The purpose of the work is to evaluate the influence of topochemical oxidation (H2O2, HNO3) of carbon prepared by alkali activation of coal on porosity and ability to adsorb 4-chlorophenol (CPh), Pb(II) cations and iodine. Carbons were oxidized at the reactant/carbon ratio of 1:1 (mol/mol, 250С, 24 h). Based on nitrogen adsorption-desorption isotherms, the volumes and specific surfaces of ultramicro- (Sumi), supermicro- (Ssmi) and other pores were evaluated. Kinetics and adsorption isotherms (250С) of CPh and Pb(II) were characterized; adsorption capacities of CPh, Pb(II) and I2 were determined. The H2O2-assisted modification was found to significantly increase Sumi (from 615 to 829 m2/g), but decrease Ssmi (from 515 to 494 m2/g). The HNO3-assisted modification slightly increases Sumi (from 615 to 651 m2/g), does not change Ssmi, but forms mesopores. The CPh adsorption is best approximated by the second-order kinetics, and isotherms are well fitted with the use of the Langmuir model. The H2O2 treatment increases the CPh capacity from 314 to 389 mg/g; and the НNO3 modification significantly decreases the CPh capacity (to 189 mg/g). Modifications reduce the iodine capacity by 1.11 times (H2O2) and 2.33 times (HNO3). The Pb(II) absorption was established to describe by the second-order kinetics equation; the adsorption isotherms obey Langmuir (R20.986) and Freundlich (R20.984) models. The Pb(II) capacity slightly increases after H2O2-assisted modification (from 87 to 95 mg/g), but increases sharply (from 87 to 298 mg/g) after HNO3-assisted treatment because of significant increasing OH-acidic groups concentration.

ADSORPTION OF CHLOROPHENOL BY ACTIVATED CARBON FROM MIXTURES OF LONG FLAME COAL AND SECONDARY COKING PRODUCTS © V.А. Кucherenko, Doctor of Chemical Sciences, Ju.V. Таmarkina, PhD in Chemical Sciences, V.А. Sabierova, PhD in Chemical Sciences, I.B. Frolova, PhD in Chemical Sciences (L.M. Litvinenko Institute of Physical-Organic and Coal Chemistry of the National Academy of Sciences of Ukraine, 02160, Kyiv, Kharkiv Highway St., 50, Ukraine) The purpose of this work is to evaluate the effect of secondary coking products (SCPs) on the adsorption properties of activated carbons (ACs) from mixtures of SCP and long-flame coal D. AC samples with specific surface area SBET = 885–1173 m2/g were prepared from coal D and mixtures of coal (85 %) and SCP (15 %). Fuses (F), acid tar (AT) of the sulfate department, polymers (P) of the benzene department, cube residue (CR) and coal tar (T) were used, and the corresponding samples are designated as AC(D), AC(F), AC(AT), AC(P), AC(CR), AC(T). The adsorption capacity for 4-chlorophenol (CP) (ACP) was determined at the AC content of 1 g/L (25°C) and the CP initial concentration СCP(0) ≤ 600 mg/L. The CP concentration was determined from the solution optical density at 280 nm (Perkin-Elmer Lambda 20 spectrophotometer). The specific adsorption capacity АCP(S) (mg/m2) was determined by the ratio АCP(S) = ACP/SBET, which is proportional to the concentration of adsorption centers on the AC surface. The degree of CP extraction and the degree of surface coverage were calculated. The CP adsorption kinetics were approximated by pseudo-first order, pseudo-second order and intraparticle diffusion models. The adsorption isotherms were approximated by the Langmuir and Freundlich models. The SCP type was established to have a significant effect on the AC adsorption activity which is expressed by significant differences in the values of adsorption capacity, kinetic characteristics, and isotherm parameters. The CP adsorption kinetics was found to obey the pseudo-second order model (determination coefficient R2 ≥ 0.996) with constants varying from 2,78·10-4 g/mg·min to 6,29·10-4 g/mg·min depending on the SCP type. By comparing the calculations of the kinetics by the pseudo-first order and intraparticle diffusion models, the rate-determining stage was found to be the physical sorption and chemisorption of СP. In the range of equilibrium concentrations of СCP(е) ≤ 350 mg/l, the adsorption isotherms were approximated by the Langmuir model (R2 ≥ 0,994) better than by the Freundlich model (R2 ≥ 0,887). The calculated capacitances of the monolayer for the obtained ACs differ by a factor of ~2 and are in the interval of АCP(L) =214,3 – 414,3 mg/g, Langmuir constants are from 1,89·10-2 l/mg to 5,29·10-2 l/mg. The CP adsorption capacity was found to increase almost linearly with increasing SBET (R2 = 0.931), but the AC(AT) sample sharply drops out of this dependence and shows a 2-fold lower capacity value, which is due to the AT composition. It is determined that the CP capacity and degree of extraction increase in the series of АC(AT) < АC(D) < АC(F) < АC(T) < АC(P) < АC(CR). Judging by the effect on the AC properties, the most effective SCP is the cube residue, which maximally contributes to the formation of adsorption centers being active in relation to CP. The AC(CR) sample exhibits the highest adsorption capacity (414 mg/g), specific capacity (0.353 mg/m2), surface coverage (80.6 %), and initial CP uptake rate. During the first 5 min, AC(CR) absorbs 35.8 % of the CP total amount at CCP(0) = 600 mg/l. The values of this parameter for other samples are lower and range from 11.5 % (AC(AT)) to 29.2 % (AC(P)). Namely SPS composition is concluded to determine the set of chemical reactions forming the AC spatial framework. All SPCs (except acid tar) promote the formation of AC with a higher capacity and an increased adsorption rate, which makes their use promising for improving the ACs adsorption characteristics. Key words: long flame coal, secondary coking product, activated carbon, adsorption, 4- chlorophenol Corresponding author: Таmarkina Ju.V., e-mail: Tamarkina@nas.gov.ua

