Cycling Of Cu Research Articles

Ornidazole degradation based on peroxymonosulfate activation induced by oxygen vacancies (OV)-enriched Cu-Co-TiO2: Coexistence of free-radical and non-radical pathways

Employing transition-metal catalysts in peroxymonosulfate (PMS) activation reactions to facilitate combined free-radical and non-radical interactions is regarded as a proficient approach for decomposing organic contaminants. However, the creation of active catalysts faces significant challenges due to low activation efficiency, inadequate action sites, and instability of current activation materials. Here, we successfully prepared bimetallic Cu and Co co-doped TiO2 (Cu-Co-TiO2) catalyst using the sol-gel technique. Excellent ornidazole (ONZ) removal efficiency (0.628 min−1) was demonstrated by the Cu-Co-TiO2/PMS system, which was applicable across a broad pH range (4−10) and unaffected by different water matrices. Moreover, the coexistence of free-radical (SO4•-, •OH and O2•−) and non-radical (1O2) routes in the Cu-Co-TiO2/PMS system, where SO4•- and 1O2 are the predominant active substances, was confirmed by quenching experiments and electron paramagnetic resonance (EPR) study. The synergistic impact of Cu/Co bimetal may hasten the redox cycles of Cu+/Cu2+ and Co2+/Co3+, causing plenty of oxygen vacancies (OV) and improving PMS activation efficiency. The quantitative structure-activity relationship (QSAR) examination of the intermediates showed a decrease in toxicity, and the potential pathways of ONZ degradation were illustrated using Liquid Chromatography Mass Spectrometry (LC-MS) technology. This work not only demonstrated the effectiveness and stability of Cu-Co-TiO2 as a PMS activator, but it also offered fresh information on how to remove organic pollutants from wastewater by using PMS activation via the radical and non-radical oxidation pathway.

Electronic structure regulation of Cu-based Ruddlesden-Popper perovskites by cobalt doping for enhanced degradation of oilfield fracturing wastewater in electrocatalytic peroxymonosulfate system

Purification of oilfield fracturing wastewater is the most challenging type of oilfield wastewater treatment. In this work, a heterogeneous electrocatalytic peroxymonosulfate (PMS) system was established to treat oilfield wastewater using Co-doping induced Cu-based Ruddlesden-Popper (RP) perovskites as catalysts. Characterization results illustrated that the obtained catalysts were generated the heterojunction of LaCoO3/La2CuO4 and the Co would transfer electrons to Cu, resulting in a higher chemical oxygen demand (COD) degradation efficiency (> 80 %) of oilfield fracturing wastewater under the neutral environment. Singlet oxygen (1O2) played the main function for COD removal with analysis results of reactive oxygen species (ROS). Experimental results and theoretical calculations indicated that the reduction effect of carbon felt (GF) cathode and the redox cycle of Cu(I)/Cu(II) and Co(II)/Co(III) accelerated the activation of PMS. Moreover, the lattice oxygen participated in the generation of ROS. Significantly, the LaCoO3/La2CuO4 heterojunction displayed a higher total density of states (TDOS) value near the Fermi level, implying their favorable electron transfer for PMS activation. This study opens new avenue for resolving the challenge of oilfield fracturing wastewater pollution.

Visible light-improved periodate activation of natural chalcopyrite particles towards effective pollutants degradation

