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In this article, the synthesis of biocompatible fibrous scaffolds with antimicrobial properties based on polycaprolactone/hydroxyapatite/amoxicillin and study of their surface morphology, antimicrobial effect, and drug release are discussed. Hydroxyapatite (1–2 $\mu $m, 97%) synthesized from biologically waste material (eggshell) was added to the composite scaffolds as a bone-replacement material. The scaffolds’ antimicrobial properties were evaluated against S. aureus and E. faecalis. The scaffolds possessed a sustained drug release from the scaffolds amounted to about 94% of the antibiotic’s total weight over a 4-week observation period. Agar diffusion confirmed the antimicrobial properties of the scaffolds against specific bacteria.

This study investigates the physical, mechanical, and structural characteristics of handmade paper samples derived from cellulose extracted from grass clippings using two distinct methods as follows: (1) alkali treatment and (2) alkali treatment followed by bleaching, coupled with the incorporation of barium sulfate as a mineral filler. Our investigation revealed that the handmade paper samples' densities, moisture contents, and thicknesses varied within the ranges of 0.436 to 0.549 g/cm3, 5.60 to 2.51%, and 0.41 to 0.50 mm, respectively. The tensile strength and folding endurance of the papers produced through alkali treatment with barium sulfate were notably superior to those produced from bleached pulp and barium sulfate. Our analysis indicates that several critical factors, including paper density, thickness, the crystallinity index, and the microfibrillar structure of cellulose, intricately influence the mechanical and strength properties of the samples. Using Fourier transform infrared spectroscopy (FT-IR) and X-ray diffraction (XRD) techniques, we identified characteristic cellulose bonds and examined cellulose's crystalline and amorphous phases. Additionally, the crystallinity index of the samples was determined using both the Segal and peak deconvolution methods. Scanning electron microscopy (SEM) micrographs revealed interconnected networks of cellulose fibers with varying thicknesses and lengths, along with incorporated mineral filler within the cellulose fiber structure. Variations in mineral particle retention were attributed to the presence or absence of cellulose microfibrils. These findings contribute to our understanding of the observed strength characteristics of the paper samples and underscore the potential applications of cellulose derived from grass clippings, especially when combined with barium sulfate as a mineral filler in paper production. [ABSTRACT FROM AUTHOR]

Some drawbacks of aqueous electrolytes, such as freezing at low temperatures and extensive evaporation at high temperatures, restrict their industrial viability. This article introduces a stabilized neutral aqueous choline nitrate electrolyte with a 10 vol.% methanol additive that improves the temperature stability of the electrolyte via enhanced hydrogen bonding with the choline cation and water and maintains the good state of health of the supercapacitor cells under extreme operating conditions. The symmetric carbon/carbon supercapacitor in 5 mol/kg choline nitrate + 10 vol.% methanol (σ = 76 ms/cm at 25°C) exhibits 103 F/g at room temperature during galvanostatic charge/discharge up to 1.5 V, which decreases to 78 F/g at -40°C due to the suppressed Faradaic reactions occurring at the carbon electrode. However, under similar charge/discharge conditions, the capacitance increases to 112 F/g when the supercapacitor operates at 60°C. This capacitance increase at high temperatures is due to the Faradaic reactions related to enhanced hydrogen adsorption and desorption. The most remarkable aspect of the proposed supercapacitor is its ability to maintain capacitance and power performance during high voltage floating at 1.5 V at three tested temperatures (-40°C, 24°C, and 60°C). [ABSTRACT FROM AUTHOR]

Transformations of high-molecular-weight compounds of oil sand natural bitumen under the heat treatment were studied in this work. For that purpose the natural bitumen isolated from oil sand taken from the Beke field (Kazakhstan) was used as a substrate. Thermal processing of natural bitumen leads to a general change in the chemical composition of components and to an increase in the output of certain fractions. The contents of oil, tar and asphaltenes were determined and the elemental composition of tar-asphaltene compounds was evaluated. Molecular structures of the tar and asphaltene components of natural bitumen before and after cracking have been defined from the data of elemental analysis, NMR spectroscopy and molecular weight. The high molecular compounds were presented as giant molecules containing small aromatic islands some of which were linked by aliphatic chains, that was proved by infrared spectroscopy.