The purpose of work is to evaluate the 4-chlorophenol (CP) adsorption capacity of brown coal activated carbons (ACs) prepared at different temperature of KOH activation. ACs were obtained in three stages: 1) impregnation of coal with a KOH solution, 2) heating (4 deg/min) in argon to a given temperature t (400-800°C) and exposure for 1 h, 3) cooling, washing from KOH, drying. The samples are designated as AC(t). Based on the N2 adsorption-desorption isotherms, the ACs total pore volume (Vt, cm3/g) and specific surface area (S, m2/g) were determined. The ACs adsorption capacity were measured at 25°С, CP concentration ≤700 mg/L, АC dosage – 1 g/L. The alkaline activation temperature was found to be a key factor in forming porosity of ACs and ability to adsorb CP. The CP maximum capacity (ACP(m), mg/g) increases 6.6 times up to 307 mg/g for AC(800) having S=1142 m2/g. The specific adsorption capacity (ACP(S) = ACP(m)/S, mg/m2) sharply decreases in a sample range from AC(400) to AC(550) and weakly depends on temperature at 550-800°C. The kinetics of CP adsorption is best described by a pseudo-second order model. The rate determining stage is the interaction of CP molecules with AC surface. The CP adsorption isotherms are best described by the Langmuir model. The dependence of the ACP(m) from S can be approximated by three linear equations that probably correspond to the three regions of forming surface adsorbtion centers (AdCs). The first (S≤370 m2/g) is characterized by a small adsorption capacity increment (kS=0.103 mg/m2), but a significant (16.4 times) decrease in the specific capacity ACP(S). In the second region (S=370-770 m2/g, t=550-750°C), capacity increment is 10 times more (kS=0.985 mg/m2) and in the third region (S≥770 m2/g, t≥750°C) the increase in CP capacity is the smallest (kS=0.067 mg/m2). The thermoinitiated formation of AdCs is assumed to be not proportional to the increase in surface area, and their chemical structure and reactivity is determined by the alkaline activation temperature.

