A green method was developed to convert the biomass of peach pomace to ultra-porous activated carbon (AC) via hydrothermal carbonization (HTC). The maximum specific surface area of AC was 2945 m2/g with a total pore volume of 1.7 cm3/g and a micropore volume of 1.58 cm3/g. The CNTs were added during HTC in different mass ratios (0.01, 0.05, 0.1, 0.5, and 1 wt

A highly efficient sorption aerogel composition based on activated carbon from oilseed production waste (sunflower meal) and graphene oxide further modified with iron oxide was developed. The final stage was supercritical drying in an isopropanol media to achieve high specific surface areas. According to scanning electron microscopy, the material has a porous structure and consists of activated carbon particles coated with graphene sheets, the surface of which contains iron oxide particles up to 100 nm in size. The presence of an iron oxide phase in the nanocomposite aerogel is confirmed by X-ray diffraction analysis. Raman spectroscopy data indicate that the combination of the original carbon materials yields an experimental sample with a hybrid structure. Fourier transform infrared spectroscopy data indicate efficient reduction of graphene oxide during the nanocomposite aerogel synthesis. The pore space parameters were assessed by nitrogen adsorption. The aerogel was found to be a mesoporous material with a predominant pore size of approximately 3.5 nm and a specific surface area according to the BET theory of 1849 m2/g, and a total pore volume according to the DFT of 1.066 cm3/g. The sorption capacity of the material was assessed using the example of liquid-phase extraction of organic dyes, namely, metanil yellow (MY) and malachite green (MG). Kinetic adsorption studies in a limited volume were conducted to determine the sorption time and the adsorption mechanism. It was established that the experimental adsorption capacity for MG was 2245 mg/g at 15 min, and for MY – 1145 mg/g at 60 min. According to the pseudo-first- and -second-order models, the Elovich model, and intra-diffusion models, the putative adsorption mechanism was established. For citation: Badin D.A., Burakova I.V., Kuznetsova T.S., Memetova A.E., Burakov A.E., Dyachkova T.P. Sorption of organic dyes on nanocomposite aerogel based on activated carbon and graphene oxide modified with iron oxide. ChemChemTech [Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol.]. 2026. V. 69. N 9. P. 65-78. DOI: 10.6060/ivkkt.20266909.7063.

The problems of synthesis of various allotropic forms of carbon under a laser impact on a carbon-containing target under the conditions of nonequilibrium phase transitions have been considered. The results of studies of the processes of controlled design of certain topological configurations of metal-carbon and diamond-like compounds in a laser experiment with laser ablation and by modeling the 1D–3D structures with a modifyable fractal dimension have been presented. The measurements of the optical and electrophysical characteristics of such structures have been discussed in terms of the possibility of controlling their functional properties.

The paper investigates the impact of carbon nanotube-based modifiers on the performance characteristics of lightweight foamed concrete (LFC). The method involves saturating quartz sand with a solution containing a catalyst for carbon nanotube (CNT) growth, followed by the subsequent chemical vapor deposition (CVD) synthesis of CNTs. Evaluation of nanomodified sand samples was conducted using SEM and TEM, thermogravimetry, Raman spectroscopy, and XRD. Compression and flexural strength tests of (LFC) specimens indicated that the optimal proportion of nanomodified sand introduced is 1% by weight with a particle size of 0.16 mm. This resulted in a notable 35% increase in compressive strength and an approximately 32% improved in flexural strength. Furthermore, the modified sample with CNT-based sand exhibited a 27% reduction in water absorption. The paper also presents a potential mechanism to explain the impact of carbon nanotube-based modified sand on the evolving structure of (LFC).

