Efficient Activation Of Persulfate Research Articles

Multiple path-dominated activation of peroxymonosulfate by MOF-derived Fe2O3/Mn3O4 for catalytic degradation of tetracycline

Sulfate radical-based advanced oxidation process (SR-AOP) has been identified as an efficient technology for the treatment of antibiotic contamination, with a focus on the development of catalysts for efficient activation of persulfate. In this work, a novel peroxymonosulfate (PMS) activator, metal organic framework (MOF) derived Fe2O3/Mn3O4 composite, was prepared and characterized. The physicochemical properties, catalytic performance of the catalyst and the degradation mechanism of tetracycline (TC) by the reaction system were thoroughly investigated. Combined with the experimental results and density functional theory (DFT) calculations, we can reasonably speculate that both radical (O2˙ˉ) and non-radical (1O2 and electron transfer) pathways contributed to the catalytic activation of PMS for TC degradation. The enhanced catalytic activity was attributed to the combination of Fe2O3 with Mn3O4 accelerated Fe(II)/Fe(III) cycle and Mn(II)/Mn(III) cycle. In addition, the extended peroxide O-O bond length facilitated the generation of 1O2. After five consecutive experiments, no significant change in catalytic performance and chemical structure was found, indicating that this catalyst had not only good chemical stability but also astonishing reusability. The research results are expected to provide some valuable theoretical basis for MOF-derived metal oxides catalytic activation of PMS for wastewater treatment.

Strongly coupled Fe3O4 quantum dots-3D N-enriched carbon aerogel towards boosting peroxydisulfate activation by electron redistribution of multiple active sites

Simultaneous regulation of electronic environment of active sites and engineering architectures with efficient exposed active sites are crucial to realize efficient persulfate activation for pollutants degradation, which remains a great challenge. This study demonstrated an ingenious platform of 0D/3D nanofibrous N-enriched carbon hybrid with incorporated ultrafine metal oxide quantum dots (QDs, ≈ 3 nm) with abundant oxygen vacancies that enabled efficient PDS activation for pollutants degradation via integrating electron density regulation and morphology modulation. The favorable structure configuration and intimate coupling action between QDs and N-doped carbon matrix promoted PDS activation on the surface of Fe3O4 QDs@NC and simultaneously modified pollutant absorption property towards catalyst, synergistically resulting in excellent TC degradation efficiency. More importantly, electron-rich Fe sites derived from electron redistribution and highly-conductive N-doped carbon matrix synergistically directed PDS activation by non-radical pathway with generation of 1O2. This work provides a fresh insight into improving persulfate activation by engineering architectures and regulating local electronic density of multiple active sites.

In-situ immobilization of MIL-100(Fe) on the microchannels in wood aerogel: Efficient persulfate activation toward antibiotic removal

Metal-organic frameworks (MOFs) are potential catalysts for persulfate exciting in antibiotic wastewater treatment while are limited in large-scale application given their powder state. Herein, benefiting from the compatibility and functionalization of natural wood supports, MIL-100(Fe) decorated wood aerogel composites (MIL-100(Fe)/WA) were constructed by chemical treatment and in-situ solvothermal synthesis. Na2SO3/NaOH-H2O2 chemical treatment could effectively achieve the partial removal of lignification and hemicellulose in wood, resulting in improved porous characteristics. The corresponding porosity and surface area of WA increased by more than 40% compared with the original wood. Accordingly, after immobilizing MIL-100(Fe) on the microchannels in WA, MIL-100(Fe)/WA-PDS system could efficiently degrade tetracycline (TC), with a satisfied mineralization rate of 64.01% owing to the open porous structure of WA with high accessibility, and its kinetic constant (0.0520 L⋅mg−1⋅min−1) was 6.19 times that of MIL-100(Fe)/wood (0.0084). Quenching results and EPR analysis made clear that TC degradation mainly contributed to the produced O2−, 1O2 and surface-bound radicals (SO4−, OH). LC-MS further uncovered the possible degradative pathways for TC. Moreover, it was found that MIL-100(Fe)/WA could behave well at pH of 2–10 and towards multiple antibiotics. This work may provide a facial way to apply MOFs-based/wood composites in water treatment.

