Search

The review considers the methods of preparation and the main surface characteristics of magnetic carbon-containing sorbents (MCSs) and summarizes data on the use of MCSs of various origins for the extraction of pharmaceuticals, heavy metals, and dyes from aqueous media. The main factors influencing the adsorption efficiency of MCSs in relation to these pollutants are discussed. It is shown that the extraction of spent MCSs has an advantage over nonmagnetic adsorbents due to their magnetic properties.

Synthesis of porous carbon materials has been carried out in two ways—by chemical and mechanochemical dehydrochlorination of polyvinyl chloride in the presence of alkali and subsequent two-stage heat treatment of the obtained polyvinylenes (carbonization up to 400°C and carbon dioxide or alkaline activation at a temperature of 850—900 and 800°C, respectively). The products obtained were studied by transmission electron microscopy and low-temperature nitrogen adsorption. It is shown that, depending on the synthesis conditions, carbon materials after activation have a developed specific surface area of 350–1100 m2/g and specific pore volume 0.3–0.47 cm3/g with a variable contribution of micropores from 30 to 85%. Thus, the effectiveness of the chosen approach to the controlled synthesis of porous CMs from PVC is confirmed.

The kinetics of adsorption of 2,4-dichlorophenoxyacetic acid (2,4-D) from an aqueous medium on two microspherical nanoporous carbon materials with different times of activation in a medium of a water vapor is studied. The effect of the redistribution of the porous structure formed during the activation on the process of adsorption is studied. The pseudo-order of adsorption is determined as well, and a comparison of the parameters of the adsorption characteristics with the earlier studied microporous and mesoporous samples is performed.

Recent developments in the use of activated carbons (ACs) of various geneses for wastewater treatment to remove copper, nickel, cadmium, and lead ions, which most frequently occur in industrial and municipal wastewaters, are summarized.

Methods for the production of metal–carbon nanoparticles of the core–shell type based on the formation of transition metal nanoparticles and a graphite-like shell on their surface containing to 50 graphene layers are considered. Various types of high-energy impacts or thermal transformations under exposure in a temperature range of 600–850°С were used for the synthesis of metal–carbon nanoparticles from initial metal- and carbon-containing components. Due to their unique properties, nanoparticles of this kind can be of interest as highly efficient catalysts, targeted drug carriers, contrasts in MRI diagnostics, and an element base of electronic and magnetic devices.

The synthesis of porous carbon materials was carried out by mechanochemical dehydrochlorination of polyvinyl chloride in the presence of alkalis (KOH, LiOH) using a high-energy planetary mill and the subsequent two-stage heat treatment of the obtained polyvinylenes (polymers with a conjugated double bond system)—carbonization to 400°C and carbon dioxide at 850°C or alkaline activation and 800°C, respectively. The structure of the obtained products was studied by Raman spectroscopy and transmission electron microscopy, analysis of isotherms of low-temperature adsorption/desorption of nitrogen. The resulting products are (micro-, meso-) porous amorphous carbon materials with specific surface SBET from 460 to 605 m2/g, micropore volume from 0.09 to 0.21 cm3/g, and mesopore volume from 0.09 to 0.6 cm3/g

This review summarizes the latest developments on the use of activated carbon adsorbents of various geneses for the adsorption of the most common pharmaceuticals in wastewater.

A method for the synthesis of metal–carbon nanocomposites in which metal-centered particles of the core–graphite-like shell type are distributed in the bulk of an amorphous sp2-carbon matrix is proposed. Polyvinyl chloride (PVC) was used as a carbon matrix precursor. The synthesis procedure included the following stages: The dehydrochlorination of PVC with diethylamine in a dimethyl sulfoxide solution in the presence of Co, Ni, Fe, or Cu nitrates; the carbonization of the product at 400°C; metal reduction with hydrogen at 500–620°C; and methane conversion at 620–850°C. The metal concentrations in the resulting composites were the following (%): Fe, 10; Ni, 10.8; Co, 11; and Cu, 21. The structure of the final metal–carbon nanocomposites was studied by transmission electron microscopy. The size of a metal core was 20–100 nm, and the number of graphene layers in a shell was to 50.