The aim of this paper is to build an efficient and low-cost advanced oxidation system to realize the antibiotic wastewater purification which has a realistic significance. In this study, a system of visible light-assisted activation of natural chalcopyrite to activate periodate was adopted to remove tetracycline (TC). The results demonstrated that the removal efficiency (100% within 60 min) of TC in the CuFeS2/PI/Light system was significantly improved compared to the CuFeS2/PI system or PI process alone, and the degradation rates of TC in the CuFeS2/PI/Light system were 5.9 times higher than that of the CuFeS2/PI system, which is attributed to the synergistic effect of light and PI activation. The system also effectively degraded sodium butyl xanthate (SBX), chlortetracycline hydrochloride (CTC) and Rhodamine B (RhB), while the efficiency of the degradation process was further enhanced in natural water quality. The active substance quenching experiment revealed that [Formula: see text]OH, 1O2, O2[Formula: see text], IO4[Formula: see text] and IO3[Formula: see text] were the main substances to achieve effective TC removal. In addition, the cycling of Cu[Formula: see text]/Cu[Formula: see text] and Fe[Formula: see text]/Fe[Formula: see text] present in chalcopyrite improved the activation of PI. Further, visible light is conducive to the valence cycling of Cu and Fe, as well as the production of more oxidizing free radicals, thus achieving the synergy of photocatalysis and PI activation. This study provides a low-cost and efficient advanced oxidation pathway for the removal of antibiotic wastewater.

In-situ complexation of Cu(II) with polyethyleneimine (PEI) triggers the enhanced formation of halonitromethanes, dichloroacetonitrile, and dichloroacetamide during UV/chlorine disinfection: Cu(I) contribution and Cl· sustainable production

The complexation of copper ions (Cu(II)) with coexisting organic ligands (e.g. polyethyleneimine (PEI)) in water may pose a new threat to water quality. This study revealed that the maxima concentrations of HNMs, DCAN, and DCAcAm from Cu(II)-PEI complex during UV/chlorine disinfection were 1.54, 2.00, and 1.25 times higher than those from PEI, and the maxima concentrations of HNMs, DCAN, and DCAcAm from Cu(II)-PEI complex during chlorination disinfection were 1.22, 1.31, and 1.10 times higher than those from PEI. Meanwhile, specific Cu(II) concentration (0.25 ∼ 3.0 mg L−1) and alkaline pH were more favorable for forming HNMs, DCAN, and DCAcAm during UV/chlorine disinfection, which were highly dependent on the involvement of HO· and Cl·. Cu(II)-PEI, an in-situ formed stable complex that permitted an efficient interconversion cycle of Cu(II)/Cu(I) via concurrent metal-to-ligand charge transfer and ligand-to-metal charge transfer. The analysis and comparison of extensive products provided solid evidence for the primary role of Cu(I) and the enhanced production of Cl· in increasing HNMs, DCAN, and DCAcAm productions, rather than only Cu(II) catalysis similar to that during chlorination. The new findings broaden the knowledge of the influence of in-situ formed Cu(II)-organic complexes on forming HNMs, DCAN, and DCAcAm during UV/chlorine disinfection.

Dissolved Cu isotope compositions in hydrothermal plumes over back-arc volcanoes in the Northeast Lau Basin, Southwest Pacific Ocean

Seafloor hydrothermal venting may be an important source of marine Cu and affect the biogeochemical cycling of Cu in the oceans. The distribution of Cu and its isotope compositions (δ65Cu) can provide insight into seafloor hydrothermal processes and their role in the mass balance of global Cu. To date, there are no published Cu isotope data for hydrothermal plumes and very few reports on Cu concentration distributions. This study presents both Cu concentrations and dissolved Cu isotope (δ65Cu) in hydrothermal plumes from back-arc volcanoes in the Northeast Lau Basin. The dissolved Cu (dCu) concentrations range from 2.14 to 5.66 nM most of which are higher than the deep seawater concentrations. However, the concentrations for some plume samples were lower than the deep seawater dCu concentrations due to adsorption onto particles in the plumes. The δ65Cu of hydrothermal plumes vary from 0.25 to 1.05 ‰. As plumes dispersed, the Cu isotopes from high-temperature Mata Fitu and Mata Ua vents shifted towards light values. In contrast, the δ65Cu in plumes from low-temperature East Mata and West Mata vents show increasingly higher values with plume dispersal. Rayleigh distillation models are built based on the adsorption of dCu onto Fe particles and complexation with organic ligands to describe the dCu isotope evolution in hydrothermal plumes. The results suggest that the adsorption and organic complexation may be the likely explanations for the observed dCu isotope compositions in plumes from high- and low-temperature venting, separately, besides the mixing with background seawater. Our measured δ65Cu in three fluid samples (0.08, 0.09 and 0.20 ‰) are lower than that of the characterized sinks (∼0.3 ‰) in the oceans, indicating that hydrothermal fluids might be a source of light Cu isotopes. However, the δ65Cu (0.53 ‰ on average) in plume samples are higher than 0.3 ‰ and these seafloor hydrothermal plumes do not seem to be a source of light Cu isotope of dCu, at least near the venting sites. Our study first reveals the Cu isotope compositions and evolution in hydrothermal plumes and provides new hints about the impact of seafloor hydrothermal venting on the modern oceanic Cu isotope budget.

