Kinetic Concepts of Heterogeneous Photocatalysis

Gaya, Umar Ibrahim

doi:10.1007/978-94-007-7775-0_2

Cited by 10 publications

(4 citation statements)

References 70 publications

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“…It can be noticed that the zero-order kinetics, in this case, comply with most of the experimental results from the anodized Ti–Ta alloy series. According to the literature in heterogeneous photocatalysis, this kinetic model is typical of reactions where the surface available for the catalytic reaction is saturated very quickly and mass diffusion becomes the controlling stage. , This assumption is in good agreement with the results of this study and the potential issue, represented by the reduction of specific surface area available for the catalytic reaction due to the presence of the surface top layer, that has already been addressed. Variation of the zero-order kinetics is shown in Figure B.…”

Section: Resultssupporting

confidence: 90%

Sub-10-nm Mixed Titanium/Tantalum Oxide Nanoporous Films with Visible-Light Photocatalytic Activity for Water Treatment

Merenda

Kong

Fahim

et al. 2019

ACS Appl. Nano Mater.

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In the present work, anodic mixed titanium/tantalum oxide nanotubes are prepared for the first time with sub-10-nm surface pore size and tube inner diameter. The morphological changes induced by the introduction of Ta into the Ti metal matrix are investigated, leading to remarkable geometrical variations dependent on the Ta loading. The UVlight activation necessary to trigger electron transfer in TiO 2 limits the range of applications, and the shift in light absorption toward the visible range represents a significant challenge. Here, the band gaps of the as-created nanotube thin-film arrays are calculated, and the results, showing the presence of a minimum in the band gap, correlated to the presence of titanium and tantalum suboxides and Ta loading. The potential of the thin films as advanced materials for photocatalytic water treatment is tested against that of pure TiO 2 , and an enhancement in the visible-light absorption and an almost 3-fold increase in the degradation kinetics under pure visiblelight irradiation are demonstrated.

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Section: Resultssupporting

confidence: 90%

Sub-10-nm Mixed Titanium/Tantalum Oxide Nanoporous Films with Visible-Light Photocatalytic Activity for Water Treatment

Merenda

Kong

Fahim

et al. 2019

ACS Appl. Nano Mater.

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“…First-order kinetics in contrast, depend on the concentration of at least one reactant and the rate law is given as: where M is the concentration of the reactant, and k is the rate constant in units of per time (s −1 , hr −1 , day −1 ). Therefore, with first-order dissolution processes, the rate of reaction is proportional to the concentration of the reactant, where doubling of the concentration will double the rate [ 62 , 64 ]. However, a reaction can be first-order with respect to one reactant but can have an overall order of greater than 1.…”

Section: Introductionmentioning

confidence: 99%

Dissolution and biodurability: Important parameters needed for risk assessment of nanomaterials

et al. 2015

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Biopersistence and biodurability have the potential to influence the long-term toxicity and hence pathogenicity of particles that deposit in the body. Therefore, biopersistence and biodurability are considered to be important parameters needed for the risk assessment of particles and fibres. Dissolution, as a measure of biodurability, is dependent on the chemical and physical properties (size, surface area, etc.) of particles and fibres and also of the suspension medium including its ionic strength, pH, and temperature. In vitro dissolution tests can provide useful insights as to how particles and fibres may react in biological environments; particles and fibres that release ions at a higher rate when suspended in vitro in a specific simulated biological fluid will be expected to do so when they exist in a similar biological environment in vivo. Dissolution of particles and fibres can follow different reaction kinetics. For example, the majority of micro-sized particles and fibres follow zero-order reaction kinetics. In this case, although it is possible to calculate the half-time of a particle or fibre, such calculation will be dependent on the initial concentration of the investigated particle or fibre. Such dependence was eliminated in the shrinking sphere and fibre models where it was possible to estimate the lifetimes of particles and fibres as a measure of their biodurability. The latter models can be adapted for the dissolution studies of nanomaterials. However, the models may apply only to nanomaterials where their dissolution follows zero-order kinetics. The dissolution of most nanomaterials follows first-order kinetics where dependence on their initial concentration of the investigated nanomaterials is not required and therefore it is possible to estimate their half-times as a measure of their biodurability. In dissolution kinetics for micro-sized and nano-sized particles and fibres, knowledge of dissolution rate constants is necessary to understand biodurability. Unfortunately, many studies on dissolution of nanoparticles and nanofibres do not determine the dissolution rates and dissolution rate constants. The recommendation is that these parameters should be considered as part of the important descriptors of particle and fibre physicochemical properties, which in turn, will enable the determination of their biodurability.

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“…The photocatalytic reaction follows the pseudo‐first‐order rate model as expressed by ln ( C / C 0 )=− kt , where C and C 0 are the concentrations of MO at time t and 0, respectively, and k is the pseudo‐first‐order rate constant . In this respect, Figure shows a good verification of the pseudo‐first‐order kinetic model with R 2 equal to 0.96 and 0.98 for S2 and S1 samples, respectively.…”

Section: Resultsmentioning

confidence: 55%

Synthesis and study of ZnO nanoparticles by polymer pyrolysis route using two different polymerization initiators

Mansour

Farha

Kotkata

2017

Int J Applied Ceramic Tech

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Ammonium persulfate (APS) and sonochemical (SON) as different polymerization initiators were used to obtain ZnO polyacrylate salt via an intermediate stabilized step for the synthesization of zinc oxide nanocrystals (nc‐ZnO). Impurity‐free nc‐ZnO with wurtzite structure was obtained, after calcinating both synthesized ZnO polyacrylic salts. The way by which the polymerization initiation was done greatly affect the morphological nature, shape, and size, of both synthesized samples. The obtained particle size values of the sample range from 15 to 45 nm when using APS (S1) and range from 58 to 120 nm when using sonochemical (S2). This difference in the range of particle size for both samples was reflected on the respective values of their optical energy gaps that found to be 3.33 and 3.26 eV for S1 and S2, respectively. The intensities and shift of the visible emissions of photoluminescence (PL) spectra showed strong correlation with the particle size of both considered samples. The photocatalytic activities (PCA) of the synthesized samples were tested using UV‐VIS irradiation for methyl orange (MO), where the difference in PCA for both samples was discussed in view of their PL spectra as well as their microstructure and morphology features.

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Kinetic Concepts of Heterogeneous Photocatalysis

Cited by 10 publications

References 70 publications

Sub-10-nm Mixed Titanium/Tantalum Oxide Nanoporous Films with Visible-Light Photocatalytic Activity for Water Treatment

Sub-10-nm Mixed Titanium/Tantalum Oxide Nanoporous Films with Visible-Light Photocatalytic Activity for Water Treatment

Dissolution and biodurability: Important parameters needed for risk assessment of nanomaterials

Synthesis and study of ZnO nanoparticles by polymer pyrolysis route using two different polymerization initiators

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