Efficient activation of persulfate by Ti3C2 MXene QDs modified ZnFe2O4 for the rapid degradation of tetracycline

Mxene-based catalysts with specific interfacial characteristics are beneficial for photocatalytic applications. Herein, Ti3C2 MXene modified ZnFe2O4 nanocomposite materials were prepared for photocatalysis. The morphology and structure of the nanocmposites were characterized by scanning electron microscopy (SEM), High-resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS), which revealed that Ti3C2 MXene as quantum dots (QDs) was uniformly distributed on the ZnFe2O4 surface. The Ti3C2 QDs modified ZnFe2O4 catalyst (ZnFe2O4/MXene-15%) under visible light achieved 87% degradation efficiency of tetracycline within 60 min when coupled with persulfate (PS) system. The initial solution pH, PS dosage and co-existing ions were found to be the main factors affecting the heterogeneous oxidation process, while quenching experiments showed that O2•- is the main oxidizing species in the removal of tetracycline in ZnFe2O4/MXene-PS system. In addition, the cyclic experiments suggested that ZnFe2O4/MXene had good stability and thus it may have practical applications in industry.

Effective degradation of tetracycline via recyclable free-standing three-dimensional copper-based graphene as a persulfate catalyst.

Water pollution by antibiotics is a serious and growing problem. Given this challenge, a free-standing three-dimensional (3D) reduced graphene oxide foam supported copper oxide nanoparticles (3D-rGO-CuxO) was synthesized using GO as a precursor and applied as an efficient persulfate activator for tetracycline (TC) degradation. The influences of CuxO mass, solution pH, persulfate dosage, and common anions on the TC degradation were investigated in detail. Analytical techniques indicated that the 3D-rGO-CuxO showed a cross-linking three-dimensional network structure, and CuxO particles with irregular shapes were uniformly loaded on graphene pore walls. The XPS and Auger spectra of Cu confirmed that Cu2O was the main component in solid copper compounds. The addition of CuxO was vitally important for the activation of the oxidation system, and the removal rate reached 98% with a CuxO load of 7:1. The pH showed little influence on the activation effect on TC degradation. For common anions, Cl- and CO32- had little influence on the system, while humic acid had a great inhibitory effect. The EPR test and quenching experiment revealed that the active substances in the oxidative degradation process mainly include SO4-·, ·OH, 1O2, and reactive Cu(III). Additionally, the 3D-rGO-CuxO material proved highly stable according to the replicated test results and was promising for the remediation of antibiotic-contaminated water.

Efficient degradation of organophosphorus herbicide by free‐standing 3D reduced graphene oxide supported nFe3O4 catalytic‐activated persulfate

AbstractBACKGROUNDOrganophosphorus herbicides in water are an increasingly critical environmental problem. Given this challenge, a free‐standing 3D reduced graphene oxide (GO) foam supporting Fe3O4 nanoparticles (3D‐rGO‐Fe3O4) was synthesized using GO as a precursor and applied as an efficient persulfate activator for glyphosate (GLY) degradation.RESULTSThe effects of Fe3O4 mass, pH, oxidant dosage, temperature and common ions on GLY degradation were investigated in detail. Analytical techniques using scanning electron microscopy (SEM), Fourier transform infrared analysis (FTIR) and X‐ray photoelectron spectroscopy (XPS) indicated that the 3D foam prevented aggregation of the Fe3O4 nanoparticles by in situ uniform formation on GO nanosheets. The addition of Fe was vitally important for activation of the oxidation system. The results of batch‐scale experiments illustrated that the GLY degradation efficiency reached 96.8% with initial GLY concentration 30 mg L−1, graphene:Fe3O4 mass ratio 1:7, solution pH 4 and persulfate mass 48 mg. High temperatures could significantly facilitate GLY degradation. Additionally, the 3D‐rGO‐Fe3O4 material proved highly stable according to the replicated test results. Furthermore, EPR test results revealed that Na2S2O8 catalytic activation by 3D‐rGO‐Fe3O4 mainly produced ·OH and SO4−·, and the predominant free radical was SO4−· in the current experiment.CONCLUSIONThe results indicate that 3D‐rGO‐Fe3O4 has good catalytic activity and stability, and, accordingly, has high application prospects for the remediation of organophosphorus herbicide‐contaminated water. © 2023 Society of Chemical Industry (SCI).

