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1.
J Hazard Mater ; 401: 123423, 2020 Jul 07.
Artigo em Inglês | MEDLINE | ID: mdl-32763710

RESUMO

Developing efficient and robust materials for emerging electrodegradation of organic pollutants has attracted broad interests. In this study, a novel controlled pyrolysis approach was employed to fabricate a quasi-MOF derivative-based electrode by pyrolyzing MIL-101(Fe) anchored on a polyaniline-modified carbon fiber paper at 400 °C. The construction of the accessible Fe-O sites, and the in situ generation of Fe3O4 nanoparticles with graphene-like carbon layers coated, would enhance the electro-Fenton activity of the electrode, which was used as the cathode. The results showed that 100 % of 50 mg L-1 p-nitrophenol and 52 % total organic carbon were removed in 120 min under a current density of 5 mA cm-2, suggesting that the prepared electrode had a more efficient mineralization current efficiency and less energy consumption compared with electrodes before pyrolysis. Notably, the stability of the electrode was greatly improved, maintaining its outstanding performance even after ten runs. The plausible reaction mechanism and degradation pathway were also proposed. This new pyrolysis strategy is expected to serve as a paradigm for designing efficient electrode in electro-Fenton remediation field.

2.
Chemosphere ; 256: 127160, 2020 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-32464363

RESUMO

Bimetallic oxide nanomaterials have received much attention owing to their competing performances in heterogeneous catalysis. Herein, hierarchically porous cobalt-iron oxide nanosheets were successfully prepared using NaBH4 as a reductant and high concentration cetyl trimethylammonium bromide (CTAB) as a surfactant. Characterization results showed that the CTAB would induce the form of a bilayer structure while NaBH4 would promote the generation of enriched oxygen vacancies. As a result, the as-prepared Co1Fe1-300 exhibited high activity for activating peroxymonosulfate and achieved 100% phenol degradation within 30 min. This excellent catalytic activity can be attributed to its hierarchically porous structure, more active sites and oxygen vacancies. Co leaching test indicated that the Co1Fe1-300 exhibited excellent catalytic stability. Mechanistic studies suggested that two main degradation pathways were involved during phenol oxidation process, in which SO4•- played a significant role. This work may offer a novel strategy for the synthesis of high activity catalysts and a promising system for the remediation of environmental pollutant.


Assuntos
Cobalto/química , Recuperação e Remediação Ambiental/métodos , Compostos Férricos/química , Óxidos/química , Peróxidos/química , Fenol/análise , Fenol/metabolismo , Catálise , Ferro/química , Nanopartículas Metálicas/química , Compostos Orgânicos , Oxirredução , Fenóis , Porosidade
3.
Bioresour Technol ; 307: 123192, 2020 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-32220819

RESUMO

This study investigated the interactions between volatile and char during biomass pyrolysis at 400 °C, employing a ß-5 lignin dimer and amino-modified graphitized carbon nanotube (CNT-NH2) as their models, respectively. The results demonstrated that both -NH2 and its carrier (CNT) facilitated the conversion of the ß-5 dimer, which significantly increased from 9.7% (blank run), to 61.6% (with CNT), and to 96.6% (with CNT-NH2). CNT mainly favored the breakage of C-O bond in the feedstock to produce dimers with a yield of 55.5%, while CNT-NH2 promoted the cleavage of both C-O and C-C bonds to yield monomers with a yield up to 63.4%. Such significant changes in the pyrolysis behaviors of the ß-5 lignin dimer after the introduction of CNT-NH2 were considered to be mainly caused by hydrogen-bond formations between -NH2 and the dimeric feedstock/products, in addition to the π-π stacking between CNT and aromatic rings.


