Synergistic Effect of Hydrochloric Acid and Phytic Acid Doping on Polyaniline-Coupled g-C3N4 Nanosheets for Photocatalytic Cr(VI) Reduction and Dye Degradation

A novel hydrogel composite of chitosan-phytic acid complex with PAAm: Characterization and adsorptive properties for UO22+and methylene blue

The composite of a polyelectrolyte combination of chitosan and phytic acid (CsPa) and its entrapped form in polyacrylamide (PAAmCsPa) were synthesized. The composites were characterized by a number of methods including ATR-FTIR, SEM-EDX, XRD and XPS. The adsorptive properties of CsPa and PAAmCsPa were analyzed and modelled for UO22+ and methylene blue (MB+). The results showed that the composites exhibited physico-chemical properties that were both inherited from the components as well as unique to them. The isotherms of UO22+ and MB+ were L-type Giles isotherms. The adsorption kinetics followed the pseudo-second-order model, in contrast to the Langmuir model, which predicts first-order kinetics for both species. According to the Weber-Morris model, the nature of the adsorption process was ion exchange and/or complex formation for both composites and ions. The thermodynamics showed that the adsorption process was endothermic (ΔH > 0), with increasing entropy (ΔS > 0) and spontaneous (ΔG < 0). The reusability tests of the composites for UO22+ adsorption showed that the composites were substantially reusable for 6 cycles. The composites were selective for UO22+ over MB+ ions, and UO22+ adsorption increased significantly when MB+ adsorbed composites were used. Reproducible measurements demonstrating the storability of the composites were obtained over a period of approximately one year.

Enhanced photocatalytic performance of the N-rGO/g-C3N4 nanocomposite for efficient solar-driven water remediation

This paper describes the synthesis and analysis of a photocatalyst made from a combination of reduced graphene oxide (rGO) and graphitic carbon nitride (g-C3N4) through a simple hydrothermal process. The effectiveness of the N-rGO/g-C3N4 heterostructure in photocatalysis was examined by studying the breakdown of different types of organic pollutants, such as cationic and anionic dyes, as well as antibiotics, under simulated solar light irradiation. Due to the presence of Schottky junctions formed between rGO and g-C3N4, the electron transfer process is significantly enhanced, leading to a reduction in the recombination of photogenerated electrons and holes. As a result, the photocatalytic activity of the rGO/g-C3N4 photocatalyst is significantly higher compared to that of g-C3N4 alone. The photocatalytic performance was further augmented through the nitrogen doping of rGO, which led to an increase in conductivity due to electron doping and an enhancement in the charge separation process. The heterojunction of rGO/g-C3N4 with an optimum concentration of 60% rGO attained a degradation efficiency of 98.7% for rhodamine B (RhB) dye after 50 minutes of light irradiation. In comparison, the nitrogen-doped photocatalyst (N-rGO/g-C3N4) achieved a photodegradation efficiency of 99.99% within 30 minutes. The reaction rate constant of the N-rGO/g-C3N4 nanocomposite was found to be 0.11 min-1 using pseudo first-order rate kinetics. This value is about 16 times more than that of pure g-C3N4 (0.007 min-1) for the degradation of rhodamine B. Additionally, N-rGO/g-C3N4 effectively degraded various contaminants, such as methylene blue, methyl orange, and tetracycline hydrochloride. The paper also addresses the photocatalytic mechanism, which entails the facilitated movement of electrons and holes produced by light, owing to the alignment of energy bands at the interface of the N-rGO/g-C3N4 heterojunction. These findings contribute to the advancement of a metal-free and porous photocatalyst that is highly interconnected and can be used for waste water treatment and environmental remediation.

Hydrothermally Synthesized Z-Scheme Nanocomposite of ZIF-9 Modified MXene for Photocatalytic Degradation of 4-Chlorophenol

4-Chlorophenol (4CP) is a well-known environmental contaminant often detected in wastewater, generally arising from industrial processes such as chemical manufacture, pharmaceutical production, and pesticide formulation. 4CP is a matter of great concern since it is persistent and has the potential to have harmful impacts on both aquatic ecosystems and human health, owing to its hazardous and mutagenic properties. Hence, degradation of 4CP is of utmost significance. This research investigates the photocatalytic degradation of 4CP using a novel Z-scheme heterojunction nanocomposite composed of MXene and ZIF-9. The nanocomposite is synthesized through a two-step hydrothermal method and thoroughly characterized by using XRD, SEM, UV-visible spectroscopy, zeta potential, and electrochemical impedance spectroscopy studies, confirming successful fabrication with improved surface properties. The comparative photocatalytic degradation studies between pristine materials and the nanocomposite were performed, and significant enhancement in performance was observed. The effect of pH on the degradation efficiency is also explored and correlated with the surface charge. The Z-scheme photocatalysis mechanism is proposed, which is supported by time-resolved photoluminescence studies and scavenger experiments. The reusability of the nanocomposite is also evaluated. The study contributes to the development of efficient and sustainable photocatalysts for wastewater treatment.