Rapid degradation of PFOA by the activated peroxymono-sulfate with FeCo/MoS2 catalyst

Doping polymetals on Fe-based catalysts is proved to be an effective way to improve the performance on activating persulfate. In this paper, a highly efficient persulfate activation catalyst (FeCo@MoS2) was successfully synthesized by introducing MoS2 onto the surface of FeCo nanoboxes. During the activation of PMS the introduced of MoS2 effectively promoted the formation of free radicals (∙OH, SO4·-), 1O2 and Fe(IV). Due to the synergistic effects between Mo and Fe, FeCo@MoS2 has better catalytic activity (2.01 times larger of defluorination efficiency and 3.91 times larger of the apparent rate constant (kobs)) than FeCo. Under the optimal conditions (catalyst dosage of 0.2 g L−1, PMS dosage of 1.0 g L−1 and initial pH 4.0), the perfluorooctanoic acid (PFOA, 10 mg L−1) could be degraded in 60 min, with 90.26 ± 2.64% of the defluorination efficiency. The LC- MS results showed that under the attack of free radicals (∙OH, SO4·-), 1O2 and Fe(IV), the PFOA underwent step-by-step defluorination process. In addition, the ECOSAR results showed that during the whole degradation of PFOA in FeCo@MoS2/PMS system, no highly toxic intermediates was accumulated, suggesting a green degradation process. This work showed new ideas and strategies for studying the influence of polymetallic doping on the catalytic process of PMS multiphase catalytic system.

Chrome shaving-derived biochar as efficient persulfate activator: Ti-induced charge distribution modulation for 1O2 dominated nonradical process

Efficient degradation of organic contaminants by oxidative radicals remains a challenge due to invalid consumption of radicals and easy generation of secondary halogenated pollutants. In this work, an efficient and recyclable bimetallic biochar (Cr-Ti/BC) was developed through peroxydisulfate (PDS) activation via nonradical pathway for sulfamethoxazole (SMX) degradation. The Cr-Ti/BC exhibited excellent catalytic activity for 99.9 % of SMX removal with a high kobs of 0.13 min−1, and negligible inhibitory effects were observed under various pH condition. The activation mechanisms were (i) metastable reactive intermediates (Cr-Ti/BC-PDS) formation via an interaction between Cr-Ti/BC and PDS on the active defective sites (e.g., OH/COC, COOH, CO, nitric oxides, graphitic N, and pyridinic N), and (ii) 1O2 generation through electron transfer between Cr-Ti/BC-PDS intermediates and dissolved oxygen. The high reusability and strong stability of Cr-Ti/BC also verified the outstanding advantage of the Cr-Ti/BC during practical application. This study not only is the first study the catalytic performance of Cr and Ti co-doped biochar for PDS activation, but also successfully provides a promising strategy to induce a nonradical pathway for PDS activation, which is of great significance for the subsequent method design, and thus paving the path for exploiting advanced oxidation systems in practical application for organic contaminant removal toward polluted site remediation.

Fe-Ti bimetals catalyst derived from biowaste for highly efficient persulfate activation: Performance and mechanisms

Sludge based catalysts (SBCs) has been considered as a promising and viable approach to sludge reclamation. Herein, we fabricated bimetallic Fe-Ti doped SBCs via a facile synthesis with sludge containing polyacrylamide (PAM) as N-precursor. The adsorption capacity and degradation efficiency of as-synthesized SBCs were assessed using tetracycline (TC) as a target pollutant, in which PAM in sludge played a dual role by promoting porosity, active sites, and structural defects beneficial for persulfate (PS) activation. Fe-Ti doping induced the activation of PS by a fast redox cycle of Fe3+/Fe2+ associated with the coexistence of Ti4+/Ti3+, which enabled an efficient electron transfer between the catalyst and PS. The synergistic effect of PAM-derived N doping and Fe-Ti bimetals resulted in prevention of iron leaching and enhanced catalyst stability over a wide pH range. The surface SO4•− was the primary oxidant in the TC degradation process based on free-radical quenching experiments, and degradation pathways of TC were proposed given the intermediate evidence from UPLC-HRMS analysis. This study promotes the reclamation of PAM-containing sludge providing an eco-friendly and efficient process to activate PS for wastewater treatments.

