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.

High surface area biocarbon monoliths for methane storage

New energy sources that reduce the volume of harmful gases such as SO_(x)and NO_(x)released into the atmosphere are in constant development.Natural gas,primarily made up of methane,is being widely used as one reliable energy source for heating and electricity generation due to its high combustion value.Currently,natural gas accounts for a large portion of electricity generation and chemical feedstock in manufacturing plastics and other commercially important organic chemicals.In the near future,natural gas will be widely used as a fuel for vehicles.Therefore,a practical storage device for its storage and transportation is very beneficial to the deployment of natural gas as an energy source for new technologies.In this tutorial review,biomaterials-based carbon monoliths(CMs),one kind of carbonaceous material,was reviewed as an adsorbent for natural gas(methane)adsorption and storage.

Highly reversible lead-carbon battery anode with lead grafting on thecarbon surface

A novel C/Pb composite has been successfully prepared by electmless plating to reduce the hydrogenevolution and achieve the high reversibility of the anode of lead-carbon battery （LCB）. The depositedlead on the surface of C/Pb composite was found to be uniform and adherent to carbon surface. Becauselead has been stuck on the surface of C/Pb composite, the embedded structure suppresses the hydrogenevolution of lead-carbon anode and strengthens the connection between carbon additive and sponge lead.Compared with the blank anode, the lead-carbon anode with C/Pb composite displays excellent charge-discharge reversibility, which is attributed to the good connection between carbon additives and leadthat has been stuck on the surface of C/Pb composite during the preparation process. The addition of CIPb composite maintains a solid anode structure with high specific surface area and power volume, andthereby, it plays a significant role in the highly reversible lead-carbon anode.

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.

Effect of activated carbon and electrolyte on properties of supercapacitor

Effect of activated carbon and electrolyte on electrochemical properties of organic supercapacitor was investigated. The results show that specific surface area and mesoporosity of activated carbon influence specific capacitance. If specific surface area is larger and mesoporosity is higher, the specific capacitance will become bigger. Specific surface area influences resistance of carbon electrode and consequently influences power property and pore size distribution. If specific surface area is smaller and mesoporosity is higher, the power property will become better. Ash influences leakage current and electrochemical cycling stability. If ash content is lower, the performance will become better. The properties of supercapacitor highly depend on the electrolyte. The compatibility of electrolyte and activated carbon is a determining factor of supercapacitor’s working voltage. LiPF6/(EC+EMC+DMC) is inappropriate for double layer capacitor. MeEt3NPF4/PC has higher specific capacitance than Et4NPF4/PC because methyl’s electronegativity value is lower than ethyl and MeEt3N+ has more positive charges and stronger polarizability than Et4N+ when an ethyl is substituted by methyl.

Catalytic Pyrolyses of Rayon and the Effect on Activated Carbon Fiber

The catalytic pyrolyses of rayon have been studied respectively by thermo-gravimetric analysis (TGA) when rayon was treated with phosphoric acid (PA), three ammonium phosphate salts and ammonium sulfate (AS). The air is favorable to the catalysis of dibasic ammonium phosphate (DAP), but not to those of ADP, PA, AP, and AS obviously. It is put forward that a peak’s shape character can be described with the ratio of height to half-height-width (H/W /2) of the peak on a differential thermo-gravimetric (DTG) curve. A flat cracking peak, presenting a more moderate dehydration reaction, has a smaller ratio and could lead to higher carbonization and activation yields. The experimental results prove this view. According to expectation, the order of catalysis is: DAP≥ADP>PA> APAS no catalyst.

Optimal Electrochemical Performances of CO_2 Activated Carbon Aerogels for Supercapacitors

Activated carbon aerogels（ACAs） derived from sol-gel polycondensation of resorcinol （R） and formaldehyde （F） were pyrolyzed under Ar flow and activated in CO2 atmosphere. The morphology of ACAs was characterized by scanning electron microscopy （SEM） and the structural properties were determined by N2 adsorption at 77 K. The results show that ACAs have a typical three-dimensional nanonetwork structure composing of cross-linking of carbon nanoparticles. The specific surface area and the total pore volume remarkably increase with increasing activation time while the previous porous structure still remains. The specific capacitance of the 950-10-ACA electrode can reach up to 212.3 F/g in 6 mol/L KOH electrolyte. The results of constant-current charge-discharge testing indicate that the ACAs electrodes present fast charge- discharge rate and long cycle life （about 98% capacitance retained after 3000 charge-discharge cycles at 1.25 mA/cm2）. Lower internal resistances can be achieved for 950-10-ACA electrode in KOH electrolyte. Our investigations are very important to improve the wettability and electrochemical performance of electrode for supercapacitors.

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.

Removal of Dyes from Wastewater by Adsorption onto Activated Carbon: Mini Review

Nowadays, wastewater from dyeing industries became a challenging issue in the world. Researchers have reported several techniques to treat those effluents based on their projects. Adsorption is the most common method because of cheap, simple and effective method. In this work, activated carbon was used for dye adsorption purpose. This adsorbent has high surface area and high porosity to remove dye. This review highlighted some important results of the last few years regarding the use of activated carbon in wastewater treatment. Research findings supported that adsorption process is spontaneous in nature. Adsorption data confirmed Langmuir model, indicating the chemisorption occurred.

A new preparation process of coal-based magnetically activated carbon

Fe/C-based magnetically activated carbon(MAC) was obtained by carbonizing and activating its precursor, that was prepared by co-precipitation of anthracite coal impregnated in ferric chloride solution. The effect of the concentrations of FeCl3 and pH of solution on BET surface area, pore volume and magnetic properties of the MAC was studied by BET N2 adsorption and VSM method. The results indicated that the magnetization of MAC gradually increases with increasing concentration of FeCl3 and pH value of solution, and BET surface area was inclined to fluctuation. The largest BET surface area and magnetization of MAC were 1327.5 m2/g and 35.56 emu/g, respectively. The form of magnetic matter in the magnetically activated carbon was mainly Fe3C by X-ray powder diffraction(XRD) and magnetic attraction test.

A comparative study of the pore characteristics and phenol adsorption performance of activated carbons prepared from oil-palm shell wastes by steam and combined steam-chemical activation

Oil-palm shell wastes were successfully converted into useful activated carbons in a systematic and novel approach by optimizing the pyrolysis conditions and subsequent steam activation conditions to maximize the BET surface area.The optimal activation conditions were a steam flow rate of 1.13 kg/h,hold time of 1.5 h and temperature of 950℃,yielding BET areas of 1432.94 and 1382.95 m^(2)/g for nitrogen-pyrolyzed and vacuumpyrolyzed chars,respectively.In steam-chemical activation,one-step activation of oil-palm shell in steam with potassium carbonate(K_(2)CO_(3)),sodium carbonate(Na_(2)CO_(3))or potassium chloride(KCl)was conducted,resulting in BET area output order of shell/K_(2)CO_(3)(710.56 m^(2)/g)>shell/KCl(498.55 m^(2)/g)>shell(366.7 m^(2)/g)>shell/Na_(2)CO_(3)(326.62 m^(2)/g).This study reported the first use of KCl and Na_(2)CO_(3)as chemical reagents in one-step steam-chemical activation of biomass.KCl-activated carbon exhibited retardation of tar formation property,resulting in better pore development than pure steam activated carbon.Phenol adsorption of activated carbon is not only a function of the BET surface area but also the type of pyrolysis used prior to physical activation.Activated carbon(BET area of 1192.29 m^(2)/g)pyrolyzed under vacuum could adsorb 87%more phenol than that pyrolyzed in nitrogen flow which had a higher BET area of 1432.94 m^(2)/g.Phenol adsorption capacities of activated carbons are:shell pyrolyzed under vacuum(275.5 mg/g)>shell pyrolyzed in N_(2)flow(147.1 mg/g)>shell/K_(2)CO_(3)(145.7 mg/g)>shell without pyrolysis(12.1 mg/g).These activated carbons would be highly suitable in industry processes to remove phenolic contaminants.

Fibrous activated alumina prepared through phase transformation using dawsonite as a template

Fibrous activated alumina is widely applied in catalysts,adsorbents,and composite materials.This work presents a green approach in preparing the fibrous activated Al_(2)O_(3) with high purity and specific surface area through multistep phase transformation of aluminum-bearing substances using intermediate dawsonite as a template.Thermodynamic calculations and experimental results show that increasing the concentration of Na_(2)CO_(3) and(NH_(4))_(2)CO_(3) is remarkably beneficial to the formation of dawsonite and ammonium aluminum carbonate hydroxide,respectively.Based on determination of dissolution and precipitation mechanism,the ultrafine granular gibbsite is converted to the uniform fibrous dawsonite with a ratio of length to diameter over 50,and the fibrous dawsonite changes into the long fibrous ammonium aluminum carbonate hydroxide with a ratio of length to diameter is about 80 in above 70 g/L(NH_(4))_(2)CO_(3) solution.Furthermore,the activated alumina remains fibrous morphology after roasting ammonium aluminum carbonate hydroxide at a slow heating rate,plentiful open mesopore and weak aggregation of particles,which contributes to the high specific surface area of 159.37 m^(2)/g at 1273 K for the activated alumina.The complete transformation of dawsonite to ammonium aluminum carbonate hydroxide and high specific surface area contribute to the purity of the activated fibrous alumina above 99.9%with low Na and Fe content.

Impact of hydrolysis on surface area and energy storage applications of activated carbons produced from corn fiber and soy hulls

Complete utilization of lignocellulosic biomass through the creation of value-added coproducts is one of the key strategies of the Bioenergy Technologies Office(BETO)for the cost-effective production of biofuels and biochemicals.A green approach to producing lightweight and high specific surface area(SSA)activated carbons(ACs)from sustainable biomass sources is of great interest to producers and users of energy devices such as batteries and supercapacitors.While direct conversion from biomass has been studied extensively,AC with relatively high surface areas can be produced more cost-effectively when leveraged as a co-product from a biorefinery.In this paper,we discuss the production of high specific surface area activated carbons from residual fiber(fiber remaining after extraction of C5-sugars)generated as part of a C5 biorefinery.The surface,morphological characteristics using SEM and TEM,and energy storage behavior of ACs produced using the C5 extracted residual fiber were evaluated in the present study.The ACs produced from the residual fiber delivered an order of magnitude higher surface area than the one directly from corn pericarp fiber and soy hulls.The surface area of the ACs produced from pre-hydrolysis DDG was only 10 m^(2)/g compared to 689 m^(2)/g for soy hulls whereas after hydrolysis these values increased significantly(DDG:1700 m^(2)/g and soy hulls:1300 m^(2)/g).TEM images indicated high exfoliation,explaining the change in surface area values.Under the same current density(500 mA/g)the cycling performance of the ACs increased as the surface area increased significantly.

稻草秸秆-煤基压块活性炭的制备及工艺优化

为降低压块破碎活性炭的制备成本,以稻草秸秆炭和大同不黏煤为主要原料,利用配煤工艺,经过成型、炭化、H_(2)O_((g))-CO_(2)联合活化成型炭制备压块破碎活性炭。采用碘吸附法、亚甲蓝吸附法以及BET、FTIR和Boehm滴定方法测试和表征不同条件下制备的压块破碎活性炭。实验结果表明,加入适量稻草秸秆炭和H_(2)O_((g))-CO_(2)联合活化对活性炭的碘吸附值和亚甲蓝吸附值均有明显提升作用。Boehm滴定结果表明,活性炭具有丰富的酸性和碱性官能团。当活化温度为900℃、活化时间为2.5 h、H_(2)O_((g))和CO_(2)流量比为2时,制备的活性炭的碘吸附值、亚甲蓝吸附值和比表面积分别达到790 mg/g、262 mg/g和809 m^(2)/g。

有机胺改性树脂基球形活性炭对二氧化碳的吸附行为

以球形结构的固废离子交换树脂为原料,经CO_(2)活化、酸洗处理制得具有较高比表面积和较大中孔孔容的树脂基球形活性炭(HRSAC),然后在其表面负载聚乙烯亚胺(PEI)制得吸附材料PEI-HRSAC。系统考察了PEI负载量和吸附温度对CO_(2)吸附性能的影响,结果表明,在活化温度为950℃、活化时间为1 h的最佳活化工艺条件下,所制得的树脂基球形活性炭经酸洗处理后其比表面积为1365 m^(2)/g,中孔孔容为2.04 cm^(3)/g,中孔孔径主要分布在10~40 nm;PEI-HRSAC吸附材料对CO_(2)的吸附性能随吸附温度和PEI负载量的升高先增大后减小;当PEI负载量为65%、吸附温度为75℃时,PEI-HRSAC吸附材料对CO_(2)的吸附量最高,约为4.09 mmol/g,在经过4次循环吸/脱附后吸附量仍保持在较高水平(3.66 mmol/g)。

高表面活性炭制备工艺的优化

为解决化学活化法制备高表面活性炭成本高、能耗大的问题,在对高表面活性炭制备工艺简单概述的基础上,结合实践生产对当前活化比条件下的生产工艺参数进行调试;为达到降低能耗和生产成本的目的对活化比参数以及活化剂添加时间点进行优化,最终达到产品比表面积等指标满足要求的基础上降低生产成本的目的。

活性炭二次活化工艺研究进展

活性炭二次活化是指对已经完成活化的活性炭进行再活化的过程。活性炭二次活化技术作为一种活性炭孔隙调控手段,在合适的工艺条件下,可以使活性炭的孔隙结构更为发达,并且使孔径分布更为集中,从而赋予活性炭特异性功能。综述了二次活化工艺在活性炭孔隙调控方面的研究进展及应用途径,并对其未来的应用及发展方向进行展望,为高性能活性炭的开发和应用提供参考。

活性炭负载锌催化剂的制备及其处理煤化工废水的试验研究

为实现煤化工高盐废水水质处理效能的提升,以宁夏生产的煤制活性炭为载体,采用直接浸渍法、沉淀-煅烧法2种负载方法,选取Zn元素作为催化剂的活性组分,制备了用于臭氧氧化降解工艺用催化剂,考察了催化剂对宁夏宁东地区煤化工高盐废水中COD去除情况的探究。结果表明:将活性炭与浓度为0.4 mol/L的氯化锌溶液按照m(活性炭)∶V(溶液)=1∶3的比例混合,完全沉淀后,在氮气环境保护下,在恒定300℃的温度下煅烧2 h,制得活性组分为氧化锌的ZnO/AC催化剂,其比表面积为1063.45 m2/g,COD去除率高达71.7%,处理后废水中Zn^(2+)质量浓度增加99.8882 mg/L,高比表面积有利于发挥物理吸附与化学催化的协同作用,提高活性炭基催化剂的催化性能。该臭氧催化剂催化效果显著,可用于煤化工高盐废水中有机物的去除。

科学研究成果与物理化学实验的融合——溶液法测定棉秸秆活性炭比表面积

在“新工科”建设背景下,探索科学研究成果与《物理化学实验》课程教学相融合的实验教学模式改革,将科研实验“生物质活性炭的制备”融入“溶液吸附法测定固体比表面积”实验。实验教学中引导学生探索利用农业废弃物“新疆阿克苏长绒棉秸秆”制备活性炭并测定其比表面积,同时考察吸附温度对吸附平衡常数K的影响,得到该吸附反应的吸附热力学函数。将科学研究与物理化学实验相融合,把验证型实验改造成创新性、综合性实验,增强学生的创新能力和科学素养的培育,促进应用型人才培养质量提升。

One-step synthesis of robust carbon nanotube foams with ultrahigh surface area for high-performance lithium ion battery

A novel three-dimensional(3D) carbon nanotube foams(CNTF) with ultrahigh specific surface area have been fabricated through a unique but facile one-step synthesis by using CO_2 as both carbon source and activating agent. The activation temperature and time have been adjusted, and the best sample demonstrates a specific surface area of 1959.8 m^2 g^(–1) and a total pore volume of 3.23 cm^3 g^(–1). A reversible capacity of about 870 mAhg^(–1) is maintained at 50 mAg^(–1) when the CNTF used as cathode materials. Meanwhile, the capacity is as large as 320 mAhg^(–1) at the current density of 2 A g^(–1) and the capacity retention is nearly 100% after 500 cycles. These excellent and highly stable battery performances should be attributed to the structural advantages of as-synthesized CNTFs generated by using a facile CO_2-assisted strategy, which may potentially be applied in large scale production of porous 3D carbon materials in the fields of energy storage and conversion.