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1.
J Hazard Mater ; 402: 123461, 2020 Jul 12.
Artigo em Inglês | MEDLINE | ID: mdl-32688192

RESUMO

While phthalate esters are commonly used as plasticizers to improve the flexibility and workability of polymeric materials, their presence and detection in various environments has become a significant concern. Phthalate esters are known to have endocrine-disrupting effects, which affects reproductive health and physical development. As a result, there is now increased focus and urgency to develop effective and energy efficient technologies capable of removing these harmful compounds from the environment. This review explores the use of semiconductor photocatalysis as an efficient and promising solution towards achieving removal and degradation of phthalate esters. A comprehensive review of photocatalysts reported in the literature demonstrates the range of materials including commercial TiO2, solar activated catalysts and composite materials capable of enhancing adsorption and degradation. The degradation pathways and kinetics are also considered to provide the reader with an insight into the photocatalytic mechanism of removal. In addition, through the use of two key platforms (the technology readiness level scale and electrical energy per order), the crucial parameters associated with advancing photocatalysis for phthalate ester removal are discussed. These include enhanced surface interaction, catalyst platform development, improved light delivery systems and overall system energy requirements with a view towards pilot scale and industrial deployment.

2.
Sci Rep ; 10(1): 2563, 2020 02 13.
Artigo em Inglês | MEDLINE | ID: mdl-32054919

RESUMO

Herein, value-added materials such as activated carbon and carbon nanotubes were synthesized from low-value Miscanthus × giganteus lignocellulosic biomass. A significant drawback of using Miscanthus in an energy application is the melting during the combustion due to its high alkali silicate content. An application of an alternative approach was proposed herein for synthesis of activated carbon from Miscanthus × giganteus, where the produced activated carbon possessed a high surface area and pore volume of 0.92 cm3.g-1 after two activation steps using phosphoric acid and potassium hydroxide. The SBET of the raw biomass, after first activation and second activation methods showed 17, 1142 and 1368 m2.g-1, respectively. Transforming this otherwise waste material into a useful product where its material properties can be utilized is an example of promoting the circular economy by valorising waste lignocellulosic biomass to widely sought-after high surface area activated carbon and subsequently, unconventional multi-walled carbon nanotubes. This was achieved when the activated carbon produced was mixed with nitrogen-based material and iron precursor, where it produced hydrophilic multi-wall carbon nanotubes with a contact angle of θ = 9.88°, compared to the raw biomass. synthesised materials were tested in heavy metal removal tests using a lead solution, where the maximum lead absorption was observed for sample AC-K, with a 90% removal capacity after the first hour of testing. The synthesis of these up-cycled materials can have potential opportunities in the areas of wastewater treatment or other activated carbon/carbon nanotube end uses with a rapid cycle time.

3.
Environ Sci Pollut Res Int ; 26(36): 37228-37241, 2019 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-31745803

RESUMO

Herein, activated carbon (AC) and carbon nanotubes (CNTs) were synthesised from potato peel waste (PPW). Different ACs were synthesised via two activation steps: firstly, with phosphoric acid (designated PP) and then using potassium hydroxide (designated PK). The AC produced after the two activation steps showed a surface area as high as 833 m2 g-1 with a pore volume of 0.44 cm3 g-1, where the raw material of PPW showed a surface area < 4 m2 g-1. This can help aid and facilitate the concept of the circular economy by effectively up-cycling and valorising waste lignocellulosic biomass such as potato peel waste to high surface area AC and subsequently, multi-walled carbon nanotubes (MWCNTs). Consequently, MWCNTs were prepared from the produced AC by mixing it with the nitrogen-based material melamine and iron precursor, iron (III) oxalate hexahydrate. This produced hydrophilic multi-wall carbon nanotubes (MWCNTs) with a water contact angle of θ = 14.97 °. Both AC and CNT materials were used in heavy metal removal (HMR) where the maximum lead absorption was observed for sample PK with a 84% removal capacity after the first hour of testing. This result signifies that the synthesis of these up-cycled materials can have applications in areas such as wastewater treatment or other conventional AC/CNT end uses with a rapid cycle time in a two-fold approach to improve the eco-friendly synthesis of such value-added products and the circular economy from a significant waste stream, i.e., PPW. Graphical abstract .