The article proposes a method for producing polyaniline-modified nanocomposite cryogel based on oxidized carbon nanotubes and reduced graphene oxide. Phenol–formaldehyde resin has been used as a crosslinking agent. Cryogel has been obtained by freeze drying in vacuum. Then, the material has been subjected to a post-processing, i.e., the carbonization in a tubular furnace. The obtained nanocomposite has been subjected to the comprehensive diagnostics by the methods of scanning and transmission electron microscopy, IR spectroscopy, X-ray diffraction analysis, and Raman spectroscopy. The parameters of the pore space have been estimated by nitrogen adsorption. It has been found that the carbonized nanocomposite cryogel is a mesoporous material with a specific surface area of 299 m2/g. IR and Raman spectra and X-ray diffraction patterns of the starting materials have been compared with the spectra of the carbonized cryogel. According to the results obtained, the nanocomposite exhibits peaks of all starting materials. The sorption capacity of the material has been evaluated by the example of the sorption of ions of a heavy metal, lead, from model aqueous solutions. Kinetic studies of adsorption in a limited volume have been carried out to determine the mechanism and time of the adsorption. It has been revealed that 99

A new method for the production of activated bio-nanocomposites by hydrothermal carbonization (HTC) of renewable plant raw materials (rapeseed meal) with the addition of graphene oxide (GO), followed by freeze-drying treatment to compact and preserve the porous space was developed. To assess changes in the morphology, chemical and phase composition of the material during carbonization/activation, the methods of transmission electron microscopy, X-ray diffractometry, FT-IR and Raman spectroscopy were used. It has been established that the nanocomposite is represented by closed fragments of fullerene- and graphene-like particles of irregular shape containing single inclusions of a linear lamellar structure. The I-D/I-G ratio, determined from the Raman spectra, is significantly higher than 1, which indicates a high content of sp(3)-hybridized carbon atoms in the nanocomposite. The X-ray diffraction pattern of the final sample contains reflections (0 0 2) and (1 0 0) of graphite, which is typical for carbon porous materials with graphene fragments. For the nanocomposite, the static adsorption capacity for various types of pollutants was determined: lead ions - 205 mg/g, molecules of organic dyes - malachite green - 1850.2 mg/g and Congo red - 620.4 mg/g.

The assessment of the effect of various modifiers introduced into the composition of non -autoclaved aerated concrete (NAC) was made. The modifiers were graphene oxide (GO) in the form of an aqueous suspension, lignosulfonate (LS) and a complex GO/LS additive. The samples of gas blocks containing GO - 0.0001, 0.0002, 0.003 wt. %; LS - 0.032, 0.16, 0.32 wt. % by weight of cement and their various combinations were molded. Thermal conductivity and water absorption tests were carried out on the samples of standard and modified NAC aged for 28 days. The research results confirmed the positive effect of reducing thermal conductivity and water absorption, which varied depending on the amount and type of additive. After the addition of LS, GO and GO/LS (0.0002/0.16 wt. %) modifiers, there was a corresponding reduction in water absorption by 12-34 %, 30-50 % and 63 %, respectively, and a decrease in the thermal conductivity coefficient by 6-12 %, 14-18 %, and 29 %, respectively. It is assumed that the introduction of the complex nanomodifier GO/LS increases the degree of crystallinity and homogeneity, as well as changes the composition and size of mineral neoformations of cement stone. Consequently, by changing the structure of silicate matrix through the addition of a modifyer developed by the authors, an improvement in the performance properties of thermal insulating cellular concrete was achieved.

Keeping the need for good water quality and the demand of climatic issues, the sunflower waste was converted into graphene hydrothermal nanocomposite absorbents for the removal of toxic Cd(II) and Pb(II) metal ions from water. The graphene composite materials were studied by scanning (SEM) and transmission electron microscopy (TEM), XRD analysis, TG and DSC, Raman and IR spectroscopy. According to SEM and TEM analysis, the decarbonized materials had a disordered structure with amorphous carbon with a small pore content. During the carbonization process, the pores space was opened due to the removal of amorphous organic matter and the formation of defects; providing a significant number of meso- and micropores. The prepared graphene composite showed 133.33 and 222.22 mg/g Langmuir adsorption of Cd(II) and Pb(II) at pH 6.0, dose 0.33 g/30 mL, initial concentration 300 mg/L, time 30 min and at 45 °C temperature using hydrothermal nanocomposite HTC/graphene oxide absorbent. The obtained results followed the sorption of heavy metal ions in a mixed-diffusion mode with the contribution of a second-order reaction between the active center of the sorbent and the metal ions. The Temkin and Dubinin-Radushkevich model’s parameters and thermodynamic results confirmed endothermic physical interactions among adsorbent and metal ions. This paper is highly useful for managing sunflower waste and purifying water; leading to the present demand for clean water and climatic issues. The production of the effective low-cost nanocomposite using green synthesis technologies (hydrothermal carbonization of raw materials) is highly useful for the removal of Cd(II) and Pb(II) toxic metal ions from water.

