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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.

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.

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

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.

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.

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.

The development of highly efficient photocatalysts with broad spectrum light response is a primary goal in the photocatalysis domain. Here we report on a novel ternary photocatalyst comprised of single atom-dispersed silver and carbon quantum dots, co-loaded with ultrathin g-C 3 N 4 (SDAg-CQDs/UCN), which exhibited a highly enhanced photoresponse and broad-spectrum (UV, visible, and near-infrared light) photocatalytic activity. The content of 1.0 wt% of CQDs and 3.0 wt% of Ag resulted in a 10-fold higher reaction rate than that of UCN under visible light irradiation. This improved broad-spectrum photocatalytic performance may be attributed to the surface plasmon resonance effect of Ag, up-converted fluorescent properties of CQDs, narrowed energy gap, as well as the electron separation and transfer capacity of both the Ag and CQDs. An electron spin resonance (ESR) technique, and reactive species (RS) scavenging experiments indicated that 1 O 2 and O 2 − were the dominant active species involved in the degradation of naproxen (NPX). Product identification and reaction site prediction revealed that the photocatalytic degradation of NPX included decarboxylation, hydroxylation, as well as the opening of the naphthalene ring. Mineralization experiments indicated that NPX and its degradation products would be finally transformed into CO 2 and H 2 O. Reactions in different water matrices indicated that SDAg-CQDs/UCN can be effectively employed for the degradation of NPX under ambient water conditions. Therefore, SDAg-CQDs/UCN offers a new strategy for the broad-spectrum utilization of solar light and provides a promising method for the remediation of water contamination.

Polymeric photocatalysts have desirable application prospects due to their low cost and controllable structures. Here, we report on the synthesis of a highly effective and stable oxygen- and nitrogen-linked heptazine-based carbon nitride organic polymer (OCN) photocatalyst that is metal-free and porous, with low crystallinity and nitrogen vacancies, which is prepared through a single-step approach. For the photocatalytic degradation of several typical PPCPs, the OCN exhibited excellent photocatalytic performance compared to C3N4. The enhanced mechanisms were investigated novelty, and the conduction band, crystallinity and recombination rate of photogenerated carriers were reduced due to the introduction of oxygen atoms and nitrogen vacancies, whereas the fabrication of porous structures provided additional adsorption sites. The mechanism of hydroxyl radical generation in the OCN system was first proposed under this system. The O linkages can form hydrogen bonds with H2O2 to promote the catalytic generation of hydroxyl radicals (˙OH). The presence of ˙OH, O2˙− and 1O2 (detected by ESR) indicated that the OCN polymer could be employed to degrade organic pollutants.

Enabling the optimal usage of solar energy is considered to be one of the most pressing challenges in the photocatalytic remediation of water resident contaminants. Herein, a single-atom dispersed Ag loaded ultrathin g-C3N4 hybrid (AgTCM/UCN) was prepared through a facile co-polymerization of dicyandiamide with silver tricyanomethanide (AgTCM) and NH4Cl, and used as a visible light driven photocatalyst for the degradation of sulfamethazine (SMT) in the presence of peroxymonosulfate (PMS). Under UV light, visible light and simulated sunlight irradiation, the AgTCM/UCN/PMS process showed higher efficiency for SMT degradation than AgTCM/UCN, UCN/PMS, and g-C3N4/PMS systems. This enhanced photocatalytic activity may be attributed to the synergistic effects encompassing the surface plasmon resonance (SPR) of Ag, high surface area of UCN, and efficient charge separation of PMS. Electron-spin resonance (ESR) and reactive species (RSs) scavenger-quenching experiments revealed that SO4˙- was generated following the addition of PMS, whereas O2˙- and h+ were predominantly responsible for the degradation of SMT. Three degradation pathways of SMT were deduced, including the cleavage of sulfonamide bonds, SO2 extrusion, and the oxidation of the aniline moiety, based on mass spectrometry and theoretical calculations. The degradation of SMT in ambient water revealed that the AgTCM/UCN/PMS photocatalytic process can be efficaciously applied for the remediation of SMT contaminated natural waters, particularly sea water.

