The paper describes the structure and sorption activity of larch bark following treatment with green reagents. The aim was to obtain sorbents from larch bark by means of chemical treatment. The study compared the effect of non-toxic and low-toxic extraction agents and reagents, such as water, hexane, ethanol and hydrogen peroxide, on the structure, sorption properties of the treated bark, as well as on the composition of the extracted substances. It was established that the process of bark extraction involves the transformation of its main components, leading to the formation of long-range ordered structures. The greatest structural changes were observed for the bark treated consecutively with ethanol and hydrogen peroxide, mainly due to the decomposition of hemicelluloses. Such treatment of the bark was revealed to contribute to the formation of a mesoporous structure. The methylene blue sorption of the treated bark is 6.5 times higher than that of the original bark. Studies of extracted substances using IR spectroscopy and GC -MS showed a similar composition of larch bark extracts obtained by aqueous and ethanol treatment, which contain mainly phenolic and alcohol compounds. In addition, the ethanol-peroxide solution contains esters and carboxylic acid derivatives. The hexane extract of larch bark was found to contain mainly terpenes and their derivatives, which are widely used as valuable components in medicine and have great potential as a source of biomaterials for green polymers.

The synthesis of metal-carbon materials based on hydrolytic lignin by its modification with subsequent carbonation is studied. It is shown the modification of hydrolysis lignin with ZnCl2 and NiCl2 leads to a significant increase of specific surface area up to 716 m2/g and the apparent specific capacity up to 350F/g of carbonized composite. It was found out that fabricated Ni/C composites are characterized by a coercive force of 80-105 Oe, a saturation magnetization of 4-11 Gs center dot cm3/g, and a residual magnetization of 0.28-0.45 Gs center dot cm3/g. This indicates the prospects of their use as a magnetically soft material.

A method for the disposal of hydrolysis lignin waste based on its modification with ZnCl2 and FeCl3 and subsequent carbonization at 800°C was proposed. The composition, structure, sorption and electrochemical properties of the resulting porous carbon materials were studied. It was established that the carbonization of mixtures of hydrolysis lignin with zinc and(or) iron chlorides results in the formation of metal-containing C/MeO carbon composites. The addition of ZnCl2 promotes the formation of a microporous structure of the composite, the addition of FeCl3 promotes the formation of iron-containing crystalline phases with a high specific capacity. Modification of hydrolysis lignin with a mixture of ZnCl2 and FeCl3 allows manufacturing a porous carbon material with the highest specific surface area (580 m2 g–1), iodine sorption capacity (694 mg g–1), and apparent specific capacity (782 F g–1) . The resulting composite materials have prospects for use as magnetic catalysts, sorbents, and in the creation of supercapacitors.

Abstract This paper presents the synthesis of carbon material from the untreated and extracted larch bark. The influence of the extracting reagents (water, ethanol, hydrogen peroxide, and sodium hydroxide) on the structural changes of ash components of the bark was revealed. It is assumed that one of the reasons for the development of the porous structure of carbon products during carbonization of the extracted bark is associated with a decrease in ash content. It was found that the carbon product obtained from washed-out water bark has the highest value of the specific surface area (401 m2/g) and the largest accumulation of electric charge.

Porous carbon tannin–lignin/formaldehyde and tannin–lignin/furfuryl gels were prepared by carbonization of organic gels synthesized by sol–gel condensation of larch bark tannins and hydrolysis lignin with formaldehyde and furfuryl alcohol. The effect of lignin addition on the porous structure formation, apparent density, and adsorption and electrochemical properties of carbon gels was determined. Analysis by the Brunauer–Emmett–Teller method shows that the carbon gels are microporous materials with high specific surface area. Introduction of lignin into the initial organic tannin–formaldehyde gel favors an increase in the specific surface area of the carbon gel from 237 to 407 m2 g–1, to a decrease in the apparent density from 0.61 to 0.37 g cm–3, and to a decrease in the fraction of micropores in the total pore volume from 88 to 85.6%. The specific surface area of carbon tannin–lignin/furfuryl gels is somewhat higher than that of tannin–lignin/formaldehyde gels and reaches 512 m2 g–1 in a sample with 20% lignin content. The density of tannin–lignin/furfuryl gels increases from 0.17 to 0.32 g cm–3 with an increase in their lignin content from 10 to 30 wt %. Examination by scanning electron microscopy shows that the structure of carbon gels is a three-dimensional network of interconnected sphere-like particles of size varying from 20 to 100 nm. The tannin–formaldehyde and tannin–furfuryl gels with 10% lignin content are capable to adsorb 35.6 and 55.2 mg g–1 Methylene Blue, respectively. The tannin–lignin/furfuryl gel containing 10 wt % lignin shows the highest performance in benzene sorption (513 mg g–1). Electrochemical trials show that the tannin–lignin/formaldehyde gel with 30% lignin content exhibits the highest ability to accumulate the electric charge.