Acid-washed zero-valent aluminum as a highly efficient persulfate activator for degradation of phenacetin.

Phenacetin (PNT) is one of the most frequently detected nonsteroidal anti-inflammatory drugs in the water ecosystems, which poses a potential risk to environmental aquatic organisms. Acid-washed zero-valent aluminum (ZVAl) as a highly efficient activator for persulfate (PS) process was investigated to degrade PNT from the aqueous solution. The results indicated that acid-washed pretreatment for ZVAl could efficiently increase the degradation efficiency of PNT in the PS treatment. The degradation efficiency of PNT (50 μM) was up to 90% in 4 hours with the addition of 0.2 g/L acid-washed ZVAl and 8 mM PS at pH 6.8 and 25 °C. The PNT degradation followed pseudo-first order kinetics in the present system. High activator dosage, PS concentration, and reaction temperature could enhance the PNT degradation. The presence of inorganic anions (i.e., NO3-, HCO3-) and humic acid (HA) showed inhibitory effects on the PNT degradation. The reuse results illustrated the acid-washed ZVAl material would have continuous and efficient activation performance for PS to degrade thePNT. Radical scavenger experiments and electron paramagnetic resonance indicated that both SO4•- and •OH were major reactive species during the PNT degradation. The possible degradation pathways of PNT mainly included the break of C-N and C-O bonds and further oxidation.

Zinc-Based Metal-Organic Framework with MLCT Properties as an Efficient Electrochemiluminescence Probe for Trace Detection of Trenbolone.

In this work, we utilized polycyclic aromatic hydrocarbon (PAH) derivatives as ligands to develop a zinc-based metal-organic framework (Zn-MOF) as an effective detection probe to construct an electrochemiluminescence (ECL) sensor for trenbolone detection. As traditional ECL emitters, PAHs and their derivatives have limited luminescence efficiency because of the aggregation-induced quenching (ACQ) effect. Therefore, Zn-PTC was designed by the coordination of 3,4,9,10-perylenetetracarboxylic (PTC) in the MOF to eliminate the ACQ effect. Meanwhile, Zn-PTC formed based on an aromatic ligand possessed the metal-to-ligand charge-transfer (MLCT) effect, which could transfer the energy of Zn2+ to the aromatic ligand for strong luminescence. The ECL efficiency of Zn-PTC was calculated to be approximately 2.2 times that of the ligand (K4PTC). Second, the Ag@Fe core-shell bimetallic nanocrystal was prepared for efficient activation of persulfate (S2O82-), thereby generating more sulfate radicals (SO4•-) to further promote ECL emission. According to ECL characterizations, UV-vis and fluorescence spectra, and density functional theory calculations, the luminescence and signal amplification mechanisms were investigated. In addition, NKFRGKYKC (NKF) was introduced as an affinity ligand to directionally immobilize the target antibodies, thus releasing specific sites in their Fab fragment to enhance binding activity. Based on the above strategies, the constructed biosensor exhibited high sensitivity, realizing trace detection of TBE with a wide detection range (10 fg/mL-100 ng/mL) and a low detection limit (3.28 fg/mL). This study provided an important reference for sensitive monitoring of steroid pollutants in the environment.

Efficient activation of persulfate by Nickel-supported cherry core biochar composite for removal of bisphenol A

In this study, low-cost and easily obtained biochar was chosen to prepare nickel-modified biochar materials (Ni/BC) through a one-step activation pyrolysis method. Characterization with X-ray diffraction, X-ray photoelectron spectroscopy and high-resolution transmission electron microscopy proved the existence of Ni0 and NiO nanocrystals in Ni/BC catalyst. The optimal Ni0.5/BC exhibited excellent peroxymonosulfate (PMS) and peroxydisulfate (PDS) activation efficiency toward bisphenol A (BPA) degradation. The Ni0.5/BC (0.03 g) reacted with 1.0 g L−1 PMS or PDS could completely remove 20 mg L−1 BPA in 10 min with the first-order kinetic constants (k1) of 0.322 min−1 (PMS) and 0.336 min−1 (PDS). More importantly, the composite has better structural and functional attributes for the BPA degradation with universal applicability at wide pH and temperature range, proving as a better degradation mediator with high adaptation for numerous organic pollutants. Catalytic activity decreased slightly even after 4 cycles. Based on the quenching experiment and electron paramagnetic resonance, it was found that SO4•−, •OH and 1O2 were the dominant active species in BPA degradation process. Therefore, this work not only supplies a promising catalyst for the removal of organic contaminants, but also is beneficial for the further development of alternative catalysts for sulfate radical based advanced oxidation processes.