Cyclic enrichment of chromium based on valence state transformation in metal-free photocatalytic reductive imprinted composite hydrogel

Cr (VI) exists in anion form and can be reduced to positive charged Cr (III) under certain conditions. Can positive charged Cr (III) be continually used for absorbing Cr (VI) to achieve cyclic accumulation of chromium? In this paper, an ion imprinting material for adsorption of Cr (VI) was prepared by dispersing polypyrrole (PPy) in a gelatin/chitosan (Gel/CS) hydrogel network, named Gel/CS/PPy. Based on the conversion of Cr (VI) to Cr (III), a cyclic enrichment process including adsorption-photoreduction-fixation-readsorption of Cr (VI) was established in Gel/CS/PPy hydrogel. The composition and structure of the Gel/CS/PPy were analyzed by scanning electron microscopy (SEM), Fourier transform-infrared spectroscopy (FT-IR), thermogravimetric (TGA), texture analyzer (Universal TA), zeta potential and ultraviolet-visible-near infrared spectra (UV-vis-NIR). The conversion of Cr (VI) and Cr (III) and its promoting effect on readsorption were verified by XPS. The results showed that Gel/CS/PPy has good adsorption capacity for Cr (VI) and excellent photocatalytic ability to reduce Cr (VI) to Cr (III). Cr (III)-loaded Gel/CS/PPy can be further used to adsorb Cr (VI) and showed good adsorption efficiency even after four cycles. The optimal operating condition for Cr (VI) adsorption is pH = 3; 2 g/L dose of Gel/CS/PPy; and the adsorption capacity of Cr (VI) was about 106.8 mg/g after six adsorption cycles. Since Gel/CS/PPy is composed of organic components, high purity chromium can be recovered by simple calcination method later. Therefore, the synthesized Gel/CS/PPy has great potential in the practical application of low concentration Cr (VI) treatment in water.

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.

Interfacial engineering of CuFeS2 quantum dots via platinum decoration with enhanced Cr(VI) reduction dynamics under UV-Vis-NIR radiation

Configuring reactive and stable catalytic interfaces is crucial to design efficient photocatalysts for Cr(VI) reduction. Herein, via the platinum decoration approach based on interfacial engineering, we developed an effective catalytic interface within novel semiconducting chalcopyrite quantum dots (Pt/CuFeS₂ QDs). Benefiting from the catalytic merits of the Pt modulated interfacial structure and electronic structure, Pt/CuFeS₂ QDs show a broader light absorption capability extending to near-infrared radiation (NIR) range with superior carriers separation performance and faster charge transfer efficiency, which delivers a three-folder faster photocatalytic Cr(VI) reduction efficiency comparing to the original CuFeS₂ QDs. Density functional theory (DFT) calculations unravel that Pt atoms prefer to be anchored with the surface S atoms to form a stable interfacial structure with faster electron transfer and Cr(VI) reduction dynamics. This work demonstrates that platinum decoration based on interfacial engineering is an effective strategy to simultaneously modulate the band structure and accelerate the interfacial reaction dynamics for semiconductor photocatalysts, which paves the way for designing highly efficient photocatalysts for light-driven environmental and energy engineering applications.

A p–n heterostructural g-C3N4/PANI composite for the remediation of heavy metals and organic pollutants in water

A novel g-C3N4/PANI composite was fabricated via surface charge-induced electrostatic self-assembly method, which showed excellent a photocatalytic performance for Cr(vi) reduction and MO degradation under visible-light.

