In situ single iron atom doping on Bi2WO6 monolayers triggers efficient photo-fenton reaction

Developing an efficient photocatalytic system for hydrogen peroxide (H2O2) activation in Fenton-like processes holds significant promise for advancing water purification technologies. However, challenges such as high carrier recombination rates, limited active sites, and suboptimal H2O2 activation efficiency impede optimal performance. Here we show that single-iron-atom dispersed Bi2WO6 monolayers (SIAD-BWOM), designed through a facile hydrothermal approach, can offer abundant active sites for H2O2 activation. The SIAD-BWOM catalyst demonstrates superior photo-Fenton degradation capabilities, particularly for the persistent pesticide dinotefuran (DNF), showcasing its potential in addressing recalcitrant organic pollutants. We reveal that the incorporation of iron atoms in place of tungsten within the electron-rich [WO4]2- layers significantly facilitates electron transfer processes and boosts the Fe(II)/Fe(III) cycle efficiency. Complementary experimental investigations and theoretical analyses further elucidate how the atomically dispersed iron induces lattice strain in the Bi2WO6 monolayer, thereby modulating the d-band center of iron to improve H2O2 adsorption and activation. Our research provides a practical framework for developing advanced photo-Fenton catalysts, which can be used to treat emerging and refractory organic pollutants more effectively.

Triggering Dual Two-electron Pathway for H2 O2 Generation by Multiple [Bi-O]n Interlayers in Ultrathin Bi12 O17 Cl2 towards Efficient Piezo-self-Fenton Catalysis

Piezo-self-Fenton system (PESF) has been emerging as a promising water treatment technology but suffering from unsatisfied H2 O2 production efficiency. Herein, we rationally design a Bi12 O17 Cl2 piezo-catalyst with multiple [Bi-O]n interlayers towards highly efficient H2 O2 production. The introduction of [Bi3 O4.25 ] layers initiates dual two-electron pathway for H2 O2 generation by altering the interlayer properties. It is found that the additional [Bi3 O4.25 ] layers not only enhance the polarization electric field but also serve as active sites for triggering dual pathways of two-electron O2 reduction and H2 O oxidation reaction for H2 O2 production. Therefore, the Bi12 O17 Cl2 exhibits an ultrahigh rate of H2 O2 generation (7.76 mM h-1  g-1 ) in pure water. Based on the adequate H2 O2 yield, a PESF was constructed for acetaminophen (ACE) degradation with an apparent rate constant of 0.023 min-1 . This work not only presents a potential strategy of tuning the activity of bismuth based piezo-catalysts but also provides a good example on the construction of highly efficient PESF for environmental remediation by using natural mechanical energy.

Resource allocation of rural institutional elderly care in China's new era: spatial-temporal differences and adaptation development

OBJECTIVES

In the new era of China, to ensure that rural residents can get the corresponding institutional elderly services equally, it is necessary to investigate the current situation of resource allocation of rural institutional elderly care and make corresponding adaptation suggestions.

STUDY DESIGN

This research discusses the characteristics and evolution pattern of rural aging, the resource allocation of rural elderly care institutions, and the adaptation degree of rural institutional elderly care resource and aging.

METHODS

The research methodology consists of the following stages: entropy-based Technique for Order Preference by Similarity to an Ideal Solution (TOPSIS), kernel density estimation, coupling coordination, spatial autocorrelation, and Theil index decomposition.

RESULTS

The degree of aging in rural areas of China is rising, and the whole population has entered a moderate aging society, showing the spatial characteristics of 'high in the east and low in the west'. The resource allocation of rural institutional elderly care in China is at a low level, and the absolute differences among provinces tend to reduce over time, and the overall resource allocation level tends to decline. The provinces that were in the mismatched adaptation relationship in the early stage have improved; however, the number of provinces with mismatched adaptability has continued to increase. The local spatial autocorrelation of resource adaptation verifies that the middle and lower reaches of the Yangtze River as the core form a hot spot, and during the observation period, the spatial agglomeration effect of the core is strengthened. The Theil index decomposition of resource adaptation indicates that the within-group differences between the eastern and western regions is significantly higher than that between the northeastern and central regions.

CONCLUSIONS

First, special attention should be paid to preventing the resource allocation of rural institutional elderly care in the eastern and western regions from falling again. Second, to avoid more and more low-adapted provinces falling into the 'mismatch dilemma' with the deepening of the aging degree. Third, strengthen cooperation among regions and promote the coordinated development of resource allocation of institutional elderly care in various regions. Fourth, the priority of institutional elderly care balanced development should be given to the eastern region and western region, thus weakening the overall difference.

Environmental energy enhanced solar-driven evaporator with spontaneous internal convection for highly efficient water purification

Solar-driven interfacial evaporation for water purification is limited by the structural design of the solar evaporator and, more importantly, by the inability to separate the water from volatile organic compounds (VOCs) present in the water source. Here, we report a three-dimensional (3D) bifunctional evaporator based on N-doped carbon (CoNC/CF), which enables the separation of fresh water from VOCs by activating PMS during the evaporation process with a VOC removal rate of 99%. There is abundant van der Waals interaction between peroxymonosulfate (PMS) and CoNC/CF, and pyrrolic N is confirmed as the active site for binding phenol, thus contributing to the separation of phenol from water. With the advantageous features of sufficient light absorption, adequate water storage capacity, and spontaneous internal convection flow on its top surface, the 3D evaporator achieves a high evaporation rate under one sun (1 kW/m2) at 3.16 kg/m2/h. More notably, through careful structural design, additional energy from the environment and water can be utilized. With such a high evaporation rate and satisfactory purification performance, this work is expected to provide a promising platform for wastewater treatment.

n→π* Electron Transitions and Directional Charge Migration Synergistically Promoting O2 Activation and Holes Utilization on Carbon Nitride for Efficiently Photocatalytic Degradation of Organic Contaminants

