Surface and Hydrogen Sorption Characteristics of Various Activated Carbons Developed from Rat Coal Mine （Zonguldak） and Anthracite

Activated carbon samples were developed from coal samples obtained from a coal mine, rat （Zonguldak, Turkey） and anthracite （Siberia, Russia）, applying pyrolysis in a temperature range of 600-900 ℃ under N2 flow, and activation using chemical agents such as KOH, NH4Cl, ZnCl2 at 650 ℃. Nitrogen adsorption at low temperature （77 K） was used to characterize the activated carbon samples, and their pore structure properties including pore volume, pore diameter and pore size distribution were determined by means of the t-plots and DFT methods. The surface area values were higher for rat coal samples than for anthracite one, and for the rat coal samples treated with KOH ＋ NH4Cl ＋ ZnCl2 at 650 °C [Rat650（2）] there are highest surface area and total pore volume, 315.6 m2·g^-1 and 0.156 ml·g^-1, respectively. The highest value of the hydrogen sorption capacity was found as 0.71% （by mass） for the rat coal sample obtained by KOH ＋ ZnCl2 treatment at 650 °C [Rat650（1）].

Preparation of magnetically separable mesoporous activated carbons from brown coal with Fe3O4

Magnetically separable mesoporous activated carbon was prepared from brown coal in the presence of Fe3O4 as a bi-functional additive.Magnetic activated carbon(MAC)was characterized by lowtemperature nitrogen adsorption,scanning electron microscopy(SEM),transmission electron microscopy(TEM),X-ray diffraction(XRD),X-ray photoelectron spectroscopy(XPS)and vibrating sample magnetometry(VSM).The evolution behaviors and transition mechanism of Fe3O4 during the preparation of MAC were investigated.The results show that prepared MAC with 6 wt%Fe3O4 addition having a specific surface area and mesopore ratio of 370 m^2·g^-1 and 55.7%,which meet the requirements of adsorption application and magnetic recovery.Highly dispersed iron-containing aggregates with the size of 0.1 lm in the MAC were observed.During the preparation of MAC,Fe3O4 could enhance the escape of volatiles during the carbonization.Fe3O4 could also accelerate burning off the carbon wall during activation,which leads to enlarging micropore size,then resulting in the generation of mesopore and macropore.As a result,a part of Fe3O4 converted into FeO,FeOOH,a-Fe,c-Fe,Fe2SiO4 and compound of Aluminum-iron-silicon.The prepared activated carbon,which was magnetized by both of residual Fe3O4,reduced a-Fe and c-Fe,can be easily separated from the original solution by external magnetic field.

Preparation of mesoporous activated carbons from coal liquefaction residue for methane decomposition

Mesoporous activated carbons were prepared from direct coal liquefaction residue （CLR） by KOH activation method, and the experiments were carried out to investigate the effects of KOH/CLR ratio, solvent for mixing the CLR and KOH, and carbonization procedure on the resultant carbon texture and catalytic activity for catalytic methane decomposition （CMD）. The results showed that optimal KOH/CLR ratio of 2 ： 1; solvent with higher solubility to KOH or the CLR, and an appropriate carbonization procedure are conductive to improving the carbon pore structure and catalytic activity for CMD. The resultant mesoporous carbons show higher and more stable activity than microporous carbons. Additionally, the relationship between the carbon textural properties and the catalytic activity for CMD was also discussed.

Additivity of pore structural parameters of granular activated carbons derived from different coals and their blends

A series of granular activated carbons （GACs） were prepared by briquetting method from Chinese coals of different ranks and their blends, with coal pitch as the binder. Pore structural parameters including BET specific surface area （SBEr）, total pore volume （Vr） and average pore diameter （da） were measured and cal- culated as well as process parameters such as yield of char （CY） and burn-off （B）. The relationship between the pore structural parameters of the GAC from coal blend （BC-GAC） and the ones of the GACs from corresponding single coals （SC-GACs） was analyzed, in which an index, the relative error （δ）, was presented to define the bias between fitted values and experimental values of these parameters of the BC-GACs. The results show that the BC-GAC keeps qualitatively the pore structural features of the SC-GACs; as concerned as the quantitative relationship, the pore structural parameters of the BC-GAC from coal blend consisting of non-caking coals can be obtained by adding proportionally the pore structural parameters of the SC-GACs with a less than 10%. Meanwhile, for the BC-GAC from coal blend containing weak caking bituminous coal, the δ increases up to 25% and the experimental pore size distribution differs greatly from the fitted one.