In this study, we systematically study the efficient production method and electrochemical characteristics of activated carbons (AC) derived from rice husk (RH) and walnut shell (WS). In particular, the effectiveness of physical activation using carbon dioxide (CO2) was investigated and compared with the more common chemical activation method using potassium hydroxide (KOH). The results show that the KOH–activated samples have remarkable specific capacities, reaching 157.8 F g−1 for RH and 152 F g−1 for WS at 1 A g−1. However, the rate capability of AC obtained via KOH decreases significantly as the scanning rate increases, retaining only 51.5% and 68% of their original capacities for RH–KOH and WS–KOH, respectively, at 20 A g–1. In contrast, CO2–activated samples show a superior rate performance with a capacity retention of 75.6% for WS and 80% for RH at the same current density. In addition, electrochemical impedance spectroscopy (EIS) analysis shows that AC obtained via CO2 has a lower charge transfer resistance compared to its KOH counterparts. CO2–activated RH and WS electrodes show Rct values of 0.1 Ω and 0.24 Ω, respectively, indicating improved ion transport kinetics and surface area utilization. These results highlight the importance of activation techniques in tailoring the electrochemical behavior of biomass–derived carbon. This study not only expands the understanding of the interaction between activation, morphology, and performance but also indicates the potential of CO2 activation as an environmentally friendly and efficient alternative. As the field of sustainable energy storage advances, this work provides valuable guidance for the development of high–performance supercapacitor electrodes with less environmental impact. [ABSTRACT FROM AUTHOR]

This article examined the characteristics of zeolites from the Chankanai and Daubabinsk deposits. In the field of water treatment, the purpose of investigating natural zeolite from the Chankanai and Daubabinsk deposits as a sorbent presents new opportunities and prospects, as this raw material is little studied. The effectiveness of the sorbents was assessed based on the results of the water specifications according to the following criteria: methods for determining the total hardness of water; methods for measuring the mass concentration of total iron in water; methods for the determination of chloride in water; methods for the determination of nitrogen-containing substances in water; methods for determining the dry residue content of water; methods for determining the sulphate content of water; on hygiene requirements and water quality control. Zeolite modifications were aimed at improving their adsorption properties, increasing the efficiency of pollutant removal and developing optimal methods of using zeolites in water filtration. Modified zeolite from the Chankanai and Daubabinsk deposits showed high efficiency as a filter. When it was used to treat natural water, which normally contains high hardness and alkalinity, the best results were achieved with zeolite from the Chankanai deposit. In terms of Fe+ and Cl content, the best results were achieved using zeolite from the Daubabinsk deposit. [ABSTRACT FROM AUTHOR]

Problems with increasing heavy metal contents in natural waters are becoming a global issue. At the same time, improved methods for water treatment are becoming increasingly important. In this context, natural zeolites can be used to purify polluted water. In this paper, we investigated how the adsorption capacity of natural zeolites can be improved. Natural zeolites from the Shankanay district, Almaty, Kazakhstan, were used as adsorbent material for experiments on improving the water treatment of heavy metals. We found that the adsorption capacity for heavy metals was increased greatly by thermal activation using furnace treatment. The optimal thermal activation condition was about 550 °C for a duration of 2 h. However, the improved adsorption capacity for different heavy metals varied depending on the heat treatment temperature. Adsorption by the heat-treated zeolites at a temperature of 550 °C was 87% for nickel, 99% for copper and cadmium, and 100% for lead. Adsorption by heat-treated zeolites at a temperature of 500 °C was 78% for nickel, 98% for copper, 83% for cadmium, and 88% for lead. The residual concentration of heavy metals in the filtered water did not exceed the maximum permissible concentrations for drinking purposes. In all experiments, intense adsorption took place during the first 10 min representing 35 to 61% of the metal ions in the water. Adsorption properties were verified using adsorption capacity (BET), IR spectroscopy, and scanning electron microscopy. The study shows that modified Shankanay natural zeolites have great potential as a low-cost adsorbent material for purifying water from heavy metals. [ABSTRACT FROM AUTHOR]

