Aquatic photolysis of high-risk fluorinated liquid crystal monomers: Kinetics, toxicity evaluation, and mechanisms.

Despite the frequent detection of fluorinated liquid-crystal monomers (FLCMs) in the environment, the level of understanding of their fate, toxicity, and transformation remains insufficient. Herein, we investigated the degradation kinetics and mechanism of an FLCM (4-cyano-3-fluorophenyl 4-ethylbenzoate, CEB-F) under ultraviolet (UV) photolysis in aquatic environment. Our findings demonstrated that the UV photolysis of CEB-F followed first-order kinetics. Photodegradation products were identified using liquid chromatography with mass spectrometry, and detailed reaction pathways were proposed. It is postulated that through the attack of reactive oxygen species, hydroxylation, and CO/C-F bond cleavage, CEB-F gradually degraded into small molecular compounds, releasing fluorine ions. Acute immobilization tests with Daphnia magna (D. magna) revealed significant acute toxicity of CEB-F, with LC50 values ranging from 1.023 to 0.0536 µM over 24 to 96 h, emphasizing the potential high risk of FLCMs in aquatic ecosystems if inadvertently discharged. Interestingly, we found that the toxicity of CEB-F photolysis reaction solutions was effectively reduced. Through catalase and acetylcholinesterase activities analysis along with molecular docking simulation, we proposed differences in the underlying toxicity mechanisms of CEB-F and its photolysis products to D. magna. These findings highlight the potential harmful effects of FLCMs on aquatic ecosystems and enrich our understanding of the photolysis behavior of FLCMs.

Degradation of sulfonamide antibiotic via UV/MgO2 system: kinetic, application, and mechanism.

In response to antibiotic residues in the water, a novel advanced oxidation technology based on MgO2 was used to remediate sulfamethazine (SMTZ) pollution in aquatic environments. Upon appropriate regulation, the remarkable removal efficiency of SMTZ was observed in a UV/MgO2 system, and the pseudo-first-order reaction constant reached 0.4074 min-1. In addition, the better performance of the UV/MgO2 system in a weak acid environment was discovered. During the removal of SMTZ, the pathways of SMTZ degradation were deduced, including nitration, ring opening, and group loss. In the mineralization exploration, the further removal of residual products of SMTZ by the UV/MgO2 system was visually demonstrated. The qualitative and quantitative researches as well as the roles of reactive species were valuated, which revealed the important role of ·O2-. Common co-existing substances in actual wastewater such as NO3- HA, Cl-, Fe2+, Co2+, and Mn2+ can slightly inhibit the degradation of SMTZ in the UV/MgO2 system. Finally, the capacity of efficient degradation of SMTZ in actual wastewater by the UV/MgO2 system was proved. The results indicated that the innovative UV/MgO2 system was of great practical application prospect in antibiotic residue wastewater remediation.

Self-assembly construction of 1D carbon nitride nanotubes and cobalt-modified for superior photocatalytic degradation of sulfonamide antibiotics.

In the present work, a cobalt-doped carbon nitride nanotubes (Co-CNt) was synthesized via self-assembly process. Contributed to the narrow band gap, enlarged specific surface area and abundant active sites, Co-CNt has excellent photoelectric properties and superior performance than pristine CN in sulfisoxazole (SIZ) degradation under blue light irradiation, which achieved 100% removal within 40 min. Meanwhile, the system not only exhibited practical applicability by efficiently degrading SIZ, but also generating high levels of H2O2. Moreover, the Co-CNt/visible light system shows superior operability over a wide pH range, micro-concentration contaminants, various anions, water matrices and other sulfonamides with promising catalytic stability and applicability. The contribution of RSs in the degradation process were elucidated based on radical scavenging and spin-trapped tests, clarifying that O2·- and h+ majorly dominated the process. In addition, 4 probable degradation pathways of SIZ were provided and the generated intermediates' toxicity were evaluated. Overall, this study successfully synthesized a self-assembled 1D tubular photocatalyst with Co-doped and demonstrated the potential Co-CNt/visible light system for environmental remediation, providing a promising approach for the development of photocatalysis.