Preparation of Activated Carbons from Mongolian Lignite and Sub-Bituminous Coal by a Physical Method

Preparation of activated carbons by a physical activation technique is performed using the methods of coal pyrolysis and gasification at different temperatures. As increasing pyrolysis temperature from 520°C to 700°C, the yield of activated carbons from the Khuut (KH) sub-bituminous coal is lowered, and amount of micropores increases gradually;however there is no development of mesopores by the KH coal pyrolysis. When the KH coal has a small loss during its physical activation due to difficulty and inactivity of its macrostructure decomposition, the smaller porosity is developed in the resulting carbons. The Aduunchuluun (AD) lignite is activated by pyrolysis and gasification at the highest temperature of 700°C in the present study. It is identified that the gasification of AD lignite develops well a porous structure with the highest surface area of 522 m2/g which is three times larger than that (155 m2/g) of the activated carbon produced by pyrolysis of the same lignite. The IR and SEM analysis confirm a significant difference in chemical and structural changes between the AD, KH raw coals and corresponding carbon samples in the physical activation processes.

Systematic physicochemical characterization,carbon balance and cost of production analyses of activated carbons derived from(Co)-HTC of coal discards and sewage sludge for hydrogen storage applications

Hydrothermal carbonization(HTC)technologies for producing value-added carbonaceous material(hydrochar)from coal waste and sewage sludge(SS)waste might be a long-term recycling strategy for hydrogen storage applications,cutting disposal costs and solving waste disposal difficulties.In this study,hydrochars(HC)with high carbon content were produced using a combination of optimal HTC(HTC and Co-HTC)and chemical activation of coal tailings(CT),coal slurry(CS),and a mixture of coal discard and sewage sludge(CB).At 850℃and 800℃,respectively,with a KOH/HC ratio of 4:1 and a residence time of 135 min,activated carbons(ACs)with the highest Brunauer–Emmett–Teller specific surface(S_(BET))of 2299.25 m^(2)g^(−1)and 2243.57 m^(2)g^(−1)were obtained.The hydrogen adsorption capability of the produced ACs was further studied using gas adsorption isotherms at 77 K.At 35 bars,the values of hydrogen adsorbed onto AC-HCT(AC obtained from HTC of CT),AC-HCS(AC obtained from HTC of CS),and AC-HCB(AC obtained from HTC of the blending of coal discard(CD)and SS)were approximately 6.12%,6.8%,and 6.57%in weight,respectively.Furthermore,the cost of producing synthetic ACs for hydrogen storage is equivalent to the cost of commercial carbons.Furthermore,the high proportion of carbon retained(>70%)in ACs synthesized by HTC from CD and SS precursors should restrict their potential carbon emissions.

Effects of coal rank, Fe_3O_4 amounts and activation temperature on the preparation and characteristics of magnetic activated carbon

Coal-based Magnetic Activated Carbons （CMAC＇s） were prepared from three representative coal samples of various ranks： Baorigele lignite from Inner Mongolia; Datong bitumite from Shanxi province; and Taixi anthracite from Ningxia Hui Auto- nomous Region. Fe3O4 was used as a magnetic additive. A nitrogen-adsorption analyzer was used to determine the specific surface area and pore structure of the resulting activated carbons. The adsorption capacity was assessed by the adsorption of iodine and methylene blue. X-ray diffraction was used to measure the evolution behavior of Fe304 during the preparation process. Magnetic properties were characterized with a vibrating-sample magnetometer. The effect of the activation temperature on the performance of CMAC＇s was also studied. The results show that, compared to Baorigele lignite and Taixi anthracite, the Datong bitumite is more appropriate for the preparation of CMAC＇s with a high specific surface area, an advanced pore structure and suitable magnetic properties. Fe304 can effectively enhance the magnetic properties and control the pore structure by increasing the ratio of meso- pores. An addition of 6.0% Fe304 and an activation temperature of 880 ℃ produced a CMAC having a specific surface area, an iodine adsorption, a methylene blue adsorption and a specific saturation magnetization of 1152.0 m2/g, 1216.7 mg/g, 229.5 mg/g and 4.623 emu/g, respectively. The coal used to prepare this specimen was Datong bitumite.

Preparation of activated carbons from mesophase pitch and their electrochemical properties

The influences of molar ratio of KOH to C and activated temperature on the pore structure and electrochemical property of porous activated carbon from mesophase pitch activated by KOH were investigated. The surface areas and the pore structures of activated carbons were analyzed by nitrogen adsorption, and the electrochemical properties of the activated carbons were studied using two-electrode capacitors in organic electrolyte. The results indicate that the maximum surface area of 3 190 m2/g is obtained at molar ratio of KOH to C of 5:1, the maximum specific capacitance of 122 F/g is attained at molar ratio of KOH to C of 4:1, and 800 ℃ is the proper temperature to obtain the maximum surface area and capacitance.

