Effect of double carbon chains on enhanced removal of phenol from wastewater by amphoteric-gemini complex-modified bentonite

A novle amphoteric-gemini complex-modified bentonite was prepared with a gemini surfactant ethylene bis (tetradecyl dimethyl ammonium chloride) (EB) on the basis of the bentonite modified by amphoteric modifier dodecyldimethyl betaine (BS). The surface and structural characteristics of modified bentonite were characterized by X-ray diffraction (XRD), specific surface area (S_BET), scanning electron microscopy (SEM), Fourier infrared spectroscopy (FTIR), total carbon (TC) and total nitrogen (TN). In addition to studying the enhanced effect of gemini surfactants on phenol adsorption by kinetics and equilibrium adsorption, the influences of modification ratio, pH, temperature and ionic strength were investigated. Results showed that BS + EB complex modification increased the interlayer spacing (IS), TC and TN of bentonite (BT), and S_BET decreased with the increase in its total modification ratio. The adsorption of phenol on modified bentonite reached equilibrium in 20 min, and the adsorption capacities were in the order of BS+50 EB (BS+50% CEC EB)>BS+100 EB > BS+150 EB > BS+25 EB > BS > BT. The adsorption capacities of phenol on BS + EB complex modified bentonite (CMB) increased by 9.98-15.96 and 1.19-3.35 times compared with those on BT and BS single modified bentonite (SMB), respectively. The phenol adsorption capacities decreased with the increases in temperature and pH, while it increased with the augment in ionic strength. This study revealed that double carbon chains increased the organic carbon content more effectively than single carbon chains at low complex modification ratios, thus promoting the adsorption of phenol by hydrophobic partitioning on the bentonite surface.

Preparation of spherical filler-like ZnFe2O4/Bi2MoO6 surrounded by nanosheets and its photocatalytic applications

In this article, the spherical filler-like ZnFe₂O₄/Bi₂MoO₆ (ZFO/BMO) surrounded by nanosheets were synthesized by a solvothermal method using spherical ZnFe₂O₄ as a matrix. Scanning electron microscope (SEM), X-ray diffraction (XRD), Photoluminescence (PL), Fourier transform infrared spectroscopy (FT-IR) and Diffuse reflectance spectra (DRS) were used to characterize the prepared samples. The photocatalytic performance of the material was detected under 420 nm visible light by Rhodamine B (RhB). The degradation results indicated that the ZFO/BMO photocatalyst with 20% ZnFe₂O₄ content (ZFO/BMO-2) demonstrated highly efficient performance. The constructed Z-type ZFO/BMO heterojunction lengthens the visible light absorption threshold and improves the photocatalytic activity. Furthermore, ZFO/BMO heterojunction composite photocatalyst can be recycled effectively by applying an appropriate external magnetic field. It has important research value in photocatalysis and recycling.

One-step, high-yield synthesis of g-C3N4 nanosheets for enhanced visible light photocatalytic activity

A facile template-free one-step synthesis method of ultrathin g-C₃N₄ nanosheets was developed through thermal polycondensation of melamine. The higher temperature, prolonged time and tightly sealed crucible reaction system contributed to the formation of ultrathin g-C₃N₄ nanosheets. The as-synthesized g-C₃N₄ nanosheets were applied to the visible light photocatalytic degradation of RhB. The photocatalytic activity was significantly enhanced with increased calcination temperature from 500 °C to 650 °C and prolonged calcination time from 4 h to 10 h. Interestingly, the obtained ultrathin g-C₃N₄ nanosheets simultaneously possess high yield and excellent photocatalytic activity. Moreover, g-C₃N₄ nanosheets can maintain photochemical stability after five consecutive runs. The remarkably enhanced photocatalytic activity can be interpreted as the synergistic effects of the enhanced crystallinity, the large surface area, the reduced layer thickness and size and the reduced number of defects. A new layer exfoliation and splitting mechanism of the formation of the ultrathin nanosheets was proposed. This work provides a new strategy to develop a facile eco-friendly template-free one-step synthesis method for potential large-scale synthesis of ultrathin nanosheets with high yield, high photocatalytic efficiency and stable activity for environmental and energetic applications.

Facile one-step economical methodology of metal free g-C3N4 synthesis with remarkable photocatalytic performance under visible light to degrade trans-resveratrol

Nanoropes crafted graphitic carbon nitride (NRCN-2), prepared by a novel, cost effective and easy to scale up method. We used naphthalene to induce nanoropes like structure inside of the graphitic carbon nitride; on industrial scale, it is easy to recycle naphthalene. The Naphthalene decomposition temperature (>700 °C) is much higher than the polymerization temperature ( = 520 °C) of NRCN-2. At higher temperature, naphthalene molecular vapors moved vigorously through graphitic carbon nitride sheets and caused the sheets to adopt nanoropes like morphology. Photocatalyst (NRCN-2) presented extraordinary specific surface area (351.08 m² g^-1), stimulated the parting effectiveness of photo-generated electrons and holes, by extending the visible light harvesting ability to 600 nm. The nanoropes adopted photocatalysts can easily degrade MO in 90 min and trans-resveratrol in 120 min. The buoyant energetic reactive species (h⁺, OH and O₂-), created during photocatalysis caused mineralization of pollutants. The apparent rate constant, half-life time period and regression coefficients for MO and trans-resveratrol calculated with the help of pseudo first order kinetics. For MO the value of K_app is 2.968 × 10^-2 min^-1, for trans-resveratrol, K_app is 2.490 × 10^-2 min^-1, corresponding half-life values are 23.354 min and 27.837 min respectively.