Assuntos
Lignina , Nanotubos de Carbono , Biomassa , Carvão Vegetal , Temperatura Alta , Pirólise
4.
Nanoscale ; 2020 Mar 20.
Artigo em Inglês | MEDLINE | ID: mdl-32196063

RESUMO

Polymeric carbon nitrides (PCNs) are promising photocatalysts and electrocatalysts for water oxidation, as they are environmentally benign materials with an adjustable structure and facilely synthesized from inexpensive and abundant starting materials. In this minireview, we examine the state-of-the-art strategies for tailoring PCNs for efficient photocatalytic, electrocatalytic, and photoelectrochemical water oxidation, including heteroatom doping and interface engineering from band structure alignment (e.g., by coupling inorganic or organic semiconductors) to hybridization with nanoscale cocatalysts (e.g., nanosheets, nanoarrays, nanoparticles, and quantum dots) and sub-nanoscale cocatalysts (e.g., metallic molecular clusters and single-atom catalysts). Through establishing the structure-activity correlations, we aim to present a clear roadmap for providing insights into the design strategies, structure modification, and the improved catalytic performances of PCN-based materials in different catalytic water oxidation processes. For future guidance, we also propose some outlooks on the perspective and challenges of PCNs towards a better application in catalytic water oxidation.

5.
Adv Mater ; 32(18): e1904037, 2020 May.
Artigo em Inglês | MEDLINE | ID: mdl-31793723

RESUMO

Low-cost, nonprecious transition metal (TM) catalysts toward efficient water oxidation are of critical importance to future sustainable energy technologies. The advances in structure engineering of water oxidation catalysts (WOCs) with single TM centers as active sites, for example, single metallic molecular complexes (SMMCs), supported SMMCs, and single-atom catalysts (SACs) in recent reports are examined. The efforts made on these configurations in terms of design principle, advanced characterization, performances and theoretical studies, are critically reviewed. A clear roadmap with the correlations between the single-TM-site-based structures (coordination and geometric structure, TM species, support), and the catalytic performances in water oxidation is provided. The insights bridging SMMCs with SACs are also given. Finally, the challenges and opportunities in the single-TM-site catalysis are proposed.

6.
J Colloid Interface Sci ; 562: 461-469, 2020 Mar 07.
Artigo em Inglês | MEDLINE | ID: mdl-31787252

RESUMO

The photocatalytic degradation of carbamazepine (CBZ) in ultra-pure water was investigated by using neodymium (Nd)-doped antimony trioxide (Sb2O3)/titanium dioxide (TiO2) photocatalyst under the UVC irradiations of 254 nm wavelength. The hydrothermal method was used for the fabrication catalyst samples with different ratios of Nd (0%-2%) dopant, and characterised by X-ray diffraction pattern (XRD) to investigate the crystallinity. Scanning electron microscopy (SEM) provided the surface morphologies, Bruanuer-Emmer-Teller (BET) analysis gave the textural properties, and UV-Vis diffuse reflectance absorption spectroscopy (DRS) was used for the investigation of the optical properties of synthesized catalysts. TEM images of Sb2O3 showed a nanorod-like structure while, in the Nd-doped Sb2O3/TiO2, a small dot-like structure was observed along with the nanorods. The surface area and band gap of 1% Nd-doped Sb2O3/TiO2 were found to be 9.56 m2 g-1 and 3.0 eV respectively. It was observed that the CBZ cannot be degraded in the absence of catalyst under UV light, while photocatalyst 1% Nd-doped Sb2O3/TiO2 at 0.5 g/L of catalyst dose showed the best photocatalytic activity towards CBZ degradation. The main degradation products were identified with high-resolution mass spectrometry. Moreover, the degradation of CBZ followed pseudo first-order kinetics and the rate constant was 0.017 min-1. Quenching tests by the addition of methanol from 100 to 500 mM were carried out to determine the major reactive oxygen species, which showed that OH radicals was involved in the CBZ degradation. Active species-trapping experiments revealed that ∙O2- is also responsible for the degradation of CBZ.