The article proposes a method for producing a hybrid sorption material based on renewable plant raw materials from agricultural production, synthesized by hydrothermal carbonization (HTC), the structure of which is modified by particles of iron and/or iron oxides. The authors obtained a series of samples and assessed the effect of high-temperature carbonization and subsequent alkaline activation on the sorption capacity of materials. Determination of physico-chemical properties was carried out using IR spectroscopy, X-ray diffractometry and thermogravimetry. X-ray diffraction patterns of the samples showed the presence of an α-cellulose crystal lattice and a Fe3O4 or γ-Fe2O3 crystallographic plane. As a result of carbonization, the α-cellulose phase is destroyed and iron oxides are partially reduced. Alkaline activation leads to more serious destruction of the plant base and complete restoration of the iron phase. The materials sorption capacity was assessed by heavy metal ions (lead) adsorption from model aqueous solutions. Confined adsorption kinetic studies were carried out to determine the sorption time and adsorption mechanism. The sorption capacity of the initial HTC material for Pb2+ was ~132 mg/g at a contact time of 30 min. For carbonated and activated hydrochar, the capacity was 66.8 and 99.2 mg/g, respectively. The adsorption kinetics of Pb2+ ions was described using pseudo-first-order, pseudo-second-order, Elovich and intraparticle diffusion models. It has been shown that sorption occurs predominantly due to the chemical interaction of metal ions with functional groups of sorbents with a partial contribution from mixed-diffusion absorption. Thus, the article proves the effectiveness of using hydrochar based on plant raw materials, modified with magnetic iron particles, in the processes of liquid-phase removal of inorganic pollutants.

AlOOH/MWCNTs/Ag composites have been prepared by oxidation of a mechanical mixture of multi-walled carbon nanotubes (MWCNTs) and electroexplosive bimetallic Al/Ag nanoparticles with water at 60 °C followed by calcination at 300 °C. The composite material obtained consists of nanosheet aluminum structures, carbon nanotubes and silver nanoparticles. Calculation of the composite material promoted the migration of silver nanoparticles to the periphery of the nanosheet structures and the surface of carbon nanotubes, which contributed to a marked increase in the antibacterial activity of the composite material. The specific surface area of the material was 265 m2/g and is determined mainly by nanosheet structures of aluminum oxide. Study of the adsorption properties of the composite material has shown high adsorption towards dyes of different types to an equal extent. The maximum adsorption capacity towards Methylene blue, Eosin and indigo carmine was from 63.1, 75.0 and 82.4 mg/g, respectively. The resulting material can be used as a non-selective adsorbent for purifying water with bacterial contamination.

Effective solid-phase extractants (SPE) have been developed based on multi-walled carbon nanotubes (CNTs) of various structures modified with an organic reagent – 2-mercaptobenzothiazole. Using scanning and transmission electron microscopy, the morphological and structural features of SPE samples and their elemental composition were determined. It has been shown that the specific surface area of modified CNTs is approximately two times lower compared to the original CNTs. It was revealed that the modified materials are coils of CNTs coated with a uniform organic shell 10-15 nm thick. The sorption capacity of the original nanotubes in 1 M HCl and their modified forms (0.1-3.0 M HCl) at room temperature and at 80°C was determined. It was found that in strongly acidic media, SPE based on G-183 CNTs and 2-mercaptobenzothiazole is effective, which sorbs Pt, Pd and Au at room temperature, and also Ru and Rh at a temperature of 80°C. The possibility of selective extraction of platinum group metals and gold with this sorbent in the presence of macroquantities of Al, Fe, Cu, Ca and Mg was assessed.