Stimulating electron transitions and promoting exciton dissociation are crucial for improving the photocatalytic performance of polymeric carbon nitride (CN) yet still challenging. Herein, a novel CN with C dopant and asymmetric structure (CC-UCN2 ) is ingeniously synthesized. The obtained CC-UCN2 not only reinforces the intrinsic π→π* electron transitions, but also successfully awakens additional n→π* electron transitions. Besides, charge centers dislocation caused by symmetry breaking induces a spontaneous polarized electric field, effectively breaking the constraints of Coulomb electrostatic interaction between electrons and holes and driving their directional migration. Along with the spatial separation of reduction and oxidation sites, CC-UCN2 shows exceptional O2 activation and holes oxidation efficiency, thus exhibits a high degradation rate constant (0.201 min-1 ) and mineralization rate (80.1%) for bisphenol A (BPA)(far outperforming pristine and other modified CNs). This work proposes a novel perspective for developing high-efficiency photocatalysts and comprehending the underlying mechanism of O2 activation and holes oxidation for pollutant degradation.

Multi-heteroatom-doping promotes molecular oxygen activation on polymeric carbon nitride for simultaneous generation of H2O2 and degradation of oxcarbazepine

Simultaneously realizing the efficient generation of H₂O₂ and degradation of pollutants is of great significance for environmental remediation. However, most polymeric semiconductors only show moderate performance in molecular oxygen (O₂) activation due to the sluggish electron-hole pair dissociation and charge transfer dynamics. Herein, we develop a simple thermal shrinkage strategy to construct multi-heteroatom-doped polymeric carbon nitride (K, P, O-CN_x). The resultant K, P, O-CN_x not only improves the separation efficiency of charge carriers, but also improves the adsorption/activation capacity of O₂. K, P, O-CN_x significantly increases the production of H₂O₂ and the degradation activity of oxcarbazepine (OXC) under visible light. K, P, O-CN₅ shows a high H₂O₂ production rate (1858 μM h^-1 g^-1) in water under visible light, far surpassing that of pure PCN. The apparent rate constant for OXC degradation by K, P, O-CN₅ increases to 0.0491 min^-1, which is 8.47 times that of PCN. Density functional theory (DFT) calculations show that the adsorption energy of O₂ near phosphorus atoms in K, P, O-CN_x is the highest. This work provides a new idea for the efficient degradation of pollutants and generation of H₂O₂ at the same time.

Highly Efficient Fe(III)-initiated Self-cycled Fenton System in Piezo-catalytic Process for Organic Pollutants Degradation

Piezo-catalytic self-Fenton (PSF) system has been emerging as a promising technique for wastewater treatment, while the competing O2 reductive hydrogen peroxide (H2O2) production and Fe(III) reduction seriously limited the reaction kinetics. Here, we develop a two-electron water oxidative H2O2 production (WOR-H2O2) coupled with Fe(III) reduction over a Fe(III)/BiOIO3 piezo-catalyst for highly efficient PSF. It is found that the presence of Fe(III) can simultaneously initiate the WOR-H2O2 and reduction of Fe(III) to Fe(II), thereby enabling a rapid reaction kinetics towards subsequent Fenton reaction of H2O2/Fe(II). The Fe(III) initiating PSF system offers exceptional self-recyclable degradation of pollutants with a degradation rate constant for sulfamethoxazole (SMZ) over 3.5 times as that of the classic Fe(II)-PSF system. This study offers a new perspective for constructing efficient PSF systems and shatters the preconceived notion of Fe(III) in the Fenton reaction.

Simultaneously Achieving Fast Intramolecular Charge Transfer and Mass Transport in Holey D-π-A Organic Conjugated Polymers for Highly Efficient Photocatalytic Pollutant Degradation

Simultaneously realizing efficient intramolecular charge transfer and mass transport in metal-free polymer photocatalysts is critical but challenging for environmental remediation. Herein, we develop a simple strategy to construct holey polymeric carbon nitride (PCN)-based donor-π-acceptor organic conjugated polymers via copolymerizing urea with 5-bromo-2-thiophenecarboxaldehyde (PCN-5B2T D-π-A OCPs). The resultant PCN-5B2T D-π-A OCPs extended the π-conjugate structure and introduced abundant micro-, meso-, and macro-pores, which greatly promoted intramolecular charge transfer, light absorption, and mass transport and thus significantly enhanced the photocatalytic performance in pollutant degradation. The apparent rate constant of the optimized PCN-5B2T D-π-A OCP for 2-mercaptobenzothiazole (2-MBT) removal is ∼10 times higher than that of the pure PCN. Density functional theory calculations reveal that the photogenerated electrons in PCN-5B2T D-π-A OCPs are much easier to transfer from the donor tertiary amine group to the benzene π-bridge and then to the acceptor imine group, while 2-MBT is more easily adsorbed on π-bridge and reacts with the photogenerated holes. A Fukui function calculation on the intermediates of 2-MBT predicted the real-time changing of actual reaction sites during the entire degradation process. Additionally, computational fluid dynamics further verified the rapid mass transport in holey PCN-5B2T D-π-A OCPs. These results demonstrate a novel concept toward highly efficient photocatalysis for environmental remediation by improving both intramolecular charge transfer and mass transport.

Highly efficient removal of organic contaminant with wide concentration range by a novel self-cleaning hydrogel: Mechanism, degradation pathway and DFT calculation

A novel carbon nitride based self-cleaning hydrogel photocatalyst (KI-PCN gel, potassium and iodine co-doped carbon nitride confined in alginate) has been successfully constructed by a facile method. Fabricated photocatalyst showed enhanced synergistic adsorption-photocatalytic degradation property on a high concentration of methylene blue (HMB) because of enhanced carrier separation efficiency and improved light adsorption capacity of KI-PCN. As expected, the KI-PCN gel showed the highest apparent rate constant value ₍K_app =0.0310 min^-1), which was about 38.8 and 5.8 times as that of blank hydrogel (K_app=0.0008 min^-1) and PCN gel (K_app=0.0053 min^-1), respectively. Meanwhile, KI-PCN gel can continuously adsorb low concentration of MB (LMB), and the MB-adsorbed KI-PCN gel can self-clean under light irradiation. The bench-scale experiments simulating real river showed that KI-PCN gel can effectively and continuously remove LMB (0.1-20 ppm), indicating the possibility for the removal of contaminants in natural rivers. Furthermore, the possible degradation pathways were proposed by combining the density functional calculations (DFT) and intermediates identified by liquid chromatography-mass spectrometry (LC-MS). This work proposed a new perspective to acquire a novel self-cleaning and easily recyclable photocatalyst for treatment of wide concentration range organic wastewater as well as remediation of natural waterbody.

