Disordering of the Crystal Structure of Cellulose Under Mechanical Activation

Podgorbunskikh, Ekaterina; Бычков, А. Л.; Булина, Н. В.; Ломовский, О. И.

doi:10.1134/s0022476618010328

Cited by 36 publications

(15 citation statements)

References 16 publications

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“…Therefore, X-ray diffraction patterns for completely amorphized samples subjected to pretreatment for 10 min were recorded. These samples were used as knowingly amorphous reference samples for calculating the crystallinity degree [23]. Table 3 lists the crystallinity degrees for the initial and mechanically activated starch samples.…”

Section: Resultsmentioning

confidence: 99%

“…Defect nucleation and accumulation causes disordering of the crystal structure. In particular, mechanical pretreatment of cellulose in a planetary ball mill gives rise to a reactive product that is characterized by disordered ultrastructure, increased specific surface area, and reduced crystallinity degree [23,24]. For starch, mechanical pretreatment also reduces the grain size and increases the content of the amorphous phase, making it possible to alter the hydrating and paste-forming properties of modified starch [25,26].…”

Section: Introductionmentioning

confidence: 99%

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Changes in the Crystallinity Degree of Starch Having Different Types of Crystal Structure after Mechanical Pretreatment

et al. 2020

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This paper examines the effect of mechanical activation on the amorphization of starch having different types of crystalline structure (A-type corn starch; B-type potato starch; and C-type tapioca starch). Structural properties of the starches were studied by X-ray diffraction analysis. Mechanical activation in a planetary ball mill reduces the degree of crystallinity in proportion to pretreatment duration. C-type tapioca starch was found to have the highest degree of crystallinity. Energy consumed to achieve complete amorphization of the starches having different types of crystalline structure was measured. The kinetic parameters of the process (the effective rate constants) were determined. The rate constant and the strongest decline in the crystallinity degree after mechanical activation change in the following series: C-type starch, A-type starch, and B-type starch.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Changes in the Crystallinity Degree of Starch Having Different Types of Crystal Structure after Mechanical Pretreatment

et al. 2020

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“…The effect of mechanochemical activation on the amorphization of the pure α-cellulose component and native cellulose in the composition of lignocellulosic material-wheat straw-is considered in (Podgorbunskikh, Bychkov, Bulina, & Lomovskii, 2018). A comparison of methods for determining the degree of cellulose crystallinity based on powder XRD patterns, in particular, by the Segal, Rietveld, and Lorentzian deconvolution methods, was made.…”

Section: Principles Of the Mechanical And Mechanochemical Methods Amentioning

confidence: 99%

Current achievements in the mechanically pretreated conversion of plant biomass

Bychkov

Podgorbunskikh

Bychkova

et al. 2019

Biotech & Bioengineering

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At present, “mechanochemistry” is synonymous with “grinding,” according to the views of a significant number of scientists and technologists. Often, one comes across the opinion that “the less the particle size, the better.” The cases of considering chemical reactions occurring during pretreatment, as well as considering changes in the ultrastructure of cell walls are extremely rare. Also, the wrong choice of the type of mechanical impact and the equipment used in most cases leads to excessive consumption of electrical energy and reduce economic efficiency. The review presents the currently available published data on mechanically activated processes for the pretreatment of plant materials and shows that when using mechanical treatment, it is necessary to look more closely at the phenomena occurring, rather than reducing everything to the production of fine and ultrafine powders. As a result of mechanical action, active surface radicals can form, hydrothermal chemical processes can occur, and mechanocomposites can form. The role of interphase processes, changes in surface chemistry, related dimensional effects, and the disordering of the crystal structure and amorphization should be taken into account. In addition, the physicochemical insights in mechanical pretreatment make it possible to more efficiently use the energy delivered to the material, and, consequently, increase the economic efficiency of the activation process.

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“…The degree of cellulose crystallinity was measured by powder X-ray diffraction analysis on a D8 Advance diffractometer (Bruker, Karlsruhe, Germany) and calculated using the Segal, Rietveld, and Lorenz methods [15,16]. Granulometric analysis was conducted using an Analysette-3 Pro vibratory sieve shaker equipped with a set of sieves (mesh size, 20–1000 µm) (FRITSCH, Markt Einersheim, Germany) and a Microsizer 201 laser particle size analyzer equipped with an ultrasonic disperser (VA Instalt, Saint Petersburg, Russia).…”

Section: Methodsmentioning

confidence: 99%

Determination of Surface Accessibility of the Cellulose Substrate According to Enzyme Sorption

2019

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As a heterogeneous process, enzymatic hydrolysis depends on the contact area between enzymes and the cellulose substrate. The surface area of a substrate is typically evaluated through the sorption of gases (nitrogen, argon, or water vapor) or sorption of high-molecular-weight pigments or proteins. However, lignocellulosic biomass uninvolved in the reaction because of inefficient binding or even the complete inhibition of the enzymes on the surface consisting of lignin or inorganic compounds is erroneously taken into account under these conditions. The initial rate of enzymatic hydrolysis will directly depend on the number of enzymes efficiently sorbed onto cellulose. In this study, the sorption of cellulolytic enzymes was used to evaluate the surface accessibility of the cellulose substrate and its changes during mechanical pretreatment. It was demonstrated that for pure cellulose, mechanical activation did not alter the chemical composition of the surface and the initial rate of hydrolysis increased, which was inconsistent with the data on the thermal desorption of nitrogen. New active cellulose sorption sites were shown to be formed upon. the mechanical activation of plant biomass (wheat straw), and the ultimate initial rate of hydrolysis corresponding to saturation of the accessible surface area with enzyme molecules was determined.

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Disordering of the Crystal Structure of Cellulose Under Mechanical Activation

Cited by 36 publications

References 16 publications

Changes in the Crystallinity Degree of Starch Having Different Types of Crystal Structure after Mechanical Pretreatment

Changes in the Crystallinity Degree of Starch Having Different Types of Crystal Structure after Mechanical Pretreatment

Current achievements in the mechanically pretreated conversion of plant biomass

Determination of Surface Accessibility of the Cellulose Substrate According to Enzyme Sorption

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