Transmission electron microscopy and X-ray energy dispersive microanalysis have been used to study structural and chemical transformations occurring in polyvinyl chloride films containing embedded nanoglobular carbon particles after intense laser irradiation. It was established that irradiation led to the conversion of nanoglobular carbon into carbon nanocapsules with sizes of 5–10 nm. The chemical composition of the composite film samples changed after laser irradiation. Thus, the average concentration of chlorine decreased from 35 to 3 wt %, and the carbon content increased by 20–30 wt %. The possibility of obtaining carbon–carbon nanocomposite film materials with carbon nanocapsules embedded in an amorphous carbon matrix was demonstrated.

Mechanically activated dehydrochlorination of polyvinyl chloride in the presence of lithium, potassium, and calcium hydroxides was studied. Short joint mechanical treatment of polyvinyl chloride with the above bases in a high-energy centrifugal planetary mill for 5–10 min ensures the formation of polymers with a conjugated double bond system (polyvinylenes). Their subsequent heat treatment at temperatures of up to 400°С yields amorphous carbon structures. Activation of the resulting material in a CO2 medium at 850°С results in the formation of a micro-, mesoporous carbon material with the prevalent mesopore volume. The results obtained can serve as a basis for the development of technologically acceptable procedures for polyvinyl chloride waste processing to obtain demanded carbon materials without dioxin formation.

The impact of a nanosecond high-energy ion beam (HEIB) on thin films of commercial chlorinated polyvinyl chloride (CPVC) and polyvinyl alcohol (PVA) containing catalytic additives (inorganic iron salts) is studied. Depending on the type of polymer, the type of additive, and the irradiation mode used, HEIB treatment results in the formation of either layers of carbon nanofibers or a carbon foam on the polymer surface. The most probable diameters of the carbon nanofibers are 70 and 40 nm for CPVC and PVA, respectively. The mechanism explaining the effect of the catalytic additive on the formation of nanostructured carbon on the surface of the considered polymers is discussed.

The adsorption of 2,4-dichlorophenoxyacetic acid (2,4-D) as a typical herbicide from aqueous solutions on activated carbons prepared based on polyvinyl chloride by its alkaline dehydrochlorination and the subsequent heat treatment was studied. The structure of the activated carbon surface and the presence of functional groups on it were established. The kinetics of the process of adsorption was studied. The influence of activated carbon preparation conditions on the properties of the adsorbents was demonstrated.

New copolymers containing reactive vinyltriazole units and polyvinylene blocks with conjugation system promising as materials with special electrical, physical, catalytic, and sorption properties have been prepared by the reaction of poly(vinyl chloride) with sodium salts of 1,2,4-triazole and 1,2,3-benzotriazole in a dimethylformamide medium.

New sulfur-containing copolymers based on poly(vinyl chloride) have been prepared by the nucleophilic substitution of chlorine atoms by sulfur atoms using sodium tetra- and pentasulfides. It has been shown that these copolymers can be carbonized to produce sulfur-containing carbon materials with residual chlorine content about 2 wt %.

It was shown that methane decomposition on metal–carbon nanocomposites with transition metal (Co, Fe, and Ni) nanoparticles distributed in the bulk of the amorphous carbon matrix leads to carbon deposition with the formation of a graphite-like shell around a metal core. The resulting “core-shell” structures have a diameter of 10–40 nm and contain up to 50 graphene layers with an interlayer distance of 0.34–0.35 nm. For the synthesis of the initial metal–carbon nanocomposites, a method that we proposed earlier was used, which involves low-temperature formation of carbon structures from carbon-chain chloropolymers based on their dehydrochlorination with the formation of polyvinylenes as reactive carbon precursors.