Ca9La1−x(PO4)7:xSm3+ phosphors (0.01 < x < 0.25) were synthesized via high temperature solid-state reaction. Their properties including crystal structure, decay performance, thermal stability and photoluminescence were examined in detail. Phase analysis indicated that the phosphors crystallized in a rhombohedral structure, and the emission spectra of the phosphors consisted of four peaks centered around 570, 607, 653, and 714 nm, attributed to Sm3+ ions transitions 4G5/2 → 6HJ (J = 5/2, 7/2, 9/2, and 11/2, respectively). The optimal Sm3+ doping content was 0.12 mol and the Ca9La(PO4)7:Sm3+ phosphor also exhibited better thermal stability compared to other phosphors. In addition, the mechanism behind the energy transfer between Sm3+ ions was determined to be dipole–dipole interactions as described by Dexter theory. The results indicated that as orange-red phosphors, Ca9La (PO4)7:Sm3+ phosphors were promising candidates for being integrated into white light emitting diodes.

A visible light-driven and environmentally compatible photocatalyst is considered to be a potential application for wastewater treatment processes. In the present study, we employed carbon quantum dots (CQDs) to modify BiOCOOH with the aim of negating the UV limit of the photocatalyst, while increasing its photocatalytic activity. The structure, morphologies, and other characteristics of CQDs/BiOCOOH composites were investigated, which confirmed that CQDs were successfully coupled with BiOCOOH. Under visible light irradiation, a very low CQDs content of 2.0% weight resulted in a 4.64-fold more rapid reaction rate in the photodegradation of diclofenac (DCF) than pristine BiOCOOH. The CQDs served to enhance the visible light absorption of BiOCOOH, which significantly improved visible-light harvesting, as well as interfacial charge transfer and separation. Through a new model study it was revealed that O 2 − was predominantly responsible for DCF degradation. Based on mass spectrometry and theoretical calculations, primary intermediates were identified, and the key pathways proceeded mainly through e − reduction, O 2 − attack, and OH addition reactions. The Vibrio fischeri , Desmodesmus subspicatus , and Daphnia magna were selected to evaluate the acute toxicity, which initially increased and further decreased when the total organic carbon and organic chlorine compounds were reduced. The excellent dechloridation, mineralization, and detoxicity properties via the synthetic CQDs/BiOCOOH photocatalysts clearly demonstrated the potential of this strategy.

The development of facile and efficient synthetic approaches of carbon quantum dots loaded with mesoporous g-C3N4 (mpg-C3N4/CQDs) is of critical urgency. Here, a facile strategy was developed to synthesize the mpg-C3N4/CQDs by using calcinations of the mixture of CQDs, cyanamide, and silica colloid. The obtained composite still retained a considerable total surface area, which could offer a larger population of adsorption sites; therefore enhance the capacity for the adsorption of fluoroquinolones antibiotics (FQs). Under visible light irradiation, mpg-C3N4/CQDs demonstrated a higher photocatalytic activity for FQs degradation than did bulk g-C3N4 or mpg-C3N4. This enhancement might have been ascribed to the high surface area of the mpg-C3N4, unique up-converted photoluminescence (PL) properties, and the efficient charge separation of the CQDs. The eradication of FQs followed the Langmuir–Hinshelwood (L–H) kinetic degradation model and absorption pseudo-second-order kinetic model, indicating that surface reactions and chemical sorption played significant roles during the photocatalysis process. The results of electron spin resonance (ESR) technology and reactive species (RSs) scavenging experiments revealed that the superoxide anion radical (O2˙−) and photo-hole (h+) were the primarily active species that initiated the degradation of FQs. Based on the identification of intermediates and the prediction of reactive sites, the degradation pathways of ofloxacin (OFX) were proposed. A residual antibiotic activity experiment revealed that mpg-C3N4/CQDs provided very desirable performance for the reduction of antibiotic activity.

Significant quantities of sulfonamide antibiotics are continuously released into the ambient environment; thus, they have emerged as serious pollutants that may inflict ecological damage. Herein, 4-phenoxyphenol-modified g-C3N4 (PCN) was initially prepared via the copolymerization of dicyandiamide and 4-phenoxyphenol, which demonstrated excellent performance for light-harvesting and the promotion of photon-generated carrier separation. Optimized PCN exhibited 4.5-fold higher photocatalytic degradation activity for sulfisoxazole (SIZ) than pure g-C3N4 under blue-light (LED) irradiation. Among SIZ, sulfapyridine (SPD), sulfadiazine (SDZ) and sulfadimethazine (SMZ), SIZ and SMZ are more vulnerable to attack in PCN photocatalytic system due to structure containing methyl. Electron spin resonance and photoelectrochemical experiments revealed that the faster charge separation of PCN promoted the formation of additional reactive oxygen species. Moreover, the potential transformation pathways of SIZ were hypothesized through the frontier molecular orbital theory and HRAM LC-MS/MS. Hence, the present work is expected to be of important reference value for sustainable environmental restoration.