3D hollow MXene@ZnIn2S4 heterojunction with rich zinc vacancies for highly efficient visible-light photocatalytic reduction

Well-designed heterojunction semicounductor coupled with high-conductive cocatalyst can obtain boosted photocatalytic activity. Herein, a novel three-dimensional (3D) hollow heterojunction was prepared by coating the indium zinc sulfide (ZnIn₂S₄) nanosheets with rich-zinc vacancies (V_Zn) on 3D hollow titanium carbide (Ti₃C₂). The obtained 3D hollow heterojunction (Ti₃C₂@ZnIn₂S₄) achieved effective optical collection and promoted the separation and transmission of photogenerated carriers as well as the surface reaction of spatial separation. In addition, time-resolved photoluminescence and steady-state photoluminescence spectra indicated that the existence of V_Zn and the introduction of hollow Ti₃C₂ spherical shell effectively inhibited the recombination of photogenerated carriers and accelerated their separation and transmission, thus further enhancing the photocatalytic activity. In addition, the introduction of 3D hollow Ti₃C₂ benefited a larger specific surface area for heavy metal adsorption. Due to the unique structural and compositional characteristics, the heterojunction showed high efficiency of Cr(VI) reduction under visible light. In particular, the optimal Ti₃C₂@ZnIn₂S₄ heterojunction (1%-Ti₃C₂@ZnIn₂S₄) achieved 100% removal of Cr(VI) within 25 min, with a reaction rate constant of 0.225, which was 8.5 times higher than that of the pristine ZnIn₂S₄. The superior reusability and structural stability further indicated the MXene-based novel photocatalyst is promising for application in environmental remediation.

The integrated production of ultrathing-C3N4and membrane assisted by edible syrup for the sustained photocatalytic treatment of Cr(VI) and tetracycline

The exfoliation of bulk raw graphitic carbon nitride (g-C₃N₄) by edible glucose syrup to produce ultrathing-C₃N₄nanosheets in concentrations of up to 0.2 mg ml^-1was achieved. Detailed characterization through TEM, AFM, FT-IR, XRD, Raman and TGA confirmed the formation of ultrathin structure and improved properties. Compared to rawg-C₃N₄, the prepared thing-C₃N₄layers exhibited a 18-fold enhancement in Cr(VI) reduction and a 3-fold enhancement in tetracycline hydrochloride degradation, which is ascribed to their larger specific surface area and more exposed active sites. The layeredg-C₃N₄membrane was constructed via direct vacuum filtration. The layer-stackedg-C₃N₄nanosheet membrane exhibited an excellent and sustained photocatalytic performance as the prepared thing-C₃N₄layers could maintain a layered lamella after stacking in filtration process. The recyclable synthesis of ultrathing-C₃N₄layers and layer-stackedg-C₃N₄membrane by our method provides a sustainable strategy to pollution treatment by 2D materials.

Self-Assembly of Poly(ethyleneimine)-Modified g-C3N4 Nanosheets with Lysozyme Fibrils for Chromium Detoxification

We disclose a straightforward approach to fabricate nanocomposites for efficient capture of Cr(VI) from an aqueous solution through the self-assembly of poly(ethyleneimine)-modified graphitic carbon nitride nanosheets (PEI-g-C₃N₄ NSs) and lysozyme fibrils (LFs). The as-made PEI-g-C₃N₄ NSs@LFs exhibited mesoporous structures with a high specific surface area of 39.6 m² g^-1, a large pore volume of 0.25 cm³ g^-1, several functional groups (e.g., -N, -NH, -NH₂, and -COOH), and a zero-point charge at pH 9.1. These merits allow the PEI-g-C₃N₄ NSs@LFs to further enhance their physical adsorption and electrostatic attraction with the negatively charged Cr(VI) species of HCrO₄^- and CrO₄^2-, which is beneficial for the uptake of Cr(VI), >80%, from an aqueous solution in a wide pH range. Interestingly, X-ray photoelectron spectra indicate that the PEI-g-C₃N₄ NSs@LFs converted Cr(VI) to Cr(III) through visible-light-induced photoreduction. The adsorption of Cr(VI) on the surface of PEI-g-C₃N₄ NSs@LFs was found to obey the Freundlich isotherm model, signifying that they have a heterogeneous surface for the multilayer uptake of Cr(VI). In contrast, the PEI-g-C₃N₄ NSs and LFs as Cr(VI) adsorbents followed the Langmuir isotherm model. Adsorption kinetic studies showed that the uptake of Cr(VI) through the PEI-g-C₃N₄ NSs@LFs was highly correlated with a pseudo-first-order model, suggesting that physisorption dominates the interaction of Cr(VI) and the PEI-g-C₃N₄ NSs@LFs. In real-life applications, the PEI-g-C₃N₄ NSs@LFs were used for the detoxification of the total chromium in the industrial effluent and sludge samples.