Characteristics of Chemical Modified Activated Carbons from Bamboo Scaffolding

In this study, bamboo scaffolding was used to produce activated carbon by carbonization at 600 ℃ and 900 ℃with the purge of nitrogen. The 600 ℃ char was then further modified chemically by acids and alkalis by reflux for 6 hours. The produced chars were then characterized by nitrogen adsorption isotherm, He pyncometry, pH, elemental analysis and Boehm titration. For most of the chemically modified carbons, the micropore surface areas and volumes have increased compared with the 600 ~C char, while the mesopore surface areas and volumes slightly decreased, which may have been due to the dissolving of some of the permeated inorganic matter and oxidizing deposited carbon that blocks the pore openings. For the acidic modified carbons, larger amounts of acidic groups were present in the carbons after being activated by phosphoric acid, phosphoric acid furth, er treated with 2 mol-L-1nitric-acid, and calcium hydroxide. Although carbon treated with 2 mol.L-1 and 5 mol·L-1 nitric acid also produced high acidity, the surface areas and pore volumes were relatively low, due to the destruction of pores by nitric acid oxidation. The reduction of porosity may impair the adsorption capacity.

Optimization of Preparation Conditions of Activated Carbons Based on the Shells of Ricinodendron heudoltii

The purpose of this work is to prepare better activated carbons from the shells of Ricinodendron Heudelotii by chemical activation with sulfuric acid (H2SO4) and sodium hydroxide (NaOH). The process was optimized by a full factorial design (2K) based on the analysis of the external specific surface area of sixteen (16) activated carbons prepared according to the parameters of the preparation. This active analysis reveals that under the preparation conditions, good carbons are obtained for a sodium hydroxide concentration equal to 1 M, an impregnation time of 24 h and carbonization at 500˚C for 1 h. The external specific surface of this carbon is 358 m2 • g-1. The characteristics of this prepared carbon are as follows: a pH at zero point charge (pHpzc) of 8.2, a predominantly amorphous structure, a basic character and a low ash content (4.2%). It also has surface functions;the lactonic and carbonyl groups (C=O) at 1600 cm-1 and the carboxylate groups (O-H or C-O) at 1340 cm-1.

Conversion of Malaysian low-rank coal to mesoporous activated carbon:Structure characterization and adsorption properties

Malaysian Selantik low-rank coal(SC)was used as a precursor to prepare a form of mesoporous activated carbon(SC-AC)with greater surface area(SA)via a microwave induced KOH-activation method.The characteristics of the SC and SC-AC were evaluated by the iodine number,ash content,bulk density,and moisture content The structure and surface characterization was carried out using pore structure analysis(BET),scanning electron microscopy with energy dispersive X-ray spectroscopy(SEM-EDX),X-ray diffraction(XRD),Fourier Transform Infrared(FTIR),elemental analysis(CHNS),thermogravimetric analysis(TGA),and determination of the point of zero charge(pH(PZC)).These results signify a mesoporous structure of SC-AC with an increase of ca.1160 times(BET SA=1094.3 m^2·g^-1)as compared with raw SC without activation(BET SA=1.23 m^2·g^-1).The adsorptive properties of the SC-AC with methylene blue(MB)was carried out at variable adsorbent dose(0.2-1.6 g·L^-1),solution pH(2-12),initial MB concentrations(25-400 mg·L^-1),and contact time(0-290 min)using batch mode operation.The kinetic profiles follow pseudo-second order kinetics and the equilibrium uptake of MB conforms to the Langmuir model with a maximum monolayer adsorption capacity of 491.7 mg g^-1 at 303 K.Thermodynamic functions revealed a spontaneous endothermic adsorption process.The mechanism of adsorption included mainly electrostatic attractions,hydrogen bonding interaction,andπ-πstacking interaction.This work shows that Malaysian Selantik low-rank coal is a promising precursor for the production of low-cost and efficient mesoporous activated carbon with substantive surface area.