Fe3O4 nanocrystals with five different morphologies (i.e., nanospheres, nanorods, nanocubes, nano-octahedrons, and nanoplates) were acquired using a simple, efficient, and economic microwave-assisted oxidation technique. The microstructure, morphology, predominant exposed facets, and iron atom local environment of Fe3O4 were revealed by powder X-ray diffraction (PXRD), scanning transmission electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectrometer (XPS), and Mossbauer spectrum. We demonstrated that the heterogeneous UVA/Fenton catalytic activities of Fe3O4 nanocrystals are morphology/facets dependent. Under UVA irradiation, the catalytic activity of the as-prepared Fe3O4 was in the sequence of nanospheres > nanoplates > nano-octahedrons ≈ nanocubes > nanorods > nano-octahedrons (by coprecipitation). The dominating factor for the catalytic performance was the particle size and BET specific surface area; moreover, the exposed {111} facets, which co...

In this study, a novel visible-light-driven N-doped carbon dot (NCDs)/g-C 3 N 4 composite was successfully synthesized by loading NCDs nanoparticles onto the interlayers and surface of g-C 3 N 4 via a facile polymerized method. The photocatalytic activity of the NCDs/g-C 3 N 4 was remarkably higher than that of g-C 3 N 4 and CDs/g-C 3 N 4 toward the degradation of indomethacin (IDM) under visible light irradiation. With increasing NCDs loading volumes, the photocatalytic activity of NCDs/g-C 3 N 4 initially increased, and then decreased. A very low NCDs content of 1.0 wt% resulted in a 13.6 fold higher reaction rate than that of pristine g-C 3 N 4 . This enhanced photocatalytic activity might have been ascribed to the unique up-converted PL properties, efficient charge separation, as well as bandgap narrowing of the NCDs. Reactive species (RS) scavenging experiments revealed that superoxide radical anions (O 2 −) and photogenerated holes (h + ) played key roles during the photocatalytic degradation of IDM. The quantification of O 2 − showed that NCDs/g-C 3 N 4 formed a larger amount of O 2 − than that of pristine g-C 3 N 4 . Potential photocatalytic pathways of IDM were proposed through the identification of intermediates using HPLC–MS/MS and the prediction of reaction sites based on Frontier Electron Densities (FEDs) calculations, which involved decarboxylation, hydroxylation, as well as the addition and cleavage of indole rings. Toxicity and mineralization evaluations revealed that NCDs/g-C 3 N 4 provided a very desirable performance for the toxicity reduction and mineralization of IDM under longer exposures of visible light irradiation.

An environmentally friendly and sunlight-driven photocatalyst is thought to be a promising alternative to conventional water treatment technology. In this study, carbon dots (C-Dots), a newly discovered material with the ability to upconvert light, were decorated to TiO2 via a facile hydrothermal-calcination synthesis approach. Under simulated sunlight irradiation, a very low C-Dots content of 5.0 wt% resulted in a 2.3 times faster reaction rate for gemfibrozil (GEM) photodegradation than pristine TiO2. Oxidative species, particularly OH, were the most important reactive species mediating the photocatalytic degradation of GEM. A notable observation was the higher formation rates of OH in the TiO2/C-Dots system than in pristine TiO2, which was determined via electron spin resonance spectroscopy. Frontier electron density calculations and mass spectrometry were used to verify that the major degradation pathways of GEM contained OH addition, H abstraction and O2 − attack. The acute toxicity of the treated solution at two trophic levels first increased slowly and then decreased rapidly as the total organic carbon decreased during photocatalytic degradation. Compared to traditional advanced oxidation processes, TiO2/C-Dots photocatalytic technology could reduce the generation of toxic by-products. These results highlight the potential application of sustainable sunlight-driven photocatalyst in water purification.