The development of new structural materials with thermal insulation properties is urgently need in the construction of smart buildings. Besides, there is a need to develop environmentally friendly and sustainable concrete mix designs. Lignosulfonate (LS) macromolecule and graphene oxide (GO) were used to prepare non-autoclaved aerated concrete (NAC). The addition of a complex GO/LS additive of the composition (0.16/0.0002 wt%) increased the compressive strength by 54 %, and bending strength by 45 % at the age of 28 days' strength gain. The addition of an effective complex GO/LS additive to NAC made it possible to achieve a reduction in water absorption by up to 63 % and thermal conductivity by up to 29 % in comparison. The thermal conductivity coefficient of such NAC specimens was 0.092 W/m·K with water absorption of 9 %. The options for the interactions of the GO/LS modifier with calcium hydroaluminates using the type of ion exchange were proposed. Thus, the introduction of GO/LS nano modifier contributed to high-quality filling of free areas of the cement mixture with mineral formations, which helpd to increase the strength of the aerated concrete and its durability.

Liquid-phase sorption is a multistage process, the success of which depends of many factors. One of the key parameters that determines the sorption efficiency is the pH of the liquid medium. This paper studied the effect of the pH of model aqueous solutions each containing ions of a single heavy metal (by the example of zinc and lead ions) and also molecules of the organic dyes methylene blue (MB) and sunset yellow (SY). The required pH value was achieved by preparing solutions in appropriate buffer systems. The sorbent was a nanostructured composite material with a polyaniline-modified matrix of carbon nanotubes (CNTs) and reduced graphene oxide (RGO), and phenol formaldehyde resin as a binder to produce various forms of the material: xerogel, cryogel, aerogel, as well their carbonized modifications. It was determined that, for all forms of the sorbent, the adsorption capacity for heavy metals (zinc and lead) and the organic dye MB is maximum at pH 6. The adsorption of the anionic dye SY is the best at pH 2.

A new nanostructured sorption material, a graphene-based nanocomposite modified with green materials—natural biopolymers—lignin and chitosan, was developed. The new material is proposed as a sorbent for removing organic and inorganic pollutants from liquid media. To find the most efficient composition of the nanocomposite, samples with different weight contents of the initial components were synthesized. The nanocomposite physicochemical properties, morphology, and structural characteristics were described by transmission electron microscopy, X-ray diffraction, thermogravimetry, Fourier transform infrared spectroscopy, and Raman spectroscopy. The functional properties of the prepared nanocomposite were evaluated during the batch sorption from aqueous solutions of heavy metals (e.g., lead) and synthetic organic dyes (e.g., methylene blue [MB]) under static conditions. The adsorption capacity of the developed nanocomposites reached 1820 mg/g toward MB and 310 mg/g for the Pb2+ ions. Moreover, 90% of the pollutant was removed during the first 10 minutes according to the sorption kinetics. The experimental data were processed using pseudo-first- and -second-order kinetic models, the internal intraparticle diffusion, and the Elovich models. The calculation results made it possible to determine the sorption mechanism and the process limiting stage. Thus the study showed that the developed nanocomposite could be an environmentally friendly, cost-effective, and suitable adsorbent for removing different pollutants from water.

In this work, graphene-based ten nanofluids were synthesized, and their viscosities were determined. Also, a theoretical analysis of the molecular interactions of graphene nanoparticles is carried out in order to understand the mechanisms affecting the viscosity of nanofluids. Based on the results of experiments, an analytical function that describes the dependence of the relative viscosity on the concentration of graphene nanoparticles was obtained. It was established that the viscosity of the base fluid was affected by the graphene sheet structure. If the graphene sheet possessed an ideal surface, a decrease in the viscosity was observed, but if it contained defects, the viscosity of the nanofluid increased rapidly with increasing concentration. The reason for this behavior of graphene nanofluids was the self-assembly of graphene nanoparticles in the base fluid flow and the formation of ordered clusters from base fluid molecules. In this case, the self-assembly of the graphene nanoparticles was inextricably linked with the formation of the nanoclusters. The struggle between these two processes generated changes in the viscosity of the graphene nanofluids. In the function herein proposed, a new parameter, B/A, was introduced, which made it possible to evaluate the nature of the interactions between the graphene nanoparticles and the base fluid molecules. The reported work is highly useful to design more future graphene-based nanofluids; depending on the requirements.