The adsorption of gold ions on carbonized apricot stones (CAS) is studied. The carbonization applied is carried out at a temperature of 500oC in an argon atmosphere. The CAS characterized by electron microscopy are used as adsorbents of [AuC14]-. It is found that Au (III) ions are quantitatively (99 - 100 %) adsorbed within a wide range of HCl concentrations. The values of the sorption rate, the semi sorption time, the sorption rate constant and the sorbent dynamic and static capacity are determined. It is shown that the presence of excessive amounts (100 - 800 times) of Fe+3, Cu+2, Cd+2, Zn+2, Hg+2, Pb+4 ions does not affect Au+3 sorption by CAS-2 sorbent. [ABSTRACT FROM AUTHOR]

The expanded graphite (EG) and carbonized rice husk (CRH) used in this study are obtained by a heat treatment at various temperatures and activation conditions. A natural graphite of the Zavalievsky deposit (Zavalievsky Graphite Ltd., Kiev) of Ukraine is used. The samples are tested as oil-in-water sorbents aiming to remove emulsified oils from wastewater. The efficiency of the oil removal in presence of CRH and EG is determined. The results show that it increases by 10-15% in case of EG samples after basic leaching. The adsorption capacity of CRH samples is almost the same with no perceptible changes observed with an activation temperature increase. All samples are characterized by various physico-chemical methods of an analysis. According to the elemental analysis, the heat treatment results in an increase of the carbon content compared to that of the feedstock and the other components presence, but a decrease of the hydrogen content. A noticeable decrease of the hydrogen content is detected with an increase of the activation temperature. It is shown that in general the carbonization process leads to an increase of the adsorption capacity. [ABSTRACT FROM AUTHOR]

The article describes processing of low-grade coal and catalytic hydrogenation of brown coal of Karazhira field (Kazakhstan). The highly dispersed iron-containing concentrates of Balkhash deposit (Kazakhstan) are studied as catalysts of the hydrogenation process in processing of sub-standard coal. The catalysts are prepared by mechanicchemical activation of the concentrate with subsequent dispergation in the coal in presence of polyethylene. It was found that use of an activated catalyst containing pyrite when coal hydrogenation in tetralin allowed to achieve practically complete decomposition of the organic mass of coal into liquid and gaseous products. Yield of maltens in presence of the activated catalyst was equal to 56.1% (by wt.). The results show that the effect of mechanic-chemical activation is caused not only increase in specific activity of the ore catalyst, but also probably change of catalytic properties of a surface. These changes can be apparently connected with the defects of crystal structure of a sample as a result of intensive mechanical influence. [ABSTRACT FROM AUTHOR]

This article is dedicated to the development of a method for the manufacture of granulated carbon sorbents made of powdered rice husk (RH) and lignosulphonate (LS) aimed at absorption of organic and inorganic vapors. The microstructure analysis of the samples reveals that the activation promotes the formation of a higher amount of small pores and the development of a spongy texture of the sorbents leading to carbon content increase when compared to that of the initial sample. The final samples have apparent mesoporosity confirmed by the form of the isotherms referring to the low-temperature adsorption of nitrogen and the results of pore size distribution using the DFT method. [ABSTRACT FROM AUTHOR]

The paper presents the results of thermal cracking of natural bitumens of the Beke and Munaily Mola oil sand deposits (Kazakhstan). The data obtained show that the high-molecular components of the bitumen of the Munaily Mola deposit are more easily cracked than those of the Beke deposit. The cracking of natural Beke bitumen in a medium of water vapor, acetonitrile and isopropanol is studied at different temperatures and pressures. The effect of the heterogeneous additive - nano-sized copper (II) oxide on the cracking efficiency of natural bitumen components is identified. The total yield of gas and coke is 3.2%, while the distillate fractions is 40.8 mass % in case of cracking of the Beke natural bitumen in a flow reactor. [ABSTRACT FROM AUTHOR]

The work is devoted to the investigation the gas-generating composition of gas generator for processing of oil wells on the basis of ammonium nitrate, a magnesium, aluminum, an epoxy resin and a nanostructured soot. The regularities of combustion of carbonaceous nanomaterials in two gas generating compositions with regard to the conditions of the oil wells were determined. The influence of different amount of nanostructured soot on the regularities of combustion of pyrotechnic gas generator composition was investigated. By adding of 1.0 % nanostructured soot the lowest rate of combustion - 0.05 mm/s was reached. The content of the combustion products by the "Terra" program for composition No.2 was calculated. An optimal composition for the processing bottomhole zones of oil wells is proposed. To determine the morphology and sizes of the resulting soot particles electronic microscopic studies of the soot samples were carried out. [ABSTRACT FROM AUTHOR]