7.
J Hazard Mater ; 382: 121059, 2020 01 15.
Artigo em Inglês | MEDLINE | ID: mdl-31470302

RESUMO

Porous FeVO4 nanorods decorated on CeO2 nanocubes (FeVO4@CeO2) were successfully prepared via a facile hydrothermal route and tested in the degradation of 4-nitrophenol (4-NP) for enhanced heterogeneous oxidation using ultrasonic (US), ultraviolet (UV), and binary irradiation US/UV, respectively. The nanostructure of the core-shell FeVO4@CeO2 was characterised using XRD, SEM, EDS elemental mapping, TEM, HRTEM, SAED, FTIR, Raman, BET, point of zero charge (PZC), XPS analysis and UV-vis DRS. The effect of various parameters, for examples, nanostructured core-shell amounts, hydrogen peroxide concentration, initial concentration, pH and irradiation time, on 4-NP degradation were investigated for the optimisation of the catalytic performance. The durability and stability of the core-shell nanostructured materials were also investigated and the obtained results revealed that the catalysts can endure the harsh sonophotocatalytic conditions even after six cycles. Mineralisation experiments were investigated using the optimised parameters. The core-shell nanostructured FeVO4@CeO2 has higher PZC than pure FeVO4 and CeO2, leading to excellent sonophotocatalytic activity even at high pH and stability for the degradation of 4-NP after six cycles. A possible mechanism over the FeVO4@CeO2 was proposed based on the special three-way Fenton-like mechanism and the dissociation of H2O2 with the experiments of active species trapping and calculated band gap energy.

8.
J Hazard Mater ; 389: 121881, 2020 05 05.
Artigo em Inglês | MEDLINE | ID: mdl-31852591

RESUMO

The biomass, bottlebrush flower, is exploited for the preparation of functionalized porous carbons by one-pot thermal activation using NaHCO3 and dicyandiamide. An intensified cross-linking effect among the precursors boosts pore (especially mesopore) formation in the pyrolysis process, producing N-doped porous carbons (NPCs) with a large specific surface area (SSA, up to 2025 m2 g-1). The biomass-derived carbon samples turn out to be highly effective in adsorption, and catalytic activation of peroxymonosulfate for degradation of aqueous phenol and p-hydroxybenzoic acid (HBA) in single and binary systems. The effects of N content, porous structure, and trace Ni species on the adsorptive and catalytic behavior of carbon are investigated. It is found that the porous structure plays a more critical role in adsorption than surface N functionality, while the contributions of various reactive species for phenol and HBA degradation are different.

9.
Water Res ; 167: 115110, 2019 Dec 15.
Artigo em Inglês | MEDLINE | ID: mdl-31577967

RESUMO

Membrane separation and advanced oxidation processes (AOPs) have been respectively demonstrated to be effective for a variety of water and/or wastewater treatments. Innovative integration of membrane with catalytic oxidation is thus expected to be more competing for more versatile applications. In this study, ceramic membranes (CMs) integrated with manganese oxide (MnO2) were designed and fabricated via a simple one-step ball-milling method with a high temperature sintering. Functional membranes with different loadings of MnO2 (1.67%, 3.33% and 6.67% of the total membrane mass) were then fabricated. The micro-structures and compositions of the catalytic membranes were investigated by a number of advanced characterisations. It was found that the MnO2 nanocatalysts (10-20 nm) were distributed uniformly around the Al2O3 particles (500 nm) of the membrane basal material, and can provide a large amount of active sites for the peroxymonosulfate (PMS) activation which can be facilitated within the pores of the catalytic membrane. The catalytic degradation of 4-hydroxylbenzoic acid (HBA), which is induced by the sulfate radicals via PMS activation, was investigated in a cross-flow membrane unit. The degradation efficiency slightly increased with a higher MnO2 loading. Moreover, even with the lowest loading of MnO2 (1.67%), the effectiveness of HBA degradation was still prominent, shown by that a 98.9% HBA degradation was achieved at the permeated side within 30 min when the initial HBA concentration was 80 ppm. The stability and leaching tests revealed a good stability of the catalytic membrane even after the 6th run. Electron paramagnetic resonance (EPR) and quenching tests were used to investigate the mechanism of PMS activation and HBA degradation. Both sulfate radicals (SO4•-) and hydroxyl radicals (•OH) were generated in the catalytic membrane process. Moreover, the contribution from non-radical process was also observed. This study provides a novel strategy for preparing a ceramic membrane with the function of catalytic degradation of organic pollutants, as well as outlining into future integration of separation and AOPs.


