Peroxymonosulfate (PMS) is extensively used as an oxidant to develop the sulfate radical-based advanced oxidation processes in the decontamination of organic pollutants and various PMS activation ...methods have been explored. Visible-light-assisted PMS activation to construct a Fenton-like process has shown a great potential for pollution control. In our work, BiVO4 nanosheets were prepared using a hydrothermal process and used to activate PMS under visible light. A rapid degradation of ciprofloxacin (CIP) was achieved by dosing PMS (0.96 g/L), BiVO4 (0.32 g/L) under visible light with a reaction rate constant of 77.72-fold higher than that in the BiVO4/visible light process. The electron spin resonance and free radical quenching experiments indicate that reactive species of •O2−, h+, •OH and SO4•− all worked, where h+, •OH and SO4•− were found as the dominant contributors to the CIP degradation. The spectroscopic analyses further demonstrate that the photoinduced electrons were directly involved in the PMS activation process. The generated •O2− was partially utilized to activate PMS and more •OH was produced because of the chain reactions between SO4•− and H2O/OH−. In this process, PMS acted as an electron acceptor to transfer the photo-induced charges from the conduction band of BiVO4 and PMS was successfully activated to yield the high-powered oxidative species. From the degradation intermediates of CIP detected by a liquid-chromatography-mass spectrometer, the possible degradation pathways were proposed. The substantially decreased toxicity of CIP after the reaction was also observed. This work might provide new insights into the visible-light-assisted PMS activation mechanisms and is useful to construct environmentally-friendly catalytic processes for the efficient degradation of organic pollutants.
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•PMS was effectively activated by BiVO4 nanosheets for water purification under visible light.•Separation of electron/hole pairs and generation of oxidative species were enhanced.•Visible-light-assisted PMS activation Fenton-like mechanism was elucidated.•High mineralization and low biotoxicity validated the application potential of the system.
Removal of organic micropollutants from water through advanced oxidation processes (AOPs) is hampered by the excessive input of energy and/or chemicals as well as the large amounts of residuals ...resulting from incomplete mineralization. Herein, we report a new water purification paradigm, the direct oxidative transfer process (DOTP), which enables complete, highly efficient decontamination at very low dosage of oxidants. DOTP differs fundamentally from AOPs and adsorption in its pollutant removal behavior and mechanisms. In DOTP, the nanocatalyst can interact with persulfate to activate the pollutants by lowering their reductive potential energy, which triggers a non-decomposing oxidative transfer of pollutants from the bulk solution to the nanocatalyst surface. By leveraging the activation, stabilization, and accumulation functions of the heterogeneous catalyst, the DOTP can occur spontaneously on the nanocatalyst surface to enable complete removal of pollutants. The process is found to occur for diverse pollutants, oxidants, and nanocatalysts, including various low-cost catalysts. Significantly, DOTP requires no external energy input, has low oxidant consumption, produces no residual byproducts, and performs robustly in real environmental matrices. These favorable features render DOTP an extremely promising nanotechnology platform for water purification.
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•Dosing reducing agents resulted in enhanced pollutant degradation and expansion of pH range.•Dosing manner of RA was a key factor governing its roles in Fenton system.•Catalytic ...mechanisms of the three reducing agents in Fenton system were proposed.•Electrical energy per order was used to estimate the costs of three reducing agents.
Fenton reaction is widely used for hazardous pollutant degradation. Reducing agents (RAs) have been proven to be efficient in promoting the generation of HO• in Fenton reaction by accelerating the redox cycle of Fe3+/Fe2+. However, the roles of different RAs in Fenton reaction remain unrevealed. In this work, the catalytic activity of three RAs, i.e., hydroxylamine (NH2OH), ascorbic acid (AA) and cysteine (Cys), on the degradation of benzoic acid (BA) and the hydroxyl radical formation in the Fenton-RAs system were investigated. Results show the catalytic performance of RAs in BA degradation by Fenton reaction followed an order of NH2OH > AA > Cys. Compared with the conventional Fenton system, the effective pH range in the Fenton-NH2OH system extended from 3.0 to 5.0, while the optimal pH in the Fenton-AA and Fenton-Cys systems ranged from 3.0 to 4.0. The Fenton-AA system exhibited a two-stage reaction toward BA degradation, which was different from the Fenton-NH2OH and Fenton-Cys systems. Furthermore, the dosing manner of AA was found to be a key factor governing its role in the Fenton-AA system. This observation suggests the different mechanisms behind the enhancement of the three RAs in Fenton system. Different from NH2OH and Cys, AA would inhibit the generation of HO•, especially at the fast stage of degradation process, where Fe3+ has not accumulated yet. In addition, the economic analysis using the electrical energy per order indicates Fenton-NH2OH system was economically feasible with the lowest energy input, compared to Fenton-AA and Fenton-Cys systems. These results are useful to better understand the roles of RAs in Fenton system, and also provide guidance about the selection and dosing manner of suitable RAs in the advanced oxidation processes.
