Oxygen Vacancy-Mediated CuCoFe/Tartrate-LDH Catalyst Directly Activates Oxygen to Produce Superoxide Radicals: Transformation of Active Species and Implication for Nitrobenzene Degradation

Ferrihydrite/B, N co-doped biochar composites enhancing tetracycline degradation: The crucial role of boron incorporation in Fe(III) reduction and oxygen activation

Harnessing the redox potential of biochar to activate airborne O2 for contaminant removal is challenging. In this study, ferrihydrite (Fh) modified the boron (B), nitrogen (N) co-doped biochars (BCs) composites (Fh/B(n)NC) were developed for enhancing the degradation of a model pollutant, tetracycline (TC), merely by airborne O2. Fh/B(3)NC showed excellent O2 activation activity for efficient TC degradation with a apparent TC degradation rate of 5.54, 6.88, and 22.15 times that of B(3)NC, Fh, and raw BCs, respectively, where 1O2 and H2O2 were identified as the dominant ROS for TC degradation. The B incorporation into the carbon lattice of Fh/B(3)NC promoted the generation of electron donors, sp2 C and the reductive B species, hence boosting Fe(III) reduction and 1O2 generation. O2 adsorption was enhanced due to the positively charged adsorption sites (C-B+and NC+). And 1O2 was generated via Fe(II) catalyzed low-efficient successive one-electron transfer (O2 → O2·- → 1O2, H2O2), as well as biochar catalyzed high-efficient two-electron transfer (O2 → H2O2 → 1O2) that does not involve .O2- as the intermediate. Moreover, Fh/B, N co-doped biochar showed a wide pH range, remarkable anti-interference capabilities, and effective detoxification. These findings shed new light on the development of environmentally benign BCs materials capable of degradading organic pollutants.

Comparative mechanisms of PDS-activated antibiotic remediation in groundwater via controlled-release materials with different mesoporous catalysts

In situ chemical oxidation (ISCO) using controlled-release oxidants materials (CRMs) is an effective method for the long-term removal of organic pollutants from groundwater. However, the complex hydrodynamic characteristics of groundwater make it extremely challenging to elucidate the mechanisms of pollutant degradation through CRMs. This study aims to construct persulfate-based CRMs using mesoporous MnO2 (Mn-CRMs) and TiO2 (Ti-CRMs) as catalysts to degrade tetracycline (TC) under static and dynamic groundwater. The types and contributions of active species, stoichiometric efficiency of the reactions, TC degradation pathways of the CRMs were compared in the static and dynamic groundwater. The results revealed the active species in the CRMs-based TC degradation depending on the structures of the powder catalysts. In the static and dynamic groundwater, the contribution rate of ·OH and SO4·- in the Mn-CRMs-based TC degradation was nearly 100 %, indicating a complete radical-based degradation pathway. TiO2 with abundant oxygen vacancies produced abundant 1O2 during the PDS activation process. Ti-CRMs showed a contribution rate of 1O2 to the TC degradation of up to 32.05 %, which indicated the co-action of ·OH and 1O2 for degrading TC. The RSE values of the CRMs-based TC degradation were similar to those of TC degradation using powder catalysts. Since the groundwater flow and PDS release, lower PDS concentrations were maintained around the CRMs in the dynamic groundwater, resulting in a higher RSE value. The results in this study provide insights into the removal mechanisms of pollutants in different groundwater and expand the application of ISCO to groundwater remediation.

Roles of oxygen vacancies in layered double hydroxides-based catalysts for wastewater remediation: fundamentals and prospects

Wastewater globally is a significant concern for environmental health and for the sustainable management of water resources. Catalysed based advanced oxidation processes (AOP), as a relatively low operation cost and high removal efficiency of pollutants method, has a promising potential to treat the wastewater. Among the numerous catalysts, Layered Double Hydroxides (LDHs) stands out for lamellar structure, high charge density, and tuneable properties. Meanwhile, oxygen vacancies engineering could modulate the electronic properties of materials and create active centres to regulate the poor charge transfer capability of LDHs. In this regard, this review is focused on how to create and confirm the oxygen vacancies, as well as the applications of the wastewater treatment from different AOPs. It starts with the synthesized of oxygen vacancies via chemical reduction method, plasma etching method, hydrothermal treatment method, ion doping strategy. Followed by the description of characterization methods, including EPR, XPS, XAS, Raman. Finally, the role of oxygen vacancies in LDHs for contaminant removal across various systems, including photocatalysis, electrocatalysis, Fenton reactions, and sulfate radical-based processes, was thoroughly examined and analyzed.