Assuntos
Poluentes Ambientais , Compostos de Manganês , Cerâmica , Óxidos , Sulfatos
10.
Environ Sci Technol ; 53(19): 11391-11400, 2019 Oct 01.
Artigo em Inglês | MEDLINE | ID: mdl-31436973

RESUMO

The maximization of the numbers of exposed active sites in supported metal catalysts is important to achieve high reaction activity. In this work, a simple strategy for anchoring single atom Fe on SBA-15 to expose utmost Fe active sites was proposed. Iron salts were introduced into the as-made SBA-15 containing the template and calcined for simultaneous decomposition of the iron precursor and the template, resulting in single atom Fe sites in the nanopores of SBA-15 catalysts (SAFe-SBA). X-ray diffraction (XRD), UV-vis diffuse reflectance spectroscopy (UV-vis DRS), high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM), and extended X-ray absorption fine structure (EXAFS) imply the presence of single atom Fe sites. Furthermore, EXAFS analysis suggests the structure of one Fe center with four O atoms, and density functional theory calculations (DFT) simulate this structure. The catalytic performances of SAFe-SBA were evaluated in Fenton-like catalytic oxidation of p-hydroxybenzoic acid (HBA) and phenol. It was found that the single atom SAFe-SBA catalysts displayed superior catalytic activity to aggregated iron sites (AGFe-SBA) in both HBA and phenol degradation, demonstrating the advantage of SAFe-SBA in catalysis.


Assuntos
Ferro , Fenol , Catálise , Oxirredução , Difração de Raios X
11.
J Colloid Interface Sci ; 555: 22-30, 2019 Nov 01.
Artigo em Inglês | MEDLINE | ID: mdl-31376766

RESUMO

Hydrogen generation from biomass reforming via solar energy utilisation has become a fascinating strategy toward future energy sustainability. In this study, ZnS nanoparticles with an average size around 10-15 nm were synthesised by a facile hydrothermal method, and then hybridised with g-C3N4 (MCN, DCN, and UCN) derived from melamine, dicyandiamide and urea, producing the heterojunctions denoted as ZMCN, ZDCN and ZUCN, respectively. Advanced characterisations were employed to investigate the physiochemical properties of the materials. ZMCN and ZDCN showed a slight red shift and better light absorbance ability. Their catalytic performances were evaluated by photocatalytic biomass reforming for hydrogen generation. The hydrogen generation rate on ZMCN, the best photocatalyst among MCN, DCN, UCN, ZDCN and ZUCN, was around 2.5 times higher than the pristine MCN. However, the photocatalytic efficiency of ZUCN experienced decrease of 36.6% compared to pure UCN. The mechanism of the photocatalytic reforming process was discussed. The photoluminescence spectra of ZMCN suggested that the introduction of ZnS for ZMCN would reduce the recombination of photoinduced carriers. It was also found that both microstructure and band structure would influence the photocatalytic reforming efficiency.


Assuntos
Hidrogênio/química , Nanopartículas/química , Nitrilos/química , Sulfetos/química , Compostos de Zinco/química , Biomassa , Catálise , Tamanho da Partícula , Processos Fotoquímicos , Propriedades de Superfície
12.
Polymers (Basel) ; 11(6)2019 Jun 11.
Artigo em Inglês | MEDLINE | ID: mdl-31212623

RESUMO

Thermal stabilizers, lubricant, and plasticizers are three crucial additives for processing poly(vinyl chloride) (PVC). In this study, a new mannitol stearate ester-based aluminum alkoxide (MSE-Al) was designed and synthesized as a novel additive for PVC. The thermal stability and processing performance of PVC stabilized by MSE-Al were evaluated by the Congo red test, conductivity measurement, thermal aging test, ultravioletevisible (UV-Vis) spectroscopy test, and torque rheometer test. Results showed that the addition of MSE-Al could not only markedly improve the long-term thermal stability of PVC, but also greatly accelerate the plasticizing and decrease the balance torque, which demonstrated that MSE-Al possessed a lubricating property. Thus, MSE-Al was demonstrated to be able to provide tri-functional additive roles, e.g., thermal stabilizer, plasticizer, and lubricant. The test results for the thermal stability of PVC indicated that the initial whiteness of PVC stabilized by MSE-Al was not good enough, thus the synergistic effect of MSE-Al with zinc stearates (ZnSt2) on the thermal stability of PVC was also investigated. The results showed that there is an appreciable synergistic effect between MSE-Al and ZnSt2. The thermal stabilization mechanism and synergism effect of MSE-Al with ZnSt2 are then discussed.

13.
Polymers (Basel) ; 11(5)2019 May 06.
Artigo em Inglês | MEDLINE | ID: mdl-31064112

RESUMO

A new di-mannitol adipate ester-based zinc metal alkoxide (DMAE-Zn) was synthesized as a bi-functional poly(vinyl chloride) (PVC) thermal stabilizer for the first time. The materials were characterized with Fourier transform infrared spectroscopy (FT-IR) and thermogravimetric analysis (TGA). Characterization results confirmed the formation of Zn-O bonds in DMAE-Zn, and confirmed that DMAE-Zn had a high decomposition temperature and a low melting point. The thermal stability of DMAE-Zn on PVC also was tested by a conductivity test, a thermal aging test, and a UV-visible spectroscopy (UV-VIS) test. PVC stabilized by DMAE-Zn had a good initial color and excellent long-term stability. UV-VIS also showed that the conjugated structure in PVC stabilized by DMAE-Zn was almost all of the triene, suggesting that the addition of DMAE-Zn would suppress the formation of conjugated structures above tetraene. The dynamic processing performance of PVC samples tested by torque rheometer indicated that, having a good compatibility with PVC chains in the amorphous regions, DMAE-Zn contributed a good plasticizing effect to PVC. DMAE-Zn thus effectively demonstrates bi-functional roles, e.g., thermal stabilizers and plasticizers to PVC. Furthermore, FT-IR, a HCl absorption capacity test, and a complex ZnCl2 test were also used to verify the thermal stability mechanism of DMAE-Zn for PVC.

15.
J Colloid Interface Sci ; 542: 421-428, 2019 Apr 15.
Artigo em Inglês | MEDLINE | ID: mdl-30771637

RESUMO

Cerium is an important rare earth element (REE), which can be used for many high-tech applications. From the industrial and environmental viewpoints, it is imperative to recover Ce3+ ions from aqueous solution. Herein, HKUST-1 metal-organic framework (MOF) was applied for adsorption and recovery of Ce3+ from aqueous solution. HKUST-1 showed a high adsorption efficiency and remarkable capacity of 353 mg/g at pH = 6. The isotherm, kinetics, effect of pH value and adsorption mechanism of the Ce3+ adsorption process were also studied. The results showed that the adsorption process fitted the Langmuir adsorption model, and the pseudo-second-order model described the kinetics well. The mechanism and reusability in Ce3+ adsorption were systematically investigated by various characterization techniques, suggesting the possible ion exchange between Ce3+ and Cu2+ and the formation of CeO covalent bonding. This work opens up a new way for Ce3+ recovery from water.

16.
Bioresour Technol ; 272: 77-82, 2019 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-30316194

RESUMO

This paper investigated pyrolysis of palm kernel shell in a proposed reactor, which is characterized by internal recycling of heavy oil between a heavy oil sorption zone and pyrolysis zone. The internal recycling of heavy oil favors conversion of heavy oil to char, gas, and light oil. Compared with the product distribution from the conventional pyrolysis without heavy oil recycling, the yields of char, gas, and GC/MS detectable organic compounds increase from 34.8, 15.2, and 9.8 wt%-(dry feedstock) to 38.5, 19.0, and 16.9 wt%-(dry feedstock), respectively, with the help of internal recycling of heavy oil. The increases in the char and gas yields are interestingly found to be nearly equivalent. Furthermore, the yields of acetic acid and phenol in the resulting bio-oil can be as high as 10.1 and 2.7 wt%-(dry feedstock), and the outputs of 2-methylfuran, 2,6-dimethoxyphenol, and H2 are increased by around 37, 7, and 4 times, respectively.