The possibility of nanostructured Co-containing carbon layers formation by means of the approach based on polyvinyl chloride alkaline dehydrochlorination in dimethyl sulfoxide in the presence of Co-nitrate is shown. From the mentioned reaction mixture, the layers of the carbon polymer precursor – polyvinylene formed during dehydrochlorination were deposited on the silicon wafer by spin coating. The obtained layers heat treatment up to 400 °C results in the formation of Co-carbon nanostructured continuous layers which structure is studied by the atomic force microscopy.The possibility of nanostructured Co-containing carbon layers formation by means of the approach based on polyvinyl chloride alkaline dehydrochlorination in dimethyl sulfoxide in the presence of Co-nitrate is shown. From the mentioned reaction mixture, the layers of the carbon polymer precursor – polyvinylene formed during dehydrochlorination were deposited on the silicon wafer by spin coating. The obtained layers heat treatment up to 400 °C results in the formation of Co-carbon nanostructured continuous layers which structure is studied by the atomic force microscopy.

The possibility of regulation of textural parameters for porous carbon materials derived from polyvinyl chloride was evaluated. Porous carbon materials were obtained by a two-stage process including dehydrochlorination of the initial polymer under the action of alkali (KOH) and subsequent heat treatment, i.e., carbonization at 400 °C and activation at 850-900 °C. Various approaches for controlling the porous structure of the final material were used. Thus, dehydrochlorination was carried out both by action of alkali in a solution in polar organic solvent and by mechanical treatment of polymer-alkali composition. In the case of dehydrochlorination in a solution, modifying additives of carbon nanoparticles (nanoglobular carbon, graphene-like species based on graphite oxide or reduced graphite oxide) were introduced. Different gases of reductive and oxidative nature, such as hydrogen, carbon dioxide and water vapor, were used for activation purpose. It was found that these approaches allow regulating the ratio of micro- and mesopores in the resulting porous carbon materials which can be used in different fields. These porous carbons are amorphous materials having a specific surface area (SBET) from 356 to 1115 m2/g, micropore volume from 0.12 to 0.39 cm3/g, and mesopore volume from 0.07 to 0.33 cm3/g.

The applicability of porous carbon materials obtained by the dehydrochlorination of poly(vinyl chloride) as supports for palladium hydrogenation catalysts was demonstrated. The efficiency of the catalysts was evaluated in the liquid-phase hydrogenations of styrene, nitrobenzene, chlorobenzene, and acetophenone. The complete conversion of the substrates with selective formation of target products was achieved under mild reaction conditions and at low Pd content in the catalysts (1.5 wt%).The applicability of porous carbon materials obtained by the dehydrochlorination of poly(vinyl chloride) as supports for palladium hydrogenation catalysts was demonstrated. The efficiency of the catalysts was evaluated in the liquid-phase hydrogenations of styrene, nitrobenzene, chlorobenzene, and acetophenone. The complete conversion of the substrates with selective formation of target products was achieved under mild reaction conditions and at low Pd content in the catalysts (1.5 wt%).

A method for carbon materials synthesis based on polyvinyl chloride has been proposed. Method includes polymer dehydrochlorination by alkali with carbon-rich conjugated structures (polyvinylenes) formation and its subsequent carbonization at relatively low temperatures. Raman and 13C NMR spectroscopy and transmission electron microscopy show that thermal treatment of the resulting polyvinylenes up to 400 °C leads to the formation of amorphous carbon material with chlorine contain less than 0.5 wt.%. These results can be used to develop dioxin-free technology of utilization of polyvinyl chloride and its wastes.

This work shows the possibility in principle of forming hydrocarbon structures in polyvinyl chloride films free of admixtures and polyvinyl chloride films modified with 5-mass % ferrocene via a radiation chemical transformation in the atmosphere with the use of an electron accelerator with a plasma cathode operating in the pulsed-periodic mode maximal electron energy no higher than 160 keV, pulse length of 40 μs, and current density of 5 mA/cm2. According to the results of semiquantitative X-ray microanalysis, an irradiated polyvinyl chloride film free of admixtures contains 92 of carbon, 6 of oxygen, and 2 mass % of chlorine; the irradiated polyvinyl chloride is an amorphous carbon material. A possible mechanism of the phenomenon is discussed.

