Complex Water Environment Research Articles

Arsenic(V) removal from water using polyelectrolyte enhanced ultrafiltration with poly(dimethyldiallylammonium chloride) (PDADMAC): Ion-selectivity based modeling and electric field influence

Polyelectrolyte enhanced ultrafiltration (PEUF) shows promise for arsenic removal. However, competing ions may serve as potential limiting factors, and membrane fouling caused by aggregation of polyelectrolytes may impact PEUF performance. This study employed poly(dimethyldiallylammonium chloride) (PDADMAC) for arsenate (As(V)) removal via ultrafiltration, and the electric field assistance was investigated on the PEUF performance. Ion exchange experiments between Cl-, and typical anions were conducted in a binary system to determine the selectivity coefficients (Ksel) of PDADMAC for different anions. The affinity of PDADMAC towards common monovalent anions was found to be Br->NO3->Cl->H2PO4->HCO3->H2AsO4-, while its affinity for divalent anions decreased in the order SO42-> HPO42-> HAsO42-. By determining the selectivity coefficients of various anions with PDADMAC and utilizing mass conservation models, a phase distribution model for anions during PEUF process was developed to predict As(V) removal. Predictions were made regarding the enhanced ultrafiltration efficiency for As(V) under different conditions (pH, ionic strength, and competing anions) in complex water environments. As the dosage of PDADMAC increased, the removal of As(V) from the actual water sample spiked with an initial concentration of 0.2mM exceeded 90%, and the experimental results closely matched the model predictions. The impact of electric field on the PEUF process was investigated by placing electrodes on both sides of the ultrafiltration membrane. Results showed that the ultrafiltration membrane, when positively charged by an electric field, repelled cationic PDADMAC, thereby alleviating membrane fouling. However, a cleaner membrane led to increased leakage of PDADMAC molecules, resulting in the co-loss of As with PDADMAC and consequently reducing the overall As removal.

Eu A-site partial substitution of BiFeO3 as a catalyst for enhanced ofloxacin degradation via singlet oxygen-dominated peroxymonosulfate activation

In this study, the as-synthesized europium (Eu) doped BiFeO3 (EBFO-3) catalyst was employed to activate peroxymonosulfate (PMS) and achieved marked improvement (26.7 %) compared to the BiFeO3 (BFO) catalyst in the degradation of target pollutant ofloxacin (OFL) under identical conditions. The substitution of BiⅢ (ionic radius 1.03 Å) with smaller EuⅢ (ionic radius 0.95 Å) caused larger lattice distortions to promote the formation of more oxygen vacancies and tremendously enhance the production of singlet oxygen (1O2) up to 67.44 % of total reactive oxygen species (ROS). Density functional theory (DFT) calculations further revealed that the electronic structure of iron active sites was effectively modulated to induce reduced covalency of Fe-O bonds, an increase in exposed Fe active sites, and the introduction of additional Eu active sites by partially A-site substituting the more electronegative BiⅢ (2.02) with less electronegative EuⅢ (1.19). The activation of PMS into dominantly selective 1O2 through the substitution of BFO with A-site Eu could improve the applicability of catalysts in treating pollutants in complex water environments, significantly reduce the toxicity of intermediates/products, and provide good insights for the field of water treatment.

Modular hydrogel selectively adsorbs phosphates and hexavalent chromium while enabling phosphate recovery

Electroplating wastewater containing high concentrations of phosphates and hexavalent chromium Cr(VI) poses serious environmental pollution. Moreover, phosphorus, as a non-renewable resource, necessitates its recovery to meet sustainable development goals. To address this issue, this study used sodium alginate as the scaffold module, synthesized lanthanum carbonate in situ within a chitosan module to serve as the phosphate adsorption module, and employed polyethyleneimine (PEI) modules to enhance the adsorption capacity for Cr(VI), successfully fabricating a modular hydrogel (LC-CSP). LC-CSP exhibits a complex porous structure and surface morphology, forming an ultra-low-density fiber network with good strength and elasticity, ensuring uniform distribution and exposure of active sites. Under optimal conditions for single-component adsorption, LC-CSP achieved adsorption capacities of 232.02 mg/g for phosphates and 474.61 mg/g for Cr(VI). Additionally, LC-CSP demonstrated excellent reusability, retaining over 83 % of its performance after five cycles. In simulated electroplating wastewater experiments with various interfering substances, LC-CSP maintained high removal efficiencies (>90.72 %) for phosphates and Cr(VI). Post-experiment, enriched water after phosphate desorption was further treated to recover phosphorus resources in complex water environments. Multiple characterization techniques elucidated the adsorption mechanisms of LC-CSP: phosphate adsorption primarily involved ligand exchange, electrostatic interactions, and hydrogen bonding, while Cr(VI) adsorption included electrostatic interactions, hydrogen bonding, and reduction reactions. Finally, fixed-bed simulated wastewater adsorption experiments validated the technical potential of LC-CSP for practical electroplating wastewater management.

