The conversion of polyethylene terephthalate (PET) waste into porous carbon adsorbents offers a dual solution to plastic pollution and CO2 capture. This study compares different preparation routes: a conventional two-step carbonization-activation (PET-400-a-850) and a novel "hydrolysis-pyrolysis" approach to PET upcycling. PET is first hydrolyzed to dipotassium terephthalate, under mild DMSO conditions (150 degrees C, 1 atm) then pyrolyzed in one step to porous carbon with a high carbon residue yield. According this method, two samples without (PET-a850) and with solvent recycling (PET-a-850-r10) were prepared. Recycling DMSO not only improved cost efficiency but also produced carbons with the largest surface area (1425.9 m2 g- 1 vs. 959.5 and 537.4 m2 g- 1 for other samples). At 298 K/1 bar, hydrolysis-derived carbons achieved CO2 uptakes of 4.55 mmol g- 1, compared to 3.86 mmol g- 1 for PET-400-a-850. Although PET-400-a-850 showed the highest selectivity (68.4), hydrolysispyrolysis samples also exhibited high selectivity (18.8). These findings demonstrate that the hydrolysis-pyrolysis strategy with integrated solvent recycling is an efficient, scalable route for upcycling PET waste into high-performance CO2 adsorbents.

The synthesis and exploration of the properties of activated porous carbons - materials capable of capture of substances - increasingly attracts the attention of researchers nowadays. However, studies generally focus on absolute values of adsorption (or other) properties. Pretreatment of carbonaceous materials, whether at high or low temperatures, plays a key role in generating the precursor structure that is subsequently activated. Our research addresses a gap in the existing literature by exploring how pretreatment conditions influence the properties of activated carbon. For the first time, we show how both the pretreatment atmosphere (inert or air) and the temperature used affect the final structure and adsorption performance of polyacrylonitrile-based activated carbons. We found that as the pretreatment temperature increases, the specific surface area decreases, and the crystallite size grows. The sample without any pretreatment showed the largest surface area of 2298.3 m2/g and the best adsorption capacity for methylene blue, reaching 508.4 mg/g. However, it also possesses the lowest nitrogen content, affecting its suitability for certain applications. Additionally, pretreatment atmosphere influences surface characteristics, with inert pretreatment resulting in higher hydroxyl group concentration compared to air pretreatment. This difference in hydroxyl groups contributed to varied adsorption values, measuring 441.2 and 422.6 mg/g for the inert and air pretreated samples, respectively. This highlights the importance of both pretreatment temperature and atmosphere in tailoring the properties of activated carbons for diverse applications.

The catalytic properties of samples containing Pd and Co metals on carbon supports (IR-pyrolyzed chitosan (CT) with an activated surface and detonation nanodiamonds (DNDs) have been studied in the ethanol steam reforming process. CT is a promising catalyst support due to its developed surface and the presence of nitrogen-containing groups capable of sorbing water molecules. The use of a membrane reactor with a Pd–Ru–In membrane has significantly increased the efficiency of the ethanol steam reforming process due to removing hydrogen from the reaction zone. The hydrogen yield in the membrane reactor increases twofold or more compared to a conventional reactor, while the proportion of reaction byproducts (CO and acetaldehyde) decreases. The highest hydrogen yield (15.8 mol/h per gram of catalyst) in the membrane reactor is achieved using a Pd–Co/CTKOH catalyst.

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In this study, we compared the conversion of polyethylene terephthalate (PET) into porous carbons for water purification using pyrolysis and post-activation with KOH. Pyrolysis was conducted at 400–850 °C, followed by KOH activation at 850 °C for samples pyrolyzed at 400, 650, and 850 °C. Both pyrolyzed and post-activated carbons showed high specific surface areas, up to 504.2 and 617.7 m2 g−1, respectively. As the pyrolysis temperature increases, the crystallite size of the graphite phase rises simultaneously with a decrease in specific surface area. This phenomenon significantly influences the final specific surface area values of the activated samples. Despite their relatively high specific surface areas, pyrolyzed PET-derived carbons prove unsuitable as adsorbents for purifying aqueous media from methylene blue dye. A sample pyrolyzed at 650 °C, with a surface area of 504.2 m2 g−1, exhibited a maximum adsorption value of only 20.4 mg g−1. We propose that the pyrolyzed samples have a surface coating of amorphous carbon poor in oxygen groups, impeding the diffusion of dye molecules. Conversely, post-activated samples emerge as promising adsorbents, exhibiting a maximum adsorption capacity of up to 127.7 mg g−1. This suggests their potential for efficient dye removal in water purification applications.

