Enhanced visible light photocurrent response and photodegradation efficiency over TiO2–graphene nanocomposite pillared with tin porphyrin

Influence of ozone supply mode and aeration on photocatalytic ozonation of organic pollutants in wastewater using TiO2 and ZnO nanoparticles

Photocatalytic ozonation, which combines the effects of lighting and ozonation, has been shown to enhance the decolorization and degradation of organic pollutants in wastewater. Dye solutions with concentrations of 10 ppm for both methylene blue and methyl orange dyes were used. The influence of ozoneation on the performance of photocatalytic activity of TiO2 and ZnO nanoparticles for the removal of organic dyes from aqueous solutions was investigated. To evaluate their efficacy for the removal of methylene blue and methyl orange dyes from aqueous solutions, the photocatalysts were exposed to UV light for 90 min, with ozone supplied either intermittently or continuously by an SDBD cold plasma reactor. The photocatalysts utilized in this study were characterized using SEM and XRD techniques. The degree of color degradation was determined using UV-Vis spectroscopy. The results demonstrate that TiO2 and ZnO nanoparticles exhibit different degrees of photocatalytic activity for the two dyes. The addition of ozone was found to enhance both the color degradation and mineralization rates of the pollutants, with intermittent ozonation proving more effective than continuous ozonation. The most significant color degradation results were obtained using TiO2 nanoparticles with intermittent ozonation for methylene blue dye (97 %) and ZnO nanoparticles with intermittent ozonation for methyl orange dye (40 %). Overall, this study provides evidence that photocatalytic ozonation represents a promising technique for water treatment.

Use of porphyrin-containing polymers of intrinsic microporosity as selective photocatalysts for oxidative detoxification of chemical warfare agent simulant

Porphyrin-based polymers of intrinsic microporosity (PIMs) in photocatalytic degradation of a mustard-gas simulant (2-chloroethyl ethyl sulfide (2-CEES)) was demonstrated. Under blue-ultraviolet (UV) light-emitting diode (LED) irradiation, porphyrin-based PIMs PP-H2 and PP-Zn(II) worked as effective heterogeneous photocatalysts for oxidation of 2-CEES. Solvent played an important role in the conversion and selectivity of 2-CEES oxidation. When AcCN was used as a solvent, PP-H2and PP-Zn(II) demonstrated complete conversion of 2-CEES in 30 and 50 min, respectively, whereas they showed complete conversion at 60 and 70 min, respectively, when MeOH was used as a solvent. Moreover, these PIMs produced 2-chloroethyl ethyl sulfoxide (2-CEESO) as a major product with small amounts of 2-chloroethyl ethyl sulfone (2-CEESO[Formula: see text], ethyl methoxyethyl sulfoxide (EMSO), and vinyl sulfoxide (EVS) as side products in most solvents. However, when MeOH was used as a solvent, highly toxic 2-CEESO2 was not observed as a side product. Furthermore, these PIMs showed no significant changes in photocatalytic activity even after five cycles of reuse, indicating their high stability. Thus, the series of PIMs prepared herein can perform well as heterogeneous catalysts in photooxidation of 2-CEES under blue-UV LED light, with PP-H2 being the most effective oxidation catalyst, leading to fast conversion and high selectivity.

Construction of a new cascade photogenerated charge transfer system for the efficient removal of bio-toxic levofloxacin and rhodamine B from aqueous solution: Mechanism, degradation pathways and intermediates study

In this work, a novel cascade system (i.e., SnTCPP/g-C₃N₄/Bi₂WO₆) is successfully constructed using stannum (II) meso-tetra (4-carboxyphenyl) porphyrin (SnTCPP) as the key photovoltaic agent for the first time. Visible light driven photocatalytic experiments indicated that wt. 12% SnTCPP and 30% Bi₂WO₆ codecorated g-C₃N₄ demonstrates the highest photodecomposition capabilities for levofloxacin and rhodamine B, achieving 85.64% and 93.64% degradation rates, respectively. The dramatically enhanced photocatalytic performance mainly raised from the synergetic co-effects among SnTCPP, g-C₃N₄ and Bi₂WO₆, including: i) the incorporation of SnTCPP extends the visible light response of the binary Bi₂WO₆/g-C₃N₄ heterojunctions, resulting in the highly efficient visible light harvesting; ii) we find that the g-C₃N₄ not only serves as a promising supporter to trap electrons from Bi₂WO₆, but also as an interfacial electron-hole pairs transfer moderator, like "volleyball setter" to facilitate the charges transfer between Bi₂WO₆ and SnTCPP. The presence of the "setter" endows a cascade system for boosting the photodegradation efficiency of levofloxacin and rhodamine B. This study provides a promising design strategy to construct efficient g-C₃N₄ based heterojunctions suitable for removing pharmaceutical antibiotics and hazardous dyes from various real wastewaters.