Pharmaceutically emerging micropollutants have become an environmental concern in recent years. In the present paper, the reactive species (RSs)-induced degradation mechanism of clofibric acid (CA) was investigated using a newly sunlight-driven g-C 3 N 4 /P25 photocatalyst. A very low g-C 3 N 4 content of 8.0 weight percent resulted in a 3.36 and a 2.29 times faster reaction rate for CA photodegradation than for pristine g-C 3 N 4 and P25, respectively. Electron spin resonance and quenching experiments demonstrated the participation of HO , h + , e − , 1 O 2 and O 2 ·- in the photocatalytic system, and the contribution rates were calculated to 73.3%, 15.3%, 5.1%, 6.7% and 33.1%, respectively. According to the pulse radiolysis measurements and the competitive kinetics approaches, the bimolecular reaction rate constants for HO , e − , and 1 O 2 with CA were (8.47 ± 0.33) × 10 9 M −1 s −1 , (6.41 ± 0.48) × 10 9 M −1 s −1 and (6.6 ± 0.37) × 10 6 M −1 s −1 , respectively. RSs were found to significantly influence the degradation of CA, and the degradation pathways occurred primarily via e − reduction, HO addition and 1 O 2 attack reactions on the basis of mass spectrometry and theoretical calculations.

Contamination with β-blockers such as propranolol (PRO) poses a potential threat to human health and ecological system. The present study investigated the kinetics and mechanisms of PRO degradation by UV-activated persulfate (UV/PS) oxidation. Here, the experimental results showed that the degradation of PRO followed pseudo-first-order reaction kinetics, the degradation rate constant ( k obs ) was increased dramatically with increasing PS dosage or decreasing initial PRO concentration. And increasing the initial solution pH could also enhance the degradation efficiency of PRO. Radical scavenging experiments demonstrated that the main radical species was sulfate radicals (SO 4 •− ), with hydroxyl radicals (HO·) playing a less important role. Meanwhile, the second-order rate constants of PRO degradation with SO 4 •− and HO· were determined to be 1.94 × 10 10 M −1 s −1 and 6.77 × 10 9 M −1 s −1 , respectively. In addition, the presence of natural organic matter (NOM) and nitrate anion (NO 3 − ) showed inhibitory effect on PRO degradation, whereas bicarbonate anion (HCO 3 − ) and chlorine anion (Cl − ) greatly enhanced the degradation of PRO. Moreover, the transformation products of PRO were identified by applying ultra performance liquid chromatography coupled with quadrupole time-of-flight mass spectrometry (UPLC/Q-TOF-MS) technique. Molecular orbital calculations were used to estimate the reaction site of PRO with radicals, simultaneously. Hence, the transformation pathways including hydroxylation, dehydration, naphthalene ring opening, and the cleavage of aldehyde groups were proposed. This work enriches the mechanism of PRO degradation under UV/PS system on the basis of results obtained by experimental characterization and Gaussian theoretical calculation.

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 TiO2 nanoparticles and formed a TiO2/ONLH nanocomposite which was responded to the natural sunlight. Under natural sunlight, the TiO2/ONLH can effectively degrade ten types of pharmaceuticals. In particular, fluoroquinolone containing N-piperazinyl, and cardiovascular drugs containing long aromatic side chains were easily degraded. The half-life of the best degradation performance of propranolol was less than 5 min. The rate constants of propranolol using the TiO2/ONLH were approximately six- and eight-fold higher than those of pristine TiO2 and ONLH, respectively. Two reactive species (OH and O2-) facilitated the rapid degradation of propranolol, which occurred primarily through the hydroxyl radical addition, ring-opening, and ipso substitution reactions. An acute toxicity test using luminescent bacteria indicated that the toxicity of the propranolol reaction solution gradually decreased with lower total organic carbon (TOC). According to the toxicity evaluation of monomer products, the TiO2/ONLH also reduced the generation of toxic transformation products. The effects of actual water/wastewater have further shown the TiO2/ONLH might be applied for the removal of pharmaceuticals in wastewater.

Aminated adsorbents are efficient in capturing high concentrations of CO2, while their efficiency in air purifier for the removal of low concentrations of CO2 from indoor air remains unclear. In this study, a polyethyleneimine-impregnated resin (PEI-MR10) was prepared and used to remove indoor CO2, and its regeneration at low temperatures was evaluated. PEI loading narrowed the pore size distribution but increased the average pore size of the PEI-MR10. The PEI-MR10 with small particle size (0.250–0.425 mm) exhibited higher adsorption capacity and faster adsorption rate than the bigger one. The PEI-MR10 was able to remove all CO2 during the first 2 h with an initial CO2 concentration of 1000 ppm. Under variable indoor conditions, the adsorbed amounts of CO2 could maintain high values from 90 to 136 mg/g. At a relative humidity of 50%, the adsorbed amount on the PEI-MR10 for 1000 ppm CO2 reached 128.4 mg/g. In consideration of real application in air purifier, a cost-effective regeneration method using ambient air was adopted, and the spent PEI-MR10 was regenerated at low temperatures no more than 70 °C. The desorption efficiency of CO2 increased with increasing temperatures, and the best regeneration was obtained at 70 °C. The adsorbed amount of CO2 on the first-regenerated PEI-MR10 decreased significantly, but the adsorbent maintained stable adsorption capacity of about 80 mg/g after three adsorption-regeneration cycles. This study demonstrated that PEI-MR10 was an effective adsorbent for CO2 removal from indoor air.

