Chuiko Institute of Surface Chemistry

This study investigated an oxidative treatment method for apricot kernel shells (AKS) to extract their polysaccharide component for subsequent conversion into liquid biofuel. The aim was to overcome the inherent recalcitrance of lignocellulosic biomass by selectively removing lignin and enriching cellulose content - critical steps for efficient enzymatic hydrolysis. The AKS were treated in an acetic acid medium with hydrogen peroxide under varied conditions, and the resulting substrates were analyzed for yield, cellulose, and lignin content. Mathematical modeling, using regression equations with statistically significant coefficients, accurately described the changes in substrate properties depending on the treatment parameters. Optimization of this multi-criteria process using a generalized Harrington desirability function identified 9% hydrogen peroxide and 120 minutes of treatment as optimal parameters, yielding a composite desirability value of 0.7966. Under these conditions, the obtained substrate exhibited a 50.1% recovery, 54.4% cellulose, and 12.4% lignin, closely matching theoretical predictions. Visual and IR spectroscopic analyses confirmed the efficiency of the treatment: the processed substrate (AKS-S) displayed a lighter color, indicating reduced lignin and increased cellulose content compared to raw AKS. IR spectra further revealed significant lignin removal and degradation of low-molecular-weight hemicelluloses, which is advantageous as it minimizes the formation of inhibitory byproducts during enzymatic hydrolysis. The treatment also doubled the specific surface area and increased porosity six-fold, improving enzyme accessibility. These findings underscore the potential of this oxidative treatment as an effective pretreatment strategy for converting agricultural waste into a high-quality substrate for biofuel production.

P-cresol, indole and indole-3-acetic acid (IAA) are catabolites of amino acids, formed by the gut microbiome. Most of these aromatic hydrocarbon derivatives are excreted by the colon before reentering the body to form “exogenous” protein-bound uremic toxins (PBUTs), which aggravate chronic kidney disease (CKD). Removal efficiencies of these PBUT precursors from model phosphate-buffered saline solutions by three different surface-modified nanoporous carbon adsorbents (PCs) were studied. PCs were produced by physicochemical and/or acid base activation of carbonized rice husk waste. Removal rates achieved values of 32–96% within a 3 h contact time. High micro/mesoporosity and surface chemistry of the N- and P-doped biochars were established by N2 adsorption studies, SEM/EDS analysis, XPS and FT-IR-spectroscopy. The ammoxidized PC-N1 had the highest adsorption capacity (1.97 mmol/g for IAA, 2.43 mmol/g for p-cresol and 2.42 mmol/g for indole), followed by “urea-nitrified” PC-N2, whilst the phosphorylated PC-P demonstrated the lowest adsorption capacity for these solutes. These results do not correlate with the total pore volume values for PC-N2 (0.91 cm3/g) < PC-P (1.56 cm3/g) < PC-N1 (1.84 cm3/g), suggesting that other parameters such as the micropore volume (PC-N1 > PC-N2 > PC-P) and the interaction of surface chemical functional groups with the solutes play key roles in the adsorption mechanism. N-doped PC-N1 and PC-N2 have basic functional groups with higher affinity with acidic IAA and p-cresol. The ion-exchange mechanism of phenolic and indolic compound chemisorption by nanoporous carbon adsorbents, modified with surface N- and P-containing functional groups, has been proposed.

Films of nanosized titanium dioxide doped with 0.1–10 mol. % of tungsten ions (hereinafter referred to in the text as W/TiO2) using titanium tetraisopropoxide Ti(OiPr)4 and (NH4)10W12O41·nH2O were obtained by the sol-gel method using non-ionic amphiphilic triblock copolymer Pluronic (P123) as a templating agent. The samples were investigated by XRD, Raman, UV-Vis and FTIR spectroscopy. W/TiO2 dispersions with the same chemical composition have been prepared via gelation of the solution of films precursors, after their drying at room temperature and calcination at 500 °C. Crystalline anatase phase was registered in XRD and Raman spectra of W/TiO2 films up to 10 % tungsten content with a minimum disturbance of the anatase-type structure. XRD patterns of W/TiO2 powders showed anatase (20–25 nm) and rutile (35–40 nm) nanocrystalline phases. The formation of tungsten oxide phases was fixed at its 10 % content. The photocatalytic activity of the films was examined in the photoreduction reaction of Cr(VI) ions to Cr3+ under UV irradiation in the presence of Na2EDTA as an electron donor. Films doped with 5–7 mol. % tungsten ions have higher photocatalytic activity compared to non-doped ones and demonstrated stable activity during 8–10 cycles. The addition of tungsten ions to titania matrix significantly improved its photocatalytic behavior. Tungsten ions doping promotes efficiency of the charge pair separation by trapping of photogenerated electrons with W5+ formation and preventing the charge recombination. When the dopant concentration was increased to 10 %, the photocatalytic efficiency a little decreased. To increase the photocatalytic activity of the coatings, the bare TiO2 and W/TiO2 samples were irradiated in a plasma mixture of hydrogen and argon (1 : 1). The efficiency of undoped TiO2 films has been increased 16 times, and W/TiO2 only by 2 times as the results of tungsten ions affecting the recombination processes.