Исследовано влияние степени метаморфизма (СМ) угля (Сdaf = 80–95.2%) на выход и характеристики активированных углей (АУ), получаемых в условиях щелочной активации (800°С, 1 ч, Ar) при соотношениях КОН/уголь 1 г/г. В этих условиях способность углей образовывать пористый материал снижается в ряду метаморфизма. Максимальную активируемость проявляет уголь марки Д (Сdaf = 80%), образуя материал с SBET = 1560 м2/г, V = 0.71 см3/г, Vmi = 0.51 см3/г. Минимальная активируемость (в условиях эксперимента ) обнаружена у антрацита (Сdaf = 95.2%), образующего АУ с плохо развитой пористостью (SBET = 306 м2/г, V = 0.15 см3/г, Vmi = 0.11 см3/г).

The efficiency of thermal shock (TS), which was introduced instead of temperature-programmed heating (4 K/min) in the alkaline activation (KOH, 800°C) of fossil coals of the entire metamorphic series (С daf = 70.4–95.6%), was evaluated by comparing the porous structure characteristics of activated carbons (ACs). ACs with increased specific surface areas (by a factor of ≤2.5) and pore volumes (by a factor of ≤2.2) but with lower (by a factor of 1.07–1.30) yields were formed upon TS. The effect of TS expressed by an increase in the specific surface area ∆ S was maximal on the conversion of brown coal (∆ S = 870 m 2 /g), and it decreased to a minimum in coals with С daf = 90 ± 1% (∆ S = 109 m 2 /g) or increased on the activation of anthracites (∆ S = 496 m 2 /g). It was shown that the efficiency of TS increased with O daf , which is responsible for the formation of subnanopores, for lignites and coals. On the activation of anthracites, an additional pore formation mechanism not associated with oxygen groups was activated.

The adsorption of phenol by activated carbons obtained by the alkaline thermolysis (KOH, 800°C) of fossil coals of various degrees of metamorphism (Cdaf = 70.4–95.6%) was studied. Kinetic dependences and adsorption isotherms were obtained at initial concentrations of ≤3 mg/cm3 (25°C). The rate constants of absorption of the adsorbate, maximum and specific capacities for phenol, and their dependences on Cdaf were determined. The main processes of the interaction of phenol with surface adsorption centers are discussed.

The aim of current work is to establish the effect of coal rank (CR) on the porous structure characteristics and adsorption properties of activated carbons (ACs) prepared by potassium hydroxide activation at the same KOH/coal ratio (1.0 g/g). Coals are samples with an increasing carbon content (C daf =70.4–95.6 %), which is selected as the CR criterion. ACs were obtained in argon in three stages: 1) thermoprogrammed heating (4 degree/min) to 800 °С; 2) isothermal exposure 1 h; 3) cooling, washing from alkali and drying. Based on low-temperature (77 K) nitrogen adsorption-desorption isotherms (Micromeritics ASAP 2020), characteristics of ACs pore structures were determined: total specific volume (V t , cm 3 /g) and surface (S, m 2 /g) of adsorbing pores, total volume of meso- and macropores V me+ma , volumes of micropores (V mi ) and micropores with diameter D ≤ 1 nm (V 1nm ). For all ACs, adsorption capacities for methylene blue (MB) and iodine at 25 °C were obtained. For ACs from brown and long-flame coals, the kinetics and isotherms of MB adsorption were studied. The kinetic curves were approximated by models of intraparticle diffusion, pseudo-first and pseudo-second orders. Adsorption isotherms were calculated by Langmuir, Freundlich, Toth and Redlich – Peterson models. With increasing C daf , the V t and S values were found to vary extremely with maxima for ACs from coals with С daf = 80.0–86.4 %. The dominant contribution to the S value is made by the micropore surface S mi : its fraction S mi /S varies in the range of 94.7–99.4 %. The contribution of meso- and macropores surface is small (≤ 5.3 %), so that the adsorption properties of ACs are determined by their microporous structure. With an C daf increasing in the range of 70.4–95.6 %, the maximum adsorption capacity of MB (A m ) increases from 197 to a maximum of 241 mg/g (AC from coal with C daf =81.0 %) and then decreases to 113 mg/g for anthracite. The iodine adsorption capacity (A I ) changes according to a similar curve with a maximum, increases from 963 to 1175 mg/g, then decreases to 502 mg/g. The MB absorption rate was determined to be limited by diffusion in micropores. The adsorption kinetics is best described by the pseudo-first order model (k 1 = 0.029–0.030 min –1 , R 2 ≥ 0.976); adsorption isotherms - by the Toth model (R 2 ≥ 0.991). The use of other models gives significant (up to 86 %) deviations from experimental data. It was shown that the increase of ACs surface increases the A m and A I values but reduces the specific capacitances expressed in mg/m 2 and proportional to the concentration of surface adsorption centers (SACs). A general pattern was found for ACs from hard coal and anthracite - an increase in CR reduces the porosity and surface of ACs, decreases MB and iodine capacities but increases specific capacities (i.e., concentration of SACs) when going to AC from anthracite.