MOF-derived FeCe@Carbon catalysts for the efficient tetracycline degradation by activated persulfate: Preparation and mechanistic study

Metal-organic frameworks (MOFs) derived materials are extensively utilized in wastewater treatment owing to their remarkable catalytic efficacy and durability. This study exploited iron-cerium-based bimetallic metal-organic framework (FeCe-MOF) as a sacrificial template, which was subsequently calcined at 700 °C to produce an iron-cerium-based bimetallic carbon nanospheres (FeCe@C). The FeCe@C has active sites of bimetallic Fe and Ce derivatives, demonstrating exceptional activation efficiency for persulfate, resulting in approximately 98.2 % elimination of tetracycline hydrochloride (TCH) within 120 min. This removal rate markedly exceeds that of the individual iron-based carbon nanospheres (Fe@C) (53.6 %) and cerium-based carbon nanospheres (Ce@C) (78.3 %). Characterization results, including X-ray photoelectron spectroscopy (XPS) and electron paramagnetic resonance (EPR), demonstrate that the Fe and Ce composite induces coordination unsaturation at the metal centers, leading to the formation of oxygen vacancies and an increase in active reaction sites. Additionally, radical quenching, EPR and electrochemical experiments demonstrate that radical (OH, O2- and SO4-) and non-radical routes (O2-, 1O2 and electron transfer) synergistically catalyze the degradation of TCH. The observed increase in catalytic activity can be primarily ascribed to the synergistic interactions among multivalent metal ions and the rapid regeneration of metals in lower oxidation states. A potential degradation process for antimicrobial organic pollutants is given, providing new research areas and techniques for the effective degradation of related toxins in the future.

LDHzyme-assisted high-performance on-site tracking of levodopa pharmacokinetics for Parkinson's disease management

Parkinson's disease (PD) is a progressive neurodegenerative disorder marked by the loss of dopaminergic neurons and the consequent decline in motor and cognitive functions. The primary therapeutic agent levodopa necessitates precise dosing due to its narrow therapeutic window and complex pharmacokinetics. This study presents the development of a novel CuCoFe-LDHzyme-based sweat sensor for real-time monitoring of levodopa concentration in PD patients. Employing differential pulse voltammetry (DPV) technique, the sensor demonstrates high sensitivity and selectivity, achieving a detection limit of 28.1 nM. The sensor's design allows for non-invasive, continuous monitoring, significantly enhancing patient convenience compared to traditional blood sampling methods. Through pH correction, precise quantification of levodopa in sweat is accomplished, and a strong correlation (Pearson coefficient = 0.833) with blood levodopa levels is established. The pharmacokinetic profile of levodopa is reconstructed in real-time, offering a promising tool for optimizing PD treatment regimens. This study highlights the potential of CuCoFe-LDHzyme sensors to advance personalized treatment strategies, aiming to improve the quality of life for PD patients by providing clinicians with real-time data for medication adjustments.

Oxygen vacancies-enriched spent lithium-ion battery cathode materials loaded catalytic membrane for effective peracetic acid activation and organic pollutants degradation

Advanced oxidation processes combined with membrane filtration technique offer a promising approach for pollution mitigation and catalyst recovery. Herein, a waste ternary lithium-ion battery cathode material of LiNixCoyMnzO2 (LNCM) loaded polytetrafluoroethylene (PTFE) membrane was synthesized for peracetic acid (PAA) activation (LNCM-PTFE/PAA) and 2,4,6-trichlorophenol (TCP) degradation. Such a novel membrane, with a catalyst loading of 10 mg (0.796 mg/cm2) of LNCM achieved 96.4 % removal of TCP (2 mg/L) within 20 min in neutral pH. The redox cycles of surface metals (such as Co3+/Co2+, Ni3+/Ni2+, and Mn4+/Mn3+/Mn2+) in spent LNCM efficiently enhance charge transfer and mediated PAA activation. And intrinsic oxygen vacancies in LNCM facilitated PAA adsorption and its cleavage. The resulting carbon-centered radicals (R-C•, CH3C(O)OO•) and 1O2 are identified as the primary reactive species that collaboratively participate in TCP degradation. Quantitative structure-activity relationship analysis demonstrated a substantial reduction in product toxicity. The successful practical application of the LNCM-PTFE/PAA membrane was exemplified by treating chlorophenol industrial wastewater. This study presents a new LNCM-PTFE/PAA catalytic membrane for high-efficiency water treatment and a novel perspective for green utilization of waste LNCM.

