The paper considers the kinetics of lead ions (Pb2+) sorption from model aqueous solutions using underoxidized and overoxidized graphene oxide samples obtained from synthetic and natural (taken as comparison material) graphite. It was experimentally found that the contaminant is sorbed in the first 5 min (for the underoxidized samples) and 30 min (for the overoxidized samples), achieving a sorption capacity of 105–138 mg g–1. Moreover, the capacity of the material increases with an increase in its oxidation state. The capacity of the synthetic material is slightly higher than that of the natural one. To study the removal mechanisms and determine the process parameters, the experimental data were fitted to kinetic (pseudo-first and pseudo-second order, as well as Elovich) and diffusion (internal diffusion – Morris-Weber and external diffusion – Boyd) models. It was found that the metal sorption is controlled by mixed diffusion of the sorbate into the bulk of the sorbent. It was also determined that this process is limited by the chemical interaction between the sorbent and the sorbate and depends on the sorbate concentration and the ambient temperature. Besides, the surface morphology of the samples was studied using scanning electron microscopy, and information on their elemental composition before and after the sorption was obtained using energy dispersive spectrometry, which confirmed the mechanism of the sorption processes occurring in the systems.

This study explores the use of lignocellulosic Tectona grandis seeds (TGs), hydrochar (HC-230-4), and activated carbon (AC-850-5) produced via hydrothermal carbonization and followed by CO2 activation for removing acridine yellow G (AYG) and acridine orange 14 (ABO) from water. HC-230-4 showed a rich presence of surface functional groups and irregular morphology with some sphere-like structures. In contrast, AC-850-5 exhibited a much higher surface area (729.7 m2/g), though with fewer surface functional groups than HC-230-4. The batch method was used to study the effects of contact time, pH, dye concentration, and temperature. Among the materials, AC-850-5 showed the highest adsorption capacity of 198 mg/g for AYG and 171 mg/g for ABO at 25 °C, around 12% higher than commercial activated carbon. The adsorption process was spontaneous and endothermic, fitting well to the Langmuir isotherm model, suggesting monolayer coverage. The adsorption kinetics followed the pseudo-second-order model, indicating that the rate depends on the surface site availability. Intraparticle diffusion analysis further confirmed a multi-step adsorption process. These findings show the strong potential of TG-derived activated carbon as an effective and sustainable material for removing acridine dyes from polluted water.

BACKGROUND: The present work describes the facile, fast and economic base-catalyzed acylation of benzenediols with vinyl acetate. The Hirshfeld surface analysis of benzene-1,4-diol O,O '-diacetate is also described. NaOH, KOH and K2CO3 were the bases used for the catalysis of the acylation of benzene-1,x-diols (x = 2, 3, 4) with vinyl acetate to obtain the corresponding O,O '-diacetyl derivatives. RESULTS: The yields were quite good, up to 99% under solvent-free conditions. This method represents an alternative 'green' process for the preparation of O-acetyl derivatives of hydroxyaryls. The benzene-1,4-diol O,O '-diacetate crystal structure was obtained and described using Hirshfeld surface analysis. A noticeable contribution of the C & ctdot;H contacts is shown (16.7%), despite the insignificant area of the Hirshfeld surface occupied by the carbon atoms (9.4%). By using two-dimensional fingerprint plots, it was proved that C & ctdot;H contacts were due to the presence of pi-stacking. The O & ctdot;H contacts (41.4%) were the most numerous ones, relating mainly to typical hydrogen bonds (d(e) + d(i) approximate to 2.6 & Aring;). The high saturation of the C & ctdot;H and O & ctdot;H contacts (enrichment ratios (E) = 1.30 and 1.36, respectively), despite their smaller contribution to the overall surface as compared to the H & ctdot;H contacts (E = 0.84), is shown. CONCLUSION: The novelty of this work is the development of a method based on an inexpensive, safe and easy-to-use catalyst (K2CO3). This method is fast with high yields. Besides, it may be used for acylation at an industrial scale. (c) 2024 Society of Chemical Industry (SCI). (c) 2024 Society of Chemical Industry (SCI).