The porous structure of activated carbons (ACs) formed by fossil coals of different ranks upon alkaline activation with thermal shock (KOH, 800°C) was studied. It was established that the specific surface area of ACs decreased from 2012 to 818 m 2 /g, the pore volume decreased from 1.088 to 0.269 cm 3 /g, and the fraction of micropores linearly increased from 0.64 to 0.92 as the C daf of the test samples increased from 70.4 to 95.6%. It was shown that an increase in coal rank was responsible for the transition from a micro–mesoporous material to a nanoporous AC.

ВПЛИВ СТУПЕНЮ МЕТАМОРФІЗМУ НА ПОРУВАТУ СТРУКТУРУ ВУГІЛЛЯ, АКТИВОВАНОГО ГІДРОКСИДОМ КАЛІЮ © Ю.В.Тамаркіна, к

The solid thermolysis products (STPs) of brown coal formed upon alkaline activation with thermal shock (TS)—the rapid introduction of coal with KOH into a reactor heated to tTS ≤ 850°С—were studied. It was established that the structural fragmentation of coal (C–O and C–C bond heterolysis) dominated at tTS ≤ 400°С. With an increase in tTS to 850°С, the formation of subnanopores (≤1 nm) occurred simultaneously the growth of polyarenes and their condensation into polyarylenes, and it was limited by the diffusion of KOH (or K) and formed the final porous structure of STPs.

ОТРИМАННЯ ВИСОКОЯКІСНОГО КОКСУ З ШИХТИ З ПІДВИЩЕНОЮ УЧАСТЮ ГАЗОВОГО ВУГІЛЛЯ З ВИКОРИСТАННЯМ МЕТОДУ ЧАСТКОВОГО БРИКЕТУВАННЯ ШИХТИ.Повідомлення 2. Коксування частково-брикетованих шихт з використанням як зв'язуючого окремих вуглеводневих продуктів коксохімічного виробництва й їх сумішей з оцінкою властивостей отримуваного коксу © * О.Л

The aim of the work is to establish the effect of temperature on the porous structure characteristics of thermolysis solids (TS) prepared from brown coal (BC) during a novel process - alkaline activation with thermal shock. The BC sample is the Alexandria deposit coal, demineralized to ash content 0.5±0.1 % by treatment with HCl and HF acids. The elemental composition of the organic coal substance is as follows (%): C 70.6, H 5.9, S 3.6, N 1.9, O 18.0 (by difference). The treatment of BC with an alkaline activator (KOH) was performed by impregnation; the mass ratio of KOH/coal is 1.0. The preparation of TS was carried out in argon in three successive stages: 1) rapid introduction of the sample into the reactor, preheated to the temperature of thermal shock t TS , varied in the interval t TS = 400–800 °С; 2) isothermal holding at t TS (1 h); 3) cooling, washing from alkali compounds and drying. Based on low-temperature (77 K) nitrogen adsorption-desorption isotherms (Micromeritics ASAP 2020), there were determined pore size distributions, total volume (V t , cm 3 /g) and surface (S, m 2 /g) of adsorbing pores, volumes of macro- (V ma ) , meso- (V mе ) and micropores (V mi ), as well as micropores with a diameter of D≤1 nm (V 1nm ). The temperature dependences of these characteristics are obtained. An increase in the t TS temperature was found to result in the forming TS with increasing specific surface areas from 14.7 (400 °C) to 1947 m 2 /g (800 °C): half S is formed in a narrow interval t TS =700–800 °C. The yield of TS is reduced from 67 to 25 %. The V t value increases by a factor of 7.2 times (from 0.124 to 0.892 cm 3 /g), the volumes of mesopores and macropores increase equally - 2.9 times. The main growth of V t volume is due to micropores: their volume V mi increases from 0 to 0.547 cm 3 /g, the contribution of micropores with D≤1 nm becomes dominant (84–98 %) at t TS =600–800 °C. Pores with D≤5 nm were found to develop most dynamically under combined effect of KOH and thermal shock. Pore size distribution is characterized by three maxima: dV 1 for micropores with D≤1 nm, dV 2 for micropores with D=1–2 nm, dV 3 for mesopores with D=3–5 nm. The dependence of dV 1 on temperature t TS is strictly exponential (R 2 =0.988), that allows us to calculate the parameter E(V1), which characterizes the effect of temperature on the increase in the volume of micropores with D≤1 nm. It has the dimension of the "classical" activation energy and is 56.1 kJ/mol. As t TS values increase, the dV 2 maximum value decreases by a factor of 22, and the pore diameter shifts from 1.85 to 1.39 nm. Values of dV 3 are an order of magnitude lower than dV 1 and approximately replicate the dependence of dV 1 -t TS in the interval of 400–750 °C. An increase in the thermal-shock temperature is concluded to promote the micropores formation (especially pores with D≤1 nm), which is limited by the diffusion of the activator (KOH or K atoms as the products of K + ion reduction) within the forming three-dimensional framework of carbonaceous solids.