Construction of BPQDs/Ti3C2@TiO2 Composites with Favorable Charge Transfer Channels for Enhanced Photocatalytic Activity under Visible Light Irradiation

Design and construction of double heterojunction is favorable to improve the separation and migration efficiency of photogenerated carriers, thus preferably solve the problems of environmental pollution and energy crisis. Herein, TiO2 nanoparticles (NPs) are in-situ grown on highly conductive Ti3C2 nanosheets via low-temperature hydrothermal strategy, and then black phosphorus quantum dots (BPQDs) are introduced on the surface of TiO2 NPs. Under hydrothermal temperature 120 °C, the BPQDs/Ti3C2@TiO2 photocatalyst exhibits remarkable enhanced photocatalytic degradation of methyl orange (MO) and hydrogen evolution reaction (HER) compared with BPQDs/Ti3C2 and Ti3C2@TiO2 composites. Enhanced photocatalytic activity can be attributed to (i) the BPQDs with tunable bandgaps are deposited on the TiO2 NPs to form intimate heterojunction, which facilitates the electrons transfer from the conduction band (CB) of BPQDs to the CB of TiO2; (ii) the electrons quickly migrate from CB of TiO2 NPs to the Ti3C2 nanosheets with excellent electronic conductivity via electron transfer channel, which is beneficial to prolong the lifetime of electrons and hinder the recombination of photogenerated carriers; (iii) the enhanced visible light absorption and enlarged specific surface area of BPQDs/Ti3C2@TiO2 further accelerate the photocatalytic reaction. This work emphasizes the essential role of quantum dots in the construction of double heterojunction and the potential application of Ti3C2 MXene for improving photocatalytic activity.

The relative importance of different carbon structures in biochars to carbamazepine and bisphenol A sorption

Biochar, a carbon-rich material, has attracted immense attention owing to its applications in soil remediation. However, the mechanisms by which heterogeneous carbon structures of biochars immobilize organic contaminants are not yet fully understood. In this study, the noncondensed aromatic components in biochars were selectively removed through bleaching. Different techniques, such as ¹³C nuclear magnetic resonance, were applied to characterize the biochar compositions, and thus the role of the different carbon structures in organic contaminant sorption was discussed. The aromatic carbon structures in biochars were gradually developed and evolved from noncondensed to condensed structure with increasing pyrolytic temperatures from 300 to 700 °C. Based on elemental analysis, the carbon removed by bleaching decreased from 43.9% to 5.92% with increasing temperatures. After the surface area normalization of the apparent sorption, bleaching increased the sorption of carbamazepine and bisphenol A on biochars produced at 500 °C, but not for those produced at 300 and 700 °C. Bleaching removed noncondensed aromatics and enriched condensed aromatics, which resulted in increased sorption. However, bleaching also resulted in the blockage of micropores in biochars with abundant condensed aromatics, causing decreased sorption. The apparent sorption was determined by the balancing of these two opposite effects.

Immobilization of laccase on hollow mesoporous carbon nanospheres: Noteworthy immobilization, excellent stability and efficacious for antibiotic contaminants removal

In this study, the hollow mesoporous carbon spheres (HMCs) were synthesized and modified for laccase (Lac) immobilization, and the structural characteristics of HMCs materials were determined by FESEM, TEM and FTIR etc. The maximum loading of Lac on the HMCs materials could reach 835 mg/g, meanwhile, the immobilized Lac exhibited excellent thermo-stability, pH stability, storage stability and reusability. The antibiotics removal experiments indicated that the immobilized Lac possess efficient removal efficiency for both tetracycline hydrochloride (TCH) and ciprofloxacin hydrochloride (CPH) in the presence of redox mediator. The synergy of the adsorption by HMCs and the degradation by Lac could be the reasons for the high removal of antibiotics. Meanwhile, for investigating degradation mechanism, the degradation product analysis and molecular docking method had been introduced to this study. According to the degradation products, dehydroxylation and demethylation are major degradation reactions for TCH degradation, and the oxidation of the piperazinyl substituent and hydroxylation are the major degradation for CPH degradation. The docking results showed that some important residues played the key role in the degradation process. This study indicated that the immobilization of Lac on HMCs could be potentially applied in environmental remediation of antibiotics.

The recent development of efficient Earth-abundant transition-metal nanocatalysts

Whereas noble metal compounds have long been central in catalysis, Earth-abundant metal-based catalysts have in the same time remained undeveloped. Yet the efficacy of Earth-abundant metal catalysts was already shown at the very beginning of the 20th century with the Fe-catalyzed Haber-Bosch process of ammonia synthesis and later in the Fischer-Tropsch reaction. Nanoscience has revolutionized the world of catalysis since it was observed that very small Au nanoparticles (NPs) and other noble metal NPs are extraordinarily efficient. Therefore the development of Earth-abundant metals NPs is more recent, but it has appeared necessary due to their "greenness". This review highlights catalysis by NPs of Earth-abundant transition metals that include Mn, Fe, Co, Ni, Cu, early transition metals (Ti, V, Cr, Zr, Nb and W) and their nanocomposites with emphasis on basic principles and literature reported during the last 5 years. A very large spectrum of catalytic reactions has been successfully disclosed, and catalysis has been examined for each metal starting with zero-valent metal NPs followed by oxides and other nanocomposites. The last section highlights the catalytic activities of bi- and trimetallic NPs. Indeed this later family is very promising and simultaneously benefits from increased stability, efficiency and selectivity, compared to monometallic NPs, due to synergistic substrate activation.

The recent development of efficient Earth-abundant transition-metal nanocatalysts

This review presents the recent remarkable developments of efficient Earth-abundant transition-metal nanocatalysts.