A method for the synthesis of core-shell structures during methane decomposition in a cobalt-carbon composite with metal particles uniformly dispersed in its bulk is proposed. These composites are obtained by the low-temperature formation of carbon structures based on reactive conjugated polymers obtained by the dehydrochlorination of chlorine-containing carbon-chain polymers. Eelectron microscopy studies show the formation of structures containing 10–50 graphene layers closely packed around a metal core with an interlayer distance of 0.34–0.35 nm.

The applicability of a porous carbon material obtained as a result of the “chemical” dehydrochlorination of chlorinated polyvinyl chloride as a support for palladium hydrogenation catalysts was demonstrated. The efficiency of the catalyst was evaluated in the liquid-phase reactions of nitrobenzene hydrogenation and chlorobenzene hydrodechlorination. Although the specific activity of the catalyst was lower by a factor of 3–4 than that of the samples based on Sibunit and carbon nanotubes, the complete conversion of the initial compounds with the selective formation of end products under mild conditions was achieved at a relatively low palladium content (1.5%).

The effect of a nanosecond high-power ion beam on thin polymer layers of chlorinated polyvinyl chloride and polymethyl methacrylate containing ferrocene as an additive is investigated. Arrays of carbon nanofibers with a characteristic diameter of 30–160 nm and lengths of up to 15 m are formed on the surface of the chlorinated polyvinyl chloride. The same effect on polymethyl-methacrylate layers leads to intense cavitation of the surface layer. The possible mechanisms of the formation of carbon nanofibers in chlorinated polyvinyl chloride with ferrocene additive under the action of a high power ion beam are discussed.

Mechanochemical activation of PVC in a high-energy centrifugal-planetary mill was shown to increase its reactivity in dehydrochlorination under the action of bases. Thus modified PVC is capable of low-temperature carbonization and can form a carbon material even at the temperatures below 400°C.

A comparative study of the effect of a high-power ion beam of nanosecond duration on layers of reactive industrial chlorinated polymers (chlorinated polyvinyl chloride, polyvinyl chloride) containing a catalytic additive (ferrocene) is carried out. The formation of amorphous carbon nanofiber layers on the surface of chlorinated polymers is revealed. The characteristic diameter and length of nanofibers depends on the type of polymer and irradiation mode and is equal to 30–250 nm and 10 μm, respectively. The growth rate of carbon nanofibers is estimated. Its value might reach ~160 μm/μs. A possible mechanism for carbon nanofiber formation on the surface of chlorinated polymers with the addition of ferrocene under high-power ion beam irradiation is discussed.

Chlorine-substituted polymers with a system of conjugated double bonds—polyvinylene chlorides, which were prepared by the chemical dehydrochlorination of carbon-chain chloropolymers with a Cl content of higher than 60 wt %, being polymeric electron acceptors, were found to form complexes with alkali metal hydroxides (LiOH, NaOH, and KOH). The resulting complexes exhibit high sorption capacity for phenol. The static exchange capacity of the alkaline complexes of polyvinylene chlorides for phenol is as high as 310 mg/g in an aqueous medium or 90 mg/g in an atmosphere of air; these values are comparable with the sorption capacity of the known sorbents of phenol.

Studies of the structural transformations of carbon black caused by laser and electron irradiation have been carried out using high-resolution transmission electron microscopy (HRTEM). The heterosystems of the Pt/C-type are obtained in the process of laser irradiation of carbon black suspensions in platinum-containing solutions. A high-energy electron irradiation of carbon black causes the formation of multimorphological carbon nanostructures, which possess a graphite-like arrangement of graphene layers.