Self-cycled photo-Fenton-like system based on an artificial leaf with a solar-to-H2O2 conversion efficiency of 1.46

Millions of families around the world remain vulnerable to water scarcity and have no access to drinking water. Advanced oxidation processes (AOPs) are an effective way towards water purification with qualified reactive oxygen species (ROSs) while are impeded by the high-cost and tedious process in either input of consumable reagent, production of ROSs, and the pre-treatment of supporting electrolyte. Herein, we couple solar light-assisted H₂O₂ production from water and photo-Fenton-like reactions into a self-cyclable system by using an artificial leaf, achieving an unassisted H₂O₂ production rate of 0.77 μmol/(min·cm²) under 1 Sun AM 1.5 illumination. Furthermore, a large (70 cm²) artificial leaf was used for an unassisted solar-driven bicarbonate-activated hydrogen peroxide (BAP) system with recycled catalysts for real-time wastewater purification with requirements for only water, oxygen and sunlight. This demonstration highlights the feasibility and scalability of photoelectrochemical technology for decentralized environmental governance applications from laboratory benchtops to industry.

Continuous generation of reactive oxygen species is desirable in the advanced oxidation process. Here, the authors report a self-cycled photoFenton-like with a scalable artificial leaf for production of H₂O₂ from water with solar-to-H₂O₂ efficiency of 1.46%.

Regulating directional transfer of electrons on polymeric g-C3N5 for highly efficient photocatalytic H2O2 production

Graphite carbon nitride (g-C₃N₅) has been widely used in various photocatalytic reactions due to its higher thermodynamic stability and better electronic properties compared to g-C₃N₄. However, it is still challenging to endow g-C₃N₅ with high performance on photocatalytic hydrogen peroxide (H₂O₂) production. Herein, potassium and iodine are co-doped into g-C₃N₅ (g-C₃N₅-K, I) for photocatalytic production of H₂O₂ with high efficiency. As expected, the photocatalytic H₂O₂ production rate over the g-C₃N₅-K, I (2933.4 μM h^-1) reaches to 84.22 times as that of g-C₃N₅. The excellent photocatalytic H₂O₂ production activity is mainly ascribed to the co-doping of K and I, which significantly improves the capacity of oxygen (O₂) adsorption, selectivity of two-electrons oxygen reduction reaction (2e^- ORR) and separation efficiency of charge carriers. The density functional theory (DFT) calculations reveal that O₂ molecules are more conducive to being adsorbed on g-C₃N₅-K, I. Besides, the result of excited states further indicates that photo-generated electrons can be directionally driven to the adsorbed O₂ molecules, which are effectively activated to form H₂O₂. The findings will contribute to new insights in designing and synthesizing g-C₃N₅ based photocatalysts for the H₂O₂ production.

Directing Charge Transfer in a Chemical-Bonded BaTiO3 @ReS2 Schottky Heterojunction for Piezoelectric Enhanced Photocatalysis

The piezo-assisted photocatalysis system, which can utilize solar energy and mechanical energy simulteneously, is promising but still challenging in the environmental remediation field. In this work, a novel metal-semiconductor BaTiO₃ @ReS₂ Schottky heterostructure is designed and it shows high-efficiency on piezo-assisted photocatalytic molecular oxygen activation. By combining experiment and calculation results, the distorted metal-phase ReS₂ nanosheets are found to be closely anchored on the surface of the BaTiO₃ nanorods, through interfacial ReO covalent bonds. The Schottky heterostructure not only forms electron-transfer channels but also exhibits enhanced oxygen activation capacity, which are helpful to produce more superoxide radicals. The polarization field induced by the piezoelectric BaTiO₃ can lower the Schottky barrier and thus reduce the transfer resistance of photogenerated electrons directing to the ReS₂ . As a result of the synergy effect between the two components, the BaTiO₃ @ReS₂ exhibits untrahigh activity for degradation of pollutants with an apparent rate constant of 0.133 min^-1 for piezo-assisted photocatalysis, which is 16.6 and 2.44 times as that of piezocatalysis and photocatalysis, respectively. This performance is higher than most reported BaTiO₃ -based piezo-assisted photocatalysis systems. This work paves the way for the design of high-efficiency piezo-assisted photocatalytic materials for environmental remediation through using green energies in nature.

Understanding the mechanism of interfacial interaction enhancing photodegradation rate of pollutants at molecular level: Intermolecular π-π interactions favor electrons delivery

Uncovering the interaction between photocatalyst and reaction substrate as well as subsequent electron transfer process is critical to achieve high-performance photodegradation of pollutants. Herein, based on the reduced density gradient (RDG) method, we visualize the simulation of the π-π interactions between photocatalyst (g-C₃N₄) and pollutant molecule (flumequine, FLU). Results revealed that π-π interactions between g-C₃N₄ and FLU favor electrons delivery, resulting in enhanced charge separation efficiency and direct hole oxidation of FLU. Moreover, it is found that the charge transfer rate is determined by the valence band (VB) level of g-C₃N₄ and E_HOMO of FLU, of which the deeper VB position of g-C₃N₄ favors faster charge transfer, leading to further enhancement in photocatalytic degradation rate of FLU. Additionally, the possible degradation pathways of FLU were proposed by theoretical calculation and the determined intermediates. Our work afforded a new insight into pollutants degradation and the rational design of highly efficient photocatalysts.