Carbon-based materials are recognized as promising candidates for pollutant degradation because of their environmental benignity. Massive and cost-effective production and efficient recovery of ...carbon-based catalysts are crucial to apply this technology. However, various nanostructured carbons with different dimensions are usually utilized as precursors while not considering their complex preparation procedures and the high costs of ingredients. Moreover, catalyst separation and recovery are not given sufficient attention. In this work, a calcium salt-assisted pyrolysis strategy is proposed to tune the catalytic site formation of carbon-based catalysts. Results show that blending equal amounts of Ca2+ (calcium chloride) and organic precursors could greatly improve the catalytic activity of the carbonated product to activate peroxymonosulfate for pollutant degradation. In addition, the proposed synthetic strategy is universal to most of the readily accessed and cost-effective organic precursors. Singlet oxygen is identified as the main reactive oxidant for pollutant removal in the catalytic reaction. By cross-linking calcium ions and alginate as a hydrogel to immobilize the catalyst, the carbon material could be readily recovered. Furthermore, a long-term continuous-flow reactor test is conducted to validate the effectiveness of applying the immobilized catalyst to treat a synthetic wastewater with 0.5 mM bisphenol A. As a result, a green synthesis and immobilization strategy for persulfate catalysts is successfully established, and the prepared catalyst might be applied for wastewater treatment through using calcium salt in two purposes.
Self‐assembly is an appealing strategy for preparing nanospheres with different interiors, which are essential for their applications. Although many assembly strategies have been proposed, ...controlling the assembly processes from kinetic aspects is a big challenge. Here, by employing the different reaction kinetics of the assembly precursors, a sequential assembly strategy is proposed to tailor the interior structure of porous carbon spheres. Through changing the feeding interval of resin and silica precursors from 0 to 60 min, their nucleation order can be controlled in the assembly process to prepare porous carbon spheres (≈450 nm in size) with tunable type (i.e., hollow or solid) and size (from less than 100 nm to around 230 nm) of interiors. The hollow spheres exhibit over three times the catalytic activity of the core–shell counterparts for activating peroxymonosulfate to remove organic water contaminants, and the activity can be further improved by decreasing the cavity size. These results show the great significance of the sequential assembly strategy for interior engineering of nanospheres. This work opens up a new approach for rational design and synthesis of interior‐structured nanospheres.
A sequential assembly approach is developed by simply changing the feeding interval of the carbon and silica precursors for preparing the porous carbon spheres with tunable type (i.e., hollow or solid) and size of interiors. The interior engineering of the carbon spheres significantly enhances their performance in catalytic water decontamination through peroxymonosulfate activation.
Precise synthesis of porous materials is essential for their applications. Self‐assembly is a widely used strategy for synthesizing porous materials, but quantitative control of the assembly process ...still remains a great challenge. Here, a quantitative coassembly approach is developed for synthesizing resin/silica composite and its derived porous spheres. The assembly behaviors of the carbon and silica precursors are regulated without surfactants and the growth kinetics of the composite spheres are quantitatively controlled. This assembly approach enables the precise control of the size and pore structures of the derived carbon spheres. These carbon spheres provide a good platform to explore the structure–performance relationships of porous materials, and demonstrate their pore structure‐dependent performance in catalytic water decontamination. This work provides a simple and robust approach for precise synthesis of porous spheres and brings insights into function‐oriented design of porous materials.
A quantitative coassembly approach is developed for synthesizing carbon/silica composite and its derived porous carbon spheres. This approach enables precise control of the pore structure of the carbon spheres and revelation of their structure–performance relationships in catalysis. The small and long pores significantly enhance the performance of carbon spheres in catalytic water decontamination.