The basic laws and features of combustion of pyrotechnic gas generating compositions were studied. The components and their ratios for preparation gas generating compositions on the base of ammonium nitrate (an oxidizer) and coal arenes (the fuel-binder) and melamine and polyvinyl alcohol (the gasification supplements) were found. The thermodynamics calculations of the characteristics (adiabatic temperature of burning and equilibrium composition of products) of pyrotechnic compositions with the use of complex of the programs "Thermo" based on the method of minimization of thermodynamics potential of energy of Gibbs were carried out. Two formulations were created and investigated. It was shown that the compressive strength of compositions of pyrotechnic products was provided by cementators (coal arenes). [ABSTRACT FROM AUTHOR]

The article shows the results of thermal cracking of natural bitumen of Kazakhstan's two deposits. The variation of the chemical and the fractional composition of the cracking products are determined depending on the process conditions. A comparative analysis of the influence of the catalyst is carried out to composition of natural bitumen. [ABSTRACT FROM AUTHOR]

Abstract: The possibility of preparing honeycomb monoliths from unconventional materials with high adsorption capacity, such as carbonized rice husk (CRH), was studied. Two schemes including modification of the porous structure by silica leaching were suggested for preparation of the monoliths: (1) preparation of CRH monoliths with the addition of Ca-montmorillonite (Ca-M) followed by leaching and (2) preliminary leaching of initial components followed by monolith extrusion. Chemical and textural properties of the materials were studied at each preparation step. The effect of temperature of rice husk (RH) pyrolysis and conditions of leaching treatment on the physico-chemical properties of CRH was investigated. By the data of nitrogen adsorption and SEM characterization, CRH has low specific surface area, pore volume less than 0.1cm3/g, and composed mainly of macropore channels 5–10μm in diameter, micropores less than 17Å in size, and a minor amount of mesopores. Treatment of the carbonized product with a 12% solution of potassium hydroxide at 80–100°C leads to a 90–95% leaching of SiO2 from the CRH composite and increases the specific surface area to 400m2/g and pore volume to 0.4cm3/g due to formation of mesoporous structure. The feasibility of CRH honeycomb monoliths preparation and applicability of silica leaching from the monolith material for modification of the porous structure are demonstrated. The resulting monoliths are characterized by specific surface area exceeding 300m2/g, pore volume 0.3cm3/g, and high mechanical strength. [Copyright &y& Elsevier]

This paper deals with the study of the optical properties of one-dimensional SrTiO 3 /PAN-based photocatalysts with the addition of metal oxide particles and the determination of their bandgaps. One-dimensional photocatalysts were obtained by the electrospinning method. Particles of metals such as iron, chromium, and copper were used as additives that are capable of improving the fibers' photocatalytic properties based on SrTiO 3 /PAN. The optimal ratios of the solutions for the electrospinning of fibers based on SrTiO 3 /PAN with the addition of metal oxide particles were determined. The transmission and reflection of composite photocatalysts with metal oxide particles were measured in a wide range of spectra, from the ultraviolet region (185 nm) to near-infrared radiation (3600 nm), to determine the values of their bandgaps. Thus, the introduction of metal oxide particles resulted in a decrease in the bandgaps of the obtained composite photocatalysts compared to the initial SrTiO 3 /PAN (3.57 eV), with the following values: -3.11 eV for SrTiO 3 /PAN/Fe 2 O 3 , -2.84 eV for SrTiO 3 /PAN/CuO, and -2.89 eV for SrTiO 3 /PAN/Cr 2 O 3 . The obtained composite photocatalysts were tested for the production of hydrogen by the splitting of water-methanol mixtures under UV irradiation, and the following rates of hydrogen evolution were determined: 344.67 µmol h -1 g -1 for SrTiO 3 /PAN/Fe 2 O 3 , 398.93 µmol h -1 g -1 for SrTiO 3 /PAN/Cr 2 O 3 , and 420.82 µmol h -1 g -1 for SrTiO 3 /PAN/CuO.