We have studied Cu–Zn and Cu–Ni containing catalysts on carbon supports based on IR-pyrolyzed chitosan and detonation nanodiamond (DND) and assessed their activity for the methanol steam reforming process. All of the catalysts have demonstrated rather high activity for this process and good stability over 30 h of continuous operation. The DND-based catalysts have been shown to have better performance, which seems to be due to their larger surface area and the nature of the functional groups on their surface. The activity of the bimetallic catalysts and the nature of the supports have been shown to be interrelated.

In this study, we investigate the effects of the duration of ultrasonic treatment during the impregnation process of a carbon precursor with an aqueous alkaline solution on the structural and electrochemical properties of KOHactivated carbon materials. Our findings using polyacrylonitrile (PAN)-derived carbon materials reveal that extended ultrasonic treatment leads to a more consistent distribution of the activating agent, promoting more uniform surface activation. This leads to notable shifts in the material's structure and surface chemistry, thereby influencing its functionality as an electrode material in supercapacitors and its electrocatalytic activity in the oxygen reduction reaction (ORR). Our results indicate a 6 % difference in the specific surface area and an 8 wt% rise in oxygen content when comparing samples without ultrasonic treatment to those treated for 10 min. Moreover, the specific capacitance increases from 133.9 to 163.5 F g-1, and the ORR activity ascends from 1.88 to 2.23 mA cm-2. This research highlights the potential of ultrasonic treatment duration as a variable to fine-tune the structure and properties of porous carbon materials, emphasizing its scientific and technological significance in the production of stable porous carbon materials.

A method for conversion of polyethylene terephthalate (PET) waste into porous carbon material is proposed. The recycling of PET bottle waste includes the stages of low-temperature hydrolysis of the polymer and subsequent pyrolysis at 800 degrees C. To provide PET hydrolysis at-150 degrees C and atmospheric pressure, the polymer was pre-dissolved in dimethyl sulfoxide and then an aqueous solution of potassium hydroxide was added. The potas-sium terephthalate formed as a result of the alkaline hydrolysis of PET allows the carbon-containing precursor to be preserved for further activation to temperatures beyond 600 degrees C. The proposed method leads to the formation of a porous carbon material, increasing the yield of carbon residue to 25 wt%, which is higher compared to the yield of carbon residue in the direct pyrolysis of PET. The obtained porous carbon is characterized by graphite-like structure and specific surface area of-1100 m(2) g(-1). It has been shown that PET-derived carbon material can be used to remove pollutants from aqueous media. The adsorption properties of the carbon material were demonstrated by adsorption of methylene blue from an aqueous solution. The capacity of the carbon material was found to be 443 mg g(-1).

In this work, membranes were obtained from PAN with the addition of particles of graphene oxide (GO), PAN pyrolyzed under the influence of IR radiation (IR-PAN-a) and nanodiamonds (ND). The pore structure of the obtained membranes was studied. It has been shown that the addition of particles slightly reduces the average pore size of the membranes from 17 to 12–15 nm, which leads to a decrease in the membranes water permeance from 158 to 80.9–119.9 kg/m2 h bar. At the same time, the addition of particles led to hydrophilization of the surface—the water contact angle decreased from 65° to 48°–55°, which contributed to an increase in the flow of oil solutions in toluene by 2–3 times compared to the PAN membrane. At the same time, the addition of GO and IR-PAN-a contributed to a significant increase in the irreversible membrane fouling. On the other hand, the addition of nanodiamonds not only reduced the overall membrane fouling and increased the permeability of the separation mixture from 4.93 to 8.47 kg/m2 h bar, but also made it possible to recover more than 96% of the pure toluene flux. The membranes rejection with the addition of ND in the filtration of oil solutions in toluene 10 g/L was 85–89%.

In this study, ultrafiltration membranes were developed via a nonsolvent-induced phase separation method for the removal of asphaltenes from crude oil. Polyacrylonitrile (PAN) and acrylonitrile copolymers with acrylic acid were used as membrane materials. Copolymerizing acrylonitrile with acrylic acid resulted in an improvement in the fouling resistance of the membranes. The addition of 10% of acrylic acid to the polymer chain decreases the water contact angle from 71° to 43°, reducing both the total fouling and irreversible fouling compared to membranes made from a PAN homopolymer. The obtained membranes with a pore size of 32–55 nm demonstrated a pure toluene permeance of 84.8–130.4 L/(m2·h·bar) and asphaltene rejection from oil/toluene solutions (100 g/L) of 33–95%. An analysis of the asphaltene rejection values revealed that the addition of acrylic acid increases the rejection values in comparison to PAN membranes with the same pore size. Our results suggest that the acrylonitrile–acrylic acid copolymer ultrafiltration membranes have promising potential for the efficient removal of asphaltenes from crude oil.