CO2-hierarchical activated carbon prepared from coal gasification residue: Adsorption equilibrium, isotherm, kinetic and thermodynamic studies for methylene blue removal

Mineral matter in a residue(RC G)from coal gasification(CG)was removed by two-stage acid leaching.Hierarchical activated carbon(HAC)was prepared by activating RC Gwith CO2.The performance of HAC on removing methylene blue(MB)from an aqueous solution was investigated.HAC was characterized by N2 adsorption–desorption isotherm,Fourier transform infrared spectroscopy,and scanning electron microscopy.The results show that HAC exhibits hierarchical pore structure with high specific surface area(862.76 m2·g-1)and total pore volume(0.684 cm3·g-1),and abundant organic functional groups.The adsorption equilibrium data of MB on HAC are best fitted to the Redlich-Peterson.The kinetic data show that the pseudo-first-order model is more suitable at low MB concentration,while the advantages of the pseudo-second-orderand the Elovich models are more obvious as the concentration increases.According to the thermodynamic parameters,the HAC-MB adsorption process is spontaneous and endothermic.

PREPARATION AND CHARACTERIZATION OF POLYMER-BASED SPHERICAL ACTIVATED CARBONS

A series of spherical activated carbons(SACs)with different pore structures were prepared from chloromethylated polydivinylbenzene by ZnCl_2 activation.The effects of activation temperature and retention time on the yield and textural properties of the resulting SACs were studied.All the SACs are generated with high yield of above 65% and exhibit relatively high mesopore fraction(me%)of 35.7%-43.6% compared with conventional activated carbons.The sample zlc28 prepared at 800℃for 2 h has the largest BET surf...

Experimental evaluation of activated carbon derived from South Africa discard coal for natural gas storage

Lacking in literature is the use of discard coal to produce activated carbon and in its subsequent use in the storage of natural gas. In this study, the characterization and gas storage evaluation of a largely porous activated carbon with large surface area synthesized from discard coal were investigated. Discard coals are waste material generated from coal beneficiation process. In developing the activated carbon, chemical activation route with the use of KOH reagent was applied. The effects of KOH/discard coal weight ratio (1:1, 2.5:1, 4:1), temperature (400-800 ℃) and particle size (0.15-0.25 mm, 0.25-0.5 mm, 0.5-1 mm) on the adsorptive properties of the activated carbon were methodically evaluated and optimized using response surface methodology. The synthesized activated carbon was characterized using BET, SEM/EDS, and XRD. The results showed that for each activation process, the surface area and pore volume of the resulting activated carbon increased with increased temperature and KOH/discard coal weight ratio. The maximum surface area of 1826.41 m2/g, pore volume of 1.252 cm^3/g and pore size of 2.77 nm were obtained at carbonization temperature of 800 ℃ and KOH/discard coal weight ratio of 4:1. Methane and nitrogen adsorption data at high pressure were fitted to Toth isotherm model with a predictive accuracy of about 99%. Adsorption parameters using the Toth model provides useful information in the design of adsorbed natural gas storage system. According to the requirements of adsorbent desired for natural gas storage, it could be stated that the synthesized activated carbon could well be applied for natural gas storage.

Adsorption of residual amine collector HAY from aqueous solution by refined carbon from coal fly ash and activated carbon

Refined carbon(RC) derived from coal fly ash(CFA) as well as powdered activated carbon(PAC) was investigated as adsorbent to remove residual amine collector HAY from aqueous solution.The RC and PAC were characterized by scanning electron microscopy(SEM),surface area measurement,Zeta potential measurement and Fourier transform infrared(FTIR) spectroscopy.The effect factors and mechanisms of HAY adsorption onto RC and PAC were studied in detail.The results show that the experimental kinetic data agree well with the pseudo second-order equation,and the Langmuir isotherm model is found to be more appropriate to explicate the experimental equilibrium isotherm results than the Freundlich model.The adsorption capacities of PAC and RC increase with pH.It is found that alkaline condition is conducive to the adsorption of HAY onto PAC and RC and the adsorption efficiency of RC is close to PAC at pH near 11.Zeta potential variation of adsorbents suggests that HAY generates electrostatic adsorption onto RC and PAC.FTIR analysis shows that the adsorption is dominantly of a physical process.The Box-Behnken design optimization conditions of process are RC 1 g/L,pH 11,temperature 302 K and initial HAY concentration 100 mg/L.Under these conditions,the measured adsorption ratio and adsorption capacity are 87.91%and 87.91 mg/g,respectively.Thus,the RC is considered to be a potential adsorbent for the removal of residual amine from aqueous solution.