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 considers the development of fillers representing mixtures of carbon nanotubes and graphene materials (graphene oxide and graphene nanoplatelets) in different mass ratios to modify epoxy resin. The graphene type and content effect on the dispersed phase particle effective sizes—both in aqueous suspensions and the resin—was analyzed. Hybrid particles were characterized by Raman spectroscopy and electron microscopy. The composites containing 0.15–1.00 wt.% CNTs/GO and CNTs/GNPs were thermogravimetrically analyzed, and their mechanical characteristics were determined. SEM images of the composite fracture surfaces were acquired. Optimal dispersions containing 75–100 nm particles were obtained at the CNTs:GO mass ratio of 1:4. It was shown that the CNTs can be located between the GO layers and on the GNP surface. The samples containing up to 0.2 wt.% CNTs/GO (at 1:1 and 1:4 ratios) were stable when heated in air up to 300 °C. For 0.15–0.20 wt.% CNTs/GO (at 1:1 ratio), the tensile strength and modulus of the composite increased by 84–88 and 40%, respectively. The increase in the strength characteristics was found to occur due to the interaction of the filler layered structure with the polymer matrix. The obtained composites can be used as structural materials in different fields of engineering.

This paper considers the synthesis of a novel nanocomposite based on reduced graphene oxide and oxidized carbon nanotubes modified with polyaniline and phenol-formaldehyde resin and developed through the carbonization of a pristine aerogel. It was tested as an efficient adsorbent to purify aquatic media from toxic Pb(II). Diagnostic assessment of the samples was carried out through X-ray diffractometry, Raman spectroscopy, thermogravimetry, scanning and transmission electron microscopy, and infrared spectroscopy. The carbonized aerogel was found to preserve the carbon framework structure. The sample porosity was estimated through nitrogen adsorption at 77 K. It was found that the carbonized aerogel predominantly represented a mesoporous material having a specific surface area of 315 m2/g. After carbonization, an increase in smaller micropores occurred. According to the electron images, the highly porous structure of the carbonized composite was preserved. The adsorption capacity of the carbonized material was studied for liquid-phase Pb(II) extraction in static mode. The experiment results showed that the maximum Pb(II) adsorption capacity of the carbonized aerogel was 185 mg/g (at pH 6.0). The results of the desorption studies showed a very low desorption rate (0.3%) at pH 6.5 and a rate of about 40% in a strongly acidic medium.

The present article considers a comparative analysis of two elastomers, polyurethane (PUC) and organosilicon (OSC), both modified with 1.0-9.0 wt.% multiwall carbon nanotubes (MWCNTs). The MWCNTs-1 and MWCNTs-2 were synthesized through CVD method using Co-Mo/Al2O3-MgO and Fe-Co/2,1Al2O3. The results obtained showed that the lowest bulk conductivity (5 x 10(-10) S x cm(-1)) was typical for PUC elastomer modified with 1 wt.% MWCNTs-2. As for OSC elastomer (modified with 9 wt.% MWCNTs-1), the lowest bulk conductivity was found to be 0.4 S x cm(-1). The maximum temperature field uniformity was established for OSC elastomer modified with 7 wt.% MWCNTs-2, whereas in the modified PUC-based elastomer, the nonuniform temperature field took place. This might be caused by local MWCNTs entanglement manifested in the formation of agglomerates or a denser packing of conductive networks. The best combination of the polymer matrix and MWCNTs type was revealed. Finally, it was established that for electric heaters, it is the most efficient to employ OSC modified with 7 wt.% MWCNTs and use MWCNTs-1 or MWCNTs-2, depending on the feeding voltage level of 12 or 24 V. This study is of special importance in household purposes, clothing with built-in heating panels, car/tractor systems, minibus interiors, onboard thermal ventilation systems, clothing, and aircraft industries.

