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Based on the enhanced heat transfer technology of the torsional flow heat exchanger (TFHE), the characteristics of fluid flow and heat transfer in the TFHE with twisted oval tube (TOT) were analyzed by combining numerical simulation and theoretical analysis. The field synergy principle was used to evaluate thermal convection on both tube and shell sides. The influences of the TOT on the heat transfer enhancement and flow resistance performance of the TFHE were discussed. The results show that contrasted with smooth tube, on the tube side, the convective heat transfer coefficient of the TOT is increased by 25.17–38.28%, and the comprehensive performance is increased by 18.56–24.21%. On the shell side, the convective heat transfer coefficient is increased by 117.99–126.53%, and the comprehensive performance is increased by 40.82–48.28%. The study provides a reference for the development of shell-and-tube heat exchangers.

Shell and tube heat exchanger is an important part of industrial heating and cooling system. Because of the harsh operating conditions, and its complex fin and baffle structure with numerous holes, it is a great challenge for engineers to design and evaluate the baffle structure on the premise of ensuring the comprehensive performance. This paper aims to provide a method to optimize the baffle structure of torsional flow heat exchanger by comprehensively considering thermal, hydraulic, and mechanical properties. Based on fluid-structure interaction method, response surface methodology was applied to improve the structure configurations of torsional flow heat exchanger. The results show that the effects of various input parameters on objectives are related to each other, and the baffle width and inclination angle have a more obvious impact on heat exchanger. The tradeoff analysis is carried out for the optimization objectives, the candidate points obtained by optimization reveal that the fluid comprehensive performance of the optimal structure is increased by 10.99%, and the maximum equivalent stress is reduced by 8.74%. The research results offer theoretical guidance for the equipment maintenance and structural design of torsional flow heat exchanger.

A novel Z-scheme heterojunction photocatalyst Bi-BOC/BO-OVs was successfully prepared. OVs and metal Bi enhanced light response and separation of photoinduced carriers. Thus, catalyst showed superior catalytic activity in simulated water matrices.

Adopting enhanced tube is an effective way to enhance the performance of a shell-and-tube heat exchanger. In this paper, a drop-shaped tube with stream?lined cross-section was used to enhance heat transfer of the torsional flow heat exchanger. The characteristics of the fluid-flow and heat transfer in torsional flow heat exchanger with drop-shaped tube were studied numerically, considering three kinds of axis ratios (a/b=1.5, 1.8, 2) of the tube. The reliability of numerical results was verified through experimental results. The results indicate that the wake size of the streamlined drop-shaped tube is smaller than that of the conventional smooth tube, and the drop-shaped tube reduces the flow dead zone in torsional flow heat exchanger. As the axis ratio of a/b increases, the shell side Nusselt number and comprehensive performance increase, due to enhancement of the turbulence kinetic energy of the transition section. When the axis ratio is 2, the Nusselt number is increased by 12.44-18.99%, and the comprehensiveness is increased by 13.27-19.2%, compared with the torsional flow heat exchanger with the smooth tube. The quantitative analysis of the velocity indicates that the relative magnitude and proportion of transverse velocity components of fluid are important factors affecting the thermal-hydraulic performance of torsional flow heat exchanger.

By using the residence time distribution method (RTD), the fluid retention zones in the shell and tube heat exchanger with segmental baffle (STHX-SB) and the heat exchanger with helical baffle (STHX-HB) are compared and discussed. The flow pattern and fluid retention zone of the similar double helical flow heat exchanger (STHX-SDH) were analyzed by using the same method. The result shows the spiral flow can reduce the fluid retention zone. The flow pattern in the STHX-SDH likes a double helical shape and leads to a very small fluid retention zone. According to the simulation results, the location of the fluid retention zone of STHX-SDH is determined. The verification line method and the zone assessment method were adopted, to discuss the flow velocity of each point on the verification line and the average flow velocities of the selected zones. The change laws of the flow velocities on the verification lines and the average flow velocities of the selected zones at different Reynolds numbers were compared. The result reveals the distribution of the fluid retention zone of the STHX-SDH and the sensitivity of each fluid retention zone to the Reynolds number. By optimization of the angle of the baffle, the volume fraction of the fluid retention zone is reduced to 1.61%, and the heat transfer performance is improved by 13.23%. It is verified that reducing the fluid retention zone can effectively enhance the heat transfer performance. This research method provides a theoretical basis for reducing the fluid retention zone of the heat exchanger and enhancing heat transfer performance.

Effective photoexcitation and carrier migration are the essential aspects to strengthen semiconductor-engaged redox reaction. Herein, a three-dimensional thin-wall hollow porous cystic-like g-C

The progress of high-efficiency photocatalysts and the suppression of photoinduced charge recombination remain the primary goals for practical applications. In this study, we demonstrate the convenient synthesis of graphite carbon nitride nanobelts (CNNB) for the enhanced photocatalytic degradation of organic contaminants through peroxydisulfate (PDS) activation. In operation, the PDS serves as an electron acceptor, whereas the organic pollutants acts as hole catchers, thus achieving an external dual transmission mechanism. Consequently, the CNNB/PDS system shows outstanding photocatalytic performance for the removal of sulfamethazine (SMT) under blue-LED light irradiation, which was ∼17- and ∼5 times more efficient than pristine g-C3N4/PDS and CNNB, respectively. Furthermore, a potential SMT degradation pathway was deduced based on the detection of degradation intermediates and theoretical calculations. Finally, reactions looking at several influencing factors indicated that the CNNB/PDS system could be used far more productively for the removal of SMT under ambient aqueous conditions. Hence, this synergistic external dual transmission mechanism process might serve as a promising technology for the removal of organic pollutants.