Tannic Acid Selective Modulation Defects to Enhance the Photocatalytic CO2 Reduction Activity of Layered Double Hydroxides

Recently, layered double hydroxides (LDH) have shown great potential in photoreduction of CO2 owing to its flexible structural adjustability. In this study, the mild acidic property of tannic acid (TA) is exploited to etch the bimetal LDH to create abundant vacancies to gain the coordination unsaturated active centers. Based on the different chelating abilities of TA to various metal ions, the active metals are remained by selective chelation while the inert metals are removed during the etching process of bimetal LDH. Furthermore, selective chelating with metal ions not only increases the percentage of highly active metals but also compensates for the structural damage caused by the etch, which achieves a scalpel-like selective construction of vacancies. The NiAl-LDH etched and functionalized by TA for 3 h exhibits superior photo-reduction of CO2 performance without co-catalysts and photo-sensitizers, which is 14 times that of the pristine NiAl-LDH. The fact that many bimetal LDHs can be functionalized by TA and exhibit significantly improved photocatalytic efficiency is confirmed, suggesting this strategy is generalized to functionalize double- or multi-metal LDH. The method provided in this work opens the door for polyphenol-functionalized LDHs to enhance their ability for light-driven chemical transformations.

Periodate activation and pH regulation using ball-milled metal-oxide-mineral-biochar composite for removal of antibiotics from contaminated water

The inclusion of mineral salts in carbon activators are beneficial for advanced oxidation processes (AOPs). Herein, we present the application of ball-milled biochar with phosphate salt for periodate (IO4-) activation and degradation of antibiotics in contaminated water. Physical characterization results showed that the catalyst is infused with Mg3(PO4)2 and ball-milling increased the specific surface area to 216 m2 g-1 from 46 m2 g-1 while reducing the particle size to less than 1.0 μ. The optimized system successfully eliminated >99% of diclofenac while maintaining the pH of the reaction medium to circumneutral levels. Scavenger and ESR experiments revealed the degradation is triggered by O2•-, 1O2 and •OH species within the system. Electrochemical studies confirmed electron transfer during diclofenac degradation. The reported system demonstrated high degradation efficiency under both neutral and acidic pH conditions. Based on the by-product analysis, the degradation pathway of diclofenac was elucidated. Further, the toxicity assessment for the identified intermediates showed minimum toxicity of the degraded products. This mineral-biochar composite exhibited promising performance in eliminating other antibiotic substances. Therefore, the present finding highlights the importance of raw materials selection for producing mineral-biochar composite that provide new insights into IO4- activation for antibiotic removal by maintaining the natural pH.

Applying molecular oxygen for organic pollutant degradation: Strategies, mechanisms, and perspectives

Molecular oxygen (O2) is an environmentally friendly, cost-effective, and non-toxic oxidant. Activation of O2 generates various highly oxidative reactive oxygen species (ROS), which efficiently degrade pollutants with minimal environmental impact. Despite extensive research on the application of O2 activation in environmental remediation, a comprehensive review addressing this topic is currently lacking. This review provides an informative overview of recent advancements in O2 activation, focusing on three primary strategies: photocatalytic activation, chemical activation, and electrochemical activation of O2. We elucidate the respective mechanisms of these activation methods and discuss their advantages and disadvantages. Additionally, we thoroughly analyze the influence of oxygen supply, reactive temperature, and pH on the O2 activation process. From electron transfer and energy transfer perspectives, we explore the pathways for ROS generation during O2 activation. Finally, we address the challenges faced by researchers in this field and discuss future prospects for utilizing O2 activation in pollution control applications. This detailed analysis enhances our understanding and provides valuable insights for the practical implementation of organic pollutant degradation.

Biodegradation of organic micropollutants by anoxic denitrification: Roles of extracellular polymeric substance adsorption, enzyme catalysis, and reactive oxygen species oxidation

The control of organic micropollutants (OMPs) in water environments have received significant attention. Denitrification was reported to exhibit good efficiency to remove OMPs, and the mechanisms involved in are too intricate to be well illustrated. In this study, we selected nitrobenzene [NB] and bisphenol A [BPA] as model pollutants and aimed to unravel the mechanisms of Paracoccus Denitrificans in the removal of OMPs, with a specific emphasis on aerobic behavior during denitrification processes. We demonstrated the formation of extracellular superoxide radicals, i.e., extracellular •O2-, using a chemiluminescence probe and found that extracellular polymeric substance adsorption, extracellular •O2-, and microbial assimilation contributed approximately 40 %, 10 %, and 50 % to OMPs removal, respectively. Transcriptome analysis further revealed the high expression and enrichment of several pathways, such as drug metabolism-other enzymes, of which a typical aerobic enzyme of polyphenol oxidase [PPO] participates in the degradation of NB and BPA. Importantly, all the immediate products showed a significant decrease in toxicity during the aerobic activity-related OMPs degradation process based on the proposed degradation pathways. This study demonstrates the formation of extracellular •O2- and the mechanisms of extracellular •O2-- and PPO-mediated OMPs biodegradation, and offers new insights into OMPs control in widely-used denitrification treatment processes.