Peroxymonosulfate activation by superparamagnetic mixed-valent Cu/N-(L-cysteine)-O-(carboxymethyl)chitosan/cobalt ferrate-rice hull hybrid nanocomposite for efficient degradation of naproxen: Synergetic adsorption-catalysis, kinetics, pathway, and relevant mechanism

Naproxen (NPX) as an emerging anthropogenic contaminant was detected in many water sources, which can pose a serious threat to the environment and human health. Peroxymonosulfate (PMS) decomposed by Cu(I) has been considered an effective activation method to produce reactive species. However, this decontamination process is restricted by the slow transformation of Cu(II)/Cu(I) by PMS. Herein, new N-(L-cysteine/triazine)-O-(carboxymethyl)-chitosan/cobalt ferrate-rice hull hybrid biocomposite was constructed to anchor the mixed-valent Cu(I)-Cu (II) (CuI, II-CCCF) for removing pharmaceutical pollutants (i.e., naproxen, ciprofloxacin, tetracycline, levofloxacin, and paracetamol). The structural, morphological, and catalytic properties of the CuI,II-CCCF have been fully identified by a series of physicochemical characterizations. Results demonstrated that the multifunctional, hydrophilic character, and negative ζ-potential of the activator, accelerating the redox cycle of Cu(II)/Cu(I) with hydroxyl amine (HA). The negligible metal leaching, well-balanced thermodynamic-kinetic properties, and efficient adsorption-catalysis synergy are the main reasons for the significantly enhanced catalytic performance of CuI,II-CCCF in the removal of NPX (98.6 % at 7.0 min). The main active species in the catalytic degradation of NPX were identified (●OH > SO4●− > 1O2 > > O2●−) and consequently suggested a degradation path. It can be noted that these types of carbohydrate-based nanocomposite offer numerous advantages, encompassing simple preparation, excellent decontamination capabilities, and long-term stability.

Experimental and theoretical studies on effective synergistic low-temperature removal of NO and typical volatile organic compounds (VOCs) from flue gas based on Cu@VWTi catalyst

The transition metal-modified VWTi structural catalysts hold great promise for simultaneously removing nitrogen oxides (NOx) and volatile organic compounds (VOCs) from industrial flue gases. A series of Cu@VWTi catalysts were prepared to investigate their synergistic low-temperature removal performance towards NO and typical VOCs, including toluene, benzene, chlorobenzene (CB), p-chlorotoluene (p-CT), and dichloromethane (DCM). The copper-enhanced samples prepared via ultrasound-assisted impregnation exhibited irregular globular and varying crystallinity. The catalysts displayed a typical anatase crystal structure with high TiO2 content or high dispersion of V and W species along with a certain adjustment effect on the morphology. Various controlling factors affecting the synergistic removal of NO and VOCs were evaluated. It was observed that the presence of VOCs in flue gas has weak impact on NO removal, except for the waste incineration using the Cu@VWTi catalyst. However, a high initial NO concentration had an adverse effect on VOCs removal. Impressively, the optimized copper-doped catalyst (5 wt% Cu loaded of smelting plant and coal-fired power plant used catalyst) exhibited excellent performance for p-CT, toluene and DCM removal of 95.0%, 99.6% and 100% at 300 °C, respectively. The toluene and p-CT conversion efficiencies were highest over the catalyst used in the smelting plant after Cu loading, surpassing the benzene conversion efficiency. Cu@VWTi demonstrated excellent performance for p-CT, toluene, and DCM removal at 250 °C. Although 5 wt% Cu loading on the catalysts significantly enhanced the stability and anti-jamming of VOCs removal, as well as their tolerance to both SO2 and water vapor. The enhanced mechanism of Cu decoration attributed to the enhanced intensity of acid sites and the stable relative proportion of Oads/Olatt species in the used 5% Cu loaded catalyst due to the redox cycles of Cu and V species. Compared with Brønsted acid, which primarily adsorbs NH4+, Lewis acid mainly adsorbs gas phase acid and forms coordinated NH3 in gas phase. The bonding between toluene and the Cu site was enhanced with an adsorption energy of −130.9 kJ mol−1, as well as the cracking adsorption of the CH2Cl2 on the Ti site with a bonding energy of −436.7 kJ mol−1, both indicating strong chemical adsorption. The first step of dechlorination and demethylation was thermodynamically and kinetically favorable for DCM and toluene decomposition.