Efficient degradation and detoxification of antibiotic Fosfomycin by UV irradiation in the presence of persulfate.

Fosfomycin (FOS) as a widely used antibiotic has been found in abundance throughout the environment, but little effort has been devoted to its treatment. In this study, we systemically looked into the degradation of FOS by ultraviolet-activated persulfate (UV/PS) in aqueous solutions. Our findings demonstrated that FOS can be degraded efficiently under the UV/PS, e.g., >90 % of FOS was degraded with 19,200 mJ cm-2 of UV irradiance and 20 µM of PS. HO was the dominant radical responsible for FOS degradation. FOS degradation increased as PS dosage increased, and higher degradation efficiency was observed at neutral pH. Natural water constitutes either promoted (e.g., Cu2+, Fe3+, and SO42-) or inhibited (e.g., humic acid, HCO3-, and CO32-) FOS degradation to varying degrees. Hydroxyl substitution, CP bond cleavage, and coupling reactions were the major degradation pathways for FOS degradation. Finally, the toxicity evaluation revealed that FOS was toxic to E. coli and S. aureus, but the toxicity of the intermediate products of FOS to E. coli and S. aureus rapidly decreased over time after UV/PS treatment. Therefore, these findings provided a fundamental understanding of the transformation process of FOS and supplied useful information for the environmental elimination of FOS contamination and its toxicity.

Mechanistic Insights into the Biodegradation of Carbon Dots by Fungal Laccase.

While carbon dots (CDs) have the potential to support the agricultural revolution, it remains obscure about their environmental fate and bioavailability by plants. Fungal laccase-mediated biotransformation of carbon nanomaterials has received little attention despite its known capacity to eliminate recalcitrant contaminants. Herein, we presented the initial investigation into the transformation of CDs by fungal laccase. The degradation rates of CDs were determined to be first-order in both substrate and enzyme. Computational docking studies showed that CDs preferentially bonded to the pocket of laccase on the basal plane rather than the edge through hydrogen bonds and hydrophobic interactions. Electrospray ionization-Fourier transform-ion cyclotron resonance mass spectrometry (ESI-FT-ICR MS) and other characterizations revealed that the phenolic/amino lignins and tannins portions in CDs are susceptible to laccase transformation, resulting in graphitic structure damage and smaller-sized fragments. By using the 13C stable isotope labeling technique, we quantified the uptake and translocation of 13C-CDs by mung bean plants. 13C-CDs (10 mg L-1) accumulated in the root, stem, and leaf were estimated to be 291, 239, and 152 µg g-1 at day 5. We also evidenced that laccase treatment alters the particle size and surface chemistry of CDs, which could facilitate the uptake of CDs by plants and reduce their nanotoxicity to plants.

Carbon nitride nanotubes anchored with Cu(I) triggers peracetic acid activation with visible light for removal of antibiotic contaminants: Probing mechanisms of non-radical pathways and identifying active sites.

The peracetic acid (PAA)-activation process has attracted much attention in wastewater treatment. However, the low electron efficiency at the interface between heterogeneous catalysts and PAA has affected its practical application. For this study, we developed a carbon nitride hollow-nanotube catalysts with dispersed Cu(I) sites (Cu(I)-TCN) for the photocatalytic activation of PAA for antibiotics degradation. The obtained Cu(I)-TCN catalyst demonstrated an enhanced capacity for visible light harvesting along with increased charge transfer rates. Specifically, the developed Cu(I)-TCN/visible light/PAA system was able to completely remove antibiotics within 20 min, with a kinetic constant that was 25 times higher than a Cu(I)-TCN/visible light system, and 83 times higher than Cu(I)-TCN/PAA systems. Scavenging experiment and electron paramagnetic resonance (EPR) indicated that singlet oxygen was dominant reactive specie for sulfisoxazole (SIZ) removal. Besides, electrochemical tests and attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy verified that the electron transfer efficiency of PAA activation was promoted due to the formation of inner-sphere interactions between PAA and Cu(I)-TCN, resulting in the quick removal of antibiotics. Further, after exposure to visible light, the Cu(I)-TCN excited photogenerated electrons which supplemented the electrons consumed in the reaction and drove the valence cycle of Cu ions. Overall, this research offered novel insights into the non-radical pathway for heterogeneous visible light-driven advanced oxidation processes and their potential for practical wastewater remediation.

Strategy for improvement of molecular oxygen activation capacity of PPECu by chlorine doping for water decontamination.

The activation of molecular oxygen and generation of reactive oxygen species (ROS) play important roles in the efficient removal of contaminants from aqueous ecosystems. Herein, using a simple and rapid solvothermal process, we developed a chlorine-doped phenylethynylcopper (Cl/PPECu) photocatalyst and applied it to visible light degradation of sulfamethazine (SMT) in aqueous media. The Cl/PPECu was optimized to have a 2.52 times higher steady-state concentration of O2•- (3.62 × 10-5 M) and a 28.87 times higher degradation rate constant (0.2252 min-1) for SMT compared to pure PPECu. Further, the effectiveness of Cl/PPECu in treating sulfonamide antibiotics (SAs) in real water systems was verified through an investigation involving natural water bodies, SAs, and ambient sunlight. The energy band structure, DFT calculation and correlation heat map indicated that the addition of chlorine modulated the local electronic structure of PPECu, leading to an improvement in the electron-hole separation, enhanced the O2 activation, and promoted the generation of ROSs. This study not only puts forward innovative ideas for the eco-compatible remediation of environmental pollution using PPECu, but also sheds new light on the activation of oxygen through elemental doping.

Simplified synthesis of direct Z-scheme Bi2WO6/PhC2Cu heterojunction that shows enhanced photocatalytic degradation of 2,4,6-TCP: Kinetic study and mechanistic insights.

For this work, we employed n-type Bi2WO6 and p-type PhC2Cu to formulate a direct Z-scheme Bi2WO6/PhC2Cu (PCBW) photocatalyst via simplified ultrasonic stirring technique. An optimal 0.6PCBW composite exhibited the capacity to rapidly photodegrade 2,4,6-TCP (98.6% in 120 min) under low-power blue LED light, which was 8.53 times and 12.53 times faster than for pristine PhC2Cu and Bi2WO6, respectively. Moreover, electron spin resonance (ESR), time-resolved PL spectra, and quantitative ROS tests indicated that the PCBW enhanced the separation capacity of photocarriers. It also more readily associated with dissolved oxygen in water to generate reactive oxygen species (ROS). Among them, the ability of PCBW to produce ·O2- in one hour was 12.07 times faster than for pure PhC2Cu. In addition, the H2O2 formation rate and apparent quantum efficiency of PCBW are 10.73 times that of PhC2Cu, which indicates that PCBW not only has excellent photocatalytic performance, but also has outstanding ROS production ability. Furthermore, Ag photodeposition, in situ X-ray photoelectron spectroscopy (XPS) and density functional theory (DFT) calculations were utilized to determine the photogenerated electron migration paths in the PCBW, which systematically confirmed that Z-scheme heterojunction were successfully formed. Finally, based on the intermediate products, three potential 2,4,6-TCP degradation pathways were proposed.

Key role of Fe(VI)-activated Bi2WO6 in the photocatalytic oxidation of sulfonamides: Mediated electron transfer mechanism.

The widespread use of sulfonamides (SAs) in animals and human infections has raised significant concerns regarding their presence in ambient waterways and potential for inducing antimicrobial resistance. Herein, we report on the capacity of ferrate (VI) (FeVIO42-, Fe(VI)) to facilitate the photocatalytic degradation of sulfamethazine (SMT) via bismuth tungstate (Bi2WO6, BWO) under blue LED light (Vis/BWO/Fe(VI)) exposure, at rates that were 45-fold faster than BWO photocatalysis. Both the stepwise and time-series addition of Fe(VI) contributed to the degradation. Multiple lines of evidence confirmed that the common reactive species (RSs) in BWO-based photocatalytic systems and Fe(VI)-involved systems (e.g., •OH/h+, O2•-, 1O2 and Fe(V)/Fe(IV)) played subtle roles in our study system. Herein, for the first time, it was discovered that the precursor complex (BWO-Fe(V)/Fe(IV)* )) was the main contributor to induce electron transfer of SAs through the "conductive bridge" effect of BWO. The studied system was able to effectively degrade SMT in synthetic hydrolyzed urine (SHU) with low interference from background substances in water. This work not only offers a novel facilitation strategy for BWO, but also holds a great application prospect for contamination remediation in urine.

Leaf-like ionic covalent organic framework for the highly efficient and selective removal of non-steroidal anti-inflammatory drugs: Adsorption performance and mechanism insights.

In recent years, ionic covalent organic frameworks (iCOFs) have become popular for the removal of contaminants from water. Herein, we employed 2-hydroxybenzene-1,3,5-tricarbaldehyde (TFP) and 1,3-diaminoguanidine monohydrochloride (DgCl) to develop a novel leaf-like iCOF (TFP-DgCl) for the highly efficient and selective removal of non-steroidal anti-inflammatory drugs (NSAIDs). The uniformly distributed adsorption sites, suitable pore sizes, and functional groups (hydroxyl groups, guanidinium groups, and aromatic groups) of the TFP-DgCl endowed it with powerful and selective adsorption capacities for NSAIDs. Remarkably, the optimal leaf-like TFP-DgCl demonstrated an excellent maximum adsorption capacity (1100.08 mg/g) for diclofenac sodium (DCF), to the best of our knowledge, the largest adsorption capacity ever achieved for DCF. Further testing under varying environmental conditions such as pH, different types of anions, and multi-component systems confirmed the practical suitability of the TFP-DgCl. Moreover, the prepared TFP-DgCl exhibited exceptional reusability and stability through six adsorption-desorption cycles. Finally, the adsorption mechanisms of NSAIDs on leaf-like TFP-DgCl were confirmed as electrostatic interactions, hydrogen bonding, and π-π interactions. This work significantly supplements to our understanding of iCOFs and provides new insights into the removal of NSAIDs from wastewater.

Cytotoxicity and hemolysis of rare earth ions and nanoscale/bulk oxides (La, Gd, and Yb): Interaction with lipid membranes and protein corona formation.

The widespread application of rare earth elements (REEs) has raised concerns about their potential release into the environment and subsequent ingestion by humans. Therefore, it is essential to evaluate the cytotoxicity of REEs. Here, we investigated the interactions between three typical REEs (La, Gd, and Yb) ions as well as their nanometer/µm-sized oxides and red blood cells (RBCs), a plausible contact target for nanoparticles when they enter the bloodstream. Hemolysis of REEs at 50-2000 µmol L-1 was examined to simulate their cytotoxicity under medical or occupational exposure. We found that the hemolysis due to the exposure of REEs was highly dependent on their concentration, and the cytotoxicity followed the order of La3+ > Gd3+ > Yb3+. The cytotoxicity of REE ions (REIs) is higher than REE oxides (REOs), while nanometer-sized REO caused more hemolysis than that µm-sized REO. The production of reactive oxygen species (ROS), ROS quenching experiment, as well as the detection of lipid peroxidation, confirmed that REEs causes cell membrane rupture by ROS-related chemical oxidation. In addition, we found that the formation of a protein corona on REEs increased the steric repulsion between REEs and cell membranes, hence mitigating the cytotoxicity of REEs. The theoretical simulation indicated the favorable interaction of REEs with phospholipids and proteins. Therefore, our findings provide a mechanistic explanation for the cytotoxicity of REEs to RBCs once they have entered the blood circulation system of organisms.

Facile synthesis of direct Z-scheme UiO-66-NH2/PhC2Cu heterojunction with ultrahigh redox potential for enhanced photocatalytic Cr(VI) reduction and NOR degradation.

Z-scheme heterojunction-based photocatalysts typically have robust removal efficiencies for water contaminants. Herein, we employed p-type PhC2Cu and n-type UiO-66-NH2 to develop a direct Z-scheme UiO-66-NH2/PhC2Cu photocatalyst with an ultrahigh redox potential for Cr(VI) photoreduction and norfloxacin (NOR) photodegradation. Moreover, UV-vis diffuse reflectance, photoelectrochemical measurements, photoluminescence (PL) spectra and electron spin resonance (ESR) technique revealed that the UiO-66-NH2/PhC2Cu composite boosted light capturing capacities to promote photocatalytic efficiencies. Strikingly, the optimized UiO-66-NH2/PhC2Cu50 wt% rapidly reduced Cr(VI) (96.2%, 15 min) and degraded NOR (97.9%, 60 min) under low-power blue LED light. In addition, the UiO-66-NH2/PhC2Cu photocatalyst also exhibited favorable mineralization capacity (78.4%, 120 min). Benefitting from the enhanced interfacial electron transfer and ultrahigh redox potential of the Z-scheme heterojunction, the UiO-66-NH2/PhC2Cu photocatalyst greatly enhanced the separation efficacies of photogenerated carriers. This resulting abundance of active species (e.g., e-, h+, O2•-, and •OH) were generated to photo-reduce Cr(VI) and photo-oxidize NOR. Base on the identified intermediates, four degradation pathways of NOR were proposed. Finally, the Z-scheme mechanism were systematically confirmed through X-ray photoelectron spectroscopy (XPS), ESR, cyclic voltammetry (CV) tests, and photodeposition techniques.

Thin-wall hollow porous cystic-like graphitic carbon nitride with awakened n→π* electronic transitions and exceptional structural features for superior photocatalytic degradation of sulfamethoxazole.

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-C3N4 (HPCN) with curved layer edge was successfully fabricated via a non-template thermal-condensation strategy. The construction of unique distorted structure can evoke the hard-to-activate n→π* electronic transition to some extent, broadening the absorption spectrum to 800 nm. And benefiting from the multiple reflections of incident light, the effective photoactivation can be further achieved. Moreover, the thin-wall porous framework can shorten the diffusion distance and accelerate migration of photogenerated charge, favouring interfacial redox reactions. The optimized HPCN1.0 demonstrated an excellent photocatalytic degradation of SMX under blue-LED light irradiation, which was dramatically superior to that of pristine g-C3N4 (CN, 11.4 times). Ultimately, in consideration of reactions under several influencing factors with four different water samples, we demonstrated that the HPCN photocatalyst could be utilized far more productively for the elimination of SMX under real-world aqueous conditions. This work provides a straightforward approach for the removal of SMX and has immense potential to contribute to global scale environmental remediation.

Selective removal of heavy metals by Zr-based MOFs in wastewater: New acid and amino functionalization strategy.

Zr-based metal-organic frameworks (MOFs) have been developed in recent years to treat heavy metals, e.g. hexavalent chromium Cr6+ pollution, which damages the surrounding ecosystem and threaten human health. This kind of MOF is stable and convenient to prepare, but has the disadvantage of low adsorption capacity, limiting its wide application. To this end, a novel formic acid and amino modified MOFs were prepared, referred to as Form-UiO-66-NH2. Due to the modification of formic acid, its specific surface area, pore size, and crystal size were effectively expanded, and the adsorption capacity of Cr6+ was significantly enhanced. Under optimal conditions, Form-UiO-66-NH2 exhibited an excellent adsorption capacity (338.98 mg/g), ∼10 times higher than that reported for unmodified Zr-based MOFs and most other adsorbents. An in-depth study on the photoelectronic properties and pH confirmed that the adsorption mechanism of Form-UiO-66-NH2 to Cr6+ was electrostatic adsorption. After modification, the improvement of Cr6+ adsorption capacity by Form-UiO-66-NH2 was attributed to the expansion of its specific surface area and the increase in its surface charge. The present study revealed an important finding that Form-UiO-66-NH2 elucidated selective adsorption to Cr6+ in mixed wastewater containing toxic heavy metal ions and common nonmetallic water quality factors. This research provided a new acid and amino functionalization perspective for improving the adsorption capacity of Zr-based MOF adsorbents while simultaneously demonstrating their pertinence to target contaminant adsorption.

Interaction of Graphitic Carbon Nitride with Cell Membranes: Probing Phospholipid Extraction and Lipid Bilayer Destruction.

Understanding how nanomaterials interact with cell membranes has important implications for ecotoxicology and human health. Here, we investigated the interactions between graphitic carbon nitride (g-C3N4, CN) and red blood cells, a plausible contact target for nanoparticles when they enter the bloodstream. Through a hemolysis assay, the cytotoxicity of CN derived from different precursors was quantitatively assessed, which is highly related to the surface area of CN. Reactive oxygen species (ROS) generation and lipid peroxidation detection confirmed that CN causes rapid cell membrane rupture by a physical interaction mechanism rather than ROS-related chemical oxidation. Dye leakage assay and theoretical simulation indicated that the less-layered CN is prone to folding inward to wrap and extract lipid molecules from cell membranes. The electron-rich inherent pores of CN play a dominant role in capturing the headgroups of phospholipids, whereas the hydrophobic interaction is critical for the anchoring of lipid tails. Our further experimental evidence demonstrated that the destructive extraction of phospholipids from cell membranes by CN occurs primarily in the outer leaflet, and phosphatidylcholine is the most easily extracted lipid. Moreover, the formation of protein corona on CN was found to decrease the nonspecific interactions but increase steric repulsion, thus mitigating CN cytotoxicity. Overall, our data provide a molecular basis for CN's cytotoxicity.

Construction of dual transfer channels in graphitic carbon nitride photocatalyst for high-efficiency environmental pollution remediation: Enhanced exciton dissociation and carrier migration.

Graphitic carbon nitride (g-C3N4) is a promising candidate for photocatalysis, but exhibits moderate activity due to strongly bound excitons and sluggish charge migration. The dissociation of excitons to free electrons and holes is considered an effective strategy to enhance photocatalytic activity. Herein, a novel boron nitride quantum dots (BNQDs) modified P-doped g-C3N4 photocatalyst (BQPN) was successfully prepared by thermal polymerization method. Photoluminescence techniques and photoelectrochemical tests demonstrated that the introduction of P atoms and BNQDs promoted the dissociation of excitons and the migration of photogenerated carriers. Specifically, theoretical calculations revealed that P substitutions were the sites of pooled electrons, while BNQDs were the excellent photogenerated hole extractors. Accordingly, compared with g-C3N4, the BQPN showed improved performance in degrading four non-steroidal anti-inflammatory drugs (NSAIDs) under visible light irradiation. This work not only establishes an in-depth understanding of excitonic regulation in g-C3N4, but also offers a promising photocatalytic technology for environmental remediation.

Incorporating Oxygen Atoms in a SnS2 Atomic Layer to Simultaneously Stabilize Atomic Hydrogen and Accelerate the Generation of Hydroxyl Radicals for Water Decontamination.

Photoelectrocatalysis (PEC) is an efficient way to address various pollutants. Surface-adsorbed atomic hydrogen (H*) and hydroxyl radicals (•OH) play a key role in the PEC process. However, the instability of H* and low production of •OH considerably limit the PEC efficiency. In this study, we noted that incorporating oxygen atoms could regulate the behavior of H* by creating a locally favorable electron-rich state of S atoms in the SnS2 catalyst. The finely modulated H* led to a 12-fold decrease in the overpotential of H2O2 generation (H*-OOH*-H2O2-•OH) by decreasing the activation energy barrier of OOH* (rate-determining step). Considering density functional theory calculations, an H*-•OH redox pair suitable for a wide pH range (3-11) was successfully constructed based on the photocathode. The optimal SnS1.85O0.15 AL@TNA photocathode exhibited a ∼90% reduction in Cr(VI) in 10 min and ∼70% TOC removal of 4-nitrophenol, nearly 2- and 3-fold higher than that without oxygen incorporation. Electron spin resonance spectrometry and radical quenching experiments verified that H* and the derived •OH via 1-electron and 3-electron reduction were the main active species. Operando Raman spectroscopy confirmed that the stable SnO2 phase helped constantly activate the production of H* and •OH.