Extensively used bisphenol A (BPA) in industry aggravates the pollution of water environment. Thus, we are committed to developing an efficient adsorbent to remove BPA, exploring the adsorption performance and mechanism. Here, a novel nitrogen-containing covalent organic framework, named PyTTA-Dva-COF as an effective adsorbent for removing BPA from aqueous solutions was prepared by a simple solvent-thermal method. PyTTA-Dva-COF exhibited uniform nanofibrous structure, abundant and robust C=N functional groups, as well as high chemical stability. The saturated adsorption capacity is 285 mg/g, and the adsorption process conforms to Langmuir isotherm model. The kinetic data conforms to the pseudo-second-order kinetic model, and the thermodynamic parameters, ∆G°

As one of the most toxic heavy metal ions, lead pollution has become an urgent problem. Here, a cubic crystal nanoparticle (Prussian blue analogue, PBA), referred to as potassium manganese ferrocyanide (KMFC) was synthesized and used as a highly-effective sorbent for removing Pb(II) from aqueous solution. KMFC is a mesoporous material that has excellent ion exchange properties, which was confirmed by a series of characterizations. This paper investigated the adsorptive attributes of KMFC for lead ions in aqueous solution. The influences of temperature, contact time and pH on adsorption were studied in batch experiments. The KMFC possessed a robust adsorption capacity for resident lead ions in aqueous solution, which attained 1075.27 mg g−1 at room temperature (25 °C), based on the Langmuir model, which was far higher than any previously reported values. The adsorption process was well fitted to a pseudo-second-order kinetic model, as well as Langmuir and Temkin isotherm models, and was endothermic and spontaneous on the basis of thermodynamic analysis. The adsorption of Pb(II) on the surface of KMFC started with electrostatic attraction, due to the electronegativity of KMFC. Further, ion exchange was the dominant mechanism in this adsorption process, which was confirmed by FTIR, XPS, and other supplementary experiments. The good chemisorption (K+ exchange) properties of KMFC suggested that it likely has excellent prospects in applications for heavy metal ions adsorption. This study not only provided a new perspective for the design and development of heavy metal sorbents but provided a deep insight into the mechanism of adsorption of heavy metal ions by PBA.

The adsorbents for water treatment and purification are commonly not recyclable because of the lack of a reagent-less "switch" to readily release the adsorbed compounds. Herein, the interface of Bi2O2CO3 (BOC) nanosheets is designed, synthesized, and modified with citric acid, namely, modified Bi2O2CO3 (m-BOC). The m-BOC is able to selectively adsorb methylene blue (MB) in the dark and the adsorbed MB could be released in the light from m-BOC without the addition of any chemicals. The adsorption mechanism is attributed to the electrostatic attraction between positively charged MB and the negatively charged surface of m-BOC. In contrast, the desorption of MB has resulted from the photo-induced charge redistribution on the surface of m-BOC, which unlocks the coordination bond between m-BOC and the carboxylic group. As a result, BOC is recycled. Such a mechanism was verified by both experimental investigation and DFT calculation. This work provides a promising interfacial engineering strategy for the remediation of dye-polluted water and smart separation in chemical engineering.

Tartaric acid (TA) is an important component of plant rhizosphere secretion, having a certain influence on the adsorption and desorption behavior of heavy metals in soil. Humin could serve as an environmentally compatible passivator of heavy metal in soil. The aims of this study were to simulate the adsorption of Pb (II) via humin in a soil solution, explore the effects of TA on the adsorption of Pb (II) by humin and elucidate the mechanism of its influence. The results indicated that the adsorption of Pb (II) on the surface of humin within and without TA was consistent with the Langmuir isotherm equation and the pseudo-secondary kinetic model (R2 > 0.99). The effect of TA on adsorption was related to the concentration of TA. With the increasing of TA concentration, the adsorption of Pb (II) by humin showed a peak change and the adsorption amount reached the maximum with 0.5 mmol L−1 humin, is 192.31 mg L−1 with 0.1 mmol TA. Basing on adsorption experiments and characterization of FTIR, SEM, EDX and XPS. It revealed that the oxygenated groups of TA can be combined with humin by hydrogen bonding, in the low concentration TA (less than 0.5 mmol L−1), which is equivalent to an increment of the carboxyl group on the surface of humin, thus adsorption amount was increased. The increasing of the concentration of TA led to an increment of free TA in the solution, which would complex with the lead ions in the solution, and indirectly reduce the amount of Pb(II) adsorption on the humin.