• Nanoporous carbon materials (NCMs) were developed for Methane Storage. • NCMs possessed high specific surface area ∼ 2722 m 2 /g with multimodal pore distribution. • Increase in pressure enhances the methane (CH 4 ) uptake. • The maximum CH 4 adsorption capacity was found to be ∼ 14.3 mmol/g. Nanoporous carbon materials (NCMs) were widely used as commercial adsorbents, due to their salient features like high specific surface area and a significant volume of micropores. The present research work considers the conversion of a mixture of compounds (furfural, hydroquinone, and urotropine) into a NCM, with properties suitable for adsorption and gas storage applications, through alkaline activation. The developed NCM have high surface area of ∼ 2722 m 2 /g with a pore volume of 1.08 cm 3 /g i.e. ∼ 80 % pores representing narrow micropores. Further, the density of the NCM is also a decisive parameter for the applications, in particular, methane (CH 4 ) storage. Moreover, the powdered NCM was compacted 2.5 times (to get a monolith NCM) with a slight change in the texture properties. The synthesized adsorbents were tested for the CH 4 adsorption, and they showed very good characteristics. Results obtained revealed that, the highest CH 4 adsorption capacity value, equal to ∼ 14.3 mmol/g at 10 MPa and 298 K, was achieved on the powdered NCM which after the compaction, to the monolith NCM decreases to ∼ 13.3 mmol/g at the same pressure. Moreover, the highest bulk methane adsorption capacity value was 336 cm 3 /cm 3 which was achieved at 10 MPa and 298 K for the monolith NCM. Thus, this adsorbent with excellent CH 4 adsorption characteristics can be used in the adsorbed natural gas (ANG) technology to enhance the energy storage and improve the efficiency.

Due to rapidly deteriorating water resources, the world is looking forward to a sustainable alternative for the remediation of noxious pollutants such as heavy metals and organic and gaseous contaminants. To address this global issue of environmental pollution, nanoporous carbon materials (NPCMs) can be used as a one-stop solution. They are widely applied as adsorbents for many toxic impurities and environmental contaminants. The present review provides a detailed overview of the role of different synthesis factors on the porous characteristics of carbon materials, activating agents, reagent-precursor ratio and their potential application in the remediation. Findings revealed that synthetic parameters result in the formation of microporous NPCMs (SBET: >4000 m3/g; VTotal (cm3/g) ≥ 2; VMicro (cm3/g) ≥ 1), micromesoporous (SBET: >2500 m3/g; VTotal (cm3/g) ≥ 1.5; VMicro (cm3/g) ≥ 0.7) and mesoporous (SBET: >2500 m3/g; VTotal (cm3/g) ≥ 1.5; VMicro (cm3/g) ≥ 0.5) NPCMs. Moreover, it was observed that a narrow pore size distribution (0.5-2.0 nm) yields excellent results in the remediation of noxious contaminants. Further, chemical activating agents such as NaOH, KOH, ZnCl2, and H3PO4 were compared. It was observed that activating agents KОН, H3PO4, and ZnCl2 were generally used and played a significant role in the possible large-scale production and commercialization of NPCMs. Thus, it can be interpreted that with a well-planned strategy for the synthesis, NPCMs with a "tuned" porosity for a specific application, in particular, microporosity for the accumulation and adsorption of energetically important gases (CO2, CH4, H2), micro-mesoporosity and mesoporosity for high adsorption capacity for towards metal ions and a large number of dyes, respectively.

Carbon porous materials obtained through KOH activation of a furfural + hydroquinone + urotropine mixture were applied as adsorbent for the remediation of methylene blue (MB). The impact of porous structure with special attention to pore size distribution along with well-known pore volume and specific surface area on the remediation of MB was well investigated and elucidated. Findings obtained revealed that pore size distribution plays a crucial role in the liquid-phase adsorption of organic dyes like MB. By varying the synthesis mode parameters, in particular, the activating agent/precursor mass ratio, with the composition and initial components ratios remaining unchanged, samples with different pore size distribution were obtained. It was found that the material predominantly containing pores with an average equivalent diameter of ~ 3.5 nm appears to be the efficient MB adsorbent. The resulting highly porous carbon materials demonstrated high MB adsorption capacity (up to 2555 mg/g). Furthermore, to fully elucidate the adsorption mechanisms occurring on the obtained materials, a comprehensive mathematical processing of experimental data was performed out using the known kinetic and diffusion models (pseudo-first- and pseudo-second order, and intraparticle diffusion), as well as adsorption equilibrium isotherm models (Langmuir, Freundlich, Temkin, and Dubinin-Radushkevich). It can be concluded that the porous carbon materials obtained and described in the present work are effective adsorbents for the removal of MB and may possess great potential for the treatment of dye-containing wastewater.