Intimately coupled photocatalysis and biodegradation for effective simultaneous removal of sulfamethoxazole and COD from synthetic domestic wastewater

The inefficiency of conventional biological treatment for removing sulfamethoxazole (SMX) is posing potential risks to ecological environments. In this study, an intimately coupled photocatalysis and biodegradation (ICPB) system consisting of Fe³⁺/g-C₃N₄ and biofilm was fabricated for the treatment of synthetic domestic wastewater containing SMX. The results showed that this ICPB system could simultaneously remove 96.27 ± 5.27% of SMX and 86.57 ± 3.06% of COD, which was superior to sole photocatalysis (SMX 100%, COD 4.2 ± 0.74%) and sole biodegradation (SMX 42.21 ± 0.86%, COD 95.1 ± 0.18%). Contributors to SMX removal in the ICPB system from big to small include LED photocatalysis, biodegradation, LED photolysis, and adsorption effect of the carrier, while COD removal was largely ascribed to biodegradation. Increasing initial SMX concentration inhibits SMX removal rate, while increasing photocatalyst dosage accelerates SMX removal rate, and both had no impact on COD removal. Our analysis of biofilm activity showed that microorganisms in this ICPB system maintained a high survival rate and metabolic activity, and the microbial community structure of the biofilm remained stable, with Nakamurella and Raoultella being the two dominant genera of the biofilm. This work provides a new strategy to effectively treat domestic wastewater polluted by antibiotics.

Iodide ions as invisible chemical scissors tailoring carbon nitride for highly efficient photocatalytic H2O2 evolution

The obtained TCN/NaI possesses Na+ and –OH co-modification, which shows the highest H2O2 generation rate. DFT calculations further reveal that the electron of β spin-orbital in TCN/NaI can transfer to the π* orbital of O2 more facile than BCN.

Probing the role of surface acid sites on the photocatalytic degradation of tetracycline hydrochloride over cerium doped CdS via experiments and theoretical calculations

Surface acid site regulation of photocatalysts is a promising strategy to improve their performance. Herein, surface acid sites of cadmium sulfide were rationally regulated by cerium doping, which resulted in significantly increased photocatalytic activity for tetracycline hydrochloride (TC-HCl) degradation. The generated Brønsted acid sites were verified to favor the adsorption of organic molecules because of their strong affinity. Meanwhile, Lewis acid sites acted as the active sites for C-C bond cleavage via a nucleophilic substitution process, which was testified by the Fukui function and electrostatic potential. Besides, Ce³⁺ doping suppressed the recombination of electron-hole pairs, which also boosted the performance of TC-HCl degradation. Moreover, the degradation pathway of TC-HCl was deduced based on theoretical calculations and HPLC-MS results. The toxicity of pollutants and intermediates was also evaluated. This work provided new insight into the rational design and preparation of highly efficient photocatalysts for environmental purification.

Numerical simulation of microcystin distribution in Liangxi River, downstream of Taihu Lake

Microcystins (MCs), the algal toxins produced by cyanobacteria, raised a worldwide concern in recent decades. Limited monitoring stations for MCs make it hard to map the MC spatial distribution in certain areas. To tackle such problems, we selected Liangxi River as our research area and developed an integrated model to get spatial continuous MC data without too many sampling sites, which integrates a hydro-environment model and an artificial neural network algorithm (ANN). The ANN algorithm can estimate concentration MCs via environmental factors. In this paper, we selected chl-a, TN, TP, NO 2 - , NO 3 - , NH₃ -N, and PO 4 3 - as stressors. The ANN model we established showed good performances both in train (R²  = 0.8407) and test set (R²  = 0.7543). In the hydro-environment model, by inputting river geometry and model boundary data, the spatial continuous water quality data could be simulated. The water quality data returned from the hydro-environmental model were used as input variables of the well-trained ANN model; the continuous MC data were derived. To evaluate this model on geo-mapping the MC distribution in Liangxi River, we compared the performance of this model and spatial interpolation on the test set, it turns out the integrated model showed a better performance. © 2020 Water Environment Federation PRACTITIONER POINTS: The cost of microcystin (MC) detection is too high for routine monitoring. We integrated regression method and hydro-environment model to predict MCs. Results derived from spatial interpolation are not robust in unmonitored area. The new integration model can minimize the drawback of spatial interpolation.

Iodide-Induced Fragmentation of Polymerized Hydrophilic Carbon Nitride for High-Performance Quasi-Homogeneous Photocatalytic H2 O2 Production

Polymeric carbon nitride (PCN) as a class of two-electron oxygen reduction reaction (2 e^- ORR) photocatalyst has attracted much attention for H₂ O₂ production. However, the low activity and inferior selectivity of 2 e^- ORR greatly restrict the H₂ O₂ production efficiency. Herein, we develop a new strategy to synthesize hydrophilic, fragmented PCN photocatalyst by the terminating polymerization (TP-PCN) effect of iodide ions. The obtained TP-PCN with abundant edge active sites (AEASs), which can form quasi-homogeneous photocatalytic system, exhibits superior H₂ O₂ generation rate (3265.4 μM h^-1 ), far surpassing PCN and other PCN-based photocatalysts. DFT calculations further indicate that TP-PCN is more favorable for electron transiting from β spin-orbital to the π* orbitals of O₂ , which optimizes O₂ activation and reduces the energy barrier of H₂ O₂ formation. This work provides a new concept for designing functional photocatalysts and understanding the mechanism of O₂ activation in ORR for H₂ O₂ production.