The effect of a nanosecond high-power ion beam on chlorinated polyvinyl chloride, reactive polymer with a conjugation system (poly-vinylene chloride), and FP-383 photoresist thin films, which are deposited onto sodium-silicate glass and ST-50 glass-ceramic substrates, is investigated. It is revealed that submicrometer particles with clearly defined crystallographic facets are formed on the irradiated surface of the chlorinated polymers. These particles include predominantly carbon and are probably carbynoid or diamond-like structures. The possible mechanisms of the observed phenomena are discussed.

Nanocapsules and stacks of graphene sheets have been prepared from carbon black by irradiation relativistic electron beam. Electrons with energy of 2.5 MeV were used in these experiments to produce carbon nanoparticles with graphite-like structure of the graphene layers. High Resolution Transmission Electron Microscopy (HRTEM), Raman spectroscopy and Electron Spin Resonance (ESR) spectroscopy were used to obtain the information about morphology, crystallinity, and interlayer distance of these nanostructures.

A new approach to the synthesis of hybrid carbon materials based on the use of reactive polyvinylenes as the precursors of carbon is proposed. The possibility of the incorporation of nitrogen- and metalcontaining modifying additives into the carbon structure in the course of its formation from the above polymers is demonstrated.

The surface morphology and the composition of polymer layers based on chlorinated polyvinylchloride with addition of ferrocene (up to 10% of the polymer mass) subject to the action of a nanosecond high-power ion beam are studied. It is demonstrated that carbon material in the form of nanofibers with an average diameter of 80 nm and a length of up to 10 μm is formed on a surface singly irradiated by such beam with a current density of ∼100 A/cm2. A possible mechanism of the observed phenomenon is discussed.

Chlorine-substituted polymers with a system of conjugated double bonds-polyvinylene chlorides, which form sp2-carbon structures under unusually mild conditions, were prepared by the dehydrochlorination of carbon-chain perchloropolymers (chlorinated polyvinyl chloride and a polyvinyl chloride-polyvinylidene chloride composition) under the action of potassium hydroxide in organic media. The results of the potentiometric titration of the reaction medium in the synthesis of polyvinylene chlorides and the characterization of the products by Raman spectroscopy and thermal analysis with the mass spectrometry of the volatile products of thermal degradation confirmed the formation of polyvinylene chlorides under the selected dehydrochlorination conditions. It was hypothesized that the observed incomplete dehydrochlorination of the perchloropolymers is explained by the stabilization of polyvinylene chloride structures in the process of their formation by donor-acceptor interaction with an alkaline agent; this is consistent with the ability of the resulting polyvinylene chlorides to reversibly bind KON from solutions.

Carbon composite materials based on nanoglobular carbon distributed in the volume of a porous carbon matrix were prepared. A reactive polymer with a conjugated system—polyvinylene chloride, which is formed upon the dehydrochlorination of chlorinated polyvinyl chloride, a carbon-chain perchloropolymer—was used as the precursor of porous carbon. Globular carbon, which was prepared by the thermal oxidative pyrolysis of heavy catalytic cracking gas oil, was dispersed in the reaction medium in the synthesis of polyvinylene chloride. The thermal treatment of the resulting compositions in an atmosphere of CO2 to 900°C led to the formation of carbon-carbon micro-mesoporous nanocomposites, as confirmed by transmission electron-microscopic data and pore structure parameters determined using an adsorption method. It was found that nanoglobular carbon exerted a clearly pronounced nucleating effect on the formation of a carbon structure from a polymer precursor.

It was found that alcohols can be synthesized from CO and H2 at 3 MPa and 280–300°C in the presence of Fe catalysts containing an activated fibrous carbon material (AFCM) as a support. It was established that 20% Fe/AFCM catalysts possess an extremely high specific activity in the conversion of carbon monoxide (∼1 × 10−4 mol CO (mol Fe)−1 s−1), which is higher than the activity of traditional bulk iron catalysts by almost an order of magnitude. The values of CO conversion and selectivity for alcohols obtained for these catalysts are close to the parameters of industrial processes (Synol process, Oxyl process, and synthesis according to Bashkirov); however, they are obtained under milder conditions in a single run rather than with the use of a recycle. The Fe/AFCM catalysts make it possible to obtain monohydric alcohols in yields to ∼50 g/m3 (to a 50% concentration in synthesis water) upon the almost complete conversion of CO. In this case, the fraction of C2-C4 alcohols was as high as 55–60%.