Assuntos
Carvão Vegetal/química , Metais Pesados/química , Nanotubos de Carbono/química , Solanum tuberosum , Biomassa , Hidróxidos , Metais Pesados/análise , Compostos de Potássio , Resíduos
4.
Sci Rep ; 9(1): 5267, 2019 03 27.
Artigo em Inglês | MEDLINE | ID: mdl-30918300

RESUMO

Global exponential increase in levels of Photovoltaic (PV) module waste is an increasing concern. The purpose of this study is to investigate if there is energy value in the polymers contained within first-generation crystalline silicon (c-Si) PV modules to help contribute positively to recycling rates and the circular economy. One such thermochemical conversion method that appeals to this application is pyrolysis. As c-Si PV modules are made up of glass, metal, semiconductor and polymer layers; pyrolysis has potential not to promote chemical oxidation of any of these layers to help aid delamination and subsequently, recovery. Herein, we analysed both used polymers taken from a deconstructed used PV module and virgin-grade polymers prior to manufacture to determine if any properties or thermal behaviours had changed. The calorific values of the used and virgin-grade Ethylene vinyl acetate (EVA) encapsulant were found to be high, unchanged and comparable to that of biodiesel at 39.51 and 39.87 MJ.Kg-1, respectively. This result signifies that there is energy value within used modules. As such, this study has assessed the pyrolysis behaviour of PV cells and has indicated the energy recovery potential within the used polymers found in c-Si PV modules.

5.
Nanoscale ; 10(21): 10221-10231, 2018 May 31.
Artigo em Inglês | MEDLINE | ID: mdl-29790548

RESUMO

The oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) are both fundamental and essential processes for various energy conversion and storage systems. The kinetics of ORR and OER play a critical role in their energy efficiency and practicality. Here, flower-like ultrathin Co3O4 nanosheets synthesized through a facile solvothermal technique were studied as a bifunctional catalyst for both water splitting and non-aqueous Li-O2 batteries. Due to the novel structure and highly active {110} and {100} exposed facets, which can effectively facilitate mass transfer and enhance catalytic capability, Co3O4 nanosheets exhibit better stability and higher ORR/OER activity than Co3O4 nanoparticles, Co3O4 bulks, Pt/C, and RuO2 in alkaline solution. More importantly, Li-O2 batteries with ultrathin Co3O4 nanosheets catalyst can enhance the initial discharge capacity from 6400 to 8600 mA h g-1 and improve the cyclability up to 160 cycles at 500 mA g-1. Unexpectedly, XRD and UV/Vis techniques suggest that the main product in Co3O4 nanosheets based cathodes is LiOH, with resulting LiOH also demonstrating reversible formation/decomposition behavior, rather than Li2O2 in pure Super P based cathodes. Further investigation confirms that Co3O4 can also catalyze the electrolyte decomposition responsible for the formation of LiOH, and a reaction mechanism was illustrated. This work highlights that the traditional high-efficiency bifunctional catalyst in aqueous media may not be suitable for non-aqueous Li-O2 batteries, and the effect of catalyst on electrolyte besides the discharge product should also be carefully considered for the design of more stable and practical Li-O2 systems.