Abstract The interaction between silver nanoparticle colloidal solutions and the bacterium Bacillus sp. under plasmon resonance conditions is studied in the present work. The resonance conditions are achieved by irradiating the bacterial/nanoparticle suspension with external light of a resonant wavelength. Three types of nanoparticles are used: obtained by chemical reduction (type I), by thermal recovery method (type II), and by photoreduction (type III). In all three types of colloids, the antibacterial effect is not observed for simple mixing of the nanoparticle colloid with the bacteria solution. The antibacterial effect is significant under irradiation with light of resonance wavelength. In particular, the effect of external irradiation of resonant wavelength leads to a decrease in the infection activity of bacteria by 15%–25% for all types of nanoparticles. The antibacterial effect is the result of the action of ponderomotive forces on the bacterium membrane after the adsorption of the nanoparticle onto it. The strength of the antibacterial effect depends on the thickness of the quercetin shell of the silver nanoparticle. In the case of a thick quercetin shell, the local field is smaller. Therefore, ponderomotive forces acting on the bacterial membrane are smaller.

Nanoscale oxide systems become the basis for research in the biotechnology field, medicine and environmental chemistry more frequently. Much attention is focused on titanium dioxide due to its low toxicity, stability of physicochemical parameters and high biocompatibility. It is known that titanium is a fairly inert material and has the ability to bind to bone tissue. It can be used for the manufacture of medical implants, the surface of which in the body is completely covered with a layer of its dioxide. This layer contacts and interacts with biological liquids directly, in which various biologically active substances may be present. In addition, understanding the nature of such interaction is very important issue, because it includes the formation of bonds of different nature between groups of biomolecules and surface functional groups of solids. Also, the issue of creation of potential carriers of biologically active substances that would be safe, biocompatible, stable and effective in the development of new therapeutic drugs is always relevant. Diamino derivatives of acridine are widely used for the treatment of wounds, skin and mucous membranes in various types of infections due to the antimicrobial, antiviral and antibacterial properties. The aim of this work was be to study the adsorption of rivanol, which is one of the diamino derivatives of acridine, on the surface of nanocrystalline titanium dioxide and elucidate qualitative characteristics of such interaction. The dependence of the stability constant of the surface complex TiO2-rivanol from the value of the ionic strength of the solution confirming the electrostatic nature of the interaction in the studied system was shoun based on the experimental dependences of rivanol adsorption on pH and ionic strength of the solution established by GRFIT program using Stern complexation models. According to the thermodynamic characteristics calculated on the basis of the effect of rivanol adsorption on its initial concentration in solution, the adsorption process is spontaneous for the studied system, has a favorable character on the surface of this sorbent and is carried out by the ion-exchange mechanism. The formation of a stable surface complex in the studied system indicates the prospects for using nanocrystalline titanium dioxide as a material for the creation of new therapeutic agents, where it can serve as a carrier of biologically active substances.