Synthesis of thin-film CuMn2O4 for low-temperature CO oxidation

Thin films, 0.5- and 1.0-nm thick, of CuMn2O4 were synthesized on γ-Al2O3 using Atomic Layer Deposition (ALD); and their catalytic activities for CO oxidation were measured and compared to that of bulk CuMn2O4. For bulk CuMn2O4, the surface area decreased dramatically when the sample was calcined at 1073 K; but the area-specific rates for CO oxidation were the same for bulk samples calcined at 473 K and 1073 K. For thin films of CuMn2O4 on γ-Al2O3, both the surface area and spinel structure were maintained following oxidation at 1073 K or reduction at 973 K. Area-specific, CO-oxidation rates on the ALD-prepared catalysts were somewhat lower than those found on bulk CuMn2O4; however, adding an additional ALD cycle of Cu on the CuMn2O4/γ-Al2O3 increased the rates to the same level as that of the bulk CuMn2O4.

Parallel additions of molybdenum and copper particles for boosted peroxydisulfate activation process: Performance, mechanism, and application

Molybdenum (Mo) has been certified as a benign cocatalyst in homogenous Fenton/Fenton-like reactions. To improve zero-valent copper (Cu) induced peroxydisulfate (PDS) reaction, Mo and Cu were parallelly added to enhance the activation of (PDS for metronidazole (MTZ) degradation in this work. The efficient MTZ elimination (96.01 %) was reached after 20 min by Cu/Mo/PDS process in terms of 0.10 g⋅L−1 PDS, 0.08 g⋅L−1 Cu, 0.30 g⋅L−1 Mo, and initial pH 6.5. This ternary system presented a broad pH adaptive capacity (pH 3.5–9.5) and well cycling effect (above 80 % after three cycles). The addition of Mo enhanced Cu(II)/Cu(I) circulation and PDS decomposition, and electrochemical test testified that could be attributed to the electron migration between Cu and Mo. The cycle of Cu(II)/Cu(I) triggered by the conversion of Mo0 and Mo4+ was further proved by X-ray photoelectron spectroscopy result. Singlet oxygen and sulfate radicals were identified as the dominant reactive substances by scavenger test, probe measurement, and electron paramagnetic resonance spectroscopy. By density functional theory calculation and mass spectrometry analyses, two possible decomposed pathways of MTZ were raised. At last, Mo and Cu powders were immobilized together by a simple physical mixing with methacrylate, which also showed the integrated catalytic property and good reusability. This work could advance the development of Cu-catalyzed Fenton-like reaction with inorganic co-catalysis in water purification.