Efficient activation of persulfate by C@Fe3O4 in visible-light for tetracycline degradation

A C@Fe3O4 material, Fe3O4 coated with carbon, was prepared by a simple one-pot hydrothermal method. The C@Fe3O4 material was investigated with persulfate (PS) and light to degrade tetracycline (TC) as a function of pH, aeration conditions and quenching. Experimental results suggest that TC was effectively degraded in the C@Fe3O4/PS/Vis system. In addition, due to the availability of different main active species in this catalytic system, TC degradation was possible under both strong acid and strong alkali pH conditions. The presence of dissolved oxygen can also generate oxygen-active species, such as superoxide radicals (O2•-) and singlet oxygen (1O2), to decompose TC organic matter in solution. Simply put, C@Fe3O4/PS/Vis catalytic system removed pollutants by the formation of O2•-, 1O2, hydroxyl radicals (•OH) and sulfate radicals (SO4•-) species for degrading TC. In addition, the stability of the C@Fe3O4 material was found to be outstanding.

Biochar modification with hematite and goethite as efficient persulfate activation catalysts for sulfamethoxazole degradation: one-step biochar synthesis method and solution matrix effect on sulfamethoxazole removal kinetics.

Using biochar to adsorb and degrade organic contaminants has attracted increasing attention due to its relatively low cost and high efficiency. In this work, two magnetic biochars were synthesized by pyrolyzing a mixture of naturally occurring hematite or goethite mineral and pine needle biomass. The biochar composite was characterized with X-ray diffraction, scanning electron microscopy, and surface area analyzer. The result demonstrated iron minerals have been deposited on carbon surfaces and been reduced to magnetite or wustite minerals. In comparison to the unmodified biochar, the iron mineral-modified biochar had better sorption ability, likely because the iron mineral particles on the carbon surface served as additional sorption sites for sulfamethoxazole (SMX) removal. After modification, the biochar also showed higher persulfate activation capacity with radical generation: at 4h, neutral pH, 67.5 and 77.9% of persulfate is activated with hematite and goethite modified biochar, where only 11.7% persulfate is activated by unmodified biochar. With persulfate, goethite-modified biochar showed better SMX removal capacity than hematite-modified biochar with about 79% of SMX removed in 4h. Solution chemistry such as pH and co-exist humic acid can affect SMX removal by affecting iron minerals. Because the magnetized biochar can be easily isolated and removed with external magnets, it can be used in various contaminant removal applications.

N and S co-doping of TiO2@C derived from in situ oxidation of Ti3C2 MXene for efficient persulfate activation and sulfamethoxazole degradation under visible light

Visible-light-driven photocatalysts with synergistic persulfate (PS) activation and photocatalysis possess enormous pollution-control potential. Herein, nitrogen and sulphur co-doped TiO2@C hybrid (N/S-TiO2@C) featuring the complementary visible-light photocatalysis and synergetic PS activation was synthesized by in situ oxidation of Ti3C2 MXene and thereafter co-doping with N and S. Both anatase and rutile phases of TiO2 were attained in N/S-TiO2@C. The decrease of TiO2 bandgap (about 1.81 eV) and the defect of carbon layer caused by the N and S co-doping in both TiO2 crystal and carbon layer enabled the synergistic enhancement of PS activation and photocatalysis. Complete degradation and 93.4% mineralization of sulfamethoxazole (SMZ, 10 mg/L) were achieved by dosing PS (2 mM) and N/S-TiO2@C (0.4 g/L) under visible light within 30 min. The degradation rate by N/S-TiO2@C through PS activation under visible light was 27.9-, 11.1-, and 2.30-fold higher than that by PS, N-TiO2@C, and S-TiO2@C alone, respectively. Reactive species SO4−,1O2, OH, and O2−, especially the former two, were determined dominating the SMZ degradation, and the degradation pathways were illustrated through intermediates identification. Moreover, N/S-TiO2@C kept excellent performance in activating PS to degrade SMZ in real water samples. These results indicate that N/S-TiO2@C is a stable and promising PS activator under visible light and has a good application potential in organic wastewater treatment.

