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In recent years, we have witnessed an increasing interest in the application of mechanochemical methods for processing materials in biomass refining techniques. Grinding and mechanical pretreatment are very popular methods utilized to enhance the reactivity of polymers and plant raw materials; however, the choice of devices and their modes of action is often performed through trial and error. An inadequate choice of equipment often results in inefficient grinding, low reactivity of the product, excess energy expenditure, and significant wear of the equipment. In the present review, modern equipment employing various types of mechanical impacts, which show the highest promise for mechanochemical pretreatment of plant raw materials, is examined and compared—disc mills, attritors and bead mills, ball mills, planetary mills, vibration and vibrocentrifugal mills, roller and centrifugal roller mills, extruders, hammer mills, knife mills, pin mills, disintegrators, and jet mills. The properly chosen type of mechanochemical activation (and equipment) allows an energetically and economically sound enhancement of the reactivity of solid-phase polymers by increasing the effective surface area accessible to reagents, reducing the amount of crystalline regions and the diffusion coefficient, disordering the supramolecular structure of the material, and mechanochemically reacting with the target substances.

Проведено исследование бактерицидного действия ряда полифенолов (гуминовых веществ и меланинов) из природного сырья, полученных в результате механохимической обработки смесей сырья с твердым окислителем - перкарбонатом натрия и восстановителем - цинком в отношении условно-патогенных бактерий, важных для птицеводства: Salmonella typhimurium, Shigella sonnei, Esherichia coli, Pasteurella multocida, Yersinia pseudotuberculosis, Streptococcus pyogenes, Staphylococcus aureus, Staphylococcus epidermidis. Исследованные гуминовые полифенолы проявляют активность в отношении бактерий семейства Enterobacteriaceae (Salmonella typhimurium, Shigella sonnei, Esherichia coli, Yersinia pseudotuberculosis) после механохимического взаимодействия с перкарбонатом натрия. Образцы после взаимодействия с цинком активности не проявляют. В отношении бактерий Pasteurella multocida (семейство Pasteurellaceae) Staphylococcus epidermidis (семейство Staphylococcаceae) активны практически все исследованные гуминовые и меланиновые препараты за исключением препаратов после взаимодействия с цинком. Активные в отношении бактерий Streptococcus pyogenes (семейство Streptococcaæae), Staphylococcus aureus (семейство Staphylococcaœae) могут быть получены механохимическим взаимодействием с перкарбонатом натрия в определенных условиях.

Research into extraction kinetics is one of the crucial factors in a technological process. Extraction is used predominantly when working with organic feedstock. The study of the kinetics of extraction of a substance is a complex process, which is influenced by a large number of factors. This paper presents an analysis of one of these factors, namely the influence of reverse sorption on the process of substance release from the matrix. Sorption can directly affect the intraparticle diffusion constants and, consequently, the rate of release of the substance. Using buckwheat husk as an example, its sorption capacity was assessed to assess the sorption factor on the rate of melanin release. To select the optimal parameters of the chemical process, the experiment was carried out at temperatures of 40, 50, and 60 degrees Celsius. The Axelrud and Baker–Lonsdale equations were used to describe the kinetic models.

Enhancing the extraction rate is one of the key objectives in optimization of extraction of substances from biogenic raw materials. Ultra-fine grinding of plant raw materials (to achieve particle size less than 300 µm) is a very appealing method for increasing the extraction rate using relatively simple equipment. However, this approach often fails to yield the desired result. This study focuses on the kinetics of melanin extraction from two types of raw materials: fungus Ganoderma applanatum and buckwheat husk. Particle size is shown to be just one of the key factors. The degree of order of plant-based feedstock strongly affects the intraparticle diffusion constants and can be a parameter controlling the diffusion rate. It has been shown that there exist optimal degrees of disorder of the crystal structure of plant raw materials, which have a dome-shaped dependence pattern and allow one to increase the diffusion coefficient by several dozen times. The kinetics of melanin extraction was described by some kinetic models that include the first order equation, the Baker and Lonsdale model, the Axelrud equation, and the Ritger–Peppas model.

The release of a spin probe (nitroxide radical) from polymer films was studied by electron paramagnetic resonance (EPR). The films were fabricated from starch having different crystal structures (A-, B-, and C-types) and disordering degrees. Film morphology (analysis of the scanning electron microscopy (SEM)) depended on the presence of dopant (nitroxide radical) to a larger extent rather than on crystal structure ordering or polymorphic modification. The presence of nitroxide radical led to additional crystal structure disordering and reduced the crystallinity index from the X-ray diffraction (XRD) data. Polymeric films made of amorphized starch powder were able to undergo recrystallization (crystal structure rearrangement), which manifested itself as an increase in crystallinity index and phase transition of the A- and C-type crystal structures to the B-type one. It was demonstrated that nitroxide radical does not form an individual phase during film preparation. According to the EPR data, local permittivity of starch-based films varied from 52.5 to 60.1 F/m, while bulk permittivity did not exceed 17 F/m, which demonstrates that local concentration of water is increased in the regions near the nitroxide radical. The mobility of the spin probe corresponds to small stochastic librations and is indicative of the strongly a mobilized state. The application of kinetic models made it possible to find out that substance release from biodegradable films consists of two stages: matrix swelling and spin probe diffusion through the matrix. Investigation of the release kinetics for nitroxide radical demonstrated that the course of this process depends on the type of crystal structure of native starch.

Adsorbed polyphenolic compound (resveratrol) to a wheat straw matrix was considered as a model system for studying the influence of particle sizes and crystallinity of cell wall cellulose on the extraction process from the matrix of plant material. The morphology of wheat straw particles was studied by scanning electron microscopy and changes in the crystal structure of cellulose were determined using X-ray diffraction. The kinetics of resveratrol extraction were studied using high-performance liquid chromatography (HPLC). The diffusion constants were determined for particles of different sizes and particles having the same size but varying in the degree of disordering of cellulose, the main component of cell walls. The applicability of the Axelrud equation for calculating the mass transfer constants for plant objects with a complex internal structure was shown. Comparison of the particle sizes, the degree of crystallinity, and the calculated mass transfer constant makes it possible to suggest that it is the disordering of pore walls and their subsequent collapse that changes the diffusion mechanism. Schemes of resveratrol fluxes were proposed for extraction from particles of a plant matrix of different sizes; the mass transfer constants were calculated using these data. It was shown that the mass transfer constant has a maximum depending on the disordering of the crystalline structure of plant materials. By disordering the plant matrix, it is possible to increase the flow of matter by seven times. At high crystallinity index, the mass transfer process is impeded by diffusion through the cell wall. Intensive grinding leads to deep disordering of the structure and collapse of pores—the main diffusion channels.