With the development of oil fields, the proportion of the highest-molecular-weight components, asphaltenes, increases in the composition of the extracted raw materials. The propensity of asphaltenes to aggregate causes a number of problems, which makes the task of oil deasphalting relevant. In this work, studies on separation of the asphaltene fraction from oil using PAN membranes are carried out. To decrease the pore size of membranes obtained by a phase inversion method, an additional component, acetone, is introduced into the casting solution. The permeability of the resulting membranes for water is 37.6 ± 1.7 L m−2 h−1 atm−1 and for toluene, 25.3 ± 1.8 L m−2 h−1 atm−1, and the pore size is 4.6 ± 0.5 nm. When filtering solutions of oil diluted with toluene (1 g/L), the retention of the membranes for asphaltenes is 73 ± 4

A method has been proposed for the synthesis of activated carbon materials (ACMs) based on polyacrylonitrile (PAN) by activation with potassium hydroxide under the action of IR heating. Two approaches to the chemical activation of the polymer precursor were presented: formation of ACM based on PAN preliminarily heat-treated at 200°C and based on PAN carbonized at 700°C by impregnation with an aqueous alkali solution followed by heating to 800°C. Due to the use of IR radiation, the heating can be performed at a rate of 50 K/min, and the exposure time at a given temperature can be reduced to 2 min. The dependence of the specific surface area and porosity of ACM according to BET on the synthesis conditions was studied. The proposed approaches lead to the formation of ACMs with specific surface areas of 1091 and 2121 m 2 /g, respectively.

Изучены катализаторы на углеродных носителях на основе ИК-пиролизованного хитозана и детонационных наноалмазов (ДНА), содержащие Cu и Zn или Ni, в процессе паровой конверсии метанола. Все исследованные образцы показали достаточно высокую активность в данном процессе и стабильность в течение 30 ч непрерывной работы. Показано преимущество катализаторов на основе ДНА, причиной чего, видимо, является их более развитая поверхность и природа присутствующих на ней функциональных групп. Показана взаимосвязь между активностью биметаллических катализаторов и природой носителя.

Fe-Co alloy nanoparticles with different sizes, supported by carbon derived from several polymers, namely polyacrylonitrile, polyvinyl alcohol and chitosan, have been synthesized by a one-pot method involving simultaneous metal nanoparticle formation and polymer carbonization. The method involves the joint dissolution of metal salts and a polymer, followed by annealing of the resulting dried film. Detailed XRD analysis confirmed the formation of Fe-Co alloy nanoparticles in each sample, regardless of the initial polymer used. Transmission electron microscopy images showed that the Fe-Co nanoparticles were all spherical, were homogeneously distributed within the carbon support and varied by size depending on the initial polymer nature and synthesis temperature. Fe-Co nanoparticles supported by polyacrylonitrile-derived carbon exhibited the smallest size (6–12 nm), whereas nanoparticles on chitosan-derived carbon support were characterized by the largest particle size (13–38 nm). The size dependence of magnetic properties were studied by a vibrating sample magnetometer at room temperature. For the first time, the critical particle size of Fe-Co alloy nanoparticles with equiatomic composition has been experimentally determined as 13 nm, indicating the transition of magnetic properties from ferromagnetic to superparamagnetic.

Metal-carbon nanocomposites consisting of Fe–Co bimetallic nanoparticles uniformly dispersed in the carbon matrix were synthesized by pyrolysis of a precursor based on chitosan and metal salts in the temperature range 500–800°C. The change in the structural characteristics of the samples after activation in the presence of potassium hydroxide was studied. It was found that alkaline activation leads to an increase in the specific surface area of the nanocomposites up to 700 m2/g and in the size of metal nanoparticles, whereas the phase composition and morphology of the carbon support remain unchanged.

With the development of oil fields, the proportion of the highest molecular weight component, asphaltenes, increases in the composition of the extracted raw materials. The tendency of asphaltenes to aggregate causes a number of problems, which makes the problem of oil deasphalting relevant. In this work, studies were carried out on the separation of the asphaltene fraction from oil using PAN membranes. In order to reduce the pore size of membranes obtained by the phase inversion method, an additional component, acetone, was introduced into the spinning solution. The permeability of the resulting membranes for water is 37.6 ± 1.7 L/(m2 h atm), and for toluene, 25.3 ± 1.8 L/(m2 h atm), and the pore size is 4.6±0.5 nm. When filtering oil solutions diluted with toluene (1 g/L), the retention capacity of membranes for asphaltenes was 73 ± 4% and more than 95% if the oil content in the solution was more than 10 g/L. A study was made of the parameters of membrane clogging during the filtration of oil solutions in toluene. It is noted that when passing from toluene to oil solutions, the permeability of membranes decreases by 10 times. At the same time, the decrease in permeability is reversible, and when the oil solution was replaced with a pure solvent, the membrane restored up to 99% of its permeability.

