring by g-C3N4 for efficient peroxymonosulfate activation
Chemosphere
Promoted peroxymonosulfate activation by electron transport channel construction for rapid Cu(II)/Cu(I) redox couple circulation
Environ. Sci. Nano
Anchoring CuFe2O4 nanoparticles into N-doped carbon nanosheets for peroxymonosulfate activation: built-in electric field dominated radical and non-radical process
Chem. Eng. J.
Sulfur and nitrogen Co-doped graphene for metal-free catalytic oxidation reactions
Small
Electronic structure modulation of graphitic carbon nitride by oxygen doping for enhanced catalytic degradation of organic pollutants through peroxymonosulfate activation
Environ. Sci. Technol.
Influence of pH on the formation of sulfate and hydroxyl radicals in the UV/peroxymonosulfate system
Environ. Sci. Technol.
Mn-O covalency governs the intrinsic activity of Co-Mn spinel oxides for boosted peroxymonosulfate activation
Angew. Chem., Int. Ed. Engl.
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