Stimulator of interferons genes (STING), which is crucial for the secretion of type I interferons and proinflammatory cytokines in response to cytosolic nucleic acids, plays a key role in the innate immune system. Studies have revealed the participation of the STING pathway in unregulated inflammatory processes, traumatic brain injury (TBI), spinal cord injury (SCI), subarachnoid haemorrhage (SAH) and hypoxic–ischaemic encephalopathy (HIE). STING signalling is markedly increased in CNS injury, and STING agonists might facilitate the pathogenesis of CNS injury. However, the effects of STING-regulated signalling activation in CNS injury are not well understood. Aberrant activation of STING increases inflammatory events, type I interferon responses, and cell death. cGAS is the primary pathway that induces STING activation. Herein, we provide a comprehensive review of the latest findings related to STING signalling and the cGAS–STING pathway and highlight the control mechanisms and their functions in CNS injury. Furthermore, we summarize and explore the most recent advances toward obtaining an understanding of the involvement of STING signalling in programmed cell death (autophagy, necroptosis, ferroptosis and pyroptosis) during CNS injury. We also review potential therapeutic agents that are capable of regulating the cGAS–STING signalling pathway, which facilitates our understanding of cGAS–STING signalling functions in CNS injury and the potential value of this signalling pathway as a treatment target.

Highly efficient oxidation, as non-thermal regeneration technology, is a promising method to solve the regeneration problem of spent activated carbon (AC) in wastewater treatment. In this study, FeOCl was confined into activated carbon (FeOCl/AC) for catalytic oxidation of contaminants on AC during the regeneration process. The characterization results of FeOCl/AC showed that amorphous FeOCl was distributed in micropores, mesopores and macropores of AC. The methylene blue (MB)-adsorbed FeOCl/AC had a regeneration efficiency of 93.7 % at neutral pH in the presence of H

The advanced oxidation processes (AOPs) was regarded as one of the effective strategies for the degradation of organic pollutant. Herein, anovel Z-scheme type MoO3/g-C3N4 composite photocatalyst synergize with peroxydisulfate (PDS) to enhanced photocatalytic activity. Systematic studies indicated that the synergistic MoO3/g-C3N4/PDS photocatalyticsystem exhibited significantly enhanced photocatalytic activity for the degradation of ofloxacin (OFLX) in contrast to MoO3/g-C3N4 and pure g-C3N4. A 94.4% removal efficiency could be accomplished with 0.6 g/L catalyst and 5 mM peroxydisulfate (PDS) under visible light within 120 min.The enhanced photocatalytic performance of MoO3/g-C3N4/PDS could be attributed to the capture of the photoinduced electrons of PDS as well as the generation of SO4•− which can oxidize water to generate •OH. Quenching experiments revealed that O2•− and h+were the dominant active species involved in the MoO3/g-C3N4/PDS system under visible light irradiation. Degradation pathways of OFLX were then proposed based on the identification of intermediates. Reactions in inorganic anions aqueous solutions showed that MoO3/g-C3N4/PDS system provided a superior approach for the remediation of OFLX from aqueous solutions.

Non-metal doping has been frequently used in g-C3N4 (CN) as a feasible and economical technique for maintaining its metal-free properties, while improving its photocatalytic performance. In this study, a novel phosphorus and oxygen co-doped graphitic carbon nitride (POCN) was successfully synthesized through a one-step thermal polymerization method and exhibited remarkable photocatalytic activity for the photocatalytic degradation of fluoroquinolones (FQs). The degradation rate of enrofloxacin (ENFX) was 6.2 times higher than that of CN. Based on the results of X-ray photoelectron spectroscopy (XPS) and nuclear magnetic resonance spectroscopy (NMR), P atoms replaced the corner and bay carbon sites, whereas O atoms replaced the nitrogen sites in the g-C3N4 framework. The improvement of the photocatalytic effect of POCN0.01 was attributed to its narrow bandgap, effective charge separation and enhanced specific surface area. This is the first report to describe the use of phosphorus doping to promote the generation of reactive oxygen species (ROS). ROS scavenging tests revealed that O2 − was the primary active species during the degradation of ENFX. Furthermore, pathways for the degradation of ENFX were proposed via the detection of intermediate products via HRAM LC–MS/MS and the prediction of active sites using the Fukui function.

In this study, the objective was mainly focusing on the mechanism investigation of ciprofloxacin (CIP) degradation by photocatalytic ozonation process which carried out by ozone and TiO2 with a low content of carbon-dots (CDs) under simulated sunlight irradiation. The physicochemical properties of the prepared photocatalysts were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscope (SEM) X-ray photoelectron spectroscopy (XPS) and zeta potential. Comprehensive investigation has proven the process to be efficient in the removal of CIP with high yield of reactive species (OH, O2-, h+, etc.). Kinetic model on pH investigation found out a repulsive force between the photocatalysts and CIP intensified with the increasing pH, so did the production rate of hydroxyl radicals (OH), while eventually reached a balance and achieved a maximum degradation rate. The results indicated that the enhancement mechanism was triggered by the photoexcited electron accumulated on CDs and transferred by ozone, resulting in the continuous generation of h+, O3- and O2-. Possible photocatalytic ozonation degradation pathways of CIP were proposed according to the identifications of intermediates using high-resolution accurate-mass spectrometry (HRAM) LC-MS/MS.