The purpose of this study is to investigate structural, electrochemical and electron-transporting properties of the carbonic materials prepared from pine bark sawdust modified with low-toxic reagents (H2O2, NaHCO3, and ZnCl2) for their possible use as environmentally friendly electrode material in supercapacitors. Comprehensive analysis of products using XRD, CV, and EPR has revealed the main reasons for the accumulation of electric charge in carbonic materials. It has been shown that the highest specific surface area (777 m2/g) and apparent specific capacity (950 F/g) occur in composites made from a mixture of pine bark and zinc chloride. The high electron conductivity, inhomogeneous electronic states, and the presence of inclusions of the crystalline phases of ZnO characterize the carbon matrix of this composite. It is assumed that one reason for accumulation of electric charge in carbonic composite is the presence of local nanostructures with high electron conductivity. The mineral impurities of metal oxides contained in bark can play the role of additional active centers of electric charge transfer during electrolysis and contribute to an increase in the specific capacity of the material.

The purpose of this study is to investigate the synthesis process of composite materials based on fir bark for thermochemical transformation and to determine the influence of additives such as zinc chloride, natural graphite of various origins on the structural and electrochemical characteristics of the carbonized products. Modification of fir bark sawdust with amorphous and/or crystalline graphite and zinc chloride allowed for the synthesis of products with a specific surface area of up to 780 m2/g and an apparent specific electrical capacity up to 540 F/g. It was revealed that carbonization of samples containing zinc chloride leads to the formation of porous carbon/zinc oxide composites. The solid residue obtained from the mixture of three components (fir bark, crystalline graphite, and zinc chloride) has the highest apparent specific electrical capacity. It is assumed that the combination of the structures of amorphous, crystalline carbon, and zinc oxide promotes the diffusion of electrolyte and the accumulation of electric charge in carbon composite.

The purpose of this study is to investigate the composition and structural changes of aspen and fir barks for thermochemical transformation and to determine the electrical capacity of the obtained carbonized barks. Significant differences of the structural and current-voltage characteristics of carbonized barks were revealed. The carbonized product from aspen bark mainly consists of the amorphous carbon and the crystalline phase of calcium hydroxide; the product from fir bark consists of amorphous-crystalline carbon. Cyclic voltammetric curves indicate the formation of electric double layer in the obtained carbon products and imply their potential use for energy accumulation and storage. Passing of Faraday processes and the pseudo-capacity are revealed in aspen carbonized at 800 degrees C. These features are absent in the carbon product obtained from fir bark. The apparent specific capacity of carbonized aspen bark (450 Fg(-1)) is higher than carbonized fir bark (83 F*g(-1)). The probable reason is the effect of oxides of metal such as calcium, magnesium, potassium and sodium, which content is two times higher in the aspen bark compared to the fir bark. The apparent specific capacity as function of the potential sweep speed is different for aspen and fir barks. This difference can be caused by the inhomogeneous distribution of mineral substances in the carbon matrix.

The possibility of using aspen bark modified with zinc and iron chlorides for preparing highly porous materials with specific properties was examined. The effect of the treatment temperature and modifiers on the structural and electrochemical parameters of the carbon-containing product was revealed. Carbonization of aspen bark modified with ZnCl2 yielded a material with the specific surface area of up to 1350 m2 g–1, containing a crystalline zinc oxide phase. The material obtained using a mixture of aspen bark with FеCl3 had the specific surface area of up to 300 m2 g–1 and contained magnetite and maghemite. Modification of the bark with zinc and iron chlorides simultaneously yielded a highly porous product with ferromagnetic properties. The apparent capacitance of the samples carbonized at 800°С was found to be 150–400 F g–1. The possibility of using these materials in electrochemical devices was suggested.

The article presented researches concerning the effect of prolonged exposure in water of wood of different species - birch, aspen and pine, on the formation of carbon materials structure during carbonization. The possibility of using wood waste of different species, subject to long exposure in water, to obtain more porous carbon materials than using original wood is shown. It was established that the aging of different species in water stimulates the disclosure of the porous structure of the carbon product. This particularly applies to the carbon product of pine wood, the specific surface area which increases from 10 to 455 m2 g-1. It was shown that the yield of the carbon product, increases by 15–25 wt.% using wood prolonged exposure in water. Using XRD and electron microscopy, features of the structural transformation of birch, aspen and pine wood subjected to water treatment were revealed. Prolonged exposure of different wood species in the water affects the degree of crystallinity of the cellulose fiber in wood. The crystalline component of pine is exposed to the greatest destruction under the action of water. It was noted that after water treatment of wood, the part of the amorphous component in the carbon product increases, regardless of the type of wood used.