Electrocatalytically enhanced Cu(II)/peroxymonosulfate (PMS) oxidation: Focus on electrically-induced sustained Cu(II)/Cu(I)/Cu(III) cycling and suppression of singlet oxygen (1O2) production

Numerous azo dyes are discharged into industrial wastewater annually, posing significant threats to ecology and human health. In this study, an applied electric field was implemented in a trace copper-activated peroxymonosulfate system (EC/Cu(II)/PMS), achieving high removal efficiency (95.40 %) of Congo red (CR). The electron-donating effect of the cathode greatly enhanced the redox cycling of Cu(II)/Cu(I). Almost complete activation of PMS occurred during the entire reaction with an electrical consumption of merely 0.85 kWh/m3. Using electron paramagnetic resonance (EPR), quenching experiments, and chemical probes, the reactive substance that dominate CR removal, including Cu(III), sulfate radical (SO4•−), hydroxyl radical (HO∙), and singlet oxygen (1O2), were investigated. Cu(III) was identified as the main reactive substance, contributing over 90 %, and was primarily formed through double electron transfer of Cu(I). HO∙ can emerge as a secondary oxide of Cu(III). SO4•− originated mainly from the electroactivation of PMS. It was noted that 1O2 can be physically quenched by water, and thus 1O2 was considered as a side reaction product of PMS. Applying an electric field lowered the overall production of 1O2 and markedly mitigated the inefficient consumption of PMS. Moreover, the degradation pathways proposed for CR, based on mass spectrometry analysis, were in agreement with the predictions made by density functional theory (DFT). The toxicological characteristics of both CR and its intermediates were comprehensively analyzed as well. The study presents a straightforward and efficient strategy for PMS activation with versatile application potential for dye wastewater treatment.

Techno economic analysis of efficient and environmentally friendly methods for hydrogen, power, and heat production using chemical looping combustion integrating plastic waste gasification and thermochemical copper chlorine cycles

Fossil fuels harm the environment and deplete resources. This study presents eco-friendly systems producing power, hydrogen, and heat with minimal pollution. Non-fossil sources like plastic waste solve waste issues and provide valuable energy. Thermochemical water splitting is another clean method for sustainable hydrogen production. The proposed systems employ chemical looping combustion in conjunction with PWG (plastic waste gasification) and thermochemical cycle of Cu–Cl (copper-chlorine), leveraging thermal integration between the CLC (chemical looping combustion) and subsequent processes. Comprehensive process simulations using Aspen Plus have been conducted for systems. The results indicated that the most desirable operational conditions for CLC occur when the molar ratio of oxygen carrier to fuel is 2.6. Under these conditions, there is no methane present in the fuel reactor products. Additionally, the thermal and exergy efficiencies of the CLC-PWG and CLC-CuCl cycles are determined to be 77.08/67.62 % and 66.11/61.1 % respectively, and the most irreversibility component for both systems is associated with the air reactor, with a value of 375 kW. Moreover, the hydrogen production rate in the CLC-PWG cycle is higher than in the CLC-CuCl cycle, with 105.6 kg/h compared to 34.6 kg/h, and the estimated lower minimum sale price for hydrogen is 2.8 USD/kg for CLC-PWG.

Anchoring single-atom Cu on tubular g-C3N4 with defect engineering for enhanced Fenton-like reactions to efficiently degrade carbamazepine: Performance and mechanism

Efficient construction of the active site is crucial for Fenton-like reactions. In this study, tubular carbon nitride with different vacancies (V-TCN) was prepared by simple temperature control. The affinity of the nitrogen atom generated by the carbon vacancy was used to anchor single-atom Cu, which achieved the precise regulation of Cu, reduced agglomeration, and maximally exposed the active site to enhance the activation of H2O2. Density functional theory calculations revealed that the single-atom Cu anchored in the C2 vacancy exhibited the lowest formation energy and the shortest Cu-N bonds. The results showed that Cu/V550-TCN had excellent degradation performance for the hard-to-degrade carbamazepine over a wide pH range (pH = 5–11), and singlet oxygen was the main active species during the degradation process. Additionally, the redox cycles of Cu(I)/Cu(II) and Cu(II)/Cu(III) accelerated the Fenton-like reaction. Five possible degradation pathways for carbamazepine were proposed based on liquid phase mass spectrometry analysis. This study provides a new insight into the role of surface defects in regulating the active site to promote the Fenton-like reaction for the degradation of stubborn pollutants.