In the world, the treatment of aquatic media contaminated with rare-earth elements (REEs) using efficient adsorbent materials is relevant to avoid contamination of natural water areas, as well as to dispose of and concentrate recovered scarce raw materials. The present review systemizes the information reported on using various materials including novel carbon nanostructures to remove REEs from aqueous systems. It considers adsorption conditions, parameters, and compares the adsorption capacity values obtained for those materials. Moreover, the present work takes into account the extraction of REEs, acting as close chemical analogs of radioactive actinides, from model aqueous solutions simulating the nuclear industry waste, as well as sulfuric-chloride solutions simulating, in particular, uranium ores leaching solutions.

The facile synthesis of the advanced cobalt-based materials [1.0Co/Al2O3 (A), 0.5Co/Al2O3 (B), 3.5CoNaY (C) and 0.4CoHY (D)] is reported. The characterization of the materials was carried out by X-ray photoelectronic, energy-dispersive X-ray, atomic absorption and low-temperature nitrogen adsorption methods. These materials were used for a comparative degradative and adsorptive removal of carmoisine azo dye in water. The adsorptive and degradative removals were 62.0–96.1% and 68.1–96.1% for all four materials. The degradation was occurred by hydroxyl radicals and peroxy free radicals. The adsorptive removal followed Langmuir, Temin and Dubinin–Radushkevich models. The adsorption obeyed pseudo-first-order kinetics and liquid film diffusion mechanism. The results indicated that both degradative and adsorptive phenomena had comparative removal capacities. The removal capacities of all four materials were C > A > D > B. The maximum removal was obtained by material C (96.1%) and A (90.0%) in a wide pH range of 3.0–9.0. The reported methods are very effective, efficient and inexpensive for the removal of carmoisine azo dye in water. These methods may be used to remove the reported dye at a large scale in any water resource.

A highly electrical conductive multi-walled carbon nanotubes based polymer composite is fabricated by iodine doping. Selective localization of carbon nanotubes in polymethyl methacrylate was obtained by intensive dry mixing of polymer and nanotubes powders followed by hot pressing. The electrical conductivity of the materials was significantly increased (10-100%) when the composites were treated with iodine by the gas phase. The electrical conductivity of the materials was significantly increased because of MWCNTs addition from the value not higher than about 10-15 to about 10-2 S/cm. The addition of iodine leads to an additional increase in electrical conductivity by 10-100%, depending on the content of MWCNTs. It is interesting to note that a more effective increase in electrical conductivity is observed at low MWCNTs concentrations. An interesting result of the work is the presentation of the fact that iodine is uniformly absorbed in the bulk of the composite filled with nanotubes; in the case of an unfilled polymer, iodine is deposited only on the sample surface. The percolation nature of the conductivity of the investigated composites was found and the percolation threshold was calculated. It was shown that the percolation threshold does not significantly change after iodination. Thus, in this work, we have shown the possibility of simple technology for producing composites with a spatial localized distribution of carbon nanotubes, providing high conductivity (2.86 x 10-2 S/cm) and a low percolation threshold (about 0.37% vol.) at the MWCNTs content of 1.55% vol.

The article analyzes and provides data on the processes of accumulation of heavy metals by bottom sediments from the point of view of environmental assessment. The purpose of this paper is to identify the degree of anthropogenic influence on the lakes of the Tazovskiy and Surgut districts, and assess the ecological state of water bodies and adjacent territories. The main processes occurring in natural reservoirs, which lead to the transfer of toxicants into the environment, are considered. The data of quantitative chemical analysis of bottom sediments of two groups of natural reservoirs with an assessment of their ecological state according to the results of statistical processing of the measured values were obtained. Excess concentrations of metals were recorded: for mobile forms – 2200 times for Fe, 1050 times for Mn, 35 times for Cr, 20 times for Co, up to 15 times for Ni, 5 times for Cu, 3 times for Pb, for acid-soluble forms – 45 000 times for Fe, 550 times for Pb, up to 75 times for Ni, 525 times for Mn, 105 times for Cr, 50 times for Cu, 16 times for Co. The geochemical interpretation of the results of the factor analysis is presented.

A hapten-protein conjugate with copper nanoparticles (Hap-Car-BSA@CuNPs) was first synthesized in the present work for the determination of carbaryl. The copper nanoparticles (CuNPs) of the conjugate were used as electrochemical labels in the direct solid-phase competitive determination of carbaryl residues in flour from different crops. The signal was read by linear sweep anodic stripping voltammetry (LSASV) of copper (through the electrochemical stripping of accumulated elemental copper) on a gold-graphite electrode (GGE). To form a recognition receptor layer of monoclonal antibodies against the carbaryl on the surface of the GGE, 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride (EDC) and 1-hydroxy-2,5-pyrrolidinedione (NHS) were used as the best covalent cross-linkers. The concentrations of the antibodies and the Hap-Car-BSA@CuNPs conjugate were optimized for carbaryl detection by the electrochemical immunosensor. The electrochemical immunosensor can be used for highly sensitive determination of carbaryl residues in flour samples in the concentration range 0.8-32.3 μg·kg-1, with a limit of detection 0.08 μg·kg-1. The present work paves the path for a novel method for monitoring carbaryl in other food products, drinks, and soil samples.

The present paper describes the efficiency of the synthesis of multi-walled carbon nanotubes (MWCNTs), which is achieved through the implementation of a non-standard approach to the preparation of a Ni/MgO catalyst. The catalyst required for MWCNTs synthesis was obtained through chemical vapor deposition method. At the same time, the pre-catalyst was treated by electromagnetic field, ultrasound and microwave waves methods. It was proved that the treatment of the catalyst initial components solution with the electromagnetic field, ultrasound and microwaves contributes to an increase in the yield of the synthesized MWCNTs by 50, 30 and 70%. Besides, ultrasonic treatment may be used if MWCNTs of relatively low degree of a defect are required. The proposed approach is economically feasible since small additional energy costs lead to a more complete conversion of carbon-containing raw materials into the target product at the activation stage. The reported method may be used to prepare MWCNTs of different types economically; leading to its industrial application to produce different types of MWCNTs.

In the present paper, the features of obtaining a metal oxide Fe-Co/Al2O3 catalyst for the synthesis of carbon nanostructured materials through thermal decomposition are considered. It was experimentally proved that the temperature and duration of the stage of thermal decomposition of the initial components solution significantly affect the catalyst activity in the synthesis of carbon nanostructured materials by the CVD method. It was found that controlling the mode parameters of the thermal decomposition of the initial components solution of the Fe-Co/Al2O3 catalyst, one can not only obtain a catalyst with the required characteristics but also directionally synthesize carbon nanostructured materials over the resulting catalytic systems. During the experiments, rational modes for the implementation of the method for producing catalysts were determined, allowing to form a metal oxide system with a specific surface area of 108 m(2)/g, the use of which in the synthesis of carbon nanostructured materials leads to the formation of multi-walled carbon nanotubes with an external diameter of 30 nm.

Abstract This article discusses the nature of the distribution of intact polyaniline-functionalized graphene nanoplatelets (GNPs) in the surface layer of nanomodified films of ultra-high molecular weight polyethylene (UHMWPE) using a Raman mapping method. On the Raman maps, D, G, and 2D peaks can be observed for the 0.1 wt.% GNPs content in the UHMWPE. In the surface layer of the films containing 1.0 wt.% GNPs, these signals are not detected, thereby indicating the displacement of the nanomodifier into the polymer bulk. In contrast, the polyaniline-functionalized GNPs tend to migrate to the surface of the UHMWPE nanocomposite film and evenly distribute in the surface layer as the concentration increases from 0.1 to 2.0 wt.%.

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