Acyclovir (ACV), an anti-virus drug, was widely detected in natural water at concentrations ranging from ng L−1 to μg L−1 due to inefficient biological treatments in sewage treatment plant. Photochemical experiments involving the irradiation from a xenon lamp simulating sunlight were conducted to explore the environmental behavior and potential risks of ACV. Isopropanol was used as a radical trapping agent for mechanism research, and the toxicity of the photoproducts of ACV was evaluated by the acute toxicity test of Photobacterium phosphoreum T3 spp. The results indicated that the ACV photodegradation followed pseudo first-order reaction kinetics, and the ACV removal rate increased when the pH was elevated from 5 to 10. The photochemical reaction pathway revealed by HPLC–MS/MS suggested that the C–C bond and C–N bond of ACV could be attacked by ·OH; thus, the photoproducts were mostly composed of hydroxyl substitution products. The intermediate photoproducts in the course of photodegradation exhibited a higher toxicity than the parent ACV, and the highest toxicity effect was observed at 6 h, which implied that the photoproducts of ACV might pose a great potential risk on aquatic environments.

A copper ferrite modified graphitic carbon nitride (CuFe2O4/g-C3N4) nanocomposite was successfully synthesized for the utilization as a visible-light responsive photocatalyst. The as-synthesized catalysts were characterized using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), UV–vis diffuse reflectance spectra (UV–vis/DRS), photoluminescence (PL) analysis, and an electrochemical workstation. Compared to g-C3N4 and CuFe2O4, the CuFe2O4/g-C3N4 composites possessed excellent photocatalytic performance for the destruction of propranolol (PRO). A removal efficiency of 82.2% was achieved with 1 g/L catalyst and 1 mM peroxydisulfate (PDS) under visible light irradiation (λ −), h+, hydroxyl radicals ( OH), and sulfate radicals (SO4 −). Moreover, the byproducts of PRO were investigated by HPLC-MS/MS, and the transformation pathways under the Vis/g-C3N4/CuFe2O4/PDS process were tentatively proposed based on the intermediates. The research provided a potential approach of CuFe2O4 modified g-C3N4 as a photocatalyst combined with PDS for the treatment of contaminated water.

In recent years, how to effectively remove emerging organic pollutants in water bodies has been studied extensively, especially in the actual complex water environment. In the present study, an effective wastewater treatment system that combined photocatalysis and an oxidizing agent was investigated. Specifically, visible-light driven reduced graphene oxide (RGO)/TiO2 composites were prepared, and peroxodisulfate (PDS) was used as electron acceptor to accelerate the photocatalytic activity of this material. The vis-RGO/TiO2/PDS system exhibited outstanding properties in the degradation of diclofenac (DCF), which was also facilitated by acidic conditions and Cl-. Lake water, tap water, river water and HCO3- decreased the DCF degradation rate, while NO3- affected the system only slightly. Low concentrations of fulvic acid (FA) promoted the degradation of DCF via the generation of excited states, whereas a high concentration of FA inhibited the degradation, which was likely due to the light screening effect. The photocatalytic mechanism revealed that PDS served as an electron acceptor for the promotion of electron-hole pair separation and the generation of additional reactive oxygen species, while the RGO served as an electric conductor. The active substances, h+, OH, 1O2, SO4- and O2- were generated in this system, O2- and h+ played significant roles in the degradation of DCF based electron spin resonance tests and radical quenching results. According to the mass spectrometry results, the amide bond cleavage, dechlorination reaction, hydroxyl addition reaction, and decarboxylation reaction were the primary transformative pathways.

The extensive use of bisphenol analogues in industry has aggravated the contamination of the water environment, and how to effectively remove them has become a research hotspot. This study presents two imine-based covalent organic frameworks with different pore sizes (COFs) [TAPB (1,3,5-tris(4-aminophenyl)benzene)-Dva (2,5-divinylterephthaldehyde)-PDA (terephthalaldehyde) (COF-1), and TAPB (1,3,5-tris(4-aminophenyl)benzene)-Dva (2,5-divinylterephthaldehyde)-BPDA (biphenyl dialdehyde) (COF-2)], which have achieved the efficient adsorption of bisphenol S (BPS) and bisphenol A (BPA). The maximum adsorption capacity of COF-2 for BPS and BPA obtained from Langmuir isotherms were calculated as 200.00 mg g

This paper aims to provide insights on mechanochemistry as a green and versatile tool to synthesize advanced materials for water remediation. In particular, mechanochemical methodologies for preparation of reagents and catalysts for the removal of organic pollutants are reviewed and discussed, focusing on those materials that, directly or indirectly, induce redox reactions in the contaminants (i.e., photo-, persulfate-, ozone-, and Fenton-catalysts, as well as redox reagents). Methods reported in the literature include surface reactivity enhancement for single-component materials, as well as multi-component material design to obtain synergistic effects in catalytic efficiency and/or reactivity. It was also amply demonstrated that mechanochemical surface activation or the incorporation of catalytic/reactive components boost the generation of reactive species in water by accelerating charge transfer, increasing superficial active sites, and developing pollutant absorption. Finally, indications for potential future developments in this field are debated.