The development of the surface of natural coal from Donets field in the course of thermolysis with KOH was studied. The dependences of the specific surface area of coal containing 90% carbon on the activation time, temperature (400–800°C), and KOH/coal ratio (0.75–4.5 g g−1) were determined. The effect exerted on the development of the porous coal structure by low-temperature (20±2°C) oxidative modification causing formation of oxygen functional groups and reorganization of the coal three-dimensional structure was studied.

The steam activation of anthracite (C daf = 95.1%), which was preliminarily intercalated with nitric acid (140°C) and converted into anthracite nitrate (AN)—a material with intercalated nitrate anions that hypothetically formed intraskeleton ion pairs with the radical-cation polyarene fragments of coal, was studied. Activated carbons (ACs) were formed in the course of the gasification of AN with water vapor (850°C); their yield decreased with time in accordance with a first-order rate equation: the rate constant of AN gasification (0.015 min –1 ) was higher by a factor of 3 than that in the case of the initial anthracite. The specific surface area (S BET ) of AC from AN was higher by a factor of 1.5 (940 vs. 600 m 2 /g), and it developed more rapidly by a factor of 4.5–10.0; that is, the intercalation promoted the formation of a porous structure. For AN, the dependence of SBET on the degree of combustion loss (φ) was extremal with a maximum at φ = 67%, and the values of S BET = 800–1000 m 2 /g acceptable for carbon adsorbents were reached in a narrow range of φ = 60–70%. At φ > 70%, differences in the characteristics of ACs from AN and anthracite were leveled. In general, the influence of intercalation on the steam activation of anthracite was manifested in an increase in the rate of gasification (by a factor of 3), a larger specific surface area (by a factor of 1.5), and a considerable increase (by a factor of 4.5–10) in the rate of its formation.

The interaction of coke coal with nitrosylsulfuric acid NOHSO4 in acetonitrile at 20–25°C, times to 24 h, and the NOHSO4/coal ratio R ≤ 50 mmol/g was studied. The process leads to the formation of oxysulfonated coal accompanied by an increase in the weight (to 46%), a decrease (by a factor of 3.8–7.3) in the concentration of radicals, and the formation of the following O-, S-, and N-containing groups in the coal structure: carboxyl, phenol, sulfo groups (≤1.9 mmol/g), and nitroso groups (≤0.9 mmol/g). Changes in the characteristics of oxysulfonated coal under varying R and upon hydrolysis were established by IR and EPR spectroscopy and elemental analysis. The results were interpreted within the framework of a mechanism that included the formation of coal radical cations as a result of electron transfer from coal to the nitronium cation, the intercalation of the bisulfate anion into the coal structure, and the nitrosation and sulfonation of coal arenes. Side oxidation reactions occurred simultaneously with the formation of carboxyl, phenol, and quinoid groups.