Intraplanar heterostructure-mediated activation of peroxydisulfate for singular-electron-transfer degradation of organic pollutants

Activating peroxydisulfate (PDS) through electron transfer pathways (ETP) is promising for degrading organic pollutants in aquatic environments. However, enhancing the activation selectivity remains a challenge. Herein, this study developed an intraplanar heterojunction with C-ring grafted g-C3N4 (CCN) as the catalyst, enabling PDS activation through a singular ETP. The CCN/PDS system achieved complete degradation and efficient mineralization (87.15 %) of bisphenol F (BPF), significantly reducing its ecological toxicity. Both experimental and theoretical investigations revealed that the intraplanar heterojunction could modulate the orbital occupation in g-C3N4/PDS, enhancing PDS adsorption and activation selectivity. Driven by the differences in the frontier orbital energy, the CCN/PDS system achieved a singular ETP without active species formation. The CCN/PDS system efficiently degraded BPF in complex water environments, showing performance stability across a wide pH range and against various coexisting ions. In a continuous-flow automatic catalytic device, the CCN/PDS system maintained a constant 100 % BPF degradation for 600 min. This study advances the understanding of PDS activation via singular ETP and introduces a new approach to water purification.

Anchoring atomic Pd on molybdenum disulfide with state-of-the-art specific activity in the electrochemical dehalogenation of florfenicol

The widespread discharge of halogenated organic pollutants (HOPs) in wastewater brings significant risks to the environment and human health due to potent high toxicity, antibacterial activity, and strong biodegradation resistance. Adsorbed atomic hydrogen (H*ads)-mediated electrocatalytic hydrodehalogenation (EHDH) has been recognized as an efficient strategy for HOPs removal through selectively breaking carbon-halogen bonds. In this work atomic Pd uniformly anchored on molybdenum disulfide (denoted as Pd-MoS2) was synthesized through a facile hydrothermal method and found with state-of-the-art specific activity in florfenicol (FLO) removal via the H*ads-mediated EHDH process. Pd-MoS2 completely dehalogenated (∼100 %) FLO within 30 min at a rate constant of 0.15 min−1, which was 6.0, 6.5 and 33.1 times the value of MoS2, Pd/C and carbon paper samples, respectively. Notably, the toxicity of the wastewater was reduced to 1/6 of its original value after the treatment. Moreover, Pd-MoS2 presented superior catalytic stability in five successive cycles. Furthermore, Pd-MoS2 was also robust in complex water environment with practical applicability for industrial wastewater treatment. A dual-active-center mechanism with enhanced H*ads production capacity and the improved H*ads utilization efficiency was contributed to the increased EHDH activity on Pd-MoS2.

High-efficiency treatment of oily wastewater by photocatalytic in-situ Fenton oxidation under visible light

Oily wastewater poses a significant threat to environmental safety, and complex water environments have caused numerous disturbances in oil pollution treatment. Therefore, constructing composite systems is expected to improve oil pollution treatment efficiency. This study developed an efficient photocatalytic in-situ Fenton oxidation system, HTCC@ZnFe2O4/Ag3PO4 (HZFA), loaded onto polypropylene spheres (PP) for treating oily wastewater (diesel oil) in complex environments. The built-in electric field of HZFA promotes photogenerated carrier separation, enhancing photocatalytic effect. At a diesel concentration of 3.2 g/L, performance of HZFA degraded diesel in deionized water and artificial seawater (ASW) were 60.80 % and 52.62 %, respectively, much higher than a pure photocatalytic system (13.84 %). The dual system compensated for single system defects like instability and narrow application range, achieving 8 effective cycles in ASW. Experimental and computational results showed that high oxidation and reduction potentials in the dual system promoted hydrocarbon oxidative degradation and H2O2 production/activation. The amount of OH, O2−, and h+ produced in different environments is fundamental for the stabilization of catalytic degradation by HZFA. GC–MS and DFT analysis revealed potential oxidative chain-breaking processes for diesel components like alkanes, aromatics, alcohols, acids, aldehydes, and esters. This study offers a new method for green and efficient oily wastewater treatment, overcoming inherent defects of traditional Fenton, with broad application prospects.