Photocatalytic degradation of typical pharmaceuticals in natural sunlight and in actual water is of great significance. In this study, the oxygen or nitrogen linked heptazine-base polymer (ONLH) was successfully incorporated with TiO

Hydrogen peroxide (H2O2) and superoxide radical (O2˙−) play a critical role in environmental remediation technologies. Here, we report on metal-free co-catalysts with the in situ incorporation of carbon dots (CDs) into a polymeric O and N co-linked carbon nitride (OCN) framework, which significantly enhanced the synthesis of H2O2 and O2˙− due to dual reactive sites. For the photocatalytic degradation of a typical pharmaceutical and personal care product (PPCP), CDs/OCN demonstrated excellent photocatalytic performance in contrast to g-C3N4 and OCN, which was 11.6 times that of pure g-C3N4. The trapping experiment has shown that O2˙− plays an important role in the degradation of DCF. CDs/OCN exhibited higher electron–hole separation efficiencies than g-C3N4 and OCN, as the result of the excellent transfer and storage performance of the CDs. The yield of H2O2 generation by CDs/OCN was higher than that by g-C3N4 and OCN. Meanwhile, the electron paramagnetic resonance (EPR) spectra revealed that additional O2˙− and ˙OH were generated via the CDs/OCN system. Density functional theory (DFT) and Raman spectroscopy analyses revealed the presence of CD/OCN-resident dual reactive sites, which had distinct selective oxygen reduction capacities. We observed that O2 was more prone to 2-electron reduction on OCN, whereas O2 was more easily reduced to O2˙− on the surface of CDs through the additional e− provided by OCN. This study clearly demonstrates a simple strategy for the design and synthesis of metal-free materials in the preparation of H2O2 and O2˙− toward the degradation of organic pollutants.

Advanced photocatalytic oxidation processes for water purification have been the subject of extensive research over the past several years; however, the low efficiency utilization of photogenerated carriers remains a major challenge. To optimize the performance of photocatalysts, we initially synthesized carbon dots (CDs) and boron nitride (BN), which were employed as photoelectron and photohole transfer receptors, respectively. These were compounded with graphitic carbon nitride (g-C3N4) to form a high-efficiency ternary photocatalytic material (CDs/g-C3N4/BN (CCN)) that possessed the double transfer characteristics of photogenerated carriers. This metal-free composite exhibited improved activity, which was ∼5 times higher than pristine g-C3N4 for the degradation of enrofloxacin under blue LED irradiation. Moreover, these hybrid photocatalysts demonstrated good reusability. According to property–photoactivity correlation analysis, the CDs and BN manifested their ability for enhancing the production of reactive oxygen species by boosting the transfer of charge carriers. Our work revealed the synergistic transfer of photogenerated electron–hole pairs to expand the use of photocatalysts, while providing a new perspective for their synthesis and development to further enrich the discipline of material design.

Climbazole (CBZ) is an emerging contaminant with adverse effects on aquatic organisms. In this study, a floral array of chromium-substituted magnetite nanoparticles was synthesized, characterized, and used in photocatalytic degradation of CBZ. The results showed that Cr incorporation did not change the spinel structure of magnetite, but resulted in the obvious decrease of its crystallinity. The Cr content greatly influenced the morphology and micro-structure of magnetite nanoparticles, which led to a significantly larger surface area, and more abundant pores and surface hydroxyl groups. Factors such as the UV light source, catalyst concentration, initial level of CBZ, solution pH, peroxymonosulfate (PMS) dosage, and Cr level in magnetite affected the transformation of CBZ. Under the optimized photocatalytic conditions, i.e., 0.2 g L−1 Fe2.52Cr0.48O4, 2.0 μmol L−1 CBZ, 1.0 mmol L−1 PMS, and pH = 3.08, CBZ was almost completely eliminated within 30 min, which was much faster than under photodegradation, biodegradation, or chlorination reported previously. The reactive oxygen species including ˙OH and SO4˙− coexisted and participated in the photocatalytic reaction. The GC-MS analysis revealed the generation of 4-chlorophenol (4-CP) as a primary intermediate following CBZ transformation, based on the stoichiometric relationship between CBZ and 4-CP. The resultant 4-CP in the present study does not increase the risk to aquatic life. The results highlight an environmentally friendly strategy for effective elimination of CBZ.

The development of broad spectrum UV–visible-near-infrared (NIR) photocatalysts is a primary strategy in the area of photocatalytically mediated pollutant elimination. Herein, we report on a novel broad-spectrum N-doped carbon quantum dot/TiO2 nanosheet with higher surface energy {0 0 1} faceted (NCDS/TNS-001) composites with significantly improved broad-spectrum utilization. Under UV, visible, and near infrared light irradiation, NCDS/TNS-001 exhibited higher photocatalytic activity than those of TNS-001, NCDs/P25, and NCDs/TiO2 with {1 0 1} facets (NCDs/T-101) toward the degradation of diclofenac (DCF). This excellent photocatalytic performance might be attributed to the synergistic effects of the highly active {0 0 1} facets, up-converted fluorescent properties of NCDs, and efficient charge separation induced by fabricated heterostructures. The determination of reactive species revealed that O2 − was the dominant species during the photocatalytic degradation of DCF. Together with the analysis of the band structure, a potential Z-scheme heterojunction mechanism for NCDs/TNS-001 was deduced. Photocatalytic pathways of the DCF were further proposed based on intermediate identification and TOC detection, which involved decarboxylation, hydroxylation, and ring opening reactions. The sufficient degradation of DCF in natural water matrices indicated that using NCDS/TNS-001 photocatalytic process for the treatment of ambient DCF wastewater is technical possible.