Enhanced peroxymonosulfate activation for carbamazepine degradation under strongly alkaline conditions using Cu-doped Mn3O4 catalyst: Characterization, catalytic performance, and mechanism insights

Activation of peroxymonosulfate (PMS) under strongly alkaline conditions for pharmaceutical removal faces the obstacle of activity because SO52− is the predominant form of PMS, which makes it difficult to be activated for radical generation. In this study, we designed Cu-doped Mn3O4 as a heterogeneous catalyst for PMS activation to degrade carbamazepine (CBZ) under alkaline conditions. Remarkably, at low catalyst dosage (30 mg/L) and low PMS dosage (100 mg/L), complete removal of CBZ (100%) was achieved within 5 min in the Cu1.5Mn1.5O4/PMS system at pH 11. The kinetic constant for CBZ degradation was determined to be 1.128 min−1, which is 94.0 times higher than that of the Mn3O4/PMS system. SO4∙-, ∙OH, and 1O2 were generated in the Cu1.5Mn1.5O4/PMS system, with SO4∙- playing a key role in CBZ degradation. The Cu site in Cu1.5Mn1.5O4 was identified as the active site responsible for PMS activation. Cu doping enhanced the –OH group generation and electron transfer of Cu1.5Mn1.5O4, leading to its high catalytic activity towards SO52−. The generation of free radicals was found to be associated with the Cu(I)/Cu(II) cycle, while Mn(III) promoted the redox cycle of Cu(I)/Cu(II). The Cu1.5Mn1.5O4/PMS system exhibited sustained activity and stability even after undergoing five cycles of recycling (>95% CBZ removal). Overall, the present study provides a novel system with superior performance for strongly alkaline pharmaceutical wastewater treatment.

Hydroxylamine enhanced the degradation of diclofenac in Cu(II)/peracetic acid system: Formation and contributions of CH3C(O)O•, CH3C(O)OO•, Cu(III) and •OH

The slow reduction of Cu(II) into Cu(I) through peracetic acid (PAA) heavily limited the widespread application of Cu(II)/PAA system. Herein, hydroxylamine (HA) was proposed to boost the oxidative capacity of Cu(II)/PAA system by facilitating the redox cycle of Cu(I)/Cu(II). HA/Cu(II)/PAA system was quite rapid in the removal of diclofenac within a broad pH range of 4.5–9.5, with a 10-fold increase in the removal rate of diclofenac compared with the Cu(II)/PAA system at an optimal initial pH of 8.5. Results of UV−Vis spectra, electron paramagnetic resonance, and alcohol quenching experiments demonstrated that CH3C(O)O•, CH3C(O)OO•, Cu(III), and •OH were involved in HA/Cu(II)/PAA system, while CH3C(O)OO• was verified as the predominant reactive species of diclofenac elimination. Different from previously reported Cu-catalyzed PAA processes, CH3C(O)OO• mainly generated from the reaction of PAA with Cu(III) rather than CH3C(O)O• and •OH. Four possible elimination pathways for diclofenac were proposed, and the acute toxicity of treated diclofenac solution with HA/Cu(II)/PAA system significantly decreased. Moreover, HA/Cu(II)/PAA system possessed a strong anti-interference ability towards the commonly existent water matrix. This research proposed an effective strategy to boost the oxidative capacity of Cu(II)/PAA system and might promote its potential application, especially in copper-contained wastewater.

Copper Isotope Fractionation in Archean Hydrothermal Systems: Evidence From the Mesoarchean Carlow Castle Cu‐Co‐Au Deposit