Herein, Eu-doped CaSrNb2O7 perovskites are synthesized by using the high-temperature solid-phase method, resulting in layered perovskite structure, with the space group of Cmc21 and a strong luminescence response under excitation wavelength of 314 nm. Moreover, these as-prepared CaSrNb2O7:xEu3+ (x = 0–0.15) phosphors are color-tunable. Specifically, the color changes from white to blue with raising temperature. After thermal stability testing, the fluorescence intensity ratio, maximum absolute and relative sensor sensitivity of CaSrNb2O7:xEu3+ are calculated to evaluate the thermal properties of materials. It turned out that the maximum absolute and relative sensor sensitivity are 0.043 K-1 and 0.0105 K-1, and the temperature resolution is as low as 0.0286K, respectively. It suggests that the high sensitivity and excellent resolution of CaSrNb2O7:xEu3+ make it a promising candidate for optical thermometers.

A series of novel phosphate orange-red phosphor, Sr9In(PO4)7:xSm3+ (0.01 97%) below 150 ℃ and the configurational coordinate diagram analysis demonstrated excellent thermal stability of Sr9In(PO4)7:Sm3+ phosphor, which is superior to that of the previously reported and commercially available phosphors. These results suggest that Sr9In(PO4)7:Sm3+ phosphor is promising orange-red phosphor materials for white light emitting diodes.

Pharmaceuticals and personal care products (PPCPs) are increasingly being scrutinized by the scientific community due to their environmental persistence. Therefore, the development of novel environmentally compatible and energy-efficient technologies for their removal is highly anticipated. In this work, a novel metal-free photocatalytic nanoreactor was successfully synthesized by anchoring carbon dots to hollow carbon nitride nanospheres (HCNS/CDs). The unique structure of these hollow nanospherical HCNS/CDs hybrids endowed them with a high population of reactive sites, while enhancing optical absorption due to internal light reflection. Simultaneously, the CDs served as “artificial antennas” to absorb and convert photons with low energy, due to their superior up-converting properties. Consequently, the HCNS/CDs demonstrated excellent photodegradation activities for the degradation of PPCPs under broad-spectrum irradiation. Remarkedly, 10 mg/L of naproxen (NPX) was completely degraded following 5 min of natural solar irradiation. It was further revealed that the O2•- played a significant role during the photocatalytic process, which could lead to the decomposition of NPX. The effects of natural water matrices and the degradation of trace PPCPs further supported that this photocatalytic system may be efficaciously applied for the remediation of PPCPs contamination in ambient waterways.

Achieving efficient solar utilization is a primary goal in the field of photocatalytic degradation of PPCPs. For this study, a broad-spectrum carbon and oxygen doped, porous g-C3N4 (COCN) was synthesized via a simple co-pyrolysis of dicyandiamide and methylamine hydroiodide (CH5N·HI). The 0.3COCN demonstrated an excellent photocatalytic degradation of indometacin (IDM), which was 5.9 times higher than bulk g-C3N4. The enhanced photocatalytic activity could be ascribed to the broad-spectrum utilization of solar light and improved charge separation efficiency. Reactive species (RSs) scavenging experiments have shown that O2·- and 1O2 were the dominant active species. Further, the 0.3COCN exhibits excellent yield of hydroxyl radicals which was confirmed by electron spin resonance (ESR) spectra. Meanwhile, the degradation pathways of IDM were proposed according the HRAM LC-MS/MS and total organic carbon (TOC). This research provided a new strategy for a broad-spectrum photocatalyst, and a promising strategy for environmental remediation.

Anatase TiO2 nanoparticles coated with P and O co-doped g-C3N4 were prepared via a single-step procedure. The resulting POCN/anatase TiO2 demonstrated remarkable performance in the degradation of enrofloxacin (ENFX). The photocatalytic activity of this heterojunction was 28.9 and 3.71 times better than that of the CN and anatase TiO2, respectively. The microtopography of the POCN/anatase TiO2 was revealed in this study. Co-doping with P and O increased the visible light adsorption capacity of the g-C3N4, whereas the anatase TiO2 nanoparticles enhanced the adsorption properties of the ENFX and the separation of the photoinduced carriers of the POCN/anatase TiO2. The O2·− and h+ were the main reactive oxidative species in the photocatalytic degradation of ENFX. The results of the detection of H2O2 and ESR confirmed that POCN/anatase TiO2 was a type Z-scheme photocatalyst. Finally, the ENFX degradation pathways were estimated through the detection of by-products.

Widespread usage of the sulfonamide class of antibiotics is causing increasing ecotoxicological concern, as they have the capacity to alter ambient ecosystems. Photocatalytic technology is an attractive yet challenging strategy for the degradation of antibiotics. For this work, the phosphate modification of m-Bi2O4 (Bi2O4-P) was prepared via a one-step hydrothermal process involving sodium bismuthate and sodium phosphate, which was employed for the degradation of sulfamethazine (SMZ) under visible light irradiation. The 0.5% Bi2O4-P exhibited excellent photocatalytic performance, which was 1.9 times that of pure m-Bi2O4. The photocatalytic degradation kinetics and mechanism of SMZ was investigated at different pH, whereupon it was revealed that m-Bi2O4-P exhibited improved SMZ adsorption and photocatalytic activities in contrast to pure m-Bi2O4. Compared with other four sulfonamide antibiotics, structures that contained additional methyl on the pyrimidine could be more easily attacked by phosphate modified m-Bi2O4. Reactive species (RS) scavenging experiments revealed that h+ was primarily responsible for the degradation of SMZ. Further studies of RS by ESR technology, and the results of photoelectrochemical properties showed phosphate-modified m-Bi2O4 could make greater use of photogenerated carriers, thereby producing additional RS. Based on the HRAM LC–MS/MS and the Frontier Molecular Orbital Theory, the degradation pathways of SMZ were proposed.

Fe-doped g-C3N4 / graphene (rGO) composites were investigated as catalysts for the activation of peroxymonosulfate (PMS) to degrade Trimethoprim (TMP) under visible light irradiation. The rapid recombination of photogenerated electron-hole pairs in g-C3N4 may be suppressed by doping with Fe and incorporating rGO. The TMP degradation efficiency using 0.2% Fe-g-C3N4/2 wt% rGO/PMS was 3.8 times than that of g-C3N4/PMS. The degradation efficiency of TMP increased with higher catalyst dosages and PMS concentrations. Acidic condition (pH = 3) was observed to significantly enhance the TMP degradation efficiency from 61.4% at pH = 6 to nearly 100%. By quenching experiments and electron spin resonance (ESR), O2 − was found to play an important role for the activation of PMS to accelerate the generation of reactive radicals for the TMP degradation. A total of 8 intermediates derived from hydroxylation, demethoxylation and carbonylation were identified through theoretical calculations and the HRAM/LC–MS-MS technique, and transformation pathways of TMP oxidation were proposed. TOC removal rate of TMP increased as reaction time was prolonged. Acute toxicity estimation by quantitative structure-active relationship analysis indicated that most of the less toxic intermediates were generated. The aim of this study was to elucidate and validate the functionality of a promising polymeric catalyst for the environmental remediation of organic contaminants.

The development of novel noble metal-free semiconductor catalysts with high photocatalytic efficiency is of great importance toward the degradation of organic compounds. In this work, a core-shell heterojunction MoS2/Cd0.9Zn0.1S photocatalytic material was successfully synthesized via a simple one-step hydrothermal method. The introduction of MoS2 led to a significant improvement in the photocatalytic degradation of diclofenac (DCF). It was confirmed that 0.1% loading content of MoS2 achieved an optimal photocatalytic efficiency of 86% in the degradation of DCF under visible light irradiation, which was 1.8 times higher than that of Cd0.9Zn0.1S. The MoS2/Cd0.9Zn0.1S heterostructured composites possessed improved photocatalytic properties, which implied that the combination of Cd0.9Zn0.1S and MoS2 shortened the carrier transport pathway and facilitated the separation efficiency of electrons and holes. Reactive species (RS) scavenging experiments and electron spin resonance (ESR) demonstrated that superoxide radicals (O2•−) and electron holes (h+) played predominant roles throughout the DCF degradation process. The primary intermediates were explored through HRAM LC/MS/MS, and a transformation pathway was tentatively proposed. This study promoted the application of an economical, highly efficient and visible light driven MoS2 co-catalyst for the degradation of organic contaminants.