Disordering of Starch Films as a Factor Influencing the Release Rate of Biologically Active Substances.

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.

Seasonal and Geographic Variation in Serotonin Content in Sea Buckthorn.

Plants growing in unfavorable environments, such as sea buckthorn, can have a high serotonin content. The potential of using different parts of sea buckthorn (Hippophae rhamnoides L.) as a natural source of serotonin was investigated. The feasibility of extracting serotonin hormone from the non-fruit parts of sea buckthorn is demonstrated. One- and two-year-old woody shoots were the best material for obtaining serotonin-containing raw product. Serotonin content in shoots of different sea buckthorn varieties growing in different regions and its dynamics during the vegetation period were determined by high-performance liquid chromatography. Serotonin is a water-soluble substance prone to microbial degradation, so proper preparation of raw materials plays a very important role in preserving serotonin in plant samples. A method for serotonin extraction using preliminary mechanochemical treatment is presented: it consists in pre-grinding, followed by mechanical treatment of raw materials with 5% adipic acid in a semi-industrial centrifugal mill. The highest degree of serotonin extraction was achieved when using air circulation at a drying temperature of 60-80 °C; serotonin concentration decreased when temperature was further increased. Serotonin content depended on the place and time of harvesting, the method used for drying the branches, and the characteristics of the plant variety. The minimum serotonin concentration (29 mg/g dry basis) was observed during summer; the maximum concentration was observed during winter; the annual changes in concentration can be as significant as 10-fold. The possibility of industrial cultivation and harvesting of different sea buckthorn varieties was also considered.

Concentrating rare earth elements in brown coal humic acids by mechanochemical treatment.

Coals are now viewed as a promising source of rare earth elements increasingly often. Rare earth elements (REE) are known to occur both in the organic and mineral components of brown coals. This study aims at investigating the applicability of mechanochemical activation for concentrating rare earth elements (including Sc, Y, La and lanthanides) in different brown coal fractions. Mechanochemical activation of brown coal in the absence of reagents, as well as additives of sodium percarbonate, monosodium phosphate, and sodium chloride, was carried out. Mechanochemical activation does not cause degradation of humic acid-REE complexes contained in pristine coal. The REE concentration process in the samples of mechanochemically activated coal can be attributed both to formation of new oxygen-containing groups in humic acids (HA) and to binding of REEs to oxygen-containing groups already contained in coal due to vigorous solid-phase mechanical mixing. A method for mechanochemical activation of coal, which allows one to transfer up to 93 ± 7% REEs into the organic alkali-soluble fraction - the HA fraction (while HA in the pristine coal contain only 38 ± 3% REE) - has been developed. The estimated total concentration of REEs in pristine coal ash is 8000 ppm. The estimated REE content in the ash of the product (HA fraction) is as high as 17 300 ppm. Concentrations of Ce, Nd and Y in the ash of the product are 6000 ppm, 4200 ppm and 2500 ppm, respectively.

Mechanochemical and Size Reduction Machines for Biorefining.

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.

Unbound water in mechanochemical reactions of brown coal.

Mechanochemical activation of coal is commonly employed in industry. However, even the simplest solid-phase reactions, such as neutralization of humic acids in brown coal, remain insufficiently studied. The hypothesis regarding the occurrence of mechanochemical neutralization under local hydrothermal conditions for humic acids in brown coal has been tested in this study. 3D modelling of the "block-interlayer" system (where coal particles are separated by air interlayers saturated with water vapor) was used. The 3D model showed that the permittivity is expected to rise from 14 to 16% as the moisture content in the system increases from 12 to 15%. The actual permittivities of coal with different moisture contents have been measured by dielectric spectroscopy. In the real system, the permittivity increases more than threefold as the moisture content rises from 12 to 15%. This increase is much greater than the calculated one, demonstrating that the phase containing unbound water appears in the system at a moisture content of ∼12-13% and may exert various effects on the solid-phase reaction. There is a correlation between the moisture content, permittivity, and predominant mechanisms of the reaction between the organic matter in brown coal and sodium percarbonate (a reagent simultaneously containing the alkaline and peroxidic components). The reactions between brown coal and alkaline reagents proceed under local hydrothermal conditions. Both the alkaline and peroxidic components of sodium percarbonate participate in the solid-phase reaction between brown coal and sodium percarbonate. The emergence of unbound water in coal significantly inhibits the oxidation reaction.

Tailoring the properties of a zero-valent iron-based composite by mechanochemistry for nitrophenols degradation in wastewaters.

Zero-valent iron (ZVI) is a valuable material for environmental remediation, because of its safeness, large availability, and inexpensiveness. Moreover, its reactivity can be improved by addition of (nano-) particles of other elements such as noble metals. However, common preparation methods for this kind of iron-based composites involve wet precipitation of noble metal salt precursors, so they are often expensive and not green. Mechanochemical procedures can provide a solvent-free alternative, even at a large scale. The present study demonstrates that it is possible to tailor functional properties of ZVI-based materials, utilizing high-energy ball milling. All main preparation parameters are investigated and discussed. Specifically, a copper-carbon-iron ternary composite was prepared for fast degradation of 4-nitrophenol (utilized as model pollutant) to 4-aminophenol and other phenolic compounds. Copper and carbon are purposely chosen to insert specific properties to the composite: Copper acts as efficient nano-cathode that enhances electron transfer from iron to 4-nitrophenol, while carbon protects the iron surface from fast oxidation in open air. In this way, the reactive material can rapidly reduce high concentration of nitrophenols in water, it does not require acid washing to be activated, and can be stored in open air for one week without any significant activity loss.