Hybrid composites based on electroactive polymers of diphenylamine-2-carboxylic acid (PDPAC) and highly porous carbon with a hierarchical pore structure were prepared for the first time. Activated IR-pyrolyzed polyacrylonitrile (IR-PAN-a), characterized by a highly developed surface, was chosen as a highly porous N-doped carbon component of the hybrid materials. IR-PAN-a was prepared using pyrolysis of polyacrylonitrile (PAN) in the presence of potassium hydroxide under IR radiation. Composite materials were obtained using oxidative polymerization of diphenylamine-2-carboxylic acid (DPAC) in the presence of IR-PAN-a both in an acidic and an alkaline medium. The composite materials were IR-heated to reduce the oxygen content and enhance their physical and chemical properties. The chemical structure, morphology, and electrical and thermal properties of the developed IR-PAN-a/PDPAC composites were investigated. The IR-PAN-a/PDPAC composites are thermally stable and electrically conductive. During the synthesis of the composites in an acidic medium, doping of the polymer component occurs, which makes the main contribution to the composite conductivity (1.3 × 10–5 S/cm). A sharp drop in the electrical conductivity of the IR-PAN-a/PDPACac-IR composites to 3.4 × 10–10 S/cm is associated with the removal of the dopant during IR heating. The IR-PAN-a/PDPACalk composites prepared before and after IR heating show a gradual increase in electrical conductivity by five orders of magnitude to 1.6 × 10–5 S/cm at 25–106 Hz. IR heating of the obtained materials leads to a significant increase in their thermal properties. The IR-heated composites lose half of their initial weight in an inert atmosphere at temperatures above 1000 °C, whereas for IR-PAN-a/PDPAC, the temperature range is 840–849 °C.

Novel ternary hybrid polyphenoxazine (PPOA)-derived nanocomposites involving Co-Fe particles and single-walled (SWCNTs) or multi-walled (MWCNTs) carbon nanotubes were prepared and investigated. An efficient one-pot method employing infrared (IR) heating enabled the formation of Co-Fe/CNT/PPOA nanocomposites. During this, the dehydrogenation of phenoxazine (POA) units led to the simultaneous reduction of metals by released hydrogen, yielding bimetallic Co-Fe particles with a size range from the nanoscale (5–30 nm) to the microscale (400–1400 nm). The synthesized Co-Fe/CNT/PPOA nanomaterials exhibited impressive thermal stability, demonstrating a half-weight loss at 640 °C and 563 °C in air for Co-Fe/SWCNT/PPOA and Co-Fe/MWCNT/PPOA, respectively. Although a slightly broader range of saturation magnetization values was obtained using MWCNTs, it was found that the type of carbon nanotube, whether an SWCNT (22.14–41.82 emu/g) or an MWCNT (20.93–44.33 emu/g), did not considerably affect the magnetic characteristics of the resulting nanomaterial. By contrast, saturation magnetization escalated with an increasing concentration of both cobalt and iron. These nanocomposites demonstrated a weak dependence of electrical conductivity on frequency. It is shown that the conductivity value for hybrid nanocomposites is higher compared to single-polymer materials and becomes higher with increasing CNT content.

In this paper, a new method of layer-by-layer formation of monopolymer membranes based on polyacrylonitrile (PAN) is proposed. The proposed approach allows independent adjustment of the structure and characteristics of individual layers of the membrane to achieve high performance characteristics. IR radiation has been used to modify PAN, the effect of which has allowed to convert the polymer into an insoluble form for the application of subsequent layers. An important feature of IR modification is that the pore size and permeability of the membranes remain unchanged. This makes it possible to form the individual membrane layers under different conditions. The obtained membranes have a well-defined spongy layer on the surface and finger-like pores in the other part of the membrane volume. The presence of the spongy layer on the surface reduces the probability of formation of undesirable defects, which reduce the membrane retention. As a result, defect-free membranes that combine a low molecular weight of MWCO cut-off equal to 1800 g/mol and a fairly good for such a dense membrane permeability of 38.7 L/m(2) h atm have been obtained. The pore size of the obtained membranes is 3.7 nm.

A method for conversion of polyethylene terephthalate (PET) waste into cobalt-carbon nanocomposites is proposed. The main feature of the procedure is the simultaneous formation of highly porous PET-derived carbon support and cobalt nanoparticles. Pyrolysis of a joint precursor obtained by mixing the three main components (PET, cobalt nitrate and KOH) in dimethyl sulfoxide results in the formation of a metal-carbon nanocomposite. The effect of the amount of KOH introduced on the structural properties of nanocomposites has been studied. It was shown that the weight ratio of PET:KOH affects both the porous characteristics of the material and the size of the cobalt nanoparticles. Also, the amount of alkali affects the yield of nanocomposite, both the yield of carbon residue, increasing it from 11.6 to 20.7 wt%, and the content of metal in the composite, which was in the range of 18.5-28.4 wt%.