The development of facile and environmentally compatible synthetic strategies for broad-spectrum response photocatalysts is a primary goal for researchers in this area. For this study, we report on a template-free thermal treatment strategy for the synthesis of an oxygen-containing ultrathin porous carbon quantum dots/polymeric carbon nitride metal-free composites (CQD/OUPCN). Morphology characterization revealed that the thermal treatment induced bulk CQD/g-C3N4 (CQD/BCN) to transform to porous ultrathin 2D nanosheets with a high specific surface area. Chemical structure characterization revealed that O atoms were involved in the chemical composition of C3N4 following the introduction of CQD and subsequent thermal treatment. Optical and electrical characterization, as well as density functional theory (DFT) calculations, confirmed that the introduction of O atoms and CQD enabled the tuning of the intrinsic electronic state, and improved the charge transfer capacity of C3N4. Together with the up-converted fluorescence properties of CQD, the CQD/OUPCN exhibited remarkable broad-spectrum activity toward the degradation of PPCPs. Under visible light irradiation, the CQD/OUPCN-0.5% showed an 18.5 fold higher indomethacin (IDM) degradation rate than did g-C3N4. Further kinetics studies, including reactive species (RS) and degradation intermediate detection, indicated that RS, particularly O2˙−, was generated during the photocatalytic process, which could lead to the decomposition, and finally mineralization of IDM.

This study describes a promising porous and efficient adsorbent, a sulfonic acid (–SO3H) functionalized covalent organic framework (COF-SO3H), for the removal of pharmaceuticals and personal care products (PPCPs) in water and wastewater. COF-SO3H was prepared through introducing sulfonic acid polar functionalities via a facile solvothermal synthesis method. Studies have shown that COF-SO3H has a strong affinity for the thirteen drugs investigated in this study, especially for diclofenac (DCF). The maximum adsorption capacity for DCF was 770 mg g−1, which amounted to 9.3 times that of commercial AC, 1.5 times that of graphene oxide (GO), and 3 times that of 18% SO3-UiO-66. Further discoveries were that the adsorption isotherm data conformed well with the Langmuir model. It was also found that adsorption of DCF follows the pseudo-second-order kinetic model and thermodynamic values, ΔH < 0 and ΔG < 0, showed the exothermic nature and spontaneity of the adsorption process. Additionally, the adsorption mechanisms observed in this experiment, such as π–π interactions and the formation of hydrogen bonds, were also verified through various characterization methods. The cyclic regeneration of adsorbents and the effects of water quality constituents were estimated to assess performance in actual water/wastewater systems. Ultimately, the overall results of this study emphasized the suitability of the COF-SO3H adsorbent to remove micropollutants from real water and wastewater systems.

The adsorbents for water treatment and purification are commonly not recyclable because of the lack of a reagent-less "switch" to readily release the adsorbed compounds. Herein, the interface of Bi

Antibiotics are widespread in the environment with notable ecological risk, for which efficient and green removal technologies are demanded. As a kind of g–C3N4–based material with remarkable photocatalytic property, OCN is an oxygen- and nitrogen-linked carbon nitride organic polymer which can be synthesized through a single-step thermal polymerization method. In this study, OCN was applied for the visible-light-driven photocatalytic degradation of a typical fluoroquinolone (FQ) antibiotics enrofloxacin (ENR). The photocatalysis process achieved over 97% ENR removal within 60 min with 0.4 mg/L OCN and 4 mg/L ENR at pH 8.2. The photocatalytic mechanism of OCN at different pH was studied for the first time. It was shown that O 2 ⋅ − , 1O2 and h+ made contributions at neutral or basic pH and 1O2 contributes the most (57.6% at pH 8.2), while ⋅ OH played a role only under acidic condition with a contribution rate of 23.8% at pH 3.2. The cleavage of the piperazine ring and the quinolone ring were two main degradation pathways. The common water constituents humic acid and NO3− showed a dual effect, but HCO3− and Cl− inhibited the degradation. The effect of different water matrices was tested under natural sunlight and it was only a tiny disturbance to the degradation rates. The biotoxicity test conducted using Vibrio fischeri indicated that the toxicity of degradation products became negligible after 3 h. This study demonstrated that OCN is a promising candidate for the advanced treatment and in-situ remediation.

