Continuous energy efficient exfoliation of vermiculite through microwave heating

Folorunso, Olaosebikan; Dodds, Chris; Dimitrakis, Georgios; Kingman, S.W.

doi:10.1016/j.minpro.2012.10.003

Cited by 48 publications

(21 citation statements)

References 25 publications

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“…Figure 3 shows the X-ray diffraction (XRD) patterns of various vermiculite samples. The neat vermiculite features multiple reflections, suggesting a mixture of different minerals as reported in the literature [14,30]. It features a strong broad peak at 2 = 8.66 (1.19 nm) and weaker reflections at 2 = 7.20 (1.43 nm) and 2 = 10.24…”

Section: Characterizationsupporting

confidence: 54%

Stiffening mechanisms in vermiculite–amorphous polyamide bio-nanocomposites

Macheca

Focke

Muiambo

et al. 2016

European Polymer Journal

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Sub-micron thick flakes were obtained by sonication of vermiculite that was first exfoliated by either thermal shock or chemical treatment with hydrogen peroxide. Dimer fatty acid polyamide nanocomposites with a mixed morphology were prepared via a solution-dispersion technique. The large (in the micrometre range) vermiculite flakes assumed random orientations in the matrix. BET surface area measurements indicated flake thickness below 100 nm but SEM showed that thicker flakes were also present. Filler content was varied up to 30 wt.%. At this loading, the tensile strength doubled, the modulus increased five-fold but the elongation-at-break decreased by a factor of ten.Dynamic mechanical analysis suggests that three stiffening mechanisms were operating. The reinforcing effect of the high stiffness inorganic flakes is the primary contributor. Together with the chain confinement effect, that expresses itself in an apparent increase in the glass transition temperature, this provided an adequate rationalisation of the stiffness variation below Tg. However, an additional stiffening effect is indicated at temperatures above Tg. The mechanism may involve dynamic network formation based on fluctuating hydrogen bonding interactions between the matrix polymer chains and the filler particles.

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Section: Characterizationsupporting

confidence: 54%

Stiffening mechanisms in vermiculite–amorphous polyamide bio-nanocomposites

Macheca

Focke

Muiambo

et al. 2016

European Polymer Journal

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show abstract

“…Microwave (MW) energy has been shown to have benefits across a range of mineral processing applications including microwave assisted comminution of ores , Jones et al, 2005, enhanced magnetic separation , leaching (Al-Harahsheh andKingman, 2004) (Al-Harahsheh, 2005) and exfoliation of vermiculite (Folorunso et al, 2012). MW energy provides selective and volumetric heating; semi-conductive sulphide minerals such as pyrite and chalcopyrite have been shown to heat significantly more than rock forming minerals such as quartz and feldspar (Walkiewicz, 1988).…”

Section: Introductionmentioning

confidence: 99%

Understanding microwave induced sorting of porphyry copper ores

Robinson

Batchelor

Ivanov

et al. 2015

Minerals Engineering

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“…The sample was sieved and particles within the -180+38μm size class were selected for measurement. The chosen range is based on the size of glass tube to obtain high packing density comparable to the processing conditions [7].…”

Section: Sample Preparationmentioning

confidence: 99%

“…Therefore, there is undoubtedly demand for processes which are more efficient in terms of energy consumption, more flexible in terms of operational characteristics and ultimately, more sustainable than the current state of the art. One technology which has the potential to realise these benefits is microwave heating [7]. Its huge success in processing of food materials created an opportunity for its industrial applications in the field of mineral processing [8].…”

Section: Introductionmentioning

confidence: 99%

“…The concept of using microwave energy to exfoliate vermiculite is not new, but there is a lack of understanding and characterising the dielectric behaviour of this material at microwave frequencies. The accurate knowledge of the dielectric properties of vermiculite can likewise be useful in the application of electrical separation technology from separating vermiculite ores from gangue materials during the mining and concentration process with a frequency varied from 0 Hz to 1 MHz [11], and is crucial for the optimum design of continuous microwave processing systems which have been shown in the literature to offer step changes in the efficiency of the exfoliation process [7].…”

Section: Introductionmentioning

confidence: 99%

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Improving the design of industrial microwave processing systems through prediction of the dielectric properties of complex multi-layered materials

et al. 2015

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Sam W. (2015) Improving the design of industrial microwave processing systems through prediction of the dielectric properties of complex multi-layered materials. Journal of Materials Science, 50 (23 A note on versions:The version presented here may differ from the published version or from the version of record. If you wish to cite this item you are advised to consult the publisher's version. Please see the repository url above for details on accessing the published version and note that access may require a subscription.For more information, please contact eprints@nottingham.ac.uk Improving the Design of Industrial Microwave Processing Systems through Prediction of the Dielectric Properties of Complex Multi-layered Materials AbstractRigorous design of industrial microwave processing systems requires in-depth knowledge of the dielectric properties of the materials to be processed. These values are not easy to measure, particularly when a material is multi-layered containing multiple phases, when one phase has a much higher loss than the other and the application is based on selective heating. This paper demonstrates the ability of the Clausius-Mossotti (CM) model to predict the dielectric constant of multi-layered materials. Furthermore, mixing rules and graphical extrapolation techniques were used to further evidence our conclusions and to estimate the loss factor. The material used for this study was vermiculite, a layered alumina-silicate mineral containing up to 10 % of an interlayer hydrated phase. It was measured at different bulk densities at two distinct microwave frequencies, namely 934 and 2143 MHz. The CM model, based on the ionic polarisability of the bulk material, gives only a prediction of the dielectric constant for experimental data with a deviation of less than 5 % at microwave frequencies. The complex refractive index model (CRIM), Landau, Lifshitz and Loyenga (LLL), Goldschmidt, Böttcher and Bruggeman-Hanai model equations are then shown to give a strong estimation of both dielectric constant and loss factor of the solid material compared to that of the measured powder with a deviation of less than 1 %. Results obtained from this work provide a basis for the design of further electromagnetic processing systems for multi-layered materials consisting of both high loss and low loss components.

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Continuous energy efficient exfoliation of vermiculite through microwave heating

Cited by 48 publications

References 25 publications

Stiffening mechanisms in vermiculite–amorphous polyamide bio-nanocomposites

Stiffening mechanisms in vermiculite–amorphous polyamide bio-nanocomposites

Understanding microwave induced sorting of porphyry copper ores

Improving the design of industrial microwave processing systems through prediction of the dielectric properties of complex multi-layered materials

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