S-RNase plays vital roles in the process of self-incompatibility (SI) in Rutaceae plants. Data have shown that the rejection phenomenon during self-pollination is due to the degradation of pollen ...tube RNA by S-RNase. The cytoskeleton microfilaments of pollen tubes are destroyed, and other components cannot extend downwards from the stigma and, ultimately, cannot reach the ovary to complete fertilisation. In this study, four S-RNase gene sequences were identified from the ‘XiangShui’ lemon genome and ubiquitome. Sequence analysis revealed that the conserved RNase T2 domains within S-RNases in ‘XiangShui’ lemon are the same as those within other species. Expression pattern analysis revealed that S3-RNase and S4-RNase are specifically expressed in the pistils, and spatiotemporal expression analysis showed that the S3-RNase expression levels in the stigmas, styles and ovaries were significantly higher after self-pollination than after cross-pollination. Subcellular localisation analysis showed that the S1-RNase, S2-RNase, S3-RNase and S4-RNase were found to be expressed in the nucleus according to laser confocal microscopy. In addition, yeast two-hybrid (Y2H) assays showed that S3-RNase interacted with F-box, Bifunctional fucokinase/fucose pyrophosphorylase (FKGP), aspartic proteinase A1, RRP46, pectinesterase/pectinesterase inhibitor 51 (PME51), phospholipid:diacylglycerol acyltransferase 1 (PDAT1), gibberellin receptor GID1B, GDT1-like protein 4, putative invertase inhibitor, tRNA ligase, PAP15, PAE8, TIM14-2, PGIP1 and p24beta2. Moreover, S3-RNase interacted with TOPP4. Therefore, S3-RNase may play an important role in the SI of ‘XiangShui’ lemon.
Developing heterogeneous catalysts with atomically dispersed active sites is vital to boost peroxymonosulfate (PMS) activation for Fenton-like activity, but how to controllably adjust the electronic ...configuration of metal centers to further improve the activation kinetics still remains a great challenge. Herein, we report a systematic investigation into heteroatom-doped engineering for tuning the electronic structure of Cu-N
sites by integrating electron-deficient boron (B) or electron-rich phosphorus (P) heteroatoms into carbon substrate for PMS activation. The electron-depleted Cu-N
/C-B is found to exhibit the most active oxidation capacity among the prepared Cu-N
single-atom catalysts, which is at the top rankings of the Cu-based catalysts and is superior to most of the state-of-the-art heterogeneous Fenton-like catalysts. Conversely, the electron-enriched Cu-N
/C-P induces a decrease in PMS activation. Both experimental results and theoretical simulations unravel that the long-range interaction with B atoms decreases the electronic density of Cu active sites and down-shifts the d-band center, and thereby optimizes the adsorption energy for PMS activation. This study provides an approach to finely control the electronic structure of Cu-N
sites at the atomic level and is expected to guide the design of smart Fenton-like catalysts.
A high-efficient, low-cost, and eco-friendly catalyst is highly desired to activate peroxides for environmental remediation. Due to the potential synergistic effect between bimetallic oxides’ two ...different metal cations, these oxides exhibit superior performance in the catalytic activation of peroxymonosulfate (PMS). In this work, novel Mn1.8Fe1.2O4 nanospheres were synthesized and used to activate PMS for the degradation of bisphenol A (BPA), a typical refractory pollutant. The catalytic performance of the Mn1.8Fe1.2O4 nanospheres was substantially greater than that of the Mn/Fe monometallic oxides and remained efficient in a wide pH range from 4 to 10. More importantly, a synergistic effect between solid-state Mn and Fe was identified in control experiments with Mn3O4 and Fe3O4. Mn was inferred to be the primary active site in the surface of the Mn1.8Fe1.2O4 nanospheres, while Fe(III) was found to play a key role in the synergism with Mn by acting as the main adsorption site for the reaction substrates. Both sulfate and hydroxyl radicals were generated in the PMS activation process. The intermediates of BPA degradation were identified and the degradation pathways were proposed. This work is expected to help to elucidate the rational design and efficient synthesis of bimetallic materials for PMS activation.
In this paper, we consider an integrated error concealment system for lost color frames and lost depth frames in multiview videos with depths. We first proposed a pixel-based color error-concealment ...method with the use of depth information. Instead of assuming that the same moving object in consecutive frames has minimal depth difference, as is done in a state-of-the-art method, a more realistic situation in which the same moving object in consecutive frames can be in different depths is considered. In the derived motion vector candidate set, we consider all the candidate motion vectors in the set, and weight the reference pixels by the depth differences to obtain the final recovered pixel. Compared with the two state-of-the-art methods, the proposed method has average peak signal-to-noise ratio gains of up to 8.73 and 3.98 dB, respectively. Second, we proposed an iterative depth frame error-concealment method. The initial recovered depth frame is obtained by depth-image-based rendering from another available view. The holes in the recovered depth frame are then filled in the proposed priority order. Preprocessing methods (depth difference compensation and inconsistent pixel removal) are performed to improve the performance. Compared with a method that uses the available motion vector in a color frame to recover the lost depth pixels, the hybrid motion vector extrapolation method, the inpainting method and the proposed method have gains of up to 4.31, 10.29, and 6.04 dB, respectively. Finally, for the situation in which the color and the depth frames are lost at the same time, our two methods jointly perform better with a gain of up to 7.79 dB.
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