Volumen 24 (2022): Edición 3 (September 2022)

β-glucanase is widely used in many fields and has great economic value and development space, but it faces the difficulties of separation and nutrient destruction in the process of industrial production. Foam separation is a simple, mild and efficient adsorption separation technique that enables efficient separation and extraction of β-glucanase. In this study, five single factors (loading volume, pH, separation gas velocity, fermentation loading concentration, surfactant concentration) of foam separation and harvest of β-glucanase produced by Pichia pastoris were studied. The best univariate condition was: 600 mL/min separation gas velocity, loading volume of 200 mL, initial enzyme concentration of 100 g/mL, surfactant concentration of 0.3 mg/mL and pH of 5. Based on the best univariate condition, the optimal separation conditions of β-glucanase were further explored, and the five-factor four-level orthogonal test was designed. From the experimental results, the best separation condition was: 600 mL/min, loading volume of 200 mL, initial enzyme concentration of 100 μg/mL, surfactant concentration of 0.5 mg/mL and pH of 5. Under this separation condition, the enrichment ratio (E) was 0.56 and the recovery rate (R) was 96.01%.

The aim of the study was to relate the influence of the chemical composition, structure, and basic properties as hardness of the tested drill bits on resistance to their wear. The chemical composition of the drill bit was investigated using the electric excitation emission spectrometry method and EDS microanalysis. Metallographic specimens were prepared and observed to determine the structure of each tool. Hardness tests were carried out on the shank and the working part of the tools. Material wear tests were carried out on the basis of measuring the wear of the drill bit flank. It has been shown that the appropriate selection of the chemical composition and heat treatment has a significant impact on the wear resistance of cutting tools, which directly translates into their quality.

The aim of the present work was the preparation and properties evaluation of two innovative fertilizers based on multicomponent polymers characterized by a controlled release of nutrients. One method was based on a multi-component liquid containing different amounts of microelements NPK 12-5-6 fertilizers with polyacrylamide hydrogel beads. The second method concerned the cross-linking of biodegradable polyvinyl alcohol with multi-component NPK fertilizers. Polyacrylamide-based compositions with the highest amount of NPK salts as well as polyvinyl alcohol-based fertilizers in dense gel form, based on 60 phr crosslinking concentrate have shown optimal properties. Regardless of the type of fertilizers used, their components were released slowly. The obtained fertilizers were classified according to the kinetics of nutrient release. Fertilizers made from polyacrylamide based fertilizers have been classified into a group of controlled release fertilizers (CRF), while those made from biodegradable environmentally friendly polyvinyl alcohol have been defined as slow released fertilizers (SRF).

The effects of different surface modifiers on the CO₂ adsorption capacity of coal-based activated carbons were studied, and the diffusion behavior, adsorption kinetics and thermodynamic parameters of CO₂ in activated carbons were analyzed. The results show that compared with ethylene glycol, 1,2-propylenediamine and zinc chloride, potassium hydroxide and sodium hydroxide can greatly improve CO₂ adsorption capacity. The adsorption rate is faster, and the adsorption capacity is larger, with the maximum CO₂ adsorption capacity being 33.54 mL/g. Fick's law can well describe the diffusion behavior of CO₂ in activated carbon. The addition of a surface modifier can increase the diffusion coefficient. The diffusion of CO₂ in activated carbon falls into the category of crystal diffusion. The adsorption kinetics of CO₂ before and after surface modification follow the Bangham equation. During the adsorption process, δ H < 0, δ G < 0, δ S < 0. Surface modification can reduce adsorption heat and promote adsorption, and the adsorption process is dominated by physisorption.

Graphite nitrogen, pyridine nitrogen and pyrrole nitrogen are the main nitrogen types in nitrogen-doped graphene materials. In order to investigate the mechanism of the oxygen reduction activity of nitrogen-doped graphene, several models of nitrogen-doped graphene with different nitrogen contents and different nitrogen types are developed. The nitrogen content is varied from 1.3 at% to 7.8 at%, and the adsorption energy is calculated according to the established models, then the band gaps are analyzed through the optimization results, so as to compare the magnitude of the conductivity. Finally, the oxygen reduction activity of graphite nitrogen-doped graphene (GNG) is found to be better than pyridine nitrogen-doped graphene (PDNG) and pyrrole nitrogen-doped graphene (PLNG) when the nitrogen content is lower than 2.6 at%, and the oxygen reduction activity of PDNG is the best when the nitrogen content was higher than 2.6 at%.

A novel series of complexes with the formula [MLCl] [M = Co(II) (1), Ni(II) (2), Cu(II) (3), Zn(II) (4)] arising from Pyridyl ligand, N,N′-bis(1-(2-pyridyl)ethylidene)-2,2-dimethylpropane-1,3-diamine), ligand, L, was synthesized and investigated by elemental analyses, FT-IR, ¹H and ¹³C NMR, Powder XRD, and thermal analyses. TGA analysis indicated that all complexes degraded in three different steps, while the PXRD examination showed well-defined sharp crystalline peaks for the complexes, indicating significant crystallinity. The antiproliferative activity of the ligand and its complexes were also evaluated in vitro against the HeLa (Human Cervical Cancer Cells) and HCT116 (Colon Cancer Cells) cell lines. The findings suggested complex 4 to be potential anticancer agent against these cell lines. In addition, ligand and its complexes also exhibited considerable emission properties.

In view of the powder feeding system, a multi-physical coupling model of the gas-powder-piston was established based on the Euler-Euler two-fluid model. The numerical simulation method was applied to explore the effects of dense gas-solid flow characteristics under different operating pressures. The results show that gas-solid pulsations at different operating pressures are mainly concentrated in the upper part of the powder tank. An elevated operating pressure efficiently decreases the powder layer area (ε_p = 0.1) fluctuation. As the operating pressure increases from 0.5 MPa to 3.0 MPa, the rising time and fluctuation rate of pressure are reduced by 71.4% and 62.3%, respectively, and the pressure in the tank has a long stabilization period. Meanwhile, the variation of the instantaneous powder flow rate is more stable and its average value is closer to the theoretical. A high-pressure environment is more conducive to the stable transportation of powder.

Two-component deep eutectic solvents (DES) based on choline dihydrogencitrate and glycerol or urea were tested as starch plasticizers. Thermal analysis techniques were applied to characterize the properties of starch/DES systems. The X-ray diffractometry measurements revealed a significant decrease in crystallinity indicating that used DES exhibited the ability to penetrate the ordered regions of potato starch, which is a necessary feature of a true plasticizer. However, the differential scanning calorimetry and dynamic thermal analysis results surprisingly showed an increase of T_g of starch materials indicating chemical crosslinking at elevated temperature. The eutectic solvents based on choline dihydrogencitrate could act as a plasticizer and a simultaneously crosslinking agent.