Construction of 2D/2D MoS2/g-C3N4 Heterostructures for Photoreduction of Cr (VI)

2D/2D MoS₂/g-C₃N₄ (MCN) surface heterostructures were created by second thermal polymerization of bulk g-C₃N₄ and the reaction of thiourea and MoO₃ at 670 °C. MoS₂ networks grew vertically along the (002) facet on superior thin g-C₃N₄ nanosheets. The layered heterostructures drastically improved the Cr(VI) removal ability. In the dark case, 27% of Cr(VI) was removed within 45 min. The result indicates that the adsorption of Cr(VI) was a chemical adsorption process involving the sharing and transfer of electrons. The equilibrium data indicate that the adsorbent was covered with a monolayer adsorbate, which conformed to the Langmuir isotherm model (R² = 0.9618). In addition, MCN nanocomposites could convert Cr(VI) into non-toxic Cr(III) by photoreduction under visible light irradiation. With an optimized composition, 100% of Cr(VI) was removed within 30 min, which was ∼10 times quicker compared with Cr(VI) removal under dark conditions. Because g-C₃N₄ nanosheets (sample CN₆₇₀) with higher photocurrent density revealed the lowest photoreduction Cr(VI) ability, adsorption plays an important role in Cr(VI) removal. For MoS₂/g-C₃N₄ nanocomposites used in Cr(VI) removal, adsorption and photoreduction were incorporated together to get excellent performance.

Influence of Photocatalysis on Blood Cell Attachment over Protein-Immobilized Polystyrene Surfaces Modified with a Poly(styrene)-b-Poly(acrylic acid) Copolymer

In the present study, thrombocytes, erythrocytes, and leukocytes were individually brought into contact with different immobilized blood proteins on the surface of polystyrene (PS), which was modified with a poly(styrene)-b-poly(acrylic acid) copolymer. When the concentration of fibronectin was greater than 5 μg mL^-1, the attachment of erythrocytes increased, which indicated that the modified PS surface was less compatible with erythrocytes. In addition, vitronectin and laminin attached on the surface increased the adhesion of thrombocytes; higher adhesion was observed for leukocytes in the cases of fibrinogen, lysozyme, and laminin. Interestingly, adhesion properties of blood cells on the protein surface could be influenced by the addition of metal oxide- and carbon-based photocatalysts. After a photocatalytic treatment by metal oxide-based TiO₂, the adhesion amounts of erythrocytes improved slightly, whereas the adhesion of leukocytes and thrombocytes decreased after treatment with a carbon-based g-C₃N₄ nanosheet. Our results suggested that the surface modification of the substrate through photocatalysis using various photocatalysts along with the grafting of the poly(styrene)-b-poly(acrylic acid) copolymer could be a promising approach to alternatively control the blood compatibility on the protein surface.

A Codoped Polymeric Photocatalyst with Prolonged Carrier Lifetime and Extended Spectral Response up to 600 nm for Enhanced Hydrogen Evolution

The intrinsic properties of photocatalysts, such as electron state and energy band structure, contribute significantly to their catalytic performance. However, it is difficult to alter these properties of semiconductors by conventional modifications. To adjust the intrinsic properties while preserving long-term conjugation of the polymeric photocatalysts, a post-thermal treatment is proposed to codope P and Na into polymeric carbon nitride in this work. After codoping, the absorption of visible irradiation is strongly extended up to 639 nm. Additionally, the lifetime of charge carriers is almost tripled from 1.09 to 2.93 ns. The photocatalytic hydrogen evolution performance under visible light is improved to 2032 μmol·h^-1 g^-1 in the optimized sample, corresponding to apparent quantum efficiencies of 6.79% and 0.09% at 420 and 600 nm, respectively. The enhanced catalytic activity is ascribed to the synergistic effects of prolonged lifetime and increased charge density that resulted from lattice distortion and extended visible utilization due to the formation of subgap state. Our work provides new pathways for the modification of polymeric catalysts toward high-performance and full-spectrum photocatalysis.

Sulfonated polyaniline-encapsulated graphene@graphitic carbon nitride nanocomposites for significantly enhanced photocatalytic degradation of phenol: a mechanistic study

The photocatalytic degradation of phenol through -s-PANI@g-C₃N₄ and its nanocomposites with graphene.

Synthesis of hollow donut-like carbon nitride for the visible light-driven highly efficient photocatalytic production of hydrogen and degradation of pollutants

Design and synthesis of highly effective, hollow, erythrocyte-like g-C₃N₄ photocatalysts towards the degradation of environmental pollutants.

Palladium nanoparticles supported on nanosheet-like graphitic carbon nitride for catalytic transfer hydrogenation reaction

Pd/g-C₃N₄ catalysts with well-dispersed, electron-enriched Pd nanoparticles immobilized on pyridinic N atoms of g-C₃N₄ are active for catalytic transfer hydrogenation under ambient conditions.