UTILIZATION OF AGRICULTURAL WASTE CORN COB FOR THE PREPARATION OF CARBON ADSORBENT

In the present study, a series of activated carbons were prepared from agricultural waste corn cob by chemical and physical activations with potassium hydroxide (KOH)/potassium carbonate (K₂CO₃) and carbon dioxide (CO₂). The effect of process variables such as impregnation ratio, impregnation time, activation temperature and soaking time of CO₂ was studied in order to relate these preparation parameters with the physical properties of final carbon products. The resulting activated carbons were characterized by nitrogen adsorption[ch-[chdesorption isotherms at 77 K. The surface areas and pore volumes of carbons were estimated by the BET equation, the Langmuir equation and the t-plot method. Under the experimental conditions investigated, the main parameters in the activation of corn cob were found to be the impregnation ratio and activation temperature. The soaking time of CO₂ is another important variable, which had a strong effect on the pore volume development. The BET surface area and total pore volume were as large as about 2000 m²/g and about 1.0 cm³/g, respectively. This study showed that the activation of agricultural waste corn cob with KOH/K₂CO₃ and CO₂ was suitable for the preparation of large-surface-area activated carbons.     

Characterization of activated carbons prepared from sugarcane bagasse by ZnCl2 activation.

Activated carbons were prepared from the agricultural waste of sugarcane bagasse by the chemical activation with zinc chloride (ZnCl2) at the activation temperature of 500 degrees C with soaking time of 0.5 hour. The influence of activation parameters on the final carbon products was examined by varying the impregnation ratio (i.e., mass ratio of added ZnCl2 to bagasse) and bagasse size. The physical properties of carbon products were characterized by nitrogen adsorption/desorption isotherms (at 77 K) and helium displacement method. The surface area and pore volume of carbons were thus obtained by the BET equation and t-plot method. Also, the particle density and porosity of carbons were estimated by the total pore volume and true density. The increases of the values of surface area and pore volume are approximately proportional to the impregnation ratio. The microporous carbon product with the BET surface area of 905 m2/g and total pore volume of 0.44 cm3/g was obtained in the present study. Further, the adsorption isotherms of two acid dyes from aqueous solutions onto the carbon products were performed at 30 degrees C. The results show that the adsorption isotherms of acid dyes with high molecular weight or large molecular size on the microporous adsorbents of activated carbons are plateau forms, indicating multilayer adsorptions, which may be attributed to the steric hindrance of the adsorbate molecules.     

Production of activated carbons from pyrolysis of waste tires impregnated with potassium hydroxide

Activated carbons were produced from waste tires using a chemical activation method. The carbon production process consisted of potassium hydroxide (KOH) impregnation followed by pyrolysis in N2 at 600-900 degrees C for 0-2 hr. The activation method can produce carbons with a surface area (SA) and total pore volume as high as 470 m2/g and 0.57 cm3/g, respectively. The influence of different parameters during chemical activation, such as pyrolysis temperature, holding time, and KOH/tire ratio, on the carbon yield and the surface characteristics was explored, and the optimum preparation conditions were recommended. The pore volume of the resulting carbons generally increases with the extent of carbon gasified by KOH and its derivatives, whereas the SA increases with degree of gasification to reach a maximum value, and then decreases upon further gasification.     

Production of Activated Carbons from Pyrolysis of Waste Tires Impregnated with Potassium Hydroxide

ABSTRACT

Activated carbons were produced from waste tires using a chemical activation method. The carbon production process consisted of potassium hydroxide (KOH) impregnation followed by pyrolysis in N₂ at 600-900 °C for 0-2 hr. The activation method can produce carbons with a surface area (SA) and total pore volume as high as 470 m²/g and 0.57 cm³/g, respectively. The influence of different parameters during chemical activation, such as pyrolysis temperature, holding time, and KOH/tire ratio, on the carbon yield and the surface characteristics was explored, and the optimum preparation conditions were recommended. The pore volume of the resulting carbons generally increases with the extent of carbon gasified by KOH and its derivatives, whereas the SA increases with degree of gasification to reach a maximum value, and then decreases upon further gasification.     