6.
J Chem Technol Biotechnol ; 92(12): 2952-2962, 2017 12.
Artigo em Inglês | MEDLINE | ID: mdl-29200585

RESUMO

BACKGROUND: Methanol to dimethyl ether (MTD) is considered one of the main routes for the production of clean bio-fuel. The effect of copper loading on the catalytic performance of different phases of alumina that formed by calcination at two different temperatures was examined for the dehydration of methanol to dimethyl ether (DME). RESULTS: A range of Cu loadings of (1, 2, 4, 6, 10 and 15% Cu wt/wt) on Al2O3 calcined at 350 and 550 °C were prepared and characterized by TGA, XRD, BET, NH3-TPD, TEM, H2-TPR, SEM, EDX, XPS and DRIFT-Pyridine techniques. The prepared catalysts were used in a fixed bed reactor under reaction conditions in which the temperature ranged from 180-300 °C with weight hourly space velocity (WHSV) = 12.1 h-1. It was observed that all catalysts calcined at 550 °C (γ-Al2O3 support phase) exhibited higher activity than those calcined at 350 °C (γ-AlOOH), and this is due to the phase support change. Furthermore, the optimum Cu loading was found to be 6% Cu/γ-Al2O3 with this catalyst also showing a high degree of stability under steady state conditions and this is attributed to the enhancement in surface acidity and hydrophobicity. CONCLUSION: The addition of copper to the support improved the catalyst properties and activity. For all the copper modified catalysts, the optimum catalyst with high degree of activity and stability was 6% copper loaded on gamma alumina. © 2017 The Authors. Journal of Chemical Technology & Biotechnology published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

7.
ACS Appl Mater Interfaces ; 9(14): 12355-12365, 2017 Apr 12.
Artigo em Inglês | MEDLINE | ID: mdl-28326762

RESUMO

Hierarchical porous three-dimensional MnCo2O4 nanowire bundles were obtained by a universal and low-cost hydrothermal method, which subsequently act as a carbon-free and binder-free cathode for Li-O2 cell applications. This system showed a high discharge capacity of up to 12 919 mAh g-1 at 0.1 mA cm-2 and excellent rate capability. Under constrained specific capacities of 500 and 1000 mAh g-1, Li-O2 batteries could be successfully operated for over 300 and 144 cycles, respectively. Moreover, their charge voltage was markedly decreased to about 3.5 V. Their excellent electrochemical performance is proposed to be related to the conductivity enhancements resulting from the hierarchical interconnected mesoporous/macroporous weblike structure of the hybrid MnCo2O4 cathode, which facilitated the electron and mass transport. More importantly, after 2 months of cycling, the microstructure of the cathode was maintained and a recyclability of over 200 cycles of the reassembled Li-O2 cells was achieved. The effects of the level of electrolyte and corrosion of the lithium anode during long-term cycling on the electrochemical property of Li-O2 cells have been explored. Furthermore, the nucleation process of the discharge product morphology has been investigated.

8.
Chem Commun (Camb) ; 51(9): 1597-600, 2015 Jan 31.
Artigo em Inglês | MEDLINE | ID: mdl-25502738

RESUMO

We describe a novel strategy for in situ fabrication of hierarchical Fe3O4 nanoclusters-GAs. Fe3O4 NCs-GAs deliver excellent rate capability (the reversible capacities obtained were 1442, 392 and 118 mA h g(-1) at 0.1C, 12C and 35C rates), and a high reversible capacity of 577 mA h g(-1) over 300 cycles at the current density of 5.2 A g(-1) (6C).

9.
ACS Appl Mater Interfaces ; 5(11): 5057-63, 2013 Jun 12.
Artigo em Inglês | MEDLINE | ID: mdl-23688074

RESUMO

A tactful ionic-liquid (IL)-assisted approach to in situ synthesis of iron fluoride/graphene nanosheet (GNS) hybrid nanostructures is developed. To ensure uniform dispersion and tight anchoring of the iron fluoride on graphene, we employ an IL which serves not only as a green fluoride source for the crystallization of iron fluoride nanoparticles but also as a dispersant of GNSs. Owing to the electron transfer highways created between the nanoparticles and the GNSs, the iron fluoride/GNS hybrid cathodes exhibit a remarkable improvement in both capacity and rate performance (230 mAh g(-1) at 0.1 C and 74 mAh g(-1) at 40 C). The stable adhesion of iron fluoride nanoparticles on GNSs also introduces a significant improvement in long-term cyclic performance (115 mAh g(-1) after 250 cycles even at 10 C). The superior electrochemical performance of these iron fluoride/GNS hybrids as lithium ion battery cathodes is ascribed to the robust structure of the hybrid and the synergies between iron fluoride nanoparticles and graphene.