Unveiling the fate of metal leaching in bimetal-catalyzed Fenton-like systems: pivotal role of aqueous matrices and machine learning prediction

Metal-based catalytic materials exhibit exceptional properties in degrading emerging pollutants within Fenton-like systems. However, the potential risk of metal leaching has become pressing environmental concern. This study addressed scientific issues pertaining to the leaching behavior and control strategies for metal-based catalytic materials. Innovative cobalt-aluminum hydrotalcite (CoAl-LDH) triggered peroxymonosulfate (PMS) activation system was constructed and achieved near-complete removal of Ciprofloxacin (CIP) across diverse water quality environments. Notably, it was found that the tunable ion exchange and Al3+ stabilization of CoAl-LDH occurred due to the particularity of neutral water quality, resulting in significantly lower Co2+ leaching levels (0.321 mg/L) compared to acidic conditions (5.103 mg/L). In light of this, machine learning technology was then employed for the first time to simulate the dynamic trend of Co2+ leaching and elucidated the critical regulatory roles and mechanisms of Al3+, aqueous matrix, and reaction rate. Furthermore, degradation systems based on different water quality and metal leaching levels regulated the generation levels of SO4.- and O2∙-, and the unique advantages of free radical attack paths were clarified through CIP degradation products and ecotoxicity analysis. These findings introduced novel insights and approaches for engineering application and pollution control in metal-based Fenton-like water treatment.

Interfacial Super-Assembly of Vacancy Engineered Ultrathin-Nanosheets Toward Nanochannels for Smart Ion Transport and Salinity Gradient Power Conversion

Ion-selective nanochannel membranes assembled from two-dimensional (2D) nanosheets hold immense promise for power conversion using salinity gradient. However, they face challenges stemming from insufficient surface charge density, which impairs both permselectivity and durability. Herein, we present a novel vacancy-engineered, oxygen-deficient NiCo layered double hydroxide (NiCoLDH)/cellulose nanofibers-wrapped carbon nanotubes (VOLDH/CNF-CNT) composite membrane. This membrane, featuring abundant angstrom-scale, cation-selective nanochannels, is designed and fabricated through a synergistic combination of vacancy engineering and interfacial super-assembly. The composite membrane shows interlayer free-spacing of ~3.62 Å, which validates the membrane size exclusion selectivity. This strategy, validated by DFT calculations and experimental data, improves hydrophilicity and surface charge density, leading to the strong interaction with K+ ions to benefit the low ion transport resistance and exceptional charge selectivity. When employed in an artificial river water|seawater salinity gradient power generator, it delivers a high-power density of 5.35 W/m2 with long-term durability (20,000s), which is almost 400 % higher than that of the pristine NiCoLDH membrane. Furthermore, it displays both pH- and temperature-sensitive ion transport behavior, offering additional opportunities for optimization. This work establishes a basis for high-performance salinity gradient power conversion and underscores the potential of vacancy engineering and super-assembly in customizing 2D nanomaterials for diverse advanced nanofluidic energy devices.

Boosting Efficient Alkaline Hydrogen Evolution Reaction of CoFe-Layered Double Hydroxides Nanosheets via Co-Coordination Mechanism of W-Doping and Oxygen Defect Engineering

While surface defects and heteroatom doping exhibit promising potential in augmenting the electrocatalytic hydrogen evolution reaction (HER), their performance remains unable to rival that of the costly Pt-based catalysts. Yet, the concurrent modification of catalysts by integrating both approaches stands as a promising strategy to effectively address the aforementioned limitation. In this work, tungsten dopants are introduced into self-supported CoFe-layered double hydroxides (LDH) on nickel foam using a hydrothermal method, and oxygen vacancies (Ov) are further introduced through calcination. The analysis results demonstrated that tungsten doping reduces the Ov formation energy of CoFeW-LDH. The Ov acted as oxophilic sites, facilitating water adsorption and dissociation, and reducing the barrier for cleaving HO─H bonds from 0.64 to 0.14 eV. Additionally, Ov regulated the electronic structure of CoFeW-LDH to endow optimized hydrogen binding ability on tungsten atoms, thereby accelerating alkaline Volmer and Heyrovsky reaction kinetics. Specifically, the abundance of Ov induced a transition of tungsten from a six-coordinated to highly active four-coordinated structure, which becomes the active site for HER. Consequently, an ultra-low overpotential of 41 mV at 10 mA cm-2, and a low Tafel slope of 35 mV dec-1 are achieved. These findings offer crucial insights for the design of efficient HER electrocatalysts.

Efficient and Durable Oxidation Removal of Formaldehyde over Layered Double Hydroxide Catalysts at Room Temperature

Room temperature catalytic oxidation (RTCO) using non-noble metals has emerged as a highly promising technique for removal of formaldehyde (HCHO) under ambient conditions; however, non-noble catalysts still face the challenges related to poor water resistance and low stability under harsh conditions. In this study, we synthesized a series of layered double hydroxides (LDHs) incorporating various dual metals (MgAl, ZnAl, NiAl, NiFe, and NiTi) for formaldehyde oxidation at ambient temperature. Among the synthesized catalysts, the NiTi-LDH catalyst showed an HCHO removal efficiency and CO2 yield close to 100.0%, and exceptional water resistance and chemical stability on running 1300 min. The abundant hydroxyl groups in LDHs directly bonded with HCHO, leading to the production of CO2 and H2O, thus inhibiting the formation of CO, even in the absence of O2 and H2O. The coexistence of O2 effectively reduced the reaction barrier for H2O molecule dissociation, facilitating the formation of hydroxyl groups and their subsequent backfill on the catalyst surface. The mechanisms underlying the involvement and regeneration of hydroxyl groups in room temperature oxidation of formaldehyde were elucidated with the combined in situ DRIFTS, HCHO-TPD-MS, and DFT calculations. This work not only demonstrates the potential of LDH catalysts in environmental applications but also advances the understanding of the fundamental processes involved in room temperature oxidation of formaldehyde.

Facile preparation of high-efficiency peroxidase mimics: modulation of the catalytic microenvironment of LDH nanozymes through defect engineering induced by amino acid intercalation

Nanozymes have gained much attention as a replacement for natural enzymes duo to their unique advantages. Two-dimensional layered double hydroxide (LDH) nanomaterials with high physicochemical plasticity are emerging as the main forces for the construction of nanozymes. Unfortunately, high-performance LDH nanozymes are still scarce. Recently, defects in nanomaterials have been verified to play a significant role in modulating the catalytic microenvironment, thereby improving catalytic performances of nanozymes. Therefore, the marriage between defect engineering and LDH nanozymes is expected to spark new possibilities. In this work, twenty kinds of natural amino acids were separately inserted into the interlayer of CoFe-LDH to obtain defect-rich CoFe-LDH nanozymes. The peroxidase (POD)-like activity and catalytic mechanism of the as-prepared LDH nanozymes were systematically studied. The results showed that the intercalation of amino acids can effectively enhance the POD-like activity of LDH nanozymes owing to the increasing oxygen/metal vacancies. And l-cysteine intercalated LDH exhibited the highest catalytic activity ascribed to its thiol group. As a proof of concept, LDH nanozymes with superb POD-like activity were used in biosensing and antibacterial applications. This work suggests that modulating the catalytic microenvironment through defect engineering is an effective way to obtain high-efficiency POD mimics.

Paint sludge derived activated carbon encapsulating with cobalt nanoparticles for non-radical activation of peroxymonosulfate

Industrial solid waste management and recycling are important to environmental sustainability. In this study, cobalt (Co) nanoparticles encapsulated in paint sludge-derived activated carbon (AC) were fabricated. The Co-AC possessed high conductivity, magnetic properties and abundant metal oxide impurities (TiAlSiOx), which was applied as multifunctional catalyst for peroxymonosulfate (PMS) activation. Compared to pure AC, the Co-AC exhibited significant enhanced performance for degradation of tetracycline hydrochloride (TCH) via PMS activation. Mechanism studies by in situ Raman spectroscopy, Fourier infrared spectroscopy, electrochemical analysis and electron paramagnetic resonance suggested that surface-bonded PMS (PMS*) and singlet oxygen (1O2) are the dominant reactive species for TCH oxidation. The non-radical species can efficiently oxidize electron-rich pollutants with high efficiency, which minimized the consumption of PMS and the catalyst. The removal percentages of TCH reached 97 % within 5 min and ∼ 99 % within 15 min in the Co-AC/PMS system. The Co active sites facilitated PMS adsorption to form the PMS* and the TiAlSiOx impurities provided abundant oxygen vacancy for generation of the 1O2. In addition, the Co-AC/PMS system achieved high efficiency and stability for oxidation of the target pollutants over a long-term continuous operation. This work not only offers a cost-effective approach for recycling industrial waste but also provides new insights into the application of waste-derived catalyst for environmental remediation.