Structure-function relationship for functional films with constructed graded channels in dye/salt separation and fouling resistance

The structural assembly of polypyrrole particle stacking, combined with polydopamine space-filling, forms composite film with a network of interconnected fluid channels. The composite films achieve high water flus, separation efficiency and ratio of organic dyes/inorganic salts (flux: >600 L m−2 h−1 bar−1; dye rejection: ~100 %; salt rejection: <5 %). Simulation using different dye fouling models show that the dye only interacts at the surface, and hardly affects internal pores of the film throughout the filtration process. Owing to the patterned surface structure as constructed by microsphere arrangement and inter-structure adaptation assembly, the functional film has excellent contamination tolerance and rinsing regeneration for macromolecular pollutants. The results of computational fluid dynamics simulations further indicate that the high shear stress above the microspheres with vortex flow in the interstitial space has a positive effect on reducing contaminant deposition. In addition to the separation property, the composite film shows good structural stability and mechanical strength in various complex water environments, benefiting their future practical applications. This work unveils the structure-function relationship for composite function films with constructed graded channels in dye/salt separation, which is important for the design and future application of these functional films.

Study on the effect of particles in oilfield produced water on the deposition process of CaCO3

In crude oil production, scale deposition significantly reduces production output and elevates operational costs, posing a severe threat to production safety. While chemical methods have been extensively explored for the scaling and inhibition of inorganic salts, the inorganic scaling triggered by solid particle scaling in complex oilfield water has largely been overlooked. This study involves the introduction of particles into a supersaturated CaCO3 solution, utilizing static scale inhibition and conductivity techniques to examine their influence on the scaling process and crystallization rate. It is evident that solid particles expedite the deposition process of CaCO3. Moreover, the deposition rate of CaCO3 is influenced by factors such as the solid particle content, particle size, and stirring speed. It is noteworthy that the presence of solid particles solely impacts the formation rate of CaCO3 crystals, without altering the total deposition. Specifically, under conditions of 70°C, 250/min stirring speed, and 0.08% SiO2 addition, the deposition rate of CaCO3 is enhanced by 13.5%. The nucleus growth rate constant increases from 11.10 × 10-3min-1 to 14.52 × 10-3min-1 and the crystal growth rate constant increases from 3.02 × 10-3min-1 to 3.36 × 10-3min-1 at most. Observations made through scanning electron microscopy (SEM) and polarized light microscopy reveal that scaling occurs predominantly on the added solid particles in later stages, indicating that solid particles in supersaturated solutions serve as crystal nuclei, inducing the growth of CaCO3 crystals and thus accelerating scaling. This research provides valuable insights for the study of scaling in complex water environments.

Insights into the removal of sulfamethazine and sulfonamide-resistant bacteria from wastewater by Fe-Mn spinel oxide modified cow manure biochar activated peroxymonosulfate: A nonradical pathway regulated by enhanced adsorption and 3d orbital electron reconstruction

Effectively regulating nonradical pathways is crucial for adapting to complex water environments in sulfate radical-based advanced oxidation processes (SR-AOPs). This study prepared manganese ferrite-modified cow-manure biochar composites (BC-FM) as peroxymonosulfate activators to remove sulfamethazine (SMT) and sulfonamide-resistant bacteria (SA-ARB) from wastewater. The extensive conjugated graphitic structure in biochar induced Fe 3d orbital electron reconstruction, promoting empty orbitals formation and enhancing peroxymonosulfate inner-sphere complexation. This facilitated 100 % electron-transfer-dominated nonradical regulation. BC-FM exhibited remarkable catalytic performance, with apparent rate constant of 0.170 min−1 for SMT, inactivating ∼8.6 log of SA-ARB, and effectively blocking horizontal transfer of antibiotic resistance genes in both single and complex pollution systems (SMT/SA-ARB). Moreover, ion leaching experiments, cycling tests, real-water experiments, fluidized-bed and fixed-bed experiments demonstrated BC-FM’s potential for prolonged utilization and practical implementation. This study offers new insights into designing high-performance, environment-friendly bimetal catalysts and provides a basis for remediating organic contaminants with SR-AOPs in livestock wastewater.