Effect of Pre-oxidation on the Properties of Crushed Bituminous Coal and Activated Carbon Prepared Therefrom

The influence of a pre-oxidation process on the chemical properties of crushed bituminous coal and on adsorption properties of the subsequently formed char and activated carbon is discussed in this paper. Datong bituminous coal samples sized 6 mm were oxidized at different temperatures and for different times and then carbonized and activated by steam to obtain activated carbons. A Uniform Design method was used to arrange the experiments,IR and adsorption experiments were used to characterize these oxidized coals,chars and activated carbon samples. The results show that the carboxyl group disappeared and α-CH2 groups joined to alkenes decreased dramatically but the carbonyl group clearly increased in the coal sample oxidized at 543 K; The chemical composition of coal samples oxidized at lower temperature is different from that of coal oxidized at 543 K. Oxidizing coal samples at higher temperatures for a short time or at lower temperatures for a longer time resulted in activated carbon samples that tended toward the same adsorption properties: Iodine number 1100 mg/g and Methylene blue value 252 mg/g. The yield of activated carbon obtained from the pre-oxidized coal is 10% higher than the yield from parent coal but the activated carbons have the same adsorption properties.

Preparation of Activated Carbon Functional Ceramics From Coal Pitch

The influences of different impregnation temperatures,pre-oxidation,carbonization temperatures and activation conditions on the iodine value and carbon deviations was discussed.SEM,EDS,and BET techniques were used to investigate the microstructures and properties of materials.Results showed that activated carbon functional ceramic exhibited excellent comprehensive properties when porous ceramics adsorbed the coal pitch at 150 ℃ for 0.5 h,oxidized at 420 ℃ for 1.0 h,and carbonizated at 700 ℃ for 1.0 h and then activated by using KOH（20wt%） as agent at 800 ℃ for 1.0 h,as confirmed by the high iodine value（162.6 mg/g） and high specific surface area（83.5 m2/g）.

Performance of water-based foams affected by chemical inhibitors to retard spontaneous combustion of coal

The micelle generating process of the sodium dodecyl sulfate(SDS) solution with the addition of chemical inhibitors was elucidated using phase separation model, and the descending order of the capacity for the selected chemical inhibitors to reduce the critical micelle concentrations of the solution are Mg Cl_2, Ca Cl_2,NH_4HCO_3 and NH_4Cl. The data to quantitatively describe the foam decay process, including foaming ratio,foam life and decay behaviors, was obtained by pressure measuring system. The results indicate that chemical inhibitors can improve the solution foamability. The capacity of the inhibitors to enhance the solution foamability is sorted as NH_4 Cl, NH_4HCO_3, Mg Cl2 and Ca Cl_2 which can distinctly improve the foam stability as well. The capacity of the inhibitors to enhance the SDS foam stability can be arranged as Mg Cl_2, NH_4 Cl, NH_4HCO_3 and Ca Cl_2. It is observed that the gravity drainage plays a leading role in the increase of proportion of diffusion drainage. The oxidation dynamic parameters of the coal samples treated by inhibition foams were investigated using thermal analysis technique, and their synergistic effects on inhibiting coal oxidation were explored.

Preparation of activated carbon with low ash content and high specific surface area from coal in the presence of KOH

An activated carbon with ash content less than 10% and specific surface area more than 1 600 m 2 /g was prepared from coal and the effect of K containing compounds in preparation of coal based activated carbon was investigated in detail in this paper. KOH was used in co carbonization with coal, changes in graphitic crystallites in chars derived from carbonization of coal with and without KOH were analyzed by X ray diffraction (XRD) technique, activation rates of chars with different contents of K containing compounds were deduced, and resulting activated carbons were characterized by nitrogen adsorption isotherms at 77 K and iodine numbers. The results showed that the addition of KOH to the coal before carbonization can realize the intensive removal of inorganic matters from chars under mild conditions, especially the efficient removal of dispersive quartz, an extremely difficult separated mineral component in other processes else. Apart from this, KOH demonstrates a favorable effect in control over coal carbonization with the goal to form nongraphitizable isotropic carbon precursor, which is a necessary prerequisite for the formation and development of micro pores. However, the K containing compounds such as K 2 CO 3 and K 2 O remaining in chars after carbonization catalyze the reaction between carbon and steam in activation, which leads to the formation of macro pores. In the end an innovative method, in which KOH is added to coal before carbonization and K containing compounds are removed by acid washing after carbonization, was proposed for the synthesis of quality coal based activated carbon.

Study on Ultra-Low Ash Activated Carbon from Coal

A new technique to deash activated carbons from coal, which uses a chemical additive together with acidwashing, is developed. By using the technique, it can decrease the ash of activated carbons to 1. 0%~3. 5%, improve the absorbability, increase the activation rate, and reduce the production cost.