Utilizing the oxygen-atom trapping effect of Co3O4 with oxygen vacancies to promote chlorite activation for water decontamination

Heterogeneous high-valent cobalt-oxo [≡Co(IV)=O] is a widely focused reactive species in oxidant activation; however, the relationship between the catalyst interfacial defects and ≡Co(IV)=O formation remains poorly understood. Herein, photoexcited oxygen vacancies (OVs) were introduced into Co3O4 (OV-Co3O4) by a UV-induced modification method to facilitate chlorite (ClO2-) activation. Density functional theory calculations indicate that OVs result in low-coordinated Co atom, which can directionally anchor chlorite under the oxygen-atom trapping effect. Chlorite first undergoes homolytic O-Cl cleavage and transfers the dissociated O atom to the low-coordinated Co atom to form reactive ≡Co(IV)=O with a higher spin state. The reactive ≡Co(IV)=O rapidly extracts one electron from ClO2- to form chlorine dioxide (ClO2), accompanied by the Co atom returning a lower spin state. As a result of the oxygen-atom trapping effect, the OV-Co3O4/chlorite system achieved a 3.5 times higher efficiency of sulfamethoxazole degradation (~0.1331 min-1) than the pristine Co3O4/chlorite system. Besides, the refiled OVs can be easily restored by re-exposure to UV light, indicating the sustainability of the oxygen atom trap. The OV-Co3O4 was further fabricated on a polyacrylonitrile membrane for back-end water purification, achieving continuous flow degradation of pollutants with low cobalt leakage. This work presents an enhancement strategy for constructing OV as an oxygen-atom trapping site in heterogeneous advanced oxidation processes and provides insight into modulating the formation of ≡Co(IV)=O via defect engineering.

Revealing the generation of reactive oxygen species in hydrochar and pyrochar: Insight into rational regulation of free radicals and catalytic mechanism

The removal of organic pollutants by biochar has been extensively studied. However, the differences in the removal mechanisms of contaminants by biochar obtained from different preparation techniques have not been thoroughly elucidated. In this study, the catalytic performances of hydrochar (HC) and pyrochar (PC) were compared in the dark and light. Owing to more persistent free radicals (PFRs), greater defects and stronger charge transfer ability on the surface, PC could produce a certain concentration of superoxide radicals (•O2-) even in the dark, making its degradation efficiency for benzoic acid (BA) 11% higher than that of HC. On the contrary, when the light was turned on, HC rather than PC can generate a higher amount of hydroxyl radical (•OH), resulting in an 11% higher degradation efficiency of BA compared to PC. The improvement of catalytic performance in HC originated from its oxygen-containing functional groups (OFGs), which was beneficial for its effective production of singlet oxygen (1O2) and ·OH under light exposure. For PC, its photocatalytic activity depended mainly on the formation of 1O2 induced by the triplet of DOM (dissolved organic matter), but the lack of oxidative ·OH in its system leads to a lower degradation efficiency than that of HC. To prove the universal applicability of this rule for biochar materials, HC and PC materials obtained from soybean residue were also prepared for degrading BA. This work is devoted to an in-depth exploration of the catalytic activation mechanism of biochar obtained by different technological methods, and can create conditions for the generation of more dominant reactive oxygen species (ROS) on biochar, thus providing the guidance for environmental remediation.

Insight into cobalt substitution in LaFeO3-based catalyst for enhanced activation of peracetic acid: Reactive species and catalytic mechanism

In this study, a hollow sphere-like Co-modified LaFeO3 perovskite catalyst (LFC73O) was developed for peracetic acid (PAA) activation to degrade sulfamethoxazole (SMX). Results indicated that the constructed heterogeneous system achieved a 99.7% abatement of SMX within 30 min, exhibiting preferable degradation performance. Chemical quenching experiments, probe experiments, and EPR techniques were adopted to elucidate the involved mechanism. It was revealed that the superior synergistic effect of electron transfer and oxygen defects in the LFC73O/PAA system enhanced the oxidation ability of PAA. The Co atoms doped into LaFeO3 as the main active site with the original Fe atoms as an auxiliary site exhibited high activity to mediate PAA activation via the Co(III)/Co(II) cycle, generating carbon-centered radicals (RO·) including CH3C(O)O· and CH3C(O)OO·. The oxygen vacancies induced by cobalt substitution also served as reaction sites, facilitating the dissociation of PAA and production of ROS. Furthermore, the degradation pathways were postulated by DFT calculation and intermediates identification, demonstrating that the electron-rich sites of SMX molecules such as amino group, aromatic ring, and S-N bond, were more susceptible to oxidation by reactive species. This study offers a novel perspective on developing catalysts with the coexistence of multiple active units for PAA activation in environmental remediation.