一次性废竹筷制备活性炭及热解过程分析

以一次性废竹筷为原料,K2CO3为活化剂,通过炭化和活化2步制备活性炭。采用全自动比表面和孔径分布分析仪、傅里叶变换红外光谱仪（FTIR）、X射线衍射分析仪（XRD）对样品的孔隙性质、表面官能团和晶相变化进行了表征,并研究了活性炭对亚甲基蓝的吸附等温线。利用热重分析（TGA）对活性炭的制备过程进行了研究,并用Coats-Redfern法确定了热解反应活化能和反应模型。结果表明,活性炭的比表面积为1 262 m2·g-1,总孔体积为0.624 cm3·g-1。K2CO3活化可导致热解炭的脂肪烃侧链断裂,并发生脱氢缩聚,其石墨微晶的轴向（100）堆积被破坏,径向（002）芳香环网状结构则更为有序。活性炭对亚甲基蓝的吸附过程符合Langmuir模型,最大吸附量为336 mg·g-1。废竹筷的2个主要热解阶段符合一维扩散模型和二级反应模型,其热解反应活化能分别为76.23和104.24 kJ·mol-1;活化过程中残存木质素的热解可由一维扩散模型描述,K2CO3浸渍使其热解反应活化能降低了44.28 kJ·mol-1。     

Preparation and characterization of activated carbons from tobacco stem by chemical activation

Activated carbons were prepared from tobacco stem by chemical activation using potassium hydroxide (KOH), potassium carbonate (K₂CO₃), and zinc chloride (ZnCl₂). The effects of the impregnation ratio (activating agent/precursor) and activating agents on the physical and chemical properties of activated carbons were investigated. The textual structure and surface properties of activated carbons were characterized by nitrogen (N₂) adsorption isotherm, scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FT-IR), x-ray photoelectron spectroscopy (XPS), and thermogravimetry (TG). ZnCl₂, acting as a superior activating agent compared to the others, produced much more porosity. The maximum specific surface area reached 1347 m²/g, obtained by ZnCl₂ activation with an impregnation ratio of 4.0. Moreover, ZnCl₂ activation yielded products with an excellent thermostability, attributed to different activation mechanisms. Various oxygen functions were detected on the activated carbon surface, and hydroxyl and ester groups were found to be in the majority.

Implications: Tobacco stem, the residue from cigarette manufacturing, is usually discarded as waste, leading to serious resource waste and environmental problems. This study provides an effective utilization available for this solid residue by using it as the starting material in the preparation of activated carbon with chemical activation. Activated carbons with high specific area and various surface functions have been prepared, and the effects of the amount and type of activating agents on the physical and chemical properties of activated carbon were investigated as well.     

Adsorption of acid dye onto activated carbons prepared from agricultural waste bagasse by ZnCl2 activation

A series of activated carbons were prepared from agricultural waste sugarcane bagasse by chemical activation with zinc chloride (ZnCl2) as an activating agent at 500 degrees C and 0.5 h soaking time. The Langmuir surface area and total pore volume were used to estimate the average pore diameter of the carbon products. The values of the surface area and pore volume increased linearly with increase in the impregnation ratio (IR) up to 100 wt%. The adsorption capacities of the derived adsorbents for Acid Orange 10 were measured at 20 degrees C and 40 degrees C to gain further insights into the acidic surface oxides of the adsorbent from the results of Fourier transform infrared (FTIR) spectroscopy analysis and pH measurement. Adsorption isotherms of the acid dye on adsorbents prepared were determined and correlated with common isotherm equations. It was found that the Langmuir model appears to fit the isotherm data better than the Freundlich model. The physical properties of these adsorbents were consistent with the parameters obtained from the isotherm equations.     