Risk prediction of microcystins based on water quality surrogates: A case study in a eutrophicated urban river network

Microcystins (MCs), the toxic by-products from harmful algal bloom (HAB), have caused world-wide concern due to their acute toxicity in freshwater ecosystems. Most studies on HAB have been conducted for shallow freshwater lakes, such as Taihu Lake in China. However, algal blooms in urban rivers located downstream of eutrophicated lakes are also a serious problem for local administrators. It is important for them to know the current and potential risk level of MCs. This environmental issue is rarely reported or discussed. Within this context, we monitored MC concentrations in the Binhu River Network (BRN) in the algal bloom season (Aug, Sep, and Oct) in 2019. To note if the MC concentrations were dangerous, we used 1.0 μg/L suggested by the World Health Organization as the standard value. The proportions of MC samples violating the standard value were 31.78% (Aug), 21.14% (Sep) and 30.77% (Oct). We also designed two statistical models to predict MC concentrations and the possibility to exceed the standard level based on 10 water quality surrogates: Artificial Neural Network (ANN) and Logistic Regression (LR) models. These two models were trained and validated by the monitoring dataset (n = 224). Both models had good performances during training and testing. Although the water quality varied diversely both in spatial and temporal scale, Cluster Analysis (CA) could detect similarities among the samples and separated them into 3 classes, with each class denoting different types of rivers based on the 10 water quality surrogates. Then the ANN and LR were applied as a function of chl-a in each class; by gradually increasing chl-a concentration, we detected chl-a thresholds in class 1, 2, 3 were 25.5, 224, and 109.5 μg/L, respectively, when MCs have a 50% possibility to exceed standard level. The threshold values provided important implications for MC management in the BRN.

Surface Properties and Environmental Transformations Controlling the Bioaccumulation and Toxicity of Cerium Oxide Nanoparticles: A Critical Review

Increasing production and utilization of cerium oxide nanoparticles (CNPs) in recent years have raised wide concerns about their toxicity. Numerous studies have been conducted to reveal the toxicity of CNPs, but the results are sometimes contradictory. In this review, the most important factors in mediating CNPs toxicity are discussed, including (1) the roles of physicochemical properties (size, morphology, agglomeration condition, surface charge, coating and surface valence state) on CNPs toxicity; (2) the phase transfer and transformation process of CNPs in various aqueous, terrestrial, and airborne environments; and (3) reductive dissolution of CNPs core and their chemical reactions with phosphate, sulfate/S^2-, and ferrous ions. The physicochemical properties play key roles in the interactions of CNPs with organisms and consequently their environmental transformations, reactivity and toxicity assessment. Also, the speciation transformations of CNPs caused by reactions with (in)organic ligands in both environmental and biological systems would further alter their fate, transport, and toxicity potential. Thus, the toxicity mechanisms are proposed based on the physical damage of direct adsorption of CNPs onto the cell membrane and chemical inhibition (including oxidative stress and interaction of CNPs with biomacromolecules). Finally, the current knowledge gaps and further research needs in identifying the toxicological risk factors of CNPs under realistic environmental conditions are highlighted, which might improve predictions about their potential environmental influences. This review aims to provide new insights into cost-effectiveness of control options and management practices to prevent environmental risks from CNPs exposure.

Effective inactivation of Microcystis aeruginosa by a novel Z-scheme composite photocatalyst under visible light irradiation

Microcystis aeruginosa is one of the most famous harmful algae. In this work, Z-scheme g-C₃N₄-MoO₃ (Mo-CN) composite photocatalysts were successfully synthesized to alleviate the algae pollution. The obtained composites exhibited excellent performance for the inactivation of M. aeruginosa. The optimal photocatalysts (15Mo-CN) achieved a removal efficiency of 97% for the algal cells after 3 h visible light irradiation, which was attributed to their remarkable surface properties and ingenious structure design. The physiological status of Microcystis aeruginosa were evaluated by the chlorophyll a (chla), relative electron transport rate (rETR) and maximum photochemical efficiency (Fv/Fm), and all of them decreased in different degrees. Furthermore, the as-prepared photocatalysts also show a certain activity for the removal of leaked macromolecule organic compounds during the process of algal cells inactivation. Finally, a possible mechanism on the photocatalytic inactivation of algal cells by the Z-scheme photocatalysts was deduced based on the experimental and characterization results. We believe this study would provide new insights into the development of promising technology and basic theory for remediation of algae pollution.

The surface engineering of ReS2 with cobalt for efficient performance in hydrogen evolution under both acid and alkaline conditions

Cobalt-modified rhenium disulfide nanosheets rich in defects, obtained by following an ingenious atom substitution strategy, exhibited boosted HER performance. The 2%-Co doped ReS2 sample was highly efficient in both acid electrolyte (149 mV) and alkaline electrolyte (240 mV), achieving a current density of 10 mA cm-2 as well as superior long-term durability.

Dual-metal-driven Selective Pathway of Nitrogen Reduction in Orderly Atomic-hybridized Re2MnS6 Ultrathin Nanosheets

The future of sustainable fertilizers and carbon-free energy carrier demands innovative breakthroughs in the exploitation of efficient electrocatalysts for synthesizing ammonia (NH₃) from nitrogen (N₂) in mild conditions. Understanding and regulating the reaction intermediates that form on the catalyst surface through careful catalyst design could bypass certain limitations associated with ambiguous adsorbate evolution mechanism. Herein, we propose ternary intermetallic Re₂MnS₆ ultrathin nanosheets that include orderly hybridized Mn-Re dual-metal sites through strong Hubbard e-e interaction, demonstrating a promising selectivity toward reaction process from N₂ to NH₃. The ordered inclusion of Mn sites leads to a structural phase transition and appearance of nonbonding semimetal states, in which the rate-limiting activation energy barrier is significantly decreased through a conversion in reaction pathway. As a result, the performance of N₂ reduction in Re₂MnS₆ is increased about 6.6 times compared to the single-metal ReS₂.