Multi-pathway on peroxymonosulfate activation by single cobalt atoms incorporated on CuO with enriched oxygen vacancies for high-efficient oxidation of tetracycline

The development of single atom catalysts (SACs) with superior catalytic performance is a long-term goal for peroxymonosulfate (PMS) activation in advanced oxidation processes (AOPs). A novel SACs that single Co atoms anchored on CuO with enriched oxygen vacancies (Ov) is synthesized successfully by choosing a metal oxide as the carrier creatively. 100% of tetracycline (TC) can be removed by Co-CuO (Ov)/PMS system within 3 min. The corresponding reaction rate constant is 3.1068 min-1, which is much higher than that of CuO (Ov), ZIF-CoN4-C, Co-CuO (without Ov) and CoNP-CuO (Ov), respectively. Co(II) is the primary source of radical pathway (·OH and SO4·-), and its regeneration is promoted by Cu(Ⅰ). The enriched Ov is the major contribution to the nonradical pathway, which promotes the singlet oxygen (1O2) generation together with accelerates the electron transfer from TC to catalyst-PMS*. Besides, the Co-CuO (Ov) exhibits an excellent stability and anti-interference capability. This study highlights a novel strategy to promote PMS activation by incorporating the single metal atoms on a metal oxide carrier with defects to accelerate the redox of dominate metal and stabilize the metal atoms simultaneously, which may inform the design for the next generation of SACs in AOPs.

Role of Impurities in Kaolinite Intercalation and Subsequent Formation of Nanoscrolls

Kaolinite (Kaol)-methanol (MeOH) compounds (Kaol-Me) are widely used as the starting materials for further intercalation. The conventional approach to prepare Kaol-Me compounds is to wash dimethyl sulfoxide (DMSO)-intercalated Kaol (Kaol-DMSO) for 16 days, and MeOH must be refreshed every day. Herein, we report a new and much more efficient method to prepare Kaol-Me from Kaol-DMSO by the promotion of AlCl3 under mild conditions, and the corresponding mechanism is investigated. The X-ray diffraction (XRD), Fourier transform infrared spectroscopy, and X-ray fluorescence characterization results reveal that the electric double layer resulting from the impurities absorbed on the kaolinite surface prevents weakly polar molecules from entering the kaolinite interlayers, which is probably the key reason that MeOH must be refreshed daily in the preparation of Kaol-Me compounds. After being treated with HCl to remove the impurities, Kaol-Me-HCl was successfully intercalated by cetyltrimethyl ammonium bromide and subsequently predominantly curled into nanoscrolls.

Regulating the concentration of dissolved oxygen to achieve the directional transformation of reactive oxygen species: A controllable oxidation process for ciprofloxacin degradation by calcined CuCoFe-LDH

Different reactive oxygen species (ROS) tend to attack specific sites on pollutants, leading to the formation of intermediates with different toxic effects. Therefore, regulating the directional transformation of ROS is a new effective approach for safe degradation of refractory organic compounds in wastewater. However, the regulation mechanism and transformation path of ROS remain unclear. In this work, the dissolved oxygen (DO) content was controlled by aeration to generate different ROS through the activation of O₂ on the calcined CuCoFe-LDH (CuCoFe-300). ROS quantitative experiments and electron paramagnetic resonance proved that O₂ was mainly activated to superoxide radical (•O₂^-) and singlet oxygen (¹O₂) under low DO concentration (0.231 mmol/L) (O₂ → •O₂^- → ¹O₂). With the increasing of DO concentration (0.606 mmol/L), O₂ was inclined to convert into hydroxyl radicals (•OH) (O₂ → •O₂^- → H₂O₂ → •OH). The density functional theory and function model of active sites utilization and DO concentration built a solid proof for ROS conversion mechanism that increasing the DO concentration promotes the increase of active sites utilization on the CuCoFe-300 system. That is, the •O₂^- was more prone to convert to •OH, not ¹O₂ in thermodynamics under high active sites utilization condition. Hence, the ROS generation was controlled by regulating DO concentration, and the nontoxic degradation pathway of ciprofloxacin was well-designed. This work is dedicated to the in-depth exploration of the mechanism between DO concentration and ROS conversion, which provides an extremely flexible, low energy consumption, and environmentally friendly wastewater treatment method in a new perspective.

Combined photothermal and sonodynamic therapy using a 2D black phosphorus nanosheets loaded coating for efficient bacterial inhibition and bone-implant integration