Hydroxyl radicals (OH) have robust non-selective oxidizing properties to effectively degrade organic pollutants. However, graphitic carbon nitride (g-C3N4) is restricted to directly generate OH due to its intrinsic valence band. In this study, we report a facile environmental-friendly self-modification strategy to synthesize reduced graphitic carbon nitride (RCN), with nitrogen vacancies and CN functional groups. The incorporation of CN enabled to downshift the valence band level, which endowed RCN with the capacity to directly generate OH via h+. Experimental and instrumental analyses revealed the critical roles of nitrogen vacancies and CN groups in the modification of the RCN band structure to improve its visible light absorption and oxidizing capacity. With these superior properties, the RCN was significantly enhanced for the photocatalytic degradation of DCF under visible light irradiation. The self-modification strategy articulated in this study has strong potential for the creation of customized g-C3N4 band structures with enhanced oxidation performance.

The development of conjugated polymers with intramolecular donor–acceptor (D-A) units has the capacity to enhance the photocatalytic performance of carbon nitride (g-C3N4) for the removal of antibiotics from ambient ecosystems. This strategy addresses the challenge of narrowing the band gap of g-C3N4 while maintaining its high LUMO position. For this study, we introduced the above donor units into g-C3N4 to construct intramolecular D-A structures through the copolymerization of dicyandiamide with creatinine, which strategically extended light absorption into the green region and expedited photoelectron separation. The introduction of electron donor blocks kept the LUMO distributed on the melem, which maintained the high LUMO energy level of the copolymer with the potential to generate oxygen radicals. The as-prepared porous D-A conjugated polymer enhanced the photocatalytic degradation of sulfisoxazole with kinetic constants 5.6 times higher than that of g-C3N4 under blue light and 15.3 times higher under green light. Furthermore, we surveyed the degradation mechanism including the effective active species and degradation pathways. This study offers a new perspective for the synchronous construction of a porous intramolecular D-A conjugated polymer to enhance water treatment and environmental remediation capacities.

Hexagonal boron nitride (BN) nanomaterials that possess an extensive specific surface area, negatively charged properties, high thermal conductivity, and excellent chemical characteristics, have significant advantages for water purification and energy storage. They are typically considered as potential catalysts due to their wide tunable bandgap. Here, carbon nitride (CN) modified BN (CMBN), which facilitated the formation of new C N B bonds, was successfully synthesized using a facile hydrothermal-calcination synthesis strategy. Such highly active bonds made the photocatalyst responsive to a wider range of wavelengths (e.g., ultraviolet to visible blue light), while significantly enhancing photocatalytic activity toward the degradation of enrofloxacin (ENFX). A 3-CMBN sample exhibited 39.3 times, and 2.4 times, higher photocatalytic properties than that of pristine BN and CN, respectively. The remarkable response of 5, 5-dimethyl-1-pyrrolidone-N-oxyl (DMPOX) was investigated through electron spin resonance spectroscopy (EPR) with 3-CMBN, which indicated higher oxidability than BN and CN under blue LED irradiation. Reactive species scavenging experiments revealed that the photodegradation of ENFX was dominated by electron holes and O2 −. Moreover, the byproducts of ENFX were detected by HPLC-Q-TOF and GC–MS, probable pathways toward these byproducts were deduced, and repeated tests confirmed good stability. These results provided a new strategy to guide the enhanced design of advanced photocatalysts with active chemical bonding species, which can be applied to environmental remediation.

Novel Sr9R(PO4)7 (R = In, Ga) host materials for Eu3+ - doped phosphors were synthesized by a high-temperature solid-state reaction method. The crystal structure, luminescence properties and thermal stability of the phosphors were explored. The phase analysis indicated that the phosphors crystallized in monoclinic structure, the emission spectra of both In and Ga containing phosphors were mainly composed of two sharp peaks centered at about 591 and 617 nm, corresponding to the 5D0→7F1 and 5D0→7F2 transitions of Eu3+ ions. While, the relative emission and excitation intensities of Sr9In(PO4)7: Eu3+ were weaker than Sr9Ga(PO4)7: Eu3+. Moreover, the energy transfer mechanism among Eu3+ ions in the phosphors depended upon energy transfer among the nearest-neighbor ions described by the Dexter theory. The selected Sr9In(PO4)7: 0.06Eu3+ and Sr9Ga(PO4)7: 0.06Eu3+ exhibited high thermal stability and the chromaticity coordinate of the phosphors were located in the red-orange light region.

Carbon quantum dots (CDs) have been frequently used for broadening spectrum light response due to their superior up-conversion photoluminescence (UPPL) property and effective charge separation capacity. In this study, a novel CDs modified Z-scheme photocatalyst (CDs/g-C3N4/MoO3) was successfully constructed. The morphologies, chemical compositions, and optical properties of the prepared catalysts were investigated via a series of characterization techniques. Systematic studies indicated that the CDs/g-C3N4/MoO3 photocatalyst exhibited remarkably enhanced visible-light photocatalytic activity for the degradation of tetracycline (TC) compared to pristine g-C3N4 and MoO3/g-C3N4 composite. Doping 0.5% CDs resulted in the highest TC degradation rate, which was 3.5 and 46.2 times higher than that of MoO3/g-C3N4 and g-C3N4, respectively. The enhanced photocatalytic performance of CDs/g-C3N4/MoO3 can be attributed to the synergistic effects of CD properties (i.e., excellent UPPL activity and high charge separation capacity and the Z-scheme heterojunction structure). Reactive species scavenging experiments revealed that photogenerated holes are the main active species during the photocatalytic process. Possible photocatalytic degradation pathways of TC were proposed through the identification of intermediates using HPLC-MS and the frontier electron density calculation. Experimental results showed that the newly fabricated Z-scheme CDs/g-C3N4/MoO3 is a promising photocatalyst for the removal of TC from the environment.

