A novel g-C3N4 nanosheet/Ag3PO4/α-Bi2O3 ternary dual Z-scheme heterojunction with increased light absorption and expanded specific surface area for efficient photocatalytic removal of TC.

A novel ternary dual Z-scheme 2D g-C3N4 nanosheet/Ag3PO4/α-Bi2O3 (CNN/AP/BO) photocatalyst was successfully synthesized by an in situ deposition and hydrothermal-calcination method. The coupling of AP and BO remarkably enhanced the photocatalytic tetracycline (TC) degradation under visible light illumination, with an optimal removal efficiency of 91.6% (60 min), which can be attributed to the extended visible-light absorption and increased specific surface area owing to the interfacial intimate coupling with well-matched energy band positions between semiconductors. The improved photocatalytic activity resulted from the abundant free radicals by the order of ˙O2- > h+ > ˙OH based on the electron spin resonance (ESR) and quenching experiment results. In addition, the possible mechanism of TC degradation over the ternary dual Z-scheme heterojunction CNN/AP/BO was proposed.

Enhancement of redox capacity derived from O-doping of g-C3N4/WO3 nanosheets for the photocatalytic degradation of tetracycline under different dissolved oxygen concentration.

Element doping is an essential method for adjusting band structure, light absorbance and charge transfer, and separation of semiconductors. Besides this, whether the photocatalyst can function in an oxygen-deficient environment is also important. Herein, a novel Z-scheme heterojunction photocatalyst O-doped g-C3N4/WO3 (OCN/W) was fabricated and used for the photocatalytic degradation of tetracycline (TC) at different dissolved oxygen concentrations. The introduction of O atoms into g-C3N4via hydrothermal treatment manipulates the band structure of the material by increasing the conduction band potential, thus producing more ˙O2-. The TC removal rate of OCN/W-2.0 is 89.8% within 60 min under visible light irradiation, which is 1.77 times higher than that of porous g-C3N4 nanosheets (PCN). Furthermore, the photocatalytic performance of OCN/W-2.0 also reaches 75% even under oxygen-deficient conditions. The effects of different anions and humic acid in the reaction system can be neglected. The enhanced performance can be attributed to the improved charge separation and the outstanding optical properties of the Z-scheme heterojunction. A possible mechanism was postulated, in which ˙O2- and h+ are the main reactive species in TC degradation. The OCN/W-2.0 shows a stable structure and outstanding reusability. This work provides insight into antibiotics removal under different dissolved oxygen conditions and the design of photocatalysts for practical applications.

A novel Z-scheme porous g-C3N4 nanosheet/Ag3PO4 photocatalyst decorated with N-doped CDs for high efficiency removal of antibiotics.

A number of porous g-C3N4 nanosheet/Ag3PO4/NCDs (PCNNS/AP/NCDs) with little amounts of Ag3PO4 were synthesized via an in situ sedimentation-calcination method. The PCNNS/AP/NCDs photocatalyst exhibited excellent photocatalytic performance for the photocatalytic degradation of tetracycline (TC) under visible light irradiation at a removal rate of 90.5% in 40 min. The study of the reaction kinetics of the as-prepared samples was in accordance with the pseudo-second-order kinetics, with the correlation coefficient (R2) being greater than 0.9776. Meanwhile, the photocatalyst was capable of degrading ciprofloxacin (CIP), and showed good performance even under actual water conditions with natural sunlight irradiation, indicating that the photocatalyst has wide practical applications. In addition, the photocatalytic performance and the XRD and FTIR spectra showed no obvious changes even after four photocatalytic degradation cycles, which revealed the high stability of the PCNNS/AP/NCDs photocatalyst. Furthermore, the possible degradation pathways of TC and the possible Z-scheme mechanism were proposed with ˙O2- and h+ as the main active species contributing to photocatalytic degradation. The results provide a novel insight into the fabrication of Z-scheme PCNNS/AP/NCDs and introduce them as an efficient visible-light-responsive photocatalyst for use in practical applications.

Relative roles of H-atom transfer and electron transfer in the debromination of polybrominated diphenyl ethers by palladized nanoscale zerovalent iron.

The relative significance of H-atom transfer versus electron transfer in the dehalogenation of halogenated organic compounds (HOCs) in bimetallic systems has long been debated. In this study, we have investigated this question through the case study of the debromination of 2, 2', 4, 4'-tetrabromodiphenyl ether (BDE-47). The debromination rates of isomer products of BDE-47 by palladized nano zero-valent iron (n-ZVI/Pd) in the same reactor were compared. The results confirmed a shift in the debromination pathway of BDE-47 when treated with unpalladized nano zero-valent iron (n-ZVI) vs. treatment with n-ZVI/Pd. Study showed that BDEs could be rapidly debrominated in a palladium-H2 system, and the debromination pathway in this system is the same as that in the n-ZVI/Pd system. These results suggest that the H-atom species adsorbed on the surface of palladium are responsible for the enhanced reaction rates and the shift of the debromination pathway in the n-ZVI/Pd system. The Mulliken charges, calculated with density functional theory, on bromine atoms of PBDEs were directly correlated with the susceptibility to the e-transfer pathway in the n-ZVI system and inversely correlated with the susceptibility to the H-transfer pathway in n-ZVI/Pd system. These experimentally verified correlations in BDE-47 permit the prediction of the dominant debromination pathway in other BDEs.

[Preparation and performance investigation of Trichoderma viride-modified corn stalk as sorbent materials for oil spills].

This work aims at preparing oil spill sorbent (TCS, Trichoderma viride-modified corn stalk) through solid-state fermentation of corn stalk by Trichoderma viride. Single-factor experiments, including the effect of modification time, solid-liquid ratio of modification and modification temperature, and adsorption experiments simulating oil spill condition, were carried out. The results indicated that the maximum oil adsorption of TCS, 13.84 g x g(-1), could be obtained under the conditions of 6 days of modification, with a solid-liquid ratio of 1:4 and a modification temperature of 25 degrees C. This oil absorption was 110.33% of that of the raw material (RCS, Raw Corn Stalk). Comparing RCS and TCS by means of Scanning Electron Microscopy (SEM), Fourier Transform Infrared Spectroscopy (FT-IR) and X-ray Diffraction (XRD), the results separately showed that TCS had rougher surface, lower cellulose content and higher instability, which explains the increase of oil absorption. Also, the component analysis indicated that bio-modification could reduce the contents of celluloses and hemicelluloses from corn stalk. Besides, sorption kinetics and oil retention performance test showed that, TCS, which could reach adsorption equilibrium after 1 h of 80 r x min(-1) oscillating, had fast oil adsorption rate, and it also had good oil retention performance, which could keep 74. 87% of the initial adsorption rate when trickling 10 min after reaching adsorption equilibrium.