Organic Contaminants In Water Research Articles

Quantitative Measurement Technique for Anodic Corrosion of BDD Advanced Oxidation Electrodes.

Electrochemical advanced oxidation (EAO) systems are of significant interest due to their ability to treat a wide range of organic contaminants in water. Boron doped diamond (BDD) electrodes have found considerable use in EAO. Despite their popularity, no laboratory scale method exists to quantify anodic corrosion of BDD electrodes under EAO conditions; all are qualitative using techniques such as scanning electron microscopy, electrochemistry, and spectroscopy. In this work, we present a new method which can be used to quantify average corrosion rates as a function of solution composition, current density, and BDD material properties over relatively short time periods. The method uses white light interferometry (WLI), in conjunction with BDD electrodes integrated into a 3D-printed flow cell, to measure three-dimensional changes in the surface structure due to corrosion over a 72 h period. It is equally applicable to both thin film and thicker, freestanding BDD. A further advantage of WLI is that it lends itself to large area measurements; data are collected herein for 1 cm diameter disk electrodes. Using WLI, corrosion rates as low as 1 nm h-1 can be measured. This enables unequivocal demonstration that organics in the EAO solution are not a prerequisite for BDD anodic corrosion. However, they do increase the corrosion rates. In particular, we quantify that addition of 1 M acetic acid to 0.5 M potassium sulfate results in the average corrosion rate increasing ∼60 times. In the same solution, microcrystalline thin film BDD is also found to corrode ∼twice as fast compared to freestanding polished BDD, attributed to the presence of increased sp2 carbon content. This methodology also represents an important step forward in the prediction of BDD electrode lifetimes for a wide range of EAO applications.

Highly Efficient Solar-Light-Driven Photodegradation of Metronidazole by Nickel Hexacyanoferrate Nanocubes Showing Enhanced Catalytic Performances.

Environmental pollution is a complex problem that threatens the health and life of animal and plant ecosystems on the planet. In this respect, the scientific community faces increasingly challenging tasks in designing novel materials with beneficial properties to address this issue. This study describes a simple yet effective synthetic protocol to obtain nickel hexacyanoferrate (Ni-HCF) nanocubes as a suitable photocatalyst, which can enable an efficient photodegradation of hazardous anthropogenic organic contaminants in water, such as antibiotics. Ni-HCF nanocubes are fully characterized and their optical and electrochemical properties are investigated. Preliminary tests are also carried out to photocatalytically remove metronidazole (MDZ), an antibiotic that is difficult to degrade and has become a common contaminant as it is widely used to treat infections caused by anaerobic microorganisms. Under simulated solar light, Ni-HCF displays substantial photocatalytic activity, degrading 94.3% of MDZ in 6h. The remarkable performance of Ni-HCF nanocubes is attributeto a higher ability to separate charge carriers and to a lower resistance toward charge transfer, as confirmed by the electrochemical characterization. These achievements highlight the possibility of combining the performance of earth-abundant catalysts with a renewable energy source for environmental remediation, thus meeting the requirements for sustainable development.

High performance of reduced graphene oxide and g-C3N4 co-doped CuFe2O4 for peroxymonosulfate activation under visible light: Degradation process of sulfamethazine via a singlet oxygen dominated pathway

Peroxymonosulfate (PMS) activation by heterogeneous metal-based catalysts has been extensively applied for the degradation of organic pollutants in water. However, the catalysts suffer from the low oxidant utilization efficiency, pH limitations and severe matrix interference. Here, a reduced graphene oxide and g-C3N4 co-doped copper ferrite (rGO-CNCF) was synthesized and its performance for PMS activation under visible light was evaluated for removal of sulfamethazine. In the condition of rGO-CNCF (0.2 g/L) and PMS (0.1 g/L), the vis/rGO-CNCF/PMS system could degrade 99.9 % of sulfamethazine (SMT, 10 mg/L) within 30 min at pH 7.0, and the system also showed high degrading abilty of SMT over a wide pH range (0–14), along with a good adaptability to common coexisting ions in water solution. The introduction of rGO not only enhanced the stability of rGO-CNCF but also changed the binding sites between PMS and rGO-CNCF which reduced the adsorption energy. Singlet oxygen (1O2) was unveiled to be the major reactive oxygen species (ROS), which was produced by the transformation between negatively charged PMS (HSO5−) and water,along with the self-degradation of PMS. SMT was decomposed through four degradation pathways in this system, and quantitative structure–activity relationship (QSAR) predictions indicated a significant decrease in its toxicity. Results of this study indicated that the material can efficiently activate persulfate for the removal of organic pollutants from water under visible light conditions and it provided a novel catalytic system for removal of organic contaminants in water.

Recent advances in degradation of N,N-diethyl-3-toluamide (DEET)-an emerging environmental contaminant: a review.

N,N-Diethyl-3-toluamide (DEET) is a commonly used insect repellent, which acts as an organic chemical contaminant in water and considered as an emerging contaminant which has been observed worldwide. It gets discharged into the environment through sewage waste. The various methods have been used to degrade DEET, such as UV based, ozonation, photocatalytic degradation, and biodegradation (based on the metabolic activity of fungi and bacteria). However, less research has been done on the degradation of DEET by deploying nanoparticles. Therefore, biodegradation and nanotechnology-based methods can be the potential solution to remediate DEET from the environment. This review is an attempt to analyze the routes of entry of DEET into the atmosphere and its environmental health consequences and to explore physical, chemical, and biological methods of degradation. Furthermore, it focuses on the various methods used for the biodegradation of the DEET, including their environmental consequences. Future research is needed with the application of biological methods for the degradation of DEET. Metabolic pathway for biodegradation was explored for the new potent microbial strains by the application of physical, chemical, and microbial genomics; molecular biology; genetic engineering; and genome sequencing methods.

Occurrence and path pollution of emerging organic contaminants in mineral water of Hranice hypogenic Karst

The Hranice hypogenic karst region includes urban, spa and agricultural areas and industry complexes that affect water quality in the region. Emerging organic contaminants (EOCs), especially pesticides and pharmaceuticals, are released into the complex aquatic system. These substances and their metabolites can affect aquatic and human life, as well as the regional development of the wider area traditionally associated with the spa. In this study, we conducted preliminary screening for pesticides and pharmaceuticals at 33 sampling sites and across different location types, including surface water, drainage water, a shallow well, groundwater and thermal karst water. Sampling occurred between February 2022 and June 2023. The results generally confirm that current land use is causing pollution in the karst system. The monitored substances were present in all water types, and in most cases the concentrations of pesticides were lower than those of their metabolites. Chloridazon desphenyl (DESPH) is the most widespread pesticide in surface, ground and hypogenic waters. Its concentrations in surface waters were 5.7 ng·L−1–2,230 ng·L−1, in groundwaters were 11.3 ng·L−1–1,490 ng·L−1 and in karst hypogenic waters 5.4 ng·L−1–378 ng·L−1. Diclofenac was the most widespread substance from the pharmaceutical group. Its concentrations ranged from 5.6 ng·L−1–549 ng·L−1 in surface waters, 8.4 ng·L−1–112 ng·L−1 in groundwaters and 5.1 ng·L−1–47.4 ng·L−1 in karst hypogenic waters. Directly in the karst hypogenic waters, the following EOCs were repeatedly detected: atrazine and its metabolites, simazin, metazachlor ethane sulfonic acid (ESA), metolachlor ESA, alachlor ESA, chloridazon DESPH, diclofenac, ibuprofen, azithromycin, bisphenol A and diethyltoluamide (DEET). The initial research hypothesis is that hydrothermal karst waters are of sub-recent age and deep circulation and, unlike surface and groundwaters, are not contaminated by recent pollutants. A certain component of these waters is therefore a shallow and shorter circulation.

Mn3O4/Vulcan XC-72R composites: preparation, physicochemical characterization and electrochemical study for purification of organic contaminants

The microwave-assisted technique was applied to the preparation of composites from manganese(II) acetate and Carbon-supported (Vulcan XC-72R). Composites were prepared by chemical deposition of manganese(II) acetate nanoparticles onto Vulcan XC-72R carbon black (catalytic mass) using microwave irradiation. The new composites were physicochemically characterized by Energy-dispersive X-ray spectroscopy (EDX) with scanning electron microscopy (SEM), BET surface area, pore size distribution and X-ray diffraction (XRD). BET analysis of Mn3O4/Vulcan XC-72R composites obtained by alkali method has shown specific surface area of 1135 m2/g. Novel composites were electrochemically studied as catalysts for the remediation of organic contaminants in industrial waters. From novel catalytic mass, double-sided coated electrodes on a Nickel mesh conductor were made by pressing and heating at 250 °C. The prepared electrodes have geometric area of 2.5 cm2. The electrodes were fabricated and studied regarding the amount of catalyst and 35 % Teflonized Vulcan XC-72R. Electrochemical studies were carried out for phenol oxidation in an aqueous solution in model electrolyte: phenol solution 200 mg.L-1 and supporting electrolyte: 18 g.L-1 NaCl and 2.6 mg.L-1 Na2SO4.

Directional growth of Bi2WO6 with highly exposed facets on 2D‐Co3O4 for different properties under two light sources

AbstractA composite of two or more materials usually results in enhanced specific properties. In this paper, a kind of composite material composed of Bi2WO6 with highly exposed {010} facets and 2D‐Co3O4 was prepared by a one‐pot reaction and then applied to decontaminate hydrocortisone in wastewater. The Bi2WO6/Co3O4 composite possessed a rose‐like surface microtopography self‐assembled from Bi2WO6 and Co3O4 nanosheets. The micro‐interface analysis showed that {110} facets of Co3O4 and {010} facets of Bi2WO6 were glued in situ and formed heterojunction. Additionally, the removal ability of hydrocortisone through Bi2WO6/Co3O4 varied under different light sources, which was 85.0 % under ultraviolet light and 97.3 % under visible light within 60 min. It was considered that Bi2WO6/Co3O4 was similar to a traditional heterojunction and the major reactive species was H2O2 under ultraviolet light, while it played a role as a Z‐scheme photocatalyst and the major reactive species was ⋅OH under visible light. Finally, product analysis of hydrocortisone demonstrated that the dexter chain broke whatever under ultraviolet or visible light, but the breakage of parent nucleus appeared only under visible light. This research revealed the enhanced catalytic properties of p‐n heterojunction catalysts and indicated the specifically exposed facets are promising for organic contaminants in water.

Predicting the concentration range of trace organic contaminants in recycled water using supervised classification

Trace Organic Contaminants (TrOCs) have evidence for many health and environmental issues. Frequent monitoring of TrOC concentration is a time-consuming and costly process, which cannot be achieved easily. Identifying surrogate markers for these contaminants is a practical solution to monitor and ensure water quality. However, this topic is seldom explored in previous literature. This study aimed to find surrogate markers to predict concentration class (i.e., three classes: low concentration, medium concentration, high concentration) for a set of widely used pharmaceutical and personal care product TrOCs (e.g., Fluoxetine, Primidone, Saccharin, Sucralose to name a few) in recycled water from Melbourne Eastern Treatment Plant (ETP), Melbourne, Australia. For this purpose, three popular supervised learning classification algorithms namely Naïve Bayes, Random Forest and Support Vector Machines were utilized. Physicochemical parameters colour, Chemical Oxygen Demand (COD) and Total Organic Carbon (TOC) were found to be the top three predictive features for the majority of the investigated TrOCs. UV Transmittance (UVT) and the total amount of suspended solids (TSS) were the next frequent features. The Random Forest model resulted in the highest classification accuracy (≥73 %) for the majority of compounds. This paper presents evidence that with the acquired intelligence of supervised machine learning, the concentration range of hard to measure TrOCs in water can be predicted from a handful of low-cost and easy-to-measure physicochemical parameters.

True Order Determination of Sonochemical Degradation Kinetics of Organic Contaminants in Water Using the Half-lives Method

In the literature, the modeling of the sonolytic decomposition kinetics of organic contaminants in water has been carried out using the pseudo-first and pseudo-second order equations. The results obtained with this method are totally biased because it requires the assumption of the order of the degradation reaction, which is a real limitation, and the sonochemical oxidation mechanism is a very complex phenomenon that cannot be described by such simple models. In this paper, for the first time, the true order of the sonochemical degradation kinetics of organic pollutants in aqueous solutions at various initial substrate concentrations was determined using the half-lives method combined with the general rate law model, i.e., the pseudo-nth order equation. Linear and nonlinear regression techniques were used to determine the order of the sonolytic destruction reaction. The half-life technique for the general rate law model can adequately describe the experimental results of the sono-destruction of the investigated pollutants. For rhodamine B and naphthol blue black, the sono-destruction mechanism for both contaminants does not change as the initial contaminant concentration varies over the range examined, while for 4-isopropylphenol and furosemide, the sono-destruction mechanism changes as the initial substrate concentration varies. A fractional order of the sonolytic destruction reaction was determined for all the pollutants tested. These fractional orders of sono-destruction reactions indicate the complex nature and behavior of the reactions, often involving multiple steps or mechanisms. They also reveal a more complex interaction between pollutant concentration and sonolytic destruction rate. In a word, the method developed in this paper should be used to determine the real order of the sono-oxidation reaction of nonvolatile organic pollutants in aqueous phase.

Lab-scale engineered hydrochar production and techno-economic scaling-up analysis

Despite the extensive use of engineered hydrochar (EHC) for contaminants adsorption in water, little is known about the scaling-up of EHC production which has kept the technology at a low readiness level (TRL). Full-scale EHC production was simulated to help bridge this knowledge gap. A systematic analysis was performed where EHC was produced from rice straw using hydrothermal carbonization (HTC) at 200 °C with iron addition. A techno-economic evaluation model was employed to simulate the production process and to estimate energy requirements, configuration, and cost scenarios for the HTC process. The minimum selling price (MSP) analysis of the engineered hydrochar was found to be almost half compared to the market price for other similar sorbents ($ 76/t vs. $136/t) suggesting that EHC production is feasible for scaling up. Finally, as a trial, the resulting material was tested for its efficacy in the adsorption of an anionic organic contaminant (e.g., Congo Red, C32H22N6Na2O6S2) in water to identify its potential for water treatment. Experimental results showed that EHC adsorbed > 95% CR suggesting significant adsorption capability and feasibility for production scale-up.

Recent Progress in Applications of Atmospheric Pressure Plasma for Water Organic Contaminants’ Degradation

Owing to current global water scarcity, there is an urgent need for advanced water treatment technologies to be invested in wastewater treatment processes. Additionally, there is growing concern that some anthropogenic contaminants have been detected in finished drinking water and wastewater slated for reuse, such as organic chemicals, pharmaceuticals, industrial dyes and even viruses, and their health effects are poorly understood at low concentrations. Atmospheric pressure plasma (APP) is a kind of advanced oxidation technology with high efficiency, low energy consumption, and little environmental impact. In recent decades, as a new method of environmental pollution abatement, APP has proven able to decompose and even completely eliminate stubborn organic contaminants. This paper focuses on the application of different types of plasma in the wastewater purification, such as water containing perfluorinated compounds, pesticides, pharmaceuticals, dyes, phenols, and viruses. Then, the effects of discharge parameters (discharge power, electrode distance, gas flow rate and working gas composition) on degradation efficiency were summarized. Finally, the existing challenges and future prospects of plasma-based wastewater purification are outlined.

Development and testing of a mechanistic model for wetland treatment of neutral and polar organic contaminants in oil sands process-affected water

A mechanistic model of the fate of neutral and polar organic contaminants in a free water surface flow wetland was developed to assess the removal efficiency of polycyclic aromatic hydrocarbons (PAHs) and naphthenic acids (O2-NAs), which are chemicals primarily responsible for oil sands process-affected water (OSPW) toxicity. The model simulates wetland mechanisms of chemical removal based on physicochemical properties, environmental conditions, and wetland design and operation. Good agreement between model estimated and observed concentrations of PAHs and O2-NAs in OSPW in the Kearl Treatment Wetland (Alberta, Canada) was observed over time. Model simulations indicate that the removal of PAHs and O2-NAs from OSPW is highly sensitive to biotransformation rates and that sustained wetland treatment is feasible with robust PAH and NA degrading microbial communities in the wetland. Wetland treatment efficiency is greatest for substances with a log KOW or log D between 3.0 and 5.5 whereas substances with a log KOW or log D >6.0 are not suitable for wetland treatment, even if they can be biodegraded. The log KOW of PAHs and log D for O2-NAs range from 0.7 to 6.7 suggesting most organic contaminants in OSPW are suitable for wetland treatment. Chemical removal via evapotranspiration is not significant pathway of chemical removal from wetlands for PAHs and O2-NAs due to their very low log KAW (less than −1.6). The treatment wetland model presented is the first model to evaluate the fate of both neutral and polar organic contaminants in a flow-through treatment wetland operation, making it a helpful tool to assess the feasibility of these treatment systems for the oil sands industry. The model is particularly useful in evaluating chemical removal efficiency of OSPW contaminants, whether specific water quality objectives can be achieved after treatment, and to assess trade-offs in wetland design and operation to balance treatment performance with design and operational features.

Colloid-bound radicals formed in NOM-enhanced Fe(III)/peroxymonosulfate process accelerate the degradation of trace organic contaminants in water

The omnipresence of natural organic matter (NOM) in water bodies traditionally hinders the degradation of trace organic contaminants (TrOCs) in peroxymonosulfate (PMS)-based advanced oxidation processes (AOPs). This study elucidates the positive role of NOM in enhancing the degradation of TrOCs through the Fe(III)/PMS process. During this process, NOM reduces Fe(III), yielding semiquinone-like radical (NOM•) and concurrently forming NOM-Fe(III) colloids. In addition to the Fe(II)-mediated activation pathway, Fe(III) sites on NOM-Fe(III) colloids effectively transfer electrons from NOM• or some redox-active moieties to PMS, resulting in the generation of long-lived colloid-bound SO4•−, which can readily undergo hydrolysis to produce HO•. The stabilization of SO4•− and HO• by NOM-Fe(III) colloids, combined with their moderate adsorption of TrOCs, results in surface-confined reactions that significantly enhance TrOC removal, despite the presence of concurrent quenching reactions between radicals and NOM. Further, the significant positive correlation between the phenolic contents of eight NOM types and TrOC degradation kinetics suggests phenolic moieties as the primary electron source for PMS activation. By in-situ utilizing NOM in raw water, a PMS-amended iron coagulation process with 0.2 mM Fe(III) and PMS effectively removes 90–100 % of six coexisting TrOCs. This study unveils the previously unrecognized role of colloid-bound radicals in decontamination processes, offering valuable insights into harnessing NOM's influence in advanced oxidation water treatment processes.

Oxidation of organic pollutants over MnO2 in cold water assisted by peroxydisulfate

MnO2 can be used in advanced oxidation processes to activate peroxydisulfate (PS) and generate reactive species such as sulfate radicals (SO4•-), hydroxyl radicals (•OH) and singlet oxygen (1O2) for the abatement of organic water contaminants. Alternatively, one can use MnO2 as particulate oxidant which, in contrast to PS, is active already at low temperatures. This low-temperature activity is particularly attractive for in situ groundwater treatment. The roles of PS and MnO2 as oxidant and catalyst, respectively, may invert: MnO2 functions as primary oxidant and PS works as re-oxidant of reduced Mn-oxides. In this way, the limited oxidation capacity of particulate MnO2 can be overcome. So far, such reaction systems have not been extensively explored.In the present study, the degradation of 4-hydroxybenzoic acid (HBA) by PS + MnO2 was studied under various experimental conditions, by varying reaction temperature (15–45 °C), reagent concentrations, and water matrix. Both PS and MnO2 alone have the ability to effect the oxidation of HBA. In the co-presence of PS and MnO2, a fast removal of HBA from water was achieved even at low temperatures (half-life of HBA about 0.5 h with 2.4 g L-1 MnO2 at 25 °C), owing to a synergic effect between the two components.Quenching experiments indicate that the primary HBA oxidation step is a heterogeneous reaction on the MnO2 surface rather than a homogeneous reaction driven by SO4•- or 1O2, as frequently reported in literature. This is in line with results from the PS driven oxidation of perfluorooctanoic acid which is not significantly enhanced in the presence of MnO2.

Scalable and Facile Formation of Microlenses on Curved Surfaces Enabling a Highly Customized Sustainable Solar‐Water Nexus

Solar‐driven water treatment suffers from low efficiency due to the solar energy loss during the energy conversion, especially in the scale‐up operation. One promising solution is using microlenses (MLs) to enhance the photodegradation of organic contaminants in water. However, most MLs fabrications apply to 2D planar surface only, which restricts their potential applications. In this study, a flexible and scalable technology is presented to fabricate MLs on curved surfaces. Precursor microdroplets form in a dilution process and are converted to MLs by photopolymerization. Optical simulations and experiments are combined to establish the correlation between optical properties of MLs and the performance of ML‐functionalized reactors in photodegradation. It is demonstrated that surface MLs on all‐shaped reactors significantly enhance the photodegradation efficiency of organic contaminants under simulated solar light or natural indoor light, with a maximum improvement of 83 folds. The surface coverage and size distribution of MLs can be adjusted by varying the solution concentration and the dilution rate when generating microdroplets. In addition, fabrication of MLs on a larger scale is achieved over an area up to 250 . MLs on 3‐dimensional curved surfaces fabricated by the technique enable significantly enhanced, highly customized, and sustainable solar‐driven water treatment.

Chitosan/MoS2/GO membrane for catalytic degradation of organic contaminants

Nanocomposite membranes were fabricated by incorporating MoS2 and GO nanomaterials in the chitosan polymer matrix. The higher polymer to nanomaterial ratio resulted in more porous CMG2 membrane than CMG1 membrane. In comparison of the membranes’ performance, the control membrane without nanomaterials only had minimal removal of organic matter, whereas both nanocomposite membranes achieved 95–100 % color removal. CMG2 also achieved 100 % TOC removals of MO solutions whereas the TOC removal by CMG1 was less complete. The MoS2 nanoparticles induced catalytic effect to degradate organic matter. The GO nanosheets also introduced a more substantial negative charge to enhance the separation and rejection of organic contaminants. In addition, a faster treatment kinetics per filtration cycle was also displayed by CMG2 than that of CMG1. This was due to its higher posoristy facilitated better access to the MoS2 nanomaterials, for the dye molecules interacting with catalytic sites. Chitosan/MoS2/GO membrane could be a promising membrane-based solution for efficient catalytic degradation of organic contaminants in water and wastewater treatment.

Efficient removal of oxytetracycline hydrochloride by ZIF-67 coated hollow spherical CuS (CuS-PVP@ZIF-67) under the synergistic effect of adsorption and PMS activation

Selective removal of organic pollutants by PMS-activated heterogeneous catalytic system has become one of the commonly used methods, but the adsorption of the catalyst is often ignored in the degradation process. Metal-organic frameworks (MOFs) are often used in the field of environment because of their high porosity and structural diversity/adjustability. However, there are still difficulties in the aggregation and recycling of nanoparticles. This study effectively synthesized the material CuS-PVP@ZIF-67 by using hollow spherical CuS as the carrier of Co-MOF (ZIF-67) to solve these problems. A high concentration of oxytetracycline hydrochloride (OTC) can be successfully adsorbed by electrostatic attraction and π-π interaction, and small amount of PMS may be quickly activated, and the removal rate of OTC is 94.82 % in 20 min. The catalyst used can be easily recovered by suction filtration and has good reusability. In addition, a potential cooperating mechanism for adsorption-PMS activation has additionally been proposed. The degradation pathway of OTC is determined, and the potential harm of intermediate products is analyzed. This work aims to create a heterogeneous catalytic system with significant adsorption and catalytic ability to remove refractory organic contaminants in water.

Polar electric field-modulated peroxymonosulfate selective activation for removal of organic contaminants via non-radical electron transfer process

Nonradical electron transfer process (ETP) in peroxomonosulfate (PMS) based advanced oxidation processes (AOPs) is regarded promising for selective degradation of organic contaminants in water, however, the subjective modulation strategy and the definitive mechanistic elucidation of ETP are still lacking. Herein, we proposed a heretofore unreported yet efficient ETP indution approach by construction of polar electrical field on biochar via nonmetallic elements co-doping. Physicochemical characterizations and density functional theory (DFT) calculations verified the electronegativity difference among boron, nitrogen, and sulfur elements bestowed robust local electric fields on biochar surface (BC-BNS), which effectively enhanced the adsorption complexation and charge transfer between biochar and PMS. Compared to the other single-doped or co-doped biochar, BC-BNS exhibited superior catalytic performance of PMS activation for degradation of atrazine (ATZ) (kobs=0.036 min−1), as well as various kinds of electron-rich organics. The remarkable catalytic degradation capacity was further verified in various aqueous matrices and background factors, representing the excellent selectivity. Analysis of contribution from reactive oxygen species and electrochemical testing together substantiated the role of polar electric fields in facilitating the modulation from singlet oxygen (1O2) to ETP as a prevailing mechanism. DFT calculations and apparent interactions revealed the dissociation of S-O bond was thermodynamically favored within this potent localized electric field, which further induced the cleavage of OO bond and ultimately promoted the dual electron transfer between ATZ and PMS. The superiority of BC-BNS/PMS system was further validated with the low ecotoxicity caused by enhanced dechlorination, the low energy consumption, and the long-term effectiveness. The novel modulation principle and atomic-level mechanism exploration gave suggestions for advancing ETP-dominated AOP to remove recalcitrant contaminants during water treatment and restoration.

Construction of surface plasmonic Bi nanoparticles and α-Bi2O3 co-modified TiO2 nanotube arrays for enhanced photocatalytic degradation of ciprofloxacin: Performance, DFT calculation and mechanism

The heterogeneous photocatalysis was considered as a sustainable and environmentally friendly technology to rapidly eliminate organic contaminants in water, but its practical application was severely limited by difficult recyclability, low visible-light utilization and high carriers recombination of traditional photocatalysts. Herein, the surface plasmonic Bi nanoparticles and α-Bi2O3 co-modified TiO2 nanotube arrays (Bi/Bi2O3/TNAs) were optimally prepared in situ on titanium foils. The interface interaction among TNAs, α-Bi2O3 and Bi nanoparticles demonstrated the successful construction of tight ternary heterojunction. Bi/Bi2O3/TNAs effectively solved the recovery of traditional photocatalysts, and exhibited more excellent photocatalytic activity (90.3%) to ciprofloxacin (CIP) than TNAs (25.3 %). The enhancing photocatalytic activity was associated with the improved visible-light utilization and suppressed carriers recombination. The coexistence of inorganic anions and natural organic matters declined CIP removal owing to competing active sites or quenching radicals. The density functional theory calculations further demonstrated that the staggered energy levels caused the generation of an internal electric field at the heterojunction interface, which promoted charges transfer. Two main degradation pathways of CIP were proposed, and Bi/Bi2O3/TNAs photocatalytic system could realize the gradually detoxification of CIP.

Dual-functional single-atomic Mo/Fe clusters–decorated C3N5 via three electron-pathway in oxygen reduction reaction for tandemly removing contaminants from water

Inspired by the development of single-atom catalysts (SACs), the fabrication of multimetallic SACs can be a promising technical approach for the in situ electro-Fenton (EF) process. Herein, dual-functional atomically dispersed Mo-Fe sites embedded in carbon nitride (C3N5) (i.e., MoFe/C3N5) were synthesized via a facile SiO2 template method. The atomically isolated bimetallic configuration in MoFe/C3N5 was identified by combining the microscopic and spectroscopic techniques. The MoFe/C3N5 catalyst on the cathode exhibited a remarkable catalytic activity toward the three electron-dominated oxygen reduction reaction in sodium sulfate, leading to a highly effective EF reaction with a low overpotential for the removal of organic contaminants from wastewater. The new catalyst showed a superior performance over its conventional counterparts, owing to the dual functions of the dual-metal active sites. Density functional theory (DFT) analysis revealed that the dual-functional 50-MoFe/C3N5 catalyst enabled a synergistic action of the Mo-Fe dual single atomic centers, which can alter the adsorption/dissociation behavior and decrease the overall reaction barriers for effective organic oxidation during the EF process. This study not only sheds light on the controlled synthesis of atomically isolated catalyst materials but also provides deeper understanding of the structure-performance relationship of the nanocatalysts with dual active sites for the catalytic EF process. Additionally, the findings will promote the advanced catalysis for the treatment of emerging organic contaminants in water and wastewater.