Activation of peracetic acid via Co3O4 with double-layered hollow structures for the highly efficient removal of sulfonamides: Kinetics insights and assessment of practical applications.

Sulfonamides (SAs) have been of ecotoxicological concern for ambient ecosystems due to their widespread application in the veterinary industry. Herein, we developed a powerful advanced oxidation peracetic acid (PAA) activation process for the remediation of SAs by Co3O4 with double-layered hollow structures (Co3O4 DLHSs). Systematic characterization results revealed that the polyporous hollow hierarchical structure endows Co3O4 DLHSs with abundant active reaction sites and enhanced mass transfer rate, which were conducive for improving the PAA activation efficiency. Laser flash photolysis experiment and mechanism studies indicated that organic radical species were dominant reactive species for SAs removal. The present system is also highly effective under natural water matrices and trace SAs concentration (20 µg/L) condition. More importantly, the chlorella acute toxicity of the SAs solution was eliminated during mineralization process, supporting this catalytic system may be efficaciously applied for the remediation of SAs contamination in ambient waterways.

Superhigh co-adsorption of tetracycline and copper by the ultrathin g-C3N4 modified graphene oxide hydrogels.

Development of economic and efficient absorbent for the simultaneous removal of antibiotics and heavy metals is needed. In this study, a three-dimensional porous ultrathin g-C3N4 (UCN) /graphene oxide (GO) hydrogel (UCN-GH) was prepared by co-assembling of UCN and GO nanosheets via the facile hydrothermal reaction. Characterizations indicated that the addition of UCN significantly decreased the reduction of CO and O-CO related groups of GO during the hydrothermal reaction and introduced amine groups on UCN-GH. The UCN-GH exhibited excellent ability on the co-removal of Cu(II) (qmax = 2.0-2.5 mmol g-1) and tetracycline (TC) (qmax = 1.2-3.0 mmol g-1) from water. The adsorption capacities were increased as UCN mass ratio increasing. The mutual effects between Cu(II) and TC were examined through adsorption kinetics and isotherm models. Characterizations and computational chemistry analysis indicated that Cu(II) is apt to coordinate with the amine groups on UCN than with oxygen groups on GO, which accounts for the enhanced adsorption ability of UCN-GH. In the binary system, Cu(II) acts as a bridge between TC and UCN-GH enhanced the removal of TC. The effects of pH and regular salt ions on the removal of Cu(II)/TC were examined. Moreover, the prepared UCN-GH also showed comparable co-adsorption capacities in practical water/wastewater.

Construction of double-functionalized g-C3N4 heterojunction structure via optimized charge transfer for the synergistically enhanced photocatalytic degradation of sulfonamides and H2O2 production.

Herein, supporting g-C3N4 embedded with benzene-ring (BCN) on P-modified g-C3N4 (PCN) successfully synthesized the homogeneous photocatalyst BCN/PCN (PBCN) via a simple thermal polymerization reaction. Under blue-light (LED) irradiation, the optimized PBCN (0.448 min-1) demonstrated excellent photocatalytic performance, attaining over 74 times the degradation rate for sulfisoxazole (SSZ) in contrast to non-functionalized g-C3N4 (CN, 0.006 min-1). Theoretical calculations revealed that the substitution of heterocyclic rings in the g-C3N4 triazine networks with benzene-rings enabled them to serve as electron donors, while promoting photoinduced spatial charge dissociation. Further, the carrier PCN tended to serve as electron acceptors to form electron-rich corner-phosphorous sites. Reactive species experiments demonstrate that the O2˙- and h+ constituted the primary photocatalytic mechanism of SSZ degradation. The potential SSZ degradation routes were predicted based on the transformation products via mass spectrometry. Finally, the composite materials also exhibited excellent photocatalytic activity in the conversion of solar energy to chemical energy (H2O2). This study guides the rational modification of g-C3N4-based semiconductors to achieve green energy production and beneficial ecological applications.