The paper describes the adsorption of toluene and benzene on a new sorption material—coconut activated carbon (AC) modified with carbon nanotubes. The new material was characterized using Raman spectroscopy, scanning and transmission electron microscopy, X-ray diffractometry and FTIR. Also, the parameters of the porous space and the specific surface area were determined. The adsorption capacity for toluene and benzene was 123.53 and 84.92 mg g −1 , respectively, the contact time was 60 min. The kinetic data were described using intraparticle diffusion, and the results of isothermal studies were described using the Langmuir, Freundlich, and Dubinin-Radushkevich equations. It was found that the adsorption of toluene and benzene considered Weber-Maurice model, that conform to a diffusion with fluid phase film resistance. In addition, the physical nature of adsorption is confirmed by the values of free energy (E = 6.92 and 8.41 kJ moL −1 for benzene and toluene, respectively). According to a thermodynamic study, the Gibbs energy values for nanomodified AC were − 16.32 kJ moL −1 for benzene and − 33.33 kJ moL −1 for toluene, which corresponds to the range of values for physical sorption. Thus, the material can be considered as a promising adsorbent for removing organic pollutants from aqueous media.

Liquid-phase sorption is a multi-stage process, the success of which depends on many factors. One of the key parameters that determines the extraction efficiency is the liquid medium pH value. In this study, the effect of the pH value of model aqueous solutions containing separately heavy metal ions (using zinc and lead ions as an example), as well as organic dyes methylene blue (MB) and sunset yellow (SY), was evaluated. The required pH value was achieved by preparing the solutions in appropriate buffer systems. As a sorbent, a nanostructured composite material was used, represented by a matrix of carbon nanotubes and graphene oxide modified with polyaniline, where phenol-formaldehyde resin acted as a binding agent. Various forms of this material were considered — xerogel, cryogel, aerogel, as well as their carbonized modifications. As a result of experimental studies, it was found that for all used heavy metal ions (zinc and lead) and MB for all sorbents forms, the maximum adsorption capacity was noted at pH = 6. At the anionic dye SY adsorption, the best result was achieved at pH = 2.

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The paper presents the technology for obtaining nanocomposite aerogels based on oxidized carbon nanotubes (o-CNTs) and reduced graphene oxide (r-GO) modified with polyaniline and phenoldehyde resin. Aerogel was obtained in high-pressure autoclave among supercritical fluid - isopropanol. The complex diagnostic of synthesized nanocomposite was carried out by the methods of scanning and transmission electron microscopy, infrared spectroscopy, X-ray diffractometry, Raman spectroscopy. The parameters of the porous space were evaluated by adsorption of nitrogen. The resulting electron images indicate that the CNTs was as structural formers, concentrating on their surface graphene sheets. It should also be noted that in the samples, particles of spherical polyaniline were found. It was established that nanocomposite aerogel is a mesoporous material with a specific surface of 289 m2/g. A comparison of infrared and Raman spectra, as well as X-ray diffractograms of the initial materials with aerogel spectra was carried out. According to the results, the nanocomposite contains combined peaks of all source materials. After drying in the supercritical isopropanol media, the ordered structure of the carbon frame is preserved. Electronodononic oxygen and nitrogen-containing groups, which are identified according to the IR spectroscopy as part of the composite, can be active centers for adsorption of heavy metals due to the possibility of the formation of coordination bonds. The nanocomposite sorption activity was evaluated by the example of the heavy metals sorption, namely lead, from model aqueous solutions. To determine the contact time and the absorption mechanism, kinetic studies of adsorption were carried out in a limited volume. It was found that 99% of the pollutant was sorbed in the first 15 min with an achievement of the adsorption capacity of 350 mg/g. Using of pseudo-first and second-order models, the Elovich model and intra-particle diffusion models the adsorption mechanism were offered. For citation: Kuznetsova T.S., Burakov A.E., Pasko T.V., Burakova I.V., Dyachkova T.P., Memetova A.E. Physico-chemical and sorption properties of nanocomposite aerogels based on modified carbon nanotubes and graphene. ChemChemTech [Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol.]. 2023. V. 66. N 3. P. 66-76. DOI: 10.6060/ivkkt.20236603.6726.