Iron catalysts supported on an activated fibrous carbon material (AFCM) and characterized by high performance in the hydrocarbon synthesis from CO and H2 have been studied. It has been shown that the promotion of Fe/AFCM catalysts with potassium and aluminum oxides or with copper reduces the optimum temperature of Fischer-Tropsch synthesis and enhances the polymerizing activity of the catalysts.

The irradiation of various commercial polymers (chlorinated polyvinyl chloride, polyvinyl chloride, polyvinyl alcohol, polymethyl methacrylate) by a high-power ion beam of nanosecond duration has been investigated. The amorphous carbon nanofibers formation was detected on the surface of low-cost commercial polymers (chlorinated polyvinyl chloride, polyvinyl chloride) containing a catalyst under the high power ion beam irradiation at room temperature. Various iron compounds (organic and inorganic) were used as catalytic additions. The electron microscopy (scanning and transmission) with an energy dispersive analyzer and Raman spectroscopy were used to investigate the morphologies and structure of irradiated polymers. Carbon nanofibers (CNFs) had a most probable diameter in the range 50-90 nm and a maximum length of up to 10 μm. The maximum CNFs growth rate was estimated as 160 μm/μs. A possible growth mechanism for CNFs is discussed.

A microporous carbon material can be obtained by dehydrochlorination of the polymeric formulation poly(vinyl chloride)-poly(vinylidene chloride) in the presence of KOH followed by thermal treatment at a relatively low temperature (350°C in a nitrogen-oxygen gas mixture (10: 1 w/w)). This is because the chemical dehydrochlorination gives highly reactive chloro-containing polyconjugate systems. The conversion of chloropolyene systems into carbon structures is confirmed by Raman spectroscopy and TGA with MS analysis of volatile pyrolysis products. The resulting carbon material has a system of pores including ultramicropores 6.5 ± 0.5 A), micropores (16 ± 1 A), and mesopores (average pore size 150 ± 7 A).

The decomposition of methane on catalysts prepared by metal deposition on carbon fiber was investigated. It was found that new carbon deposits having a threadlike form and a nanotube structure are formed on nickel-containing samples.

The main volatile products of the pyrolysis of polyvinyl alcohol (PVA)—water, carbon oxides, acetaldehyde, methane, and hydrogen—were determined by gas chromatography with the use of a pyrolytic attachment to a chromatograph (so-called stepwise pyrolysis gas chromatography). The correlations of product ratios over various temperature ranges were found. It was demonstrated that the preliminary thermal oxidation of PVA in air at 200°C, which was responsible for the partial dehydration of PVA and the formation of thermally labile oxygen-containing groups in it, facilitated the occurrence of the subsequent carbonization phase. This manifested itself in much more intense dehydrogenation and methane release from the coke residue of thermally oxidized PVA in the region 700–900°C, when the elimination of oxygen-containing compounds was mainly complete, and in an increase in the yield of coke residue and the C: H ratio in this residue.

Exposure of carbon black to pulsed electron and laser beams leads to structural transformations of carbon and formation of nanocapsules and rose-like particles with highly ordered graphite like structure.

The possibility of preparing carbonaceous materials with a developed microporous structure by low-temperature dehydrohalogenation of carbon-chain halogenated polymers under the action of a strong base followed by thermal treatments (carbonation in an inert atmosphere and activation in an oxidative medium) was demonstrated for the example of the polyvinyl chloride-polyvinylidene chloride system.

Electrophysical properties of polymer composites with disperse, fiber or fabric fillers are examined. The methods for controlling their electrical, magnetic, thermal and other properties by changing the ingredients and compounding methods are reported. Some examples of using polymer composites in the form of functional elements or structures, prospective for different fields of science and technology are presented.