Preparation of Activated Carbons from Raw and Biotreated Agricultural Residues for Removal of Volatile Organic Compounds

ABSTRACT

Activated carbons with diverse physical and chemical properties were produced from four agriculture residues, including raw barley husk, biotreated barley husk, rice husk, and pistachio shell. Results showed that with adequate steam activation (30–90 min, 50% H₂O_(g)/50% N₂), activated carbons with surface areas between 360 and 950 m² g^?1 were developed. Further increases in the activation time destroyed the pore structure of activated carbons, which resulted in a decrease in the surface area and pore volume. Biotreated agricultural residues were found to be suitable precursors for producing mesoporous activated carbons. The oxygen content of activated carbons increased with increasing activation time. Results from X-ray photoelectron spectroscopy examination further suggested that H₂O molecules react with the carbon surface, enhancing the deconvoluted peak area of carbonyl and carboxyl groups. Equilibrium adsorption of toluene indicated that the adsorption capacities increased with an increase in the inlet toluene concentration and a decrease in temperature. The adsorption isotherms were successfully fitted with Freundlich, Langmuir, and Dubinin– Radushkevich equations. Activated carbons derived from agricultural residues appear to be more applicable to adsorb volatile organic compounds at a low concentration and high-temperature environment.

IMPLICATIONS This paper presents data on the preparation of activated carbons from agricultural residues, especially the waste from biohydrogen generation. Experimental results indicated that with proper carbonization and steam activation, activated carbons with diverse characteristics can be produced from various agricultural residues. The resulting activated carbons effectively adsorb toluene. This work provides useful information for reutilization of these agricultural residues, helping in decreasing the cost of biological waste treatment and providing a cost-effective alternative to conventional adsorbent production and application.     

KOH活化花生壳生物质炭对亚甲基蓝吸附性能研究

以花生壳生物质炭(P-BC)为原料,KOH为活化剂,采用化学活化法制得活化生物质炭(K-BC),通过考察对亚甲基蓝的吸附性能,研究了花生壳生物质炭的最佳活化条件,并利用N2吸附-脱附实验、SEM等对最佳活化条件下的生物质炭进行表征.结果表明,K-BC活化的最佳条件为碱炭比为1.5:1,活化温度为800℃,活化时间为90 min,此时K-BC的比表面积达到597.93 m2/g,总孔容达到0.76 cm3/g.并考察了亚甲基蓝初始浓度、pH等对K-BC吸附亚甲基蓝的影响,随着初始浓度的增加,吸附平衡时间显著延长,亚甲基蓝去除率显著降低;当pH=6时,K-BC对亚甲基蓝的吸附量最大;K-BC对亚甲基蓝的吸附动力学曲线符合伪二阶动力学模型,吸附平衡时K-BC对亚甲基蓝的吸附能力为80~149.95 mg/g.     

The removal of uranium (VI) from aqueous solutions onto activated carbon developed from grinded used tire

In this study, activated carbon was prepared from waste tire by KOH chemical activation. The pore properties including the BET surface area, pore volume, pore size distribution, and average pore diameter were characterized. BET surface area of the activated carbon was determined as 558 m²/g. The adsorption of uranium ions from the aqueous solution using this activated carbon has been investigated. Various physico-chemical parameters such as pH, initial metal ion concentration, and adsorbent dosage level and equilibrium contact time were studied by a batch method. The optimum pH for adsorption was found to be 3. The removal efficiency has also been determined for the adsorption system as a function of initial concentration. The experimental results were fitted to Langmuir, Freundlich, and Dubinin–Radushkevich (D-R) isotherm models. A comparison of best-fitting was performed using the coefficient of correlation and the Langmuir isotherm was found to well represent the measured sorption data. According to the evaluation using the Langmuir equation, the saturated monolayer sorption capacity of uranium ions onto waste tire activated carbon was 158.73 mg/g. The thermodynamic equilibrium constant and the Gibbs free energy were determined and results indicated the spontaneous nature of the adsorption process. Kinetics data were best described by pseudo-second-order model.     