Assuntos
Óleo de Palmeira/metabolismo , Reciclagem , Ácido Acético/química , Ácido Acético/metabolismo , Cromatografia Gasosa-Espectrometria de Massas , Temperatura Alta , Óleo de Palmeira/química , Fenol/química , Fenol/metabolismo , Óleos Vegetais/química , Óleos Vegetais/metabolismo , Polifenóis/química , Polifenóis/metabolismo , Pirólise
17.
J Colloid Interface Sci ; 532: 321-330, 2018 Dec 15.
Artigo em Inglês | MEDLINE | ID: mdl-30096526

RESUMO

Photocatalysis has been believed as one of the green and sustainable avenues to address energy and environmental crises by converting solar energy to chemical energy via reactions. Temperature is usually a vital factor controlling kinetics and thermodynamics of a reaction, but it has been less investigated in photocatalysis. In this work, the effect of reaction temperature on photocatalysis was investigated in a simple process, photocatalytic degradation of Congo Red (CR) on three typical catalysts, g-C3N4, TiO2 and ZnO, to differentiate the interfacial radical generation and reaction mechanism. The results showed that the temperature has a positive effect on the photocatalytic activity of the three catalysts. The scavenger experiments at various temperatures indicated that the generation of reactive species from the three photocatalysts is different and that the free radicals can be produced more quickly at higher temperatures, causing improved activities in photocatalysis. However, photocurrent analysis and EIS at various temperatures showed that the temperature had a different effect on recombination rate and transfer barriers of the charge carriers from each catalyst. Therefore, the dramatic enhancement in photodegradation activities probably originated from a novel mechanism of the photothermocatalytic oxidation. The interfacial reaction and mechanism from the influence of reaction temperature on the photocatalytic process was proposed.

18.
Adv Mater ; 30(39): e1803351, 2018 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-30059172

RESUMO

Quasi-1D cadmium chalcogenide quantum rods (QRs) are benchmark semiconductor materials that are combined with noble metals to constitute QR heterostructures for efficient photocatalysis. However, the high toxicity of cadmium and cost of noble metals are the main obstacles to their widespread use. Herein, a facile colloidal synthetic approach is reported that leads to the spontaneous formation of cadmium-free alloyed ZnSx Se1-x QRs from polydisperse ZnSe nanowires by alkylthiol etching. The obtained non-noble-metal ZnSx Se1-x QRs can not only be directly adopted as efficient photocatalysts for water oxidation, showing a striking oxygen evolution capability of 3000 µmol g-1 h-1 , but also be utilized to prepare QR-sensitized TiO2 photoanodes which present enhanced photo-electrochemical (PEC) activity. Density functional theory (DFT) simulations reveal that alloyed ZnSx Se1-x QRs have highly active Zn sites on the (100) surface and reduced energy barrier for oxygen evolution, which in turn, are beneficial to their outstanding photocatalytic and PEC activities.

19.
J Colloid Interface Sci ; 528: 271-280, 2018 Oct 15.
Artigo em Inglês | MEDLINE | ID: mdl-29859452

RESUMO

Platinum (Pt) free micro/nanomotors (MNMs) using a low content of fuels are highly desired for many applications. Herein, we demonstrate that cathodic electrofabrication can produce modified MnO2 based microtubes and microrods as highly efficient MNMs in hydrogen peroxide (H2O2) as low as 0.2%. The speed of graphene/Ag-MnO2 micromotors could be smartly regulated using a surfactant and the maximum speed of an individual micromotor exceeds 1.3 mm s-1 in 0.5% H2O2. The propelling force and output power of the micromotors are 3.4 and 10 times as high as those of the best Pt-based micromotors reported. These Ag-MnO2 based micromotors are envisioned to be a great promise for practical applications from biomedical delivery to environmental decontamination.

20.
Chem Commun (Camb) ; 54(37): 4653-4656, 2018 May 03.
Artigo em Inglês | MEDLINE | ID: mdl-29623976

RESUMO

Herein, we demonstrate that iron oxide modified MnO2 (FeOx-MnO2) catalyzed micromotors can be fabricated via electrochemical co-reduction and exhibit exceptional high performance at an extremely low hydrogen peroxide (H2O2) fuel concentration. We observed that graphene/FeOx-MnO2 microtubes could show motion behaviors at fuel concentration as low as 0.03% H2O2, which is nearly one order of magnitude lower than Pt-based micromotors (normally at above 0.2% H2O2). Moreover, the micromotors exhibit higher speeds than any other reported catalytic micro/nanomotors (MNMs) at low peroxide levels. The FeOx-MnO2 systems are better catalytic MNMs, due to their excellent catalytic activity, easy fabrication, robust structure and movement, as well as low-cost, biocompatible and abundance nature, showing great potential for future applications.

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