All-solid-state Z-scheme WO3 nanorod/ZnIn2S4 composite photocatalysts for the effective degradation of nitenpyram under visible light irradiation

A Z-scheme WO₃/ZnIn₂S₄ photocatalyst was synthesized via a simple solvothermal method. Compared with pure WO₃ and ZnIn₂S₄, photocatalytic experiments showed that these Z-scheme photocatalysts exhibited enhanced activity for the degradation of nitenpyram (NTP). The apparent rate constant (k) of NTP degradation on 50WZ (WO₃/ 50 wt% Znln₂S₄) was 0.042 min^-1 (∼3.8 times higher than WO₃ and ∼2.5 times higher than ZnIn₂S₄). Photoluminescence (PL), photocurrent (PC), and electrochemical impedance spectroscopy (EIS) showed that the separation and transfer efficiency of photogenerated carriers in 50WZ was markedly enhanced, which was favorable for improving its photocatalytic activity. Active species capture experiments and electron spin resonance (ESR) measurements showed that superoxide radicals and holes were the main active species for NTP degradation, and they confirmed the formation of the Z-scheme structure. Furthermore, a possible NTP degradation pathway was deduced based on the results of high-performance liquid chromatography mass spectrometry (HPLC-MS).

Synthesis of novel ternary heterogeneous anatase-TiO2 (B) biphase nanowires/Bi4O5I2 composite photocatalysts for the highly efficient degradation of acetaminophen under visible light irradiation

Bi₄O₅I₂ loaded anatase-TiO₂ (B) biphase nanowires composite photocatalysts were fabricated by an in situ calcination method and exhibited outstanding photocatalytic activity. The microstructure, optical performance and band structure of the composite photocatalysts were investigated by relevant characterizations. The results demonstrated the successful formation of heterojunction between anatase-TiO₂ (B) biphase nanowires and Bi₄O₅I₂, which integrated the advantages of homojunction and heterojunction. Therefore, it definitely improved separation efficiency of photo-induced electron-holes because of the formation of multi-junctions. In order to test the enhanced photocatalytic activity, acetaminophen was chosen as target pollutant. The sample with 67% Bi₄O₅I₂ (TiO₂-Bi₄O₅I₂-3) presented the highest photocatalytic activity on the degradation of acetaminophen and its reaction apparent rate constant was 10 and 25 times as that of Bi₄O₅I₂ and TiO₂ biphase nanowires, respectively. Through trapping experiments and LC-MS/MS analysis, OH was proved to be the key active specie during the photocatalytic process of acetaminophen degradation. Meanwhile a possible degradation pathway was proposed based on the detected intermediate products.

Long-term exposure to antibiotic mixtures favors microcystin synthesis and release in Microcystis aeruginosa with different morphologies

The ecological risks of antibiotics in aquatic environments have raised great concerns worldwide, but the chronic effect of antibiotic contaminants on cyanotoxin production and release remains unclear. This study investigated the long-term combined effects of spiramycin (SP) and ampicillin (AMP) on microcystin (MC) production and release in both unicellular and colonial Microcystis aeruginosa (MA) through semi-continuous exposure test. At exposure concentration of 300 ng L^-1, MA growth rates were stimulated till the end of exponential phase accompanied with the up-regulation of photosynthesis-related gene. The exponential growth phases of unicellular and colonial MA were prolonged for 2 and 4 days, respectively. The stimulation rate of growth rate and MC content in unicellular MA were significantly higher than that in colonial MA. The highest concentrations of intracellular MC (IMC) and extracellular MC (EMC) were observed in the binary mixture at equivalent SP/AMP ratio (1:1). The promotion of IMC concentration was in consistent with the stimulated expression of MC-synthesis-related gene and nitrogen-transport-related gene. The malondialdehyde content and activities of superoxide dismutase and catalase in unicellular MA were significantly higher than those in colonial MA. The EMC concentration and the antioxidant responses of both unicellular and colonial MA significantly increased with exposure time. Long-term exposure to mixture of SA and AMP at environmentally relevant concentrations would aggravate the disturbance to aquatic ecosystem balance through the stimulation of MA proliferation as well as the promotion of MC production and release.

The functional difference of eight chitinase genes between male and female of the cotton mealybug, Phenacoccus solenopsis

The cotton mealybug Phenacoccus solenopsis Tinsley (Hemiptera: Pseudococcidae) is a polyphagous insect that attacks tens of plant and causes substantial economic loss. Insect chitinases are required to remove the old cuticle to allow for continued growth and development. Though insect chitinases have been well studied in tens of insects, their functions in mealybug are still not addressed. Here, we sequenced the transcriptomes of adult males and females, from which eight chitinase genes were identified. We then used the method of rapid amplification of cDNA ends to amplify their full length. Phylogenetic analysis indicated that these genes clustered into five subgroups. Among which, group II PsCht2 had the longest transcript and was highly expressed at second instar nymph. PsCht10, PsCht3-3 and PsIDGF were highly expressed in the adult females, whereas PsCht4 and PsCht4-1 were significantly expressed at the male pupa and adult male. Next, we knocked down all eight chitinase genes by feeding the double-stranded RNA. Knockdown of PsCht4 or PsCht4-1 led to the failure of moult and, silencing PsCht5 resulted in pupation defect, while silencing PsCht10 led to small body size, suggesting these genes have essential roles in development and can be used as a potential target for pest control.

Effects of interactions between humic acid and heavy metal ions on the aggregation of TiO2 nanoparticles in water environment

Nanoparticles (NPs), heavy metal and natural organic matter (NOM) may simultaneously exist in the aquatic environment, where they will affect the behavior of each other and may enhance their toxicities. Studies on the influences of interactions between NOM and heavy metal ions on the behavior of NPs are scarce. In this study, combined effects of Pb²⁺ and HA on the aggregation behavior of TiO₂ NPs in water environment were investigated by Dynamic light scattering (DLS) and Nanoparticle tracking analysis (NTA). The results illustrated that interactions between Pb²⁺ and HA could case the aggregation of TiO₂ NPs obviously. The concurrence of Pb²⁺ and HA resulted in decreased critical coagulation concentration (CCC) and increased attachment efficiencies. Meanwhile, we found that the addition sequences of HA and heavy metal clearly influenced the aggregation kinetics of TiO₂ NPs. At different addition sequences, the complex reaction between Pb²⁺ and HA changed the surface charge of TiO₂ NPs, and caused the different aggregation behavior which depended on the complex locations and complex sites. Furthermore, the excitation-emission-matrix (EEM) fluorescence spectra was used to verify the significant effects of the complex interactions between Pb²⁺ and HA on the aggregation of TiO₂ NPs. Our results would be significant for interpreting TiO₂ behavior in the complicated water system. The complexation between Pb²⁺ and HA promoted the aggregation of TiO₂ NPs, meanwhile, complex locations and complex sites played an important role.

Modification strategies for enhancing the visible light responsive photocatalytic activity of the BiPO4nano-based composite photocatalysts

The present issues related to environmental purification have led to a great need for the development of a superior oxidation process to solve the life-threatening problem. The use of the BiPO₄nanomaterial in photocatalysis is one of the best methods for the treatment of wastewater due to its less harmful nature.

2D ultrathin CoP modified MnxCd1−xS with controllable band structure and robust photocatalytic performance for hydrogen generation

Considerable efforts have been directed towards constructing high-efficiency, earth-abundant and low-cost photocatalysts for hydrogen evolution under visible light irradiation.

Mini Review on the Structure and Properties (Photocatalysis), and Preparation Techniques of Graphitic Carbon Nitride Nano-Based Particle, and Its Applications

Graphite carbon nitride (g-C3N4) is well known as one of the most promising materials for photocatalytic activities, such as CO2 reduction and water splitting, and environmental remediation through the removal of organic pollutants. On the other hand, carbon nitride also pose outstanding properties and extensive application forecasts in the aspect of field emission properties. In this mini review, the novel structure, synthesis and preparation techniques of full-bodied g-C3N4-based composite and films were revealed. This mini review discussed contemporary advancement in the structure, synthesis, and diverse methods used for preparing g-C3N4 nanostructured materials. The present study gives an account of full knowledge of the use of the exceptional structural and properties, and the preparation techniques of graphite carbon nitride (g-C3N4) and its applications.

Titanium Phosphate Nanoplates Modified With AgBr@Ag Nanoparticles: A Novel Heterostructured Photocatalyst With Significantly Enhanced Visible Light Responsive Activity

AgBr@Ag modified titanium phosphate composites were fabricated through a two-step approach. The prepared samples were characterized by X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. The optical properties of the composites were characterized by using UV-vis diffuse reflectance spectroscopy. The photocatalytic activities of the composites were investigated on the degradation of Rhodamine B and ciprofloxacin under visible light irradiation. AgBr@Ag/titanium phosphate was determined to exhibit considerably higher photocatalytic activity than the corresponding individual components. The mechanism on the enhancement of the photocatalytic activity was proposed based on the results of photoluminescence spectra and photocurrent measurements. Furthermore, the possible photocatalytic mechanisms of organic compounds degradation were also proposed.

Investigation of the rheological behavior of activated sludge in response to CeO2 nanoparticles and potential mechanism

With the rapid development of CeO₂ nanoparticles (NPs), the released CeO₂ NPs entering into wastewater treatment plants might bring the challenges for sludge pumping and mixing. In this study, we firstly elucidated the rheological behavior of 4.0 wt% sludge at various concentrations of CeO₂ NPs. With the increase of CeO₂ NPs to 5 mg/L, the shear stress at any given shear rate was reduced and the limiting viscosity was also decreased, indicating the sludge became more flowability. The dynamic sweep tests further demonstrated the decreased elastic behavior and weakened internal structure in response to low concentrations of CeO₂ NPs (≤ 5 mg/L). However, 20 mg/L CeO₂ NPs had negative effects on the rheological evolution of sludge, namely, better solid-like property and higher elastic structure. These results were mainly attributed to the combination of the decreased β-D-glucopyranose polysaccharides which support the rigid structure of sludge and the dramatically increased protein content (especially in 20 mg/L CeO₂ NPs). These results can potentially provide novel information for the efficient design of sludge treatment when coped with CeO₂ NPs. Graphical abstract ᅟ.

Efficient degradation of atrazine by BiOBr/UiO-66 composite photocatalyst under visible light irradiation: Environmental factors, mechanisms and degradation pathways

Atrazine, a typical herbicide, has caused extensive concern due to its wide application and persistance. In this work, a visible light responsive photocatalyst BiOBr/UiO-66 was synthesized and applied to the degradation of atrazine. The BiOBr/UiO-66 materials exhibited significantly enhanced photocatalytic performance on the degradation of atrazine under visible light irradiation compared to pure BiOBr. Moreover, the effects of typical environment factors (i.e. pH, common anions, inorganic cations and water matrix) on the degradation of atrazine were investigated extensively. Results showed that atrazine was degraded with the fastest rate at the strong acidity conditions of pH = 3.1 in the investigated pH region (3.1-9.4). The photocatalytic degradation of atrazine was obviously inhibited by HCO₃^- and SO₄^2-. However, Cl^- had negligible influence on the degradation of atrazine. Inorganic cations had little influence on the degradation of atrazine. Futhermore, the water matrix showed apparent impacts on the photocatalytic degradation of atrazine by BiOBr/UiO-66. In mineral water, tap water and river water, the removal efficiency of atrazine was evidently lower than that in pure water. The main active species that responsible for the degradation of atrazine by BiOBr/UiO-66 were determined to be ·O₂^- and h⁺. Ultimately, the degradation pathways of atrazine were proposed based on the intermediates detected by LC-MS/MS.