Non-radical activation of peracetic acid by Fe-Co sulfide modified activated carbon for the degradation of refractory organic matter

Recently, the non radical activation system had attracted much attention due to its strong anti-interference ability. In this study, a novel FeCo2S4/activated carbon (AC) catalyst was prepared and used to construct a non radical dominated degradation system. Due to the electron-donating groups (C-OH) of AC and the conversion of free radicals generated from the activation of PAA by iron (Fe) and cobalt (Co) ions, a large amount of singlet oxygen (1O2) were produced, making the activation system possessed excellent universality and applicability for the removal of organic pollutants. Within 5 min, about 89.87 % of tetracycline hydrochloride (TCH) was removed in FeCo2S4 /AC + PAA. After only 20 min of reaction, the TCH removal efficiency reached 94.12 %, accompany with the reaction rate reached 0.099 min−1. Other organic pollutants including ibuprofen (IBU), sulfamethoxazole (SMX), ciprofloxacin (CIP), p-nitrophenol (PNP) and atrazine (ATZ) were also efficiently removed within 20 min, with the removal efficiencies were 92.0 %, 91.5 %, 89.4 %, 88.3 %, and 84.5 %, respectively. When the solution pH changed from 5.01 to 9.48, FeCo2S4 /AC also showed excellent catalytic performances, with the TCH removal rates were maintained at over 85.18 %. Moreover, the removal rate of TCH still reached 90.23 % after 5 recycles. This study offered an efficient non-radical peracetic acid (PAA) activation system, which can be effectively used to degrade refractory organic pollutants from complex water environment.

Oxygen vacancy-dependent synergistic disinfection of antibiotic-resistant bacteria by BiOBr nanoflower induced H2O2 activation

Antibiotic-resistant bacteria (ARB) and antibiotic-resistant genes (ARGs) pose a significant threat to both ecosystems and human health. Owing to the excellent catalytic activity, eco-safety, and convenience for defect engineering, BiOBr with oxygen vacancies (OVs) of different density thus were fabricated and employed to activate H2O2 for ARB disinfection/ARGs degradation in present study. We found that BiOBr with OVs of appropriate density induced via ethanol reduction (BOB-E) could effectively activate H2O2, achieving excellent ARB disinfection and ARGs degradation efficiency. Moreover, this disinfection system exhibited remarkable tolerance to complex water environments and actual water conditions. In-situ characterization and theoretical calculations revealed that OVs in BOB-E could effectively capture and activate aqueous H2O2 into HO· and O2·−. The generated reactive oxygen species combined with electron transfer could damage the cell membrane system and degrade genetic materials of ARB, leading to effective disinfection. The impressive reusability, high performance achieved in two immobilized reaction systems (packed column and baffled ditch reactor), excellent degradation of emerging organic pollutants supported the feasibility of BOB-E/H2O2 system towards practical water decontamination. Overall, this study not only provides insights into fabrication of bismuth-based catalysts for efficient ARB disinfection/ARGs degradation via OVs regulation, but also paves the way for their practical applications.

Amino-rich silicon quantum dots as efficient activator with intrinsic chemiluminescence for the detection of peroxydisulfate