New insights into N, S doped carbon from conjugated polymers for efficient persulfate activation: Role of hydrogel beads in enhancement of stability

One-pot design of heteroatoms doped carbocatalysts for remediation of wastewater via persulfate (PS) activation is strongly desirable. Herein, a novel nitrogen and sulfur doped and co-doped carbons with controllable N, S doping is rationally prepared using pyrolysis strategy from polypyrrole-polythiophene polymers and copolymer. The N, S co-doped carbon (NS-C) show highly catalytic oxidation compared by N doped carbon (N-C) and S doped carbon (S-C) due to the synergistic effect between N and S dopants. It’s supposed that N and S doping can effectively create highly and main active sites to the electron transfer via PS activation, which could generate reactive oxygen species (ROS). Structure-dependent activity during activation of PS was confirmed by quenching experiments and electron paramagnetic resonance (EPR) analysis, prove that the non-radical species (1O2) is the main ROS generated. To improve the carbocatalyst separation and stability, the hydrogel beads-based alginate NS-C@Alginate were easily prepared. The catalytic efficiency rate by using the real water matrix shows that the NS-C/PS synergic system non-radical-led pathway exhibited a high ability to remediation of surrounding inorganic or organic compounds. This approach provides an innovative method for production and proves an efficient and environmentally benign carbocatalyst to PS activation for practical applications.

Highly efficient activation of persulfate by encapsulated nano-Fe0 biochar for acetaminophen degradation: Rich electron environment and dominant effect of superoxide radical

In this study, an encapsulated nanoscale zero-valent iron biochar (BC-Fe0) derived from waste lignocellulose rice straw (RS) was synthesized. BC-Fe0 has excellent properties, including long-term stability, a large specific surface area, many micropore structures, active defects active and oxygen-containing groups. The material was first used to activate persulfate (PDS), showing a highly efficient catalysis for acetaminophen (ACT) degradation. The removal efficiency of ACT within 20 min reached 100%, and the degradation rate constant (kobs) reached 0.37475 min−1 at the ACT concentration of 10 mg/L, BC-Fe0 of 0.5 g/L, temperature of 298 K. EPR demonstrated that ·OH, SO4−·, ·O2− and 1O2 occurred during the reaction process, and ·O2−, 1O2 and electron transfer played major roles in PDS/BC-Fe0 system. Fe0 nanoparticles promoted the activation of PDS to generate ·O2−, which induced a series of other reactive oxygen species (ROS) to attack ACT. C = O might also contribute to the production of 1O2. In addition, graphitic carbon, C–O, defects and micropores on BC-Fe0 together created a rich electron environment, which is conducive to the redox reaction between ACT and ROS. Satisfyingly, BC-Fe0 not only had a high catalytic activation capacity, but also exhibited a desirable durability and recyclability. The development of BC-Fe0 catalysts and the study of PDS activation for organic pollutant degradation are significant to biomass conversion and advanced oxidation processes in environmental remediation.

Graphene/Fe@N-doped carbon hybrid derived from spent MOF adsorbent as efficient persulfate activator for degradation of tetracycline hydrochloride