Optimization of preparation process of activated carbon from chestnut burs assisted by microwave and pore structural characterization analysis

In this study, activated carbon was prepared from Chinese chestnut burs assisted by microwave irradiation with potassium hydroxide (KOH) as activator, and the process conditions were optimized employing Box-Behnken design (BBD) and response surface methodology (RSM). The optimized variables were irradiation time, impregnation time, and mass ratio of alkali-to-carbon, and the iodine adsorption value was used to evaluate the adsorption property of activated carbon. The optimal preparation conditions were determined as follows: irradiation time 17 min, impregnation time 240 min, and mass ratio of alkali-to-char 1.5:1. Meanwhile, the relatively high iodine adsorption value (1141.4 mg/g) was also obtained. Furthermore, the pore structural characterization of activated carbon was analyzed. The analyzed results showed a larger Brunauer-Emmett-Teller (BET) specific surface area (1254.5 m²/g) and a higher microporosity ratio (87.2%), a bigger total pore volume (0.6565 m³/g), but a smaller average pore size (2.093 nm), which demonstrated the obtained activated carbon possessed strong adsorption capacity and well-developed microporous structure. This research could not only establish the foundation of utilizing chestnut burs to prepare activated carbon, but also provide the basis for exploitation of Chinese chestnut by-products.

Implications: Because Chinese chestnut burs are the by-products and usually discarded upon harvesting subsequently, the utilization of chestnut burs as a potential source of activated carbon is of great profit to the chestnut processing industries.     

Preparation of sulfurized powdered activated carbon from waste tires using an innovative compositive impregnation process

The objective of this study is to develop an innovative compositive impregnation process for preparing sulfurized powdered activated carbon (PAC) from waste tires. An experimental apparatus, including a pyrolysis and activation system and a sulfur (S) impregnation system, was designed and applied to produce sulfurized PAC with a high specific surface area. Experimental tests involved the pyrolysis, activation, and sulfurization of waste tires. Waste-tire-derived PAC (WPAC) was initially produced in the pyrolysis and activation system. Experimental results indicated that the Brunauer-Emmett-Teller (BET) surface area of WPAC increased, and the average pore radius of WPAC decreased, as water feed rate and activation time increased. In this study, a conventional direct impregnation process was used to prepare the sulfurized PAC by impregnating WPAC with sodium sulfide (Na2S) solution. Furthermore, an innovative compositive impregnation process was developed and then compared with the conventional direct impregnation process. Experimental results showed that the compositive impregnation process produced the sulfurized WPAC with high BET surface area and a high S content. A maximum BET surface area of 886 m2/g and the S content of 2.61% by mass were obtained at 900 degrees C and at the S feed ratio of 2160 mg Na2S/g C. However, the direct impregnation process led to a BET surface area of sulfurized WPAC that decreased significantly as the S content increased.     

Effect of potassium hydroxide activation in the desulfurization process of activated carbon prepared by sewage sludge and corn straw

Series sludge straw–based activated carbons were prepared by sewage sludge and corn straw with potassium hydroxide (KOH) activation, and the desulfurization performance of activated carbons was studied. To obtain the best desulfurization performance, the optimum ratio between the raw materials and the activator was investigated. The results showed that when the mass ratio of sewage sludge, corn straw, and KOH was 3:7:2, the activated carbon obtained the best breakthrough and saturation sulfur sorption capacities, which were 12.38 and 5.74 times, respectively, those of samples prepared by the nonactivated raw materials. The appropriate KOH could improve the microporosity and alkaline groups, meanwhile reducing the lactone groups, which were all beneficial to desulfurization performance. The chemical adsorption process of desulfurization can be simplified to four main steps, and the main desulfurization products are elemental sulfur and sulfate.