The specific detection of peroxydisulfate (S2O82−, PDS) is significant and challenging due to the rapid development of PDS-related technologies and their widespread application in multiple fields. However, traditional analytical methods are mainly based on their strong oxidizing properties, making it difficult to simultaneously achieve specific identification and high sensitivity for PDS detection in complex water environments. Here, we purposely prepared amino-rich SiQDs (N-SiQDs) as an effective catalyst and introduced H2O2 acts as a co-reactant for PDS activation and determination with strong intrinsic chemiluminescence (CL) emission. High yield of reactive active oxygen (mainly O2˙− and ˙OH) were generated during CL process, which trigger electron-hole annihilation between the N-SiQDs˙+ and N-SiQDs˙− accounted for extraordinary CL emission. On this basis, a new CL assay for PDS detection was fabricated with broad linear range of 5 × 10−7M-5 × 10−5 M and low detection limit (3.2 × 10−7 M). Due to the absence of SO4˙− involvement during CL emission, the sensing platform is sensitive enough, satisfactory selectivity and does not respond to transition-metal ions and inorganic anions that have interferences in the PDS CL sensors reported before. This work not only deepens insight into the mechanisms of nanomaterials assisted PDS activation but also provides a new perspective on the modified metal-free QDs CL probe for chemical species detection.

Hydrothermal carbonization of coking sludge: Migration behavior of heavy metals and magnetic separation performance of hydrochar

This study comprehensively investigated the migration behavior and environmental risk of heavy metals (HMs) during the hydrothermal carbonization (HTC) of coking sludge (CS). The results indicated that over 90 % of HMs accumulated in the coking sludge hydrochar (CHC). The decomposition and loss of organic matter led to an increased concentration of HMs with rising temperatures. However, HTC also facilitated the transformation of HMs from bioavailable fractions to more stable fractions. Higher hydrothermal temperatures positively influenced the control of HMs' environmental risks. Ecological risk assessments revealed that the Potential Ecological Risk Index (RI) values of HMs in CHC decreased from 631.15 to 134.23, reaching considerate risk levels. Risk assessment codes indicated that, except for Mn, other HMs were reduced to no risk or low risk after hydrothermal treatment. Furthermore, the magnetic separation performance of CHC was explored, and its practical value was validated using a semi-continuous adsorption-separation device. The results showed that CHC achieved removal rates of 80.41–87.15 % for Congo red (CR) and tetracycline (TC), maintaining stability in various complex water environments. The CHC was rapidly separated after adsorption with a simple magnetic field, achieving a separation and recovery rate of over 80 %. These findings provided theoretical support for the stabilization of HMs in CS and the resource utilization of hydrochar in water treatment applications.

Simple synthesis of 2D/3D mpg-C3N4/ZnO nanocages with built-in driven Z-scheme heterostructures: Photocatalytic degradation of tetracycline antibiotics and lifting the limitation of the complex water environment

Tetracycline antibiotics have attracted attention due to their difficulty in being degraded by the natural environment. In this work, 2D/3D mesoporous graphitic carbon nitride (mpg-C3N4)/ zinc oxide (ZnO) hollow nanocage (MCNZH) complexes with Z-scheme heterostructure were prepared for the photocatalytic degradation of tetracycline antibiotics. The catalysts were characterized by SEM, TEM, BET, XRD, FT-IR, EIS, etc. The degradation of tetracycline hydrochloride (40 mg L–1) by MCNZH (1.2 g L–1) can reach 92.08 %. Further, the energy band structure of the catalysts were calculated and the possible degradation mechanism was proposed. The results showed that ·OH– and ·O2– were the main active species, and the internal electric field suppressed the compounding of photogenerated carriers. The catalysts exhibited broad-spectrum degradation of tetracycline antibiotics. Practical sample spiking experiments on soil and river water confirmed its practicability, which provide great significance for the application of the photocatalytic technology in the practical environmental purification.

Decomposition of tetracycline with peroxymonosulfate activated by an ordered hierarchical pores Fe-N/C catalyst rich in FeNx sites: Insights into singlet oxygen mechanism

FeNx sites show significant superiority in the degradation of antibiotic contaminants, but there are difficulties in successfully constructing highly dispersed FeNx sites. In this work, Fe-N/C catalysts doped with hierarchical ordered pores structure and FeNx active sites were prepared by metal node exchange strategy. Among them, Fe-N/C-2 had more excite species for peroxymonosulfate (PMS) owing to the synergy between Fe and N coordination, which achieved 89.36 % tetracycline (TC) removal rate within 20 min, and its reaction kinetic (k = 0.245 min−1) is 7.66 times more than original PMS system. Moreover, the material exhibited excellent activation performance in a variety of complex water environments, such as the coexistence of multiple anions, strong acids and alkalis (pH = 2.90 ∼ 10.73), and natural organic matter interference. Chemical bond detection confirmed the successful formation of FeNx sites, free radical trapping experiments showed that FeNx was the main catalytic site, and 1O2 was the main active component. Furthermore, the reaction principle of the FeNx site catalyzing the production of 1O2 from PMS was revealed in detail through mechanism exploration. Next, the probable pathways of TC decomposition were elaborated in terms of the intermediates identified by Liquid Chromatograph Mass Spectrometer (LC-MS). This study emphasized the significant potential of synthesizing Fe-N/C catalysts with activated FeNx sites, elucidated mechanism of FeNx in PMS activation, and confirmed its feasibility in TC degradation.

A synergistic adsorption-catalysis with co-doped Fe/Mn porous PET waste for simultaneous and ambient remediation of hazardous pharmaceutical drugs and dye in multi-component systems by enhancing singlet oxygen

Valorizing single-use plastic waste as an effective activator in environmental protection has gained great interest from policymakers, legislators, and scientific research communities. Herein, low-cost and highly porous alkali Fe/Mn-doped carbon nanomaterials derived from polyethylene terephthalate (PET) waste (MF/cPET-x) were fabricated via facile pyrolysis and alkali-metal impregnation methods. Detailed characterizations of MF-cPET-x demonstrated that the ratio of alkaline impregnation and pyrolysis temperature affects the porous characteristics, content, and size of active sites, specific surface area, and yield of carbon residue/nanocomposite. The main aim of this study was to evaluate and optimize the MF/cPET-x applied for the detoxification of various kinds of pharmaceutical drugs (tetracycline, naproxen, paracetamol, and levofloxacin) and various dyestuff in their single, binary, ternary, and quaternary solutions. The magnetic porous MF/cPET-1 was found to show a most effective PMS activation for single/multiple toxic pollutants removal attaining levels >91.0 % in a wide range of temperatures (5–35 °C) and pH (3.0–9.0), without significant detectable metal leaching (>0.16 mg L−1). The outstanding catalytic performance in complex water environments was mainly attributed to the deposition of Mn/Fe nanoparticles with small grain size on a polymeric scaffold, bimetal synergistic effect, high specific surface area, high stability, and excellent anti-interference capability against coexisting substances. Physicochemical properties of the recycled composite, masking, and EPR analyses confirmed that the dominant reactive species in the following order: 1O2 > OH > SO4− > O2−. This work offers a new and straightforward approach for preparing porous alloy composite from plastic waste for pollutant degradation in various water matrices.

Multi-dimensional signals coupling of simultaneous acquisition stripping current with laser-induced breakdown spectroscopy for accurate analysis of Cd(II) in coexisting Cu(II)

BackgroundDespite significant advancements in detecting Cd(II) using nanomaterials-modified sensitive interfaces, most detection methods rely solely on a single electrochemical stripping current to indicate concentration. This approach often overlooks potential inaccuracies caused by interference from coexisting ions. Therefore, establishing multi-dimensional signals that accurately reflect Cd(II) concentration in solution is crucial. ResultsIn this study, we developed a system integrating concentration, electrochemical stripping current, and laser-induced breakdown spectroscopy (LIBS) characteristic peak intensity through in-situ laser-induced breakdown spectroscopy and electrochemical integrated devices. By simultaneously acquiring multi-dimensional signals to dynamically track the electrochemical deposition and stripping processes, we observed that replacement reactions occur between Cu(II) and Cd(II) on the surface of Ru-doped MoS2 modified carbon paper electrodes (Ru-MoS2/CP). These reactions facilitate the oxidation of Cd(0) to Cd(II) during the stripping process, significantly increasing the currents of Cd(II). Remarkably, the ingenious design of the Ru-MoS2 sensitive interface allowed for the undisturbed deposition of Cu(II) and Cd(II) during the electrochemical deposition process. Consequently, our in-situ integrated device achieved accurate detection of Cd(II) in complex environments, boasting a detection sensitivity of 8606.5 counts μM⁻1. SignificanceBy coupling multi-dimensional signals from stripping current and LIBS spectra, we revealed the interference process between Cu(II) and Cd(II), providing valuable insights for accurate electrochemical analysis of heavy metal ions in complex water environments.