• Spent MOF adsorbent was successfully recycled and reused by one-step pyrolysis. • Fe x NC displayed higher catalytic activity than the pristine MOF-derived. • Wide pH applicability and kinetics of 0.042 min −1 for TCH degradation was achieved. • The iron species in Fe x NC for PS activation was limited by the core–shell structure. • Non-radical oxidation was dominant for TCH degradation in Fe x NC/PS system. Metal-organic frameworks (MOF) have shown significant potential as efficient adsorbing materials for treating antibiotic wastewater. However, little attention has been paid to the proper disposal of dangerous antibiotic-polluted MOF adsorbents. In this study, tetracycline hydrochloride (TCH)-saturated MIL-100(Fe) as spent MOF adsorbent was converted into graphene/Fe@N-doped carbon hybrid (Fe x NC) by one-step pyrolysis to activate persulfate (PS) for TCH degradation. The existence of the TCH adsorbate on the MIL-100(Fe) precursor significantly affected the physicochemical properties of the obtained Fe@carbon product, which can be responsible for the higher catalytic activity of Fe x NC than the pristine MIL-100(Fe)-derived. Fe x NC was shown to have wide pH applicability (2–10) and the kinetics of TCH (96.2 mg/L) degradation was 0.042 min −1 with 0.3 g/L Fe x NC, 1 mM PS and pH 6. During TCH degradation, the carbon matrix and doped nitrogen in Fe x NC were more important than the iron species. Because of the inaccessibility of iron species encapsulated by carbon, 1 O 2 and O 2 •— were the dominant reactive oxygen species in Fe x NC/PS, with less contribution from SO 4 •— and •OH. Importantly, interfacial electron transfer was revealed to dominate the TCH oxidation process. This study provides not only a practical way for the disposal and reuse of waste MOF materials but also new ideas for the design of MOF-derived heteroatoms doping metal@carbon hybrids.

Vacancy-rich structure inducing efficient persulfate activation for tetracycline degradation over Ni-Fe layered double hydroxide nanosheets

Layered double hydroxide (LDH)-based catalysts have been corroborated to be effective for persulfate (PS) activation towards wastewater remediation. However, the effect of vacancies especially the role of cation vacancies in LDH has not been well illustrated. In this study, NiFe-LDH with Ni(II) vacancies (NiFe-LDH-VNi) or Fe(III) vacancies (NiFe-LDH-VFe) were fabricated via defect-engineering to tune catalytic activity on PS activation for tetracycline (TC) degradation. Characterizations of X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy confirmed cation vacancies were successfully implanted in NiFe-LDH catalyst. Experiments demonstrated that cation vacancies enhance the catalytic performance while NiFe-LDH-VNi exhibited better activation performance since vacancies could facilitate the electron transfer, thereby forming more reactive oxygen species. Meanwhile, theoretical calculations disclosed that the NiFe-LDH with Ni(II) or Fe(III) vacancies possessed larger surface energy, lower Fermi energy and more positive Mulliken atomic charges than bare NiFe-LDH. About 80% of 30 mg·L−1 TC could be mineralized through the catalysis of NiFe-LDH-VNi/PS system in 90 min. Furthermore, quenching experiments confirmed that the SO4− and OH generated by interface reaction accounted for the TC degradation. 1O2 and O2− species were also identified in the presence of oxygen vacancies through nitrogen gas cleaning experiments. Ultimately, a possible mechanism of TC degradation was proposed in NiFe-LDH/PS system with Ni(II) or Fe(III) vacancies. This study provides a possible guideline to discover the appropriate cation vacancies that contribute to the activation process and also provides a strategy to rationally design high-activity catalysts based on defect engineering.

Photoassisted highly efficient activation of persulfate over a single-atom Cu catalyst for tetracycline degradation: Process and mechanism

A single-atomic-site Cu catalyst (SAS-Cu) supported on carbon nitride (CN) material was synthesized by a pyrolyzing coordinated polymer (PCP) strategy. The introduction of a single-atomic Cu site improved the charge transfer and separation efficiency. The reaction rate constant of SAS-Cu1.0 is 4.5 times higher than that of CN. Under the condition of only 0.1 mM sodium persulfate (PS) and 0.1 g/L catalyst, the removal rate of tetracycline (TC) reached 82.5% after 30 min of LED illumination, which greatly improved the utilization of oxidant. Mechanistic analysis shows that there are free radical (•O2-, SO4•-, •OH) and nonradical pathways (1O2 and direct electron transfer) in the system, and they have synergistic effect. Density functional theory (DFT) calculations show that SAS-Cu1.0 can optimize the adsorption and activation of PS. This work illustrates the application value of SAC combined with activated persulfate and the low energy consumption of the LED light in the field of environment, which provides a new strategy for reducing the salinity and treatment cost of treated water.