10.
J Phys Chem B ; 117(6): 1938-49, 2013 Feb 14.
Artigo em Inglês | MEDLINE | ID: mdl-23320846

RESUMO

The knowledge of the chemical stability as a function of the temperature of ionic liquids (ILs) in the presence of other molecules such as water is crucial prior to developing any industrial application and process involving these novel materials. Fluid phase equilibria and density over a large range of temperature and composition can give basic information on IL purity and chemical stability. The IL scientific community requires accurate measurements accessed from reference data. In this work, the stability of different alkyl sulfate-based ILs in the presence of water and various alcohols (methanol, ethanol, 1-butanol, and 1-octanol) was investigated to understand their stability as a function of temperature up to 423.15 K over the hydrolysis and transesterification reactions, respectively. From this investigation, it was clear that methyl sulfate- and ethyl sulfate-based ILs are not stable in the presence of water, since hydrolysis of the methyl sulfate or ethyl sulfate anions to methanol or ethanol and hydrogenate anion is undoubtedly observed. Such observations could help to explain the differences observed for the physical properties published in the literature by various groups. Furthermore, it appears that a thermodynamic equilibrium process drives these hydrolysis reactions. In other words, these hydrolysis reactions are in fact reversible, providing the possibility to re-form the desired alkyl sulfate anions by a simple transesterification reaction between hydrogen sulfate-based ILs and the corresponding alcohol (methanol or ethanol). Additionally, butyl sulfate- and octyl sulfate-based ILs appear to follow this pattern but under more drastic conditions. In these systems, hydrolysis is observed in both cases after several months for temperatures up to 423 K in the presence of water. Therein, the partial miscibility of hydrogen sulfate-based ILs with long chain alcohols (1-butanol and 1-octanol) can help to explain the enhanced hydrolytic stability of the butyl sulfate- and octyl sulfate-based ILs compared with the methyl or ethyl sulfate systems. Additionally, rapid transesterification reactions are observed during liquid-liquid equilibrium studies as a function of temperature for binary systems of (hydrogen sulfate-based ionic liquids + 1-butanol) and of (hydrogen sulfate-based ionic liquids + 1-octanol). Finally, this atom-efficient catalyst-free transesterification reaction between hydrogen sulfate-based ILs and alcohol was then tested to provide a novel way to synthesize new ILs with various anion structures containing the alkyl sulfate group.

11.
Chem Commun (Camb) ; 46(34): 6279-81, 2010 Sep 14.
Artigo em Inglês | MEDLINE | ID: mdl-20664876

RESUMO

Selective hydrogenation of carboxylic acids to alcohols and alkanes has been achieved under remarkably mild reaction temperatures and H(2) pressures (333 K, 0.5 MPa) using Pt/TiO(2) catalyst.


Assuntos
Álcoois/química , Álcoois/síntese química , Ácidos Carboxílicos/química , Platina/química , Titânio/química , Alcanos/síntese química , Alcanos/química , Catálise , Hidrogenação
12.
Chem Commun (Camb) ; (7): 903-5, 2005 Feb 21.
Artigo em Inglês | MEDLINE | ID: mdl-15700076

RESUMO

Chloroindate(III) ionic liquids are versatile reaction media for Friedel-Crafts acylation reactions; the system is catalytic and totally recyclable, using an aqueous workup, with no leaching of the indium into the product phase.


Assuntos
Hidrocarbonetos Aromáticos , Índio/química , Acilação , Catálise , Hidrocarbonetos Aromáticos/síntese química , Hidrocarbonetos Aromáticos/química , Estrutura Molecular , Fatores de Tempo
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