Surgical site infection (SSI) remains a major threat for implant failure in orthopedics. Herein, we report a dual-functional coating on Ti implants (named Ti/PDA/BP) with the integration of two-dimensional (2D) photo-sono sensitive black phosphorus nanosheets (BPNSs) and polydopamine (PDA) for efficient bacterial inhibition and bone-implant integration. For the first time, we employ BPNSs as generators of reactive radicals (ROS) under ultrasound (US) stimuli for implant associated infection. Additionally, the application of PDA improves the stability of BPNSs, the biocompatibility and photothermal performance of this hybrid coating. The as-prepared Ti/PDA/BP coating exhibits superior biocompatibility, bioactivity, photothermal and sonodynamic conversion abilities. Owing to the synergistic effect of hyperthermia and ·OH, Ti/PDA/BP damages the membrane and antioxidant system of Staphylococcus aureus, reaching a high antibacterial activity of 96.6% in vitro and 97.3% in vivo with rapid 10 min NIR irradiation and 20 min US treatment. In addition, we firstly unveil the significant effect of Ti/PDA/BP-based sonodynamic therapy (SDT) on bacterial membrane and oxidative stress at the transcriptome level. Moreover, the Ti/PDA/BP coating remarkably promotes osteogenesis in vitro and bone-implant osseointegration in vivo. Overall, development of Ti/PDA/BP bioactive coating provides a new strategy for combating the implant associated infection.

Enhanced H2O2 utilization efficiency in Fenton-like system for degradation of emerging contaminants: Oxygen vacancy-mediated activation of O2

Hydrogen peroxide (H₂O₂) is the most commonly used oxidant in advanced oxidation processes for emerging organic contaminant degradation. However, the activation of H₂O₂ to generate reactive oxygen species is always accompanied by O₂ generation resulting in H₂O₂ waste. Here, we prepare a Ti doped Mn₃O₄/Fe₃O₄ ternary catalyst (Ti-Mn₃O₄/Fe₃O₄) to create abundant oxygen vacancies (OVs), which yields electron delocalization impacts on enhancing the electrical conductivity, accelerating the activation of O₂ to produce H₂O₂. In Ti-Mn₃O₄/Fe₃O₄/H₂O₂ system, OVs-mediated O₂/O₂^•-/H₂O₂ redox cycles trigger the activation of locally generated O₂, boost the regeneration of O₂^•- and on site produce H₂O₂ for replenishment. This leads to a 100% removal of tiamulin in 30 min at an unprecedented H₂O₂ utilization efficiency of 96.0%, which is 24 folds higher than that with Fe₃O₄/H₂O₂. Importantly, further integration of Ti-Mn₃O₄/Fe₃O₄ catalysts into membrane filtration achieved high rejections of tiamulin (> 83.9%) from real surface water during a continuous 12-h operation, demonstrating broad pH adaptability, excellent catalytic stability and leaching resistance. This work demonstrates a feasible strategy for developing OVs-rich catalysts for improving H₂O₂ utilization efficiency via activation of locally generated oxygen during the Haber-Weiss reaction.

Comprehension of the Synergistic Effect between m&t-BiVO4/TiO2-NTAs Nano-Heterostructures and Oxygen Vacancy for Elevated Charge Transfer and Enhanced Photoelectrochemical Performances

Through the utilization of a facile procedure combined with anodization and hydrothermal synthesis, highly ordered alignment TiO2 nanotube arrays (TiO2-NTAs) were decorated with BiVO4 with distinctive crystallization phases of monoclinic scheelite (m-BiVO4) and tetragonal zircon (t-BiVO4), favorably constructing different molar ratios and concentrations of oxygen vacancies (Vo) for m&t-BiVO4/TiO2-NTAs heterostructured nanohybrids. Simultaneously, the m&t-BiVO4/TiO2-NTAs nanocomposites significantly promoted photoelectrochemical (PEC) activity, tested under UV-visible light irradiation, through photocurrent density testing and electrochemical impedance spectra, which were derived from the positive synergistic effect between nanohetero-interfaces and Vo defects induced energetic charge transfer (CT). In addition, a proposed self-consistent interfacial CT mechanism and a convincing quantitative dynamic process (i.e., rate constant of CT) for m&t-BiVO4/TiO2-NTAs nanoheterojunctions are supported by time-resolved photoluminescence and nanosecond time-resolved transient photoluminescence spectra, respectively. Based on the scheme, the m&t-BiVO4/TiO2-NTAs-10 nanohybrids exhibited a photodegradation rate of 97% toward degradation of methyl orange irradiated by UV-visible light, 1.14- and 1.04-fold that of m&t-BiVO4/TiO2-NTAs-5 and m&t-BiVO4/TiO2-NTAs-20, respectively. Furthermore, the m&t-BiVO4/TiO2-NTAs-10 nanohybrids showed excellent PEC biosensing performance with a detection limit of 2.6 μM and a sensitivity of 960 mA cm-2 M-1 for the detection of glutathione. Additionally, the gas-sensing performance of m&t-BiVO4/TiO2-NTAs-10 is distinctly superior to that of m&t-BiVO4/TiO2-NTAs-5 and m&t-BiVO4/TiO2-NTAs-20 in terms of sensitivity and response speed.