Curvature strain tunes electron transfer accelerates peroxymonosulfate activation to achieve high-efficiency advanced oxidation

The development of high performance and stable heterogeneous catalysts is conducive to promoting the advanced oxidation process (AOPs) to promote the degradation of organic pollutants efficiently, low-cost and environmentally friendly. Here nitrogen-doped hollow carbon spheres (NHCSs) and rigid organic molecule were used to create space confinement and complexation confinement conditions, respectively, and an advanced single-atom catalyst capable of strongly activating peroxymonosulfate (PMS) to degrade organic pollutants was finally constructed. The AOPs system driven by CoNC/NHCSs (20 mg) combined with PMS (20 mg) can degrade nearly 100 % of 20 mg/L (100 mL) bisphenol A (BPA, a microplastic) pollutant within 30 min, and the mineralization rate is up to 70.5 %. Face the complex water environment, such as sewage containing coexisting anions and cations, or acidic or alkaline sewage, the CoNC/NHCSs/PMS system still has high catalytic stability, and universality for other organic pollutants. The filter column with CoNC/NHCSs as the core also realizes the continuous purification of organic pollutants, which shortens the distance between laboratory research and practical application. Radical quenching and electron paramagnetic resonance techniques confirmed that CoNC/NHCSs activated PMS to SO4·−, ·OH, and 1O2, and these reactive oxygen species combined to eliminate organic pollutants. Density functional theory (DFT) calculations jointly confirm that the strong activation of PMS by CoNC/NHCSs is the key to achieving efficient degradation of organic pollutants, and the activity of CoNC/NHCSs is derived from high exposure rate of active sites and curvature effect caused by structural bending.

Efficient removal of diclofenac sodium from aqueous environments by magnetic ionic covalent organic frameworks based on polydopamine: Adsorption performance and mechanism study

In recent years, ion covalent organic frameworks (iCOFs) have shown excellent adsorption performance in the removal of non-steroidal anti-inflammatory drugs (NSAIDs), but powdered iCOFs are faced with problems in separation and recovering from solution and are prone to environmental pollution. In this work, polydopamine (PDA) was used as the mediated coating, Fe3O4 as the magnetic nucleus, and iCOFs consisting of benzene-1,3,5-triscarbaldehyde (BT) and 1,3-diaminoguanidine hydrochloride (DGCl) as organic ligands were in-situ grown on the surface of the PDA coating by Schiff base reaction, resulting in a magnetic nanocomposite (Fe3O4@PDA@BT-DGCl) with a coral-like structure. The adsorption kinetics and adsorption isotherms showed that the adsorption behavior of diclofenac sodium (DS) on Fe3O4@PDA@BT-DGCl followed the pseudo-second-order kinetic model and Langmuir model, and the maximum adsorption capacity could reach up to 420.17 mg g−1 (25 ℃, pH 5). The adsorption of DS on Fe3O4@PDA@BT-DGCl was dominated by electrostatic interactions, along with hydrogen bonding, π-π interactions, and ion exchange, according to the analysis of the adsorption mechanism. The Fe3O4@PDA@BT-DGCl consistently maintained high adsorption efficiency after six adsorption–desorption cycles, making it an efficient adsorbent for the removal of NSAIDs in complex water environments.

A Review on the Video-Based River Discharge Measurement Technique.

The hydrological monitoring of flow data is important for flood prevention and modern river management. However, traditional contact methods are increasingly struggling to meet the requirements of simplicity, accuracy, and continuity. The video-based river discharge measurement is a technique to monitor flow velocity without contacting the water body by using the image-recognition algorithms, which has been verified to have the advantages of full coverage and full automation compared with the traditional contact technique. In order to provide a timely summary of the available results and to inform further research and applications, this paper reviews and synthesizes the literature on the general implementation routes of the video-based river discharge measurement technique and the principles and advances of today's popular image-recognition algorithms for velocity detection. Then, it discusses the challenges of image-recognition algorithms in terms of image acquisition conditions, parameter uncertainties, and complex meteorological and water environments. It is concluded that the performance of this technique can be improved by enhancing the robustness and accuracy of video-based discharge measurement algorithms, minimizing weather effects, and improving computational efficiency. Finally, future development directions for further perfecting this technique are outlined.