The structure and electrochemical properties of the products of the thermochemical transformation of aspen modifi ed and unmodifi ed with zinc chloride have been studied.It is shown that the addition of ZnCl 2 to the lignin-cellulose mass leads to a signifi cant increase of the specifi c surface area of the carbonized product up to 1800 m 2. g -1 and the formation of ZnO crystalline phase. The infl uence of the conditions of material synthesis and electrolyte concentration (1M and 3M KOH)on the shape of voltammetric curves is revealed by cyclic voltammetry.It is established that aspen wood after prolonged exposure in water can be successfully used to produce porous carbon electrode materials.

Highly porous ZnO/carbon composite with a specific surface area of up to 2050 m2 g–1 was prepared from aspen sawdust modified with zinc chloride. The effect of temperature, modifier, and long preliminary keeping in water on the structural characteristics of the final product was examined. The possibility of using porous materials synthesized from aspen wood waste as electrode materials was demonstrated. As shown by cyclic voltammetry, the apparent specific electrical capacitance reaches 104 F g–1.

Highly porous materials containing zinc oxide were prepared form modified pine wood. The growth dynamics of zinc oxide microcrystallites in the course of carbonization of pine sawdust mixed with ZnCl2 was studied. The hexagonal wurtzite-type ZnO phase is formed at 400°С and is broken down at approximately 800°С. The synthesized composite material has a high specific surface area, up to 1900 m2 g–1. The relationships of the porous structure formation in the composite in relation to the temperature and subsequent treatment with water were revealed. Opening of the porous structure of the composite in the course of carbonization of modified pine sawdust is associated with the formation of crystal-like phases of carbon and ZnO.

The structural changes of birch and pinewood under the influence of prolonged exposure to water were studied. It has been shown that prolonged aqueous treatment of birch increases the degree of crystallinity of cellulose. On the contrary, similar treatment of pinewood leads to its decrease. The specific role of hydroxyl groups of cellulose in the interaction of wood with water has been revealed. It has been noted that the O/H ratio for wood correlates to the hydrophilicity and crystallinity of cellulose. The possibility of producing porous products from different species of wood after prolonged soaking in water has been shown. The carbonization of the samples up to 800 °C leads to significant growth of the specific surface area of carbon product from 10–20 to 200–400 m2/g. It is assumed that a soft change of wood structure under the influence of water leads to the formation of weakly bound low molecular weight fragments, which are converted into volatile products for carbonization, and the formation of porous carbon product.

Получены пористые углеродсодержащие материалы из сосновых опилок, модифицированных FeCl3, ZnCl2 и H3PO4. Проведен сравнительный анализ их структуры и свойств при различных температурах карбонизации и последующей водной обработки, используя тепловую адсорбцию азота для определения удельной поверхности, электронную микроскопию и рентгенографический анализ. Выявлено, что в процессе нагревания образцов с H3PO4 формируется однородная аморфнокристаллическая структура продукта; при нагревании образцов с FeCl3 проявляются кристаллические железосодержащие фазы, включая магнетит, а при нагревании образцов с добавкой ZnCl2, образуются основные две фазы – аморфнокристаллическая и гексагональные кристаллиты оксида цинка, которые придают специальные свойства продуктам.Показано, что добавка хлорида железа позволяет получить магнетит/углеродный композит с удельной поверхностью до 470 м2 г-1; добавка хлорида цинка в биомассу приводит к образованию оксид цинка/углерод композита с удельной поверхностью до 1900 м2 г-1; а добавка фосфорной кислоты приводит к полифосфатно-углеродной структуре с удельной поверхностью до 1300 м2 г-1. Выявлено, что пористость продукта связана главным образом с образованием водонерастворимых кристаллоподобных фрагментов в процессе карбонизации.

It was established that the main factors responsible for the yield and specific surface area of porous carbon materials obtained by the chemical activation of the wood of birch are the nature of a modifying agent and the temperature of pyrolysis. The additional opening of the porous structure of the product of the chemical activation of wood occurs at the stage of its water treatment as a result of the removal of water-soluble compounds. The conditions of the carbonization of birch wood modified with H 3 PO 4 , KOH, and ZnCl 2 were chosen in order to provide the significant development of the porous structure of carbon materials. The porous carbon material with the highest specific surface area (more than 2560 m 2 /g) was obtained by the water washing of the product of the carbonization of birch wood modified H 3 PO 4 at 400°C.

The influence of birch and aspen wood modification by explosive autohydrolysis and ZnCl 2 additive on the yield, composition and porous structure of carbon products obtained for carbonization of modified wood has been studied.It was shown that the aspen wood is subjected to a more profound transformation in the processes of explosive autohydrolysis and carbonation than the birch wood.The yield of the carbon product increases up to 40 %, and the specific surface area rises by two orders for carbonation of autohydrolyzed wood modified by ZnCl 2 regardless on the nature of wood.It was shown that the processes of intensive thermal decomposition of the modified wood are carried out at lower temperatures, as compared to the initial wood.