Significantly enhanced visible light photocatalytic efficiency of phosphorus doped TiO2 with surface oxygen vacancies for ciprofloxacin degradation: Synergistic effect and intermediates analysis

In the present work, we reported a simple method for the simultaneous phosphorus (P) doping and oxygen vacancies creation on TiO₂ in a single step. The obtained P-doped TiO₂ with surface oxygen vacancies (PTSOV) samples exhibited efficient photocatalytic activity for the degradation of fluoroquinolone antibacterial agent (ciprofloxacin) under visible light irradiation. The optimized sample showed a rate constant of 0.065 min^-1 for degradation of ciprofloxacin (CIP) and it was about 16.2 times as high as that of TiO₂ (0.004 min^-1). The transformation products of CIP were identified by liquid chromatography-mass spectrometry (LC-MS), and degradation pathway was tentatively proposed. The doping state of P and the formation of surface oxygen vacancies (SOVs) were investigated by different methods. X-ray diffraction (XRD) and X-ray Photoemission Spectroscopy (XPS) revealed P⁵⁺ doped via formation TiOP bond. Electron paramagnetic resonance (EPR) spectroscopy revealed that SOVs were generated on P-doped TiO₂. It turned out that the synergistic effect between doping P and SOVs on TiO₂ greatly improved transfer and separation efficiency of photogenerated charges, thus significantly enhanced the visible light photocatalytic performance of TiO₂. Our work would provide an effective way to design new photocatalysts with high performance under visible light irradiation.

Photocatalytic properties of P25-doped TiO2 composite film synthesized via sol-gel method on cement substrate

TiO₂ films have received increasing attention for the removal of organic pollutants via photocatalysis. To develop a simple and effective method for improving the photodegradation efficiency of pollutants in surface water, we herein examined the preparation of a P25-TiO₂ composite film on a cement substrate via a sol-gel method. In this case, Rhodamine B (RhB) was employed as the target organic pollutant. The self-generated TiO₂ film and the P25-TiO₂ composite film were characterized by X-ray diffraction (XRD), N₂ adsorption/desorption measurements, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and diffuse reflectance spectroscopy (DRS). The photodegradation efficiencies of the two films were studied by RhB removal in water under UV (ultraviolet) irradiation. Over 4day exposure, the P25-TiO₂ composite film exhibited higher photocatalytic performance than the self-generated TiO₂ film. The photodegradation rate indicated that the efficiency of the P25-TiO₂ composite film was enhanced by the addition of the rutile phase Degussa P25 powder. As such, cooperation between the anatase TiO₂ and rutile P25 nanoparticles was beneficial for separation of the photo-induced electrons and holes. In addition, the influence of P25 doping on the P25-TiO₂ composite films was evaluated. We found that up to a certain saturation point, increased doping enhanced the photodegradation ability of the composite film. Thus, we herein demonstrated that the doping of P25 powders is a simple but effective strategy to prepare a P25-TiO₂ composite film on a cement substrate, and the resulting film exhibits excellent removal efficiency in the degradation of organic pollutants.

The effects of extracellular polymeric substances on magnetic iron oxide nanoparticles stability and the removal of microcystin-LR in aqueous environments

The behaviors of nanoparticles rely on the aqueous condition such as natural organic matter (NOM). Therefore the presence of NOM would influence the interaction of nanoparticles with other substances possibly. Here, microcystin-LR (MC-LR) adsorption on iron oxide nanoparticles (IONPs) was studied in an aqueous solution with different types of NOM, including extracellular polymeric substances (EPS) from cyanobacteria and alginic acid sodium salt (AASS) from brown algae. Results revealed that EPS played an important role in stabilizing IONPs and in the toxin adsorption efficiency. The stability of IONPs was heavily depended on the concentration and type of NOM, which can affect the surface charge of IONPs significantly in solution. The enhanced stability of IONPs was due to the electrostatic interactions. Adsorption kinetics and isotherm studies confirmed that NOM can affect the IONPs' adsorption efficiency, and pseudo-second-order kinetics better explained this process. The removal efficiency for MC-LR decreased in the presence of NOM (Control > EPS-M1 > AASS > EPS-M9), indicating that NOM and MC-LR compete for limited adsorption sites. The presence of NOM in a eutrophic environment stabilized the IONPs while inhibiting the MC-LR removal efficiency. This investigation emphasized the negative effect of cyanobacterial EPS on the removal of microcystins when using magnetic separation technology. And this results could also be used to model the transportation of iron minerals carrying toxic substances in aqueous environment.

Effect of a typical antibiotic (tetracycline) on the aggregation of TiO2 nanoparticles in an aquatic environment

The effect of tetracycline (TC) on the behavior of TiO₂ nanoparticles (NPs) in solution is investigated. The results illustrate that TC molecules do not exhibit an obvious effect on the aggregation of TiO₂ NPs under circumneutral conditions (pH of approximately 5.5). However, the TC molecules exhibit a remarkable effect on the behavior of TiO₂ NPs when the environmental factors (such as pH, ionic strength, and humic acid; HA) are adjusted. In the pH range from 3.0 to 10.0, the zeta potentials of NPs become more positively charged after TC adsorption. The point of zero charge of the TiO₂ NPs increases from 6.5 to 7.5. The stability of the TiO₂ NPs is improved after TC adsorption in different salt solutions. The critical coagulation concentration (CCC) increases from 10.57mmol/L to 17.21mmol/L, 4.95mmol/L to 9.73mmol/L, and 0.23-1.67mmol/L in the presence of NaCl, CaCl₂, and Na₂SO₄ (where Cl^- and SO₄^2- are the counter-ions), respectively. Under different HA concentrations, the C_HAPZC (the HA concentration that causes the zeta potential of NPs to be zero) increases from 0.5mg/L to 1.3mg/L after TC adsorption. The sizes of the TiO₂ NP aggregates are larger than those without TC adsorption. All of these results are due to an increase in the surface charge of the TiO₂ NPs after TC adsorption. The adsorption of H⁺ during TC adsorption causes protonation of the dimethylamine group on the TC molecules.

In situ surface engineering of ultrafine Ni2P nanoparticles on cadmium sulfide for robust hydrogen evolution

Here we report the in situ growth of well-dispersed ultrafine Ni₂P nanoparticles on CdS nanorods by a simple solvothermal method and a further surface phosphatization treatment for the first time.

Oxygen vacancies of the TiO2nano-based composite photocatalysts in visible light responsive photocatalysis

The TiO₂nano-based composite photocatalyst is best known for application in solving the recent issues related to energy and environmental purification.