AbstractCopper isotope analysis has emerged as a promising tool for understanding genetic processes in Cu ore deposits. However, applications of this analytical technique to Archean Cu deposits have been extremely limited, even though Archean terranes are among the most economically endowed on Earth. As such, this study presents the first Cu isotope analysis of an Archean Cu deposit, the Mesoarchean Carlow Castle hydrothermal Cu‐Co‐Au deposit. Archean primary Cu sulfide ore samples and Cenozoic supergene Cu ore samples were analyzed. Primary ore samples are isotopically light, with δ65Cu values ranging between −0.80 ± 0.02‰ and 0.00 ± 0.007‰, whilst supergene samples are isotopically heavier and range between −0.50 ± 0.01‰ and 0.62 ± 0.005‰. In primary ore samples, a relationship is observed between the Cu isotope signature, ore grade, and alteration assemblage that records the isotopic and physicochemical evolution of the Carlow Castle deposit's hydrothermal ore‐forming system. A mafic igneous source is suggested as a metal source in the Carlow Castle Cu‐Co‐Au deposit. The limited heavy isotopic fractionation of supergene Cu ore samples in this study is interpreted to reflect limited redox cycling of Cu due to in situ oxidative weathering of vein‐hosted Cu sulfides in the overlying Cenozoic supergene system. This differs from previously studied deposits where significant Cu transport and multiple stages of isotopic enrichment are often evident in supergene Cu enrichment layers. The results of this study suggest that Cu isotope analysis could be valuable in understanding genetic processes in hydrothermal Cu deposits, including Archean ore deposits and terranes.

Self-driven degradation of TC-HCl by CuFe2O4/Bi2O3 activated peroxymonosulfate

CuFe2O4/Bi2O3 (hereinafter CFBO) was successfully synthesized by a straightforward sol–gel calcination approach based on citrate complexation in order to efficiently break down tetracycline hydrochloride (TC-HCl) in organic effluent. When there was no light, the degradation rate of 60 min TC-HCl increased from 56.2% to 95.7%, and it had a wide pH application range (3–11). The degrading capacity of activated CFBO by peroxymonosulfate (PMS) was substantially superior than that of the Bi2O3/PMS system. The activation and recoverability of Bi2O3 were significantly enhanced by the magnetic transition metal composite CuFe2O4. The key reaction mechanism of the catalytic process of the CFBO/PMS system was the cycling of Cu(I) and Cu(II), Fe(II) and Fe(III), Bi(III), and Bi(V) species. This efficiently drove the formation of reactive oxygen radicals by CFBO/PMS. In addition, CFBO/PMS possesses strong chemical stability and only exhibits a 6.8% decline in degrading performance after four magnetic recoveries. A potential catalytic mechanism for the self-driven breakdown of TC-HCl by CFBO composite activated PMS is suggested in light of the aforementioned findings.

Selective degradation of antibiotic in a novel Cu7S4/peroxydisulfate system via heterogeneous Cu(III) formation: Performance, mechanism and toxicity evaluation

Efficient degradation of antibiotic by peroxydisulfate (PDS)-based advanced oxidation processes in complex water environment is challenging due to the interference of impurities and the low activation efficiency of PDS caused by its symmetric structure. Herein, a novel Cu7S4/PDS system was developed, which can selectively remove tetracycline hydrochloride (TC) without interference of inorganic ions (e.g., Cl- and HCO3-) and natural organic matter (e.g., humic acid). The results of quenching and probe experiments demonstrated that surface high-valent copper species (Cu(III)), rather than radicals and 1O2, are main active species for TC degradation. Cu(III) can be generated via Cu(I)/O2 and Cu(II)/Cu(I)/PDS systems and the S species on the surface of Cu7S4 promotes the cycle of Cu(II)/Cu(I) and Cu(III)/Cu(II), resulting in continuous generation of Cu(III). In addition, the degradation pathways of TC were proposed based on product analysis and DFT theory calculations. The acute toxicity, developmental toxicity and mutagenicity of treated TC were significantly reduced according to the results of toxicity estimation software tool. This study shows a promising Cu7S4/PDS system for the degradation and detoxication of antibiotic in complex water environment, while also providing a comprehensive understanding of PDS activation by Cu7S4 to generate active Cu(III) species.