Composite hydrogels (HGs) based on sodium alginate (Alg), with nanoclay montmorillonite (MMT) and LaponiteRD (Lap) fillers, were synthesized using ionic cross-linking with calcium ions (Ca2+). The HGs structure was investigated by SEM-EDX, XRD, and FTIR, whereas сation exchange capacity (CEC) and variable surface charge were determined using potentiometric titration. The influence of filler content, cross-linking agent concentration, and pH on the swelling and sorption capacity towards cadmium ions (Cd2+) of HGs was analyzed in detail. The cross-linking agent concentration influenced the swelling mechanism of the alginate-based composites with clays as well as their specific type of water diffusion based on the Fick equation. The CaCl2 concentration (CCaCl2) of 0.3-0.5wt% was found as optimal for synthesizing mechanically stable HGs with a large swelling degree and sorption ability for Cd2+ ions. The sorption capacities calculated based on the Langmuir model were 1.36, 1.19, and 1.33mmol/g for Alg, Alg/20%MMT, and Alg/20%Lap synthesized using 0.3wt% CaCl2, respectively. The in vitro tests on genotoxicity and cytotoxicity of HGs, performed using the mouse fibroblast cell culture L-929, proved the biosafety of the developed composites for the environment.

Leucyl-tRNA synthetase (LeuRS) activates cognate leucine and wrongly activates norvaline (and other proteinogenic and non-proteinogenic amino acids), but then mischarges tRNA. Here, we studied the editing mechanisms of Thermus thermophilus LeuRS (TthLeuRS) by combination of biochemical and computational investigations with the appropriate substrate, norvalyl-tRNA, as previously reported for E. coli LeuRS (EcLeuRS). Based on DFT (density functional theory) calculations, we have proposed three alternative hydrolysis mechanisms. These mechanisms differ according to which group of water molecules present in the editing site of the enzyme-substrate complex participates in the chemical reaction of ester bond cleavage. The main feature of the proposed deacylation pathways is direct assistance by the substrate in the hydrolysis process. In all three cases, the 3'-OH group of the substrate directly participates in the reaction. To confirm the proposed models, the experimental substitution of the 76 3'-OH group of the tRNALeu was constructed yielding a tRNA that is devoid of editing activity. QM and metadynamics have shown that hydrolysis occurs via a common underlying catalysis mechanism involving more than one water molecule. An important element of hydrolysis is the involvement of several amino acid residues of the active centre of enzymatic editing (Asp-347/Asp-344 and Thr-247) in the process of catalytic deacylation. In conclusion, it was noted that the possibility of several alternative hydrolysis pathways may indicate that a sufficiently protected and flexible error-editing mechanism has been implemented for prokaryotic leucyl-tRNA synthetase.

Scale formation in pipelines and on equipment surfaces is a serious problem in many branches of industry. Different scales are formed in cooling water systems and caused heat transfer problems. A common method for controlling scale deposition is the use of chemicals which act as antiscalants. This study focuses on the selection of antiscalant and the parameters of the process for the creation of resource-saving technologies for the use of water in industry. To inhibit the scale formation in cooling water systems, antiscalant RT-2024-4 was used, characterised and the ability of the reagent to mitigate the scale formation was tested. Artesian, tap water and water from the Desna River and model solutions with a hardness of 7.33-14.65 mg-eq/L were used as test objects. The conducted studies show that the temperature increase in the range of 80-90°С and the time of thermostating in the range of 2-5 hours have practically no effect on the stabilisation and anti-scale effects. The statistical data processing method was used to analyse the experimental data. High stability of water with respect to scale formation was established. The expediency of using the scale stabilizer RT-2024-4 for mineralised and highly mineralized waters was shown.

The role of metal additives in the synthesis of composite materials based on the silicon and carbon-containing materials to create the desired structural and adsorption properties is analyzed. A two-step procedure was applied to obtain a series of nanocomposites doped with metal oxides. Various techniques were used to characterize the phase composition and the textural, structural, morphological, and thermal properties of the synthesized materials: X-ray diffraction, scanning electron microscopy, Raman spectroscopy, nitrogen adsorption-desorption, and thermal analysis. The adsorption processes on the obtained nanocomposites were studied for aqueous solutions of aniline, benzoic acid, and phenol. The influence of the metal additives on the formation of carbonaceous structures, the adsorption efficiency, and the adsorption mechanism was determined. The synthesized composites show mesoporous and microporous structures, with varied proportions of both pore types. They are differentiated, taking into account the quality of the carbon material (defect density and degree of graphitization), which decreases in the Co > Ni > Cu > Zn > SiO line. The complex effect of the factors determining the adsorption mechanism and efficiency was investigated: textural, structural, and morphological characteristics and the role of the active metal centers. Generally, the results provide valuable insights into the adaptation of hybrid materials for various industrial applications and underline their versatility.