The occurrence of fluoroquinolones (FQs) in the ambient environment has raised serious concerns. In this study, the photocatalytic degradation kinetics and mechanism of ciprofloxacin (CIP) was investigated in ordered mesoporous g-C3N4 (ompg-C3N4). Under simulated sunlight irradiation, ompg-C3N4 exhibited a 2.9 fold more rapid reaction for CIP degradation than bulk g-C3N4. This enhancement may be attributed to the large specific surface area and effective charge separation of ompg-C3N4. The eradication of CIP followed the Langmuir–Hinshelwood (L–H) kinetics model, and surface reactions played a significant role during the photocatalysis process. Further study of reactive species (RSs) by both ESR technology and RSs scavenging experiments revealed that the superoxide anion radical (O2 −) and photohole (h+) were primarily responsible for the degradation of CIP. Based on the identification of intermediates using liquid chromatography with tandem mass spectrometry (HPLC-MS/MS), and the prediction of reactive sites via Frontier Electron Densities (FEDs), the degradation pathways of CIP were proposed. A comparison of the degradation among FQs revealed that the piperazine moiety showed a dramatic effect on the degradation of FQs during the photocatalysis process. A residual antibiotic activity experiment revealed that ompg-C3N4 provided a very desirable performance for the reduction of antibiotic activity. The sufficient photocatalytic degradation of CIP in ambient water revealed that a sunlight-driven ompg-C3N4 photocatalytic process may be efficiently applied for the remediation of CIP contaminated natural waters.

In this study, a novel and highly efficient ternary photocatalytic ZnFe2O4/TiO2/CDs nanocomposite was successfully synthesized by a hydrothermal method. The properties and structures of the samples were characterized by X-ray diffraction (XRD), X-ray Photoelectron Spectroscopy (XPS), Fourier transform infrared spectrometry (FT-IR), and photoluminescence spectrum (PL). The UV–vis diffuse reflectance spectrum was used to demonstrate that carbon quantum dots could increase the absorption of visible light wavelengths. When compared with TiO2/3.00 wt%CDs and ZnFe2O4/TiO2 nanocomposites, the ternary photocatalysts exhibited the enhanced photocatalytic activity under solar-spectrum irradiation. A low CDs content of 3.00 wt% in the ternary photocatalysts possessed excellent performance in the decomposition of Rhodamine B (RhB). Act as donator and receiver, CDs can efficiently improve the ability of electron transfer and separate the electron-hole pairs. OH and O2 − were confirmed to be involved in the photocatalytic degradation of RhB base on the Electron spin resonance (ESR) tests, and the photocatalytic mechanism of the ZnFe2O4/TiO2/3.00 wt%CDs was proposed. After four sequential operational cycles, the ZnFe2O4/TiO2/CDs maintained its photocatalytic efficiency, indicating its high photocatalytic stability. Therefore, our results provide a high efficient photocatalytic nanocomposite that synthetized by a facile method, and have implications in the removal of environmental persistent pollutants under ternary photocatalysts mediated solar degradation

In this study, novel carbon dots/BiPO4 (CDBP) photocatalytic complexes were successfully synthesized via a facile hydrothermal-calcination synthesis strategy. The physicochemical properties of the synthesized samples were studied by X-ray diffraction (XRD), UV–vis diffuse reflectance spectra (DRS), Fourier infrared spectrometer (FT-IR), Raman spectrometer, scanning electron microscopy (SEM), high resolution transmission electron microscopy (HRTEM), photoluminescence26spectra (PL), electrochemical workstation, etc. The activities of the CDBP were evaluated through the photocatalytic degradation of Indometacin(IDM) in an aqueous solution under simulated sunlight irradiation. With increasing concentrations of carbon dots (CDs), the photocatalytic activity of the CDBP initially increased, and then decreased. A CDs content of 3.0 wt% shows 12 times higher photocatalytic activity than that of pristine BiPO4. Reactive oxidative species, particularly O2 − and h+, were the two critical reactive oxidative species to mediator immediate the photocatalytic degradation of IDM. A notable sign of 5, 5-dimethyl-1-pyrrolidone-N-oxyl(DMPOX) was observed through electron spin resonance spectroscopy(EPR) with CDBP as the photocatalyst, which indicated higher oxidability than pristine BiPO4 under simulated sunlight irradiation. This enhanced photocatalytic activity might due to high-efficiency charge separation, unique up-converted PL properties, as well as the bandgap narrowing of the CDs. Moreover, the byproducts of IDM were detected by HPLC–MS/MS and GC–MS, and the probable pathways were deduced. The acute toxicity at three trophic levels initially increased slowly and then decreased rapidly as the IDM dechlorination and total organic carbon(TOC) decreased during photocatalytic degradation.