Efficient activation of peroxymonosulfate-based Fenton-like system using CuCo2O4/g-C3N4 prepared by Cu+-Co2+ self-doped: g-C3N4 driven reduction-oxidation cycling mechanism of Cu and Co metals

A large specific surface area Cu+-Co2+ self-doped CuCo2O4/g-C3N4 composite was synthesized in situ by a simple hydrothermal combined calcination method. This material is a kind of highly active catalyst suitable for peroxymonosulfate (PMS)-based Fenton-like system, with strong resistance to impurity ions interference, universality to pollutants, and good recyclability. Through XRD (X-ray diffraction), FTIR (Fourier transform infrared spectrometer), XPS (X-ray photoelectron spectrum), TEM (transmission electron microscopy) and catalytic experiments, it can be seen that CuCo2O4 nanoparticles with diameter of 6–9 nm are uniformly distributed on the surface of g-C3N4 to form CuCo2O4/g-C3N4. At room temperature, PMS-based Fenton-like system catalyzed by CuCo2O4/g-C3N4 could degraded tetracycline (TC) to 85.8% in 8 min. The mechanism of CuCo2O4/g-C3N4 activating PMS was discussed in detail. The results show that the surface electron transfer ability of C in g-C3N4 can promote the efficient reduction-oxidation (REDOX) cycle of Cu+/Cu2+ and Co2+/Co3+ on the catalyst surface, thus provide a continuous impetus for the activation of PMS.

ZIF-8-derived nitrogen-doped porous carbon supported CuFeO2 for sulfamethoxazole removal: Performances, degradation pathways and mechanisms

The magnetic CuFeO2 anchored on nitrogen-doped porous carbon (CuFeO2/NC) hybrid catalysts were further synthesized via hydrothermal reaction without the addition of a chemical reductant. The systematic CuFeO2/NC with larger specific surface areas (SSAs) and abundant active sites exhibited strong adsorption ability and great catalytic performance towards activating peroxymonosulfate (PMS) for sulfamethoxazole (SMX) removal. It was noted that 18 mg/L SMX was completely removed after 40 min of pre-adsorption and 30 min of oxidative degradation in CuFeO2/NC and PMS system. The degradation rate constant (k) was calculated by fitting as 0.166 min−1, being about 7.9 times that in the CuFeO2 and PMS system (0.021 min−1). The SO4·-,·OH, and 1O2 as the dominant reactive oxygen species (ROSs) contributed to sulfamethoxazole degradation. The N species, active oxygen and the redox cycles of Cu(Ⅱ)/Cu(Ⅰ) and Fe(Ⅲ)/Fe(Ⅱ) were confirmed to play a vital role in the activation of PMS for the generation of ROSs. Based on the LC-MS analysis, the possible degradation routes of SMX in the PMS activation system by CuFeO2/NC were proposed.

Three-Dimensionally Printed Zero-Valent Copper with Hierarchically Porous Structures as an Efficient Fenton-like Catalyst for Enhanced Degradation of Tetracycline

Three-dimensionally printed materials show great performance and reliable stability in the removal of refractory organic pollutants in Fenton-like reactions. In this work, hierarchically porous zero-valent copper (3DHP-ZVC) was designed and fabricated via 3D printing and applied as a catalyst for the degradation of tetracycline (TC) through heterogeneous Fenton-like processes. It was found that the 3DHP-ZVC/H2O2 system could decompose over 93.2% of TC within 60 min, which is much superior to the homogeneous Cu2+/H2O2 system under similar conditions. The leaching concentration of Cu2+ ions in the 3DHP-ZVC/H2O2 system is 2.14 times lower than that in the Cu powder/H2O2 system in a neutral environment, which could be ascribed to the unique hierarchically porous structure of 3DHP-ZVC. Furthermore, 3DHP-ZVC exhibited compelling stability in 20 consecutive cycles. The effects of co-existing inorganic anions, adaptability, and pH resistance on the degradation of TC were also investigated. A series of experiments and characterizations revealed that Cu0 and superoxide radicals as reducing agents could facilitate the cycling of Cu(II)/Cu(I), thus enhancing the generation of hydroxyl radicals to degrade TC. This study provides new insights into employing promising 3D printing technology to develop high-reactivity, stable, and recycling-friendly components for wastewater treatment.