Highly efficient degradation of 2,4-dichlorophenol over CeO2/g-C3N4 composites under visible-light irradiation: Detailed reaction pathway and mechanism

Herein, we report for the first time the highly efficient degradation of 2,4-dichlorophenol (2,4-DCP) over CeO₂/g-C₃N₄ composites (xCeO/CN) prepared via wet-chemical solution method. It is shown that the resultant nanocomposites with a proper mass ratio percentage (15%) of CeO coupled exhibit greatly enhanced visible-light activity for 2,4-dichlorophenol (2,4-DCP) degradation compared to the bare g-C₃N₄. From photoluminescence (PL) and Fluorescence (FL) results, it is suggested that enhanced photo-degradation is attributed to the significantly improved charge separation and transfer as a result of the proper band alignments between g-C₃N₄ and CeO components. Further, from radical trapping experiments, it is confirmed that hydroxyl radicals (OH) are the predominant oxidants involved in the degradation of 2,4-DCP over CeO/CN composites. Furthermore, a possible reaction pathway and detailed photocatalytic mechanism for 2,4-DCP degradation is proposed mainly based on the detected liquid chromatography tandem mass spectrometry (LC-MS) intermediate products, that readily transform into CO₂ and H₂O. This work would help researchers to deeply understand the reaction mechanism of 2,4-DCP and would provide feasible routes to fabricate g-C₃N₄-based highly efficient photocatalysts for environmental remediation.

Nitrogen-doped fluorescent graphene nanosheets as visible-light-driven photocatalysts for dye degradation and selective sensing of ascorbic acid

Facile synthesis of water soluble fluorescent N-doped graphene nanosheets for multifunctional applications in photocatalysis and sensing.

Facile hydrothermal synthesis of magnetic adsorbent CoFe2O4/MMT to eliminate antibiotics in aqueous phase: tetracycline and ciprofloxacin

A highly resourceful, eco-friendly, and recyclable magnetic adsorbent based on montmorillonite (CoFe₂O₄/MMT) was fabricated via a facile hydrothermal method to harvest tetracycline (TC) and ciprofloxacin (CIP) from pollutant water. The prepared adsorbent was characterized by XRD, FT-IR, SEM, and VSM methods to comprehend its structure, morphology, and magnetism. Effects of experimental parameters including solution pH, adsorption time, initial concentration, and ion strength were studied in details. The experimental adsorption data of TC and CIP fitted into pseudo-second-order kinetic model and Langmuir isotherm, respectively. The maximum adsorptions of TC and CIP could reach up to 240.91 and 224.00 mg/g. The thermodynamic study indicates that the adsorption process is spontaneous. In addition, the antibiotics can be further degraded under visible light environment and the magnetic sorbent can also be thermally regenerated. Graphical abstract ᅟ.

Adsorption properties, kinetics & thermodynamics of tetracycline on carboxymethyl-chitosan reformed montmorillonite

This paper describes a modification method of Na-montmorillonite (Na-Mt) with carboxymethyl-chitosan (CMC). The as-prepared samples were analyzed by Fourier transform infrared (FT-IR), X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET) surface analyzer and thermogravimetric analysis (TGA). Two common tetracycline antibiotics, tetracycline (TET) and chlortetracycline (CTC), were selected as the represented pollutants and adsorbed by CMC-Mt under different experimental conditions. The intercalation of CMC obviously amplified the basal spacing of the interlayers confirmed by XRD measurements and improved the adsorption capacities of montmorillonite to some degree. The results showed that the tetracycline antibiotic sorption onto CMC-Mt was mainly dependent on pH and was not affected by temperature. Besides, the removal of TET and CTC rapidly attained an equilibrium within 2 h of contact time. The kinetic data of adsorption was determined by first-order, second-order kinetics and intraparticle diffusion models. The kinetic study indicates that the TET and CTC adsorption processes obeyed the second-order kinetics. The Freundlich isotherm study was in agreement with the practical data, suggesting a heterogeneous sorption process. Furthermore, the thermodynamic studies revealed that the removal process was more spontaneous at a lower temperature, implying it an exothermic reaction. The synthesized adsorbent CMC-Mt can be widely used in the treatment of wastewater.

Sensitization of TiO2 nanosheets with Cu-biphenylamine framework to enhance photocatalytic degradation performance of toxic organic contaminants: synthesis, mechanism and kinetic studies

TNS/Cu(X) composite materials were firstly synthesized via simple overnight stirring of TNS in the methanolic solution of Cu complexes. The developed TNS/Cu(X) composites had a well-designed nanostructure, in which the TNS and Cu complexes were closely bounded with each other. The biphenylamine complexes fixed on the TNS surface in form of nanocapsules, which were confirmed by TEM and SEM, thus improving the surface area and subsequently charge separation. Innovatively merged photocatalysts of Cu complexes with TNS were successfully verified for photocatalytic mineralization of colored and colorless organic contaminants under the visible light degradation. As compared to original TNS, TNS/Cu(BA) showed prominent improvement in the catalytic actions. Kinetics i.e. t _1/2 (half-life times period), K _app, and R ² (linear regression co-efficient) were also studied. The amended materials created charge separation, by means of electrons gathering at the higher CB, and holes gathering at the lower level valence band of the Cu complex, therefore improving mineralization efficiency of the electrons and holes. TNS/Cu(BA) degrade 99%-99.6% of methyl orange (MO) and rhodamine B (RhB) dyes at 120 min, and 160 min, respectively, and 68% of phenol and 53% of TCP were destroyed in 180 min. The resilient holes can directly destroy MO, RhB, phenol, and TCP.