Implications: Sewage sludge (SS) and corn straw (CS) both have great production and wide distribution and are readily available in China. Much attention has been paid on how to deal with them effectively. Based on the environment protection idea of waste treatment with waste and resource recycling, low-cost adsorbents were prepared by these processes. The proposed method can be expanded to the municipal solid waste recycling programs and renewable energy plan. Thus, proceeding with the study of preparing activated carbon by SS and straw as a carbon-based dry desulfurization agent could obtain huge social, economic, and environmental benefits.     

稻壳活性炭对噻吩类硫化物的吸附

以稻壳为原料、采用KOH浸渍和高温活化法制备稻壳活性炭,研究其对模拟油中噻吩类硫化物的吸附脱除性能,利用环己烯、甲苯为竞争组分,研究燃油中烯烃、芳烃对稻壳活性炭吸附脱硫性能的影响。通过静态吸附实验分别考察炭化温度、KOH浸渍质量分数及活化温度对稻壳活性炭吸附脱硫性能的影响,从而确定最佳制备条件。采用Langmuir和Freundlich吸附模型对稻壳活性炭的吸附噻吩进行拟合,用准n阶和修正准n阶动力学模型进行分析。采用热重（TG）、N2吸附/脱附（BET）、扫描电镜（SEM）对样品表征,考察其受热分解状况、孔隙结构、表面形貌等特性。结果表明：在最佳制备条件下,制备的稻壳活性炭比表面积和平均孔径分别为1 207.649 m2·g-1和2.24 nm。用固定床进行动态吸附实验,得到稻壳活性炭对噻吩类硫化物的总穿透硫容为7.092 4 mg·g-1。在模拟油中加入环己烯、甲苯后,稻壳活性炭对噻吩类硫化物的穿透硫容分别下降了36.4%和63.5%,由等温吸附和动力学模拟分析得实验数据很好的符合Langmuir和修正的准n阶动力学吸附模型。     

Preparation of Sulfurized Powdered Activated Carbon from Waste Tires Using an Innovative Compositive Impregnation Process

Abstract

The objective of this study is to develop an innovative compositive impregnation process for preparing sulfurized powdered activated carbon (PAC) from waste tires. An experimental apparatus, including a pyrolysis and activation system and a sulfur (S) impregnation system, was designed and applied to produce sulfurized PAC with a high specific surface area. Experimental tests involved the pyrolysis, activation, and sulfurization of waste tires. Waste-tire-derived PAC (WPAC) was initially produced in the pyrolysis and activation system. Experimental results indicated that the Brunauer-Emmett-Teller (BET) surface area of WPAC increased, and the average pore radius of WPAC decreased, as water feed rate and activation time increased. In this study, a conventional direct impregnation process was used to prepare the sulfurized PAC by impregnating WPAC with sodium sulfide (Na₂S) solution. Furthermore, an innovative compositive impregnation process was developed and then compared with the conventional direct impregnation process. Experimental results showed that the compositive impregnation process produced the sulfurized WPAC with high BET surface area and a high S content. A maximum BET surface area of 886 m²/g and the S content of 2.61% by mass were obtained at 900°C and at the S feed ratio of 2160 mg Na₂S/g C. However, the direct impregnation process led to a BET surface area of sulfurized WPAC that decreased significantly as the S content increased.     

Preparation of activated carbons from raw and biotreated agricultural residues for removal of volatile organic compounds

Activated carbons with diverse physical and chemical properties were produced from four agriculture residues, including raw barley husk, biotreated barley husk, rice husk, and pistachio shell. Results showed that with adequate steam activation (30-90 min, 50% H2O(g),/50% N2), activated carbons with surface areas between 360 and 950 m2 g(-1) were developed. Further increases in the activation time destroyed the pore structure of activated carbons, which resulted in a decrease in the surface area and pore volume. Biotreated agricultural residues were found to be suitable precursors for producing mesoporous activated carbons. The oxygen content of activated carbons increased with increasing activation time. