Every year the problem of water purification becomes more relevant. This is due to the continuous increase in the level of pollution of natural water sources, an increase in the population, and sharp climatic changes. The growth in demand for affordable and clean water is not always comparable to the supply that exists in the water treatment market. In addition, the amount of water pollution increases with the increase in production capacity, the purification of which cannot be fully handled by conventional processes. However, the application of novel nanomaterials will enhance the characteristics of water treatment processes which are one of the most important technological problems. In this review, we considered the application of carbon nanomaterials in membrane water purification. Carbon nanofibers, carbon nanotubes, graphite, graphene oxide, and activated carbon were analyzed as promising materials for membranes. The problems associated with the application of carbon nanomaterials in membrane processes and ways to solve them were discussed. Their efficiency, properties, and characteristics as a modifier for membranes were analyzed. The potential directions, opportunities and challenges for application of various carbon nanomaterials were suggested.

This work is dedicated to the study of the treatment of multi-walled carbon nanotubes (MWCNTs) with dichromic acid. The dichromic acid was formed by dissolving different concentrations of CrO₃ in water. The effect of the concentration of dichromic acid on the change in texture characteristics, elemental composition, defectiveness, graphitization degree, and surface chemistry of MWCNTs was investigated using various analytical techniques, such as transmission electron microscopy, energy-dispersive X-ray spectroscopy (EDX), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction, and X-ray photoelectron spectroscopy (XPS). Testing of MWCNTs as electrodes for supercapacitors in 3.5 M H₂SO₄ solution was carried out using cyclic voltammetry. A decrease in the average diameter of CNTs after treatment was found. The EDX and XPS showed that the oxygen content on the surface of MWCNTs increased after treatment with dichromic acid. The formation of Cr₂O₃ after treatment with dichromic acid was detected by XPS. High angle annular dark field scanning transmission electron microscopy was used to confirm the intercalation of the chromium-containing compound between graphene layers of MWCNTs after treatment with dichromic acid. It was found that two different types of MWCNTs showed diverse behavior after treatment. The highest specific capacitance of the MWCNTs after treatment was 141 F g⁻¹ (at 2 mV s⁻¹) compared to 0.3 F g⁻¹ for the untreated sample.

The proton conductivity and structural properties of (1–x)CsH₂PO₄–xZnSnO₃ composites with compositions of x = 0.2–0.8 were studied. Zinc stannate ZnSnO₃ was prepared by the thermal decomposition of zinc hydroxostannate ZnSn(OH)₆, which was synthesized by hydrolytic codeposition. To optimize the microstructure of ZnSnO₃, thermal decomposition products of ZnSn(OH)₆ were characterized by thermal analysis and X-ray diffraction, Fourier transform infrared spectroscopy, low-temperature nitrogen adsorption, and electron microscopy. The study reveals that the thermolysis of ZnSn(OH)₆ at temperatures of 300–520 °C formed an X-ray amorphous zinc stannate with a high surface area of 85 m²/g possessing increased water retention, which was used as a matrix for the formation of the composite electrolytes CsH₂PO₄–ZnSnO₃. The CsH₂PO₄ crystal structure remained in the composite systems, but dispersion and partial salt amorphization were observed due to the interface interaction with the ZnSnO₃ matrix. It was shown that the proton conductivity of composites in the low-temperature region increased up to 2.5 orders of magnitude, went through a smooth maximum at x = 0.2, and then decreased due to the percolation effect. The measurement of the proton conductivity of the ZnSnO₃–CsH₂PO₄ composites revealed that zinc stannate can be used as a heterogeneous additive in other composite solid electrolytes. Therefore, such materials can be applied in hydrogen production membrane reactors.

This article is devoted to the investigation of the sensing behavior of chemically treated multi-walled carbon nanotubes (MWNTs) at room temperature. Chemical treatment of MWNTs was carried out with a solution of either sulfuric or chromic acids. The materials obtained were investigated by transmission electron microscopy, scanning electron microscopy, Raman-spectroscopy, X-ray diffraction, and Fourier transform infrared spectroscopy. The active layer of chemiresistive gas sensors was obtained by cold pressing (compaction) at 11 MPa of powders of bare and treated multi-walled carbon nanotubes. The sensing properties of pellets were investigated using a custom dynamic type of station at room temperature (25 ± 2 °C). Detection of NO₂ was performed in synthetic air (79 vol% N₂, 21 vol% O₂). It was found that the chemical treatment significantly affects the sensing properties of multi-walled carbon nanotubes, which is indicated by increasing the response of the sensors toward 100–500 ppm NO₂ and lower concentrations.

This study explores the development of new room-temperature NO₂ sensors utilizing carbon nanofibers (CNFs), single-walled carbon nanotubes (SWCNTs), and their hybrids with reduced graphite oxide (rGO), fabricated via a facile drop casting method with varying concentrations of carbon/ethanol mixtures. The concentration-dependent relation of sensor response to NO₂ has been found. Comprehensive characterization techniques, including electron microscopy, Raman spectroscopy, optical microscopy, and X-ray diffraction were employed to analyze the sensing materials. Our results reveal that CNFs exhibit superior sensitivity, reaching −1.32%/ppm at an optimal suspension concentration of 1.5 mg/mL, outperforming SWCNTs. The creation of hybrid composites, specifically CNFs/rGO and SWCNTs/rGO, further enhances sensing performance due to synergistic effects. Molecular dynamics simulations revealed increased adsorption behavior of the CNFs/rGO hybrid sensing material. The fabricated devices, based on all-carbon composites, are effective and energy-efficient platforms for NO₂ detection, offering promising solutions for environmental monitoring, the chemical industry, and industrial safety applications.

In this work, general purpose rubber composites were created based on a mixture of non-polar cis-1,4-isoprene rubber and cis-1,4-divinyl rubber as components. The main filler used was carbon black, while various graphite-like materials (graphite oxide, reduced graphite oxide, expanded graphite, and graphite nanoplatelets) served as additives. It was determined that the addition of these graphite-like materials resulted in a reduction in Mooney viscosity, with the introduction of graphene nanoplatelets having the most significant effect, contributing to a viscosity decrease of 8.5%. The relaxation rate increased, positively impacting elastic recovery and consequently reducing shrinkage. The introduction of graphite oxide, graphite nanoplatelets, and expanded graphite also increased the time to the onset of the vulcanization reaction; moreover, these additives lengthened the time needed to reach the optimum level of vulcanization. The addition of various graphite-like materials significantly affected the elongation at break, with the highest increase attributable to the addition of expanded graphite and reduced graphite oxide. It was found that the conditional tensile strength of these additives had little effect. Upon assessing the elastic-strength properties after aging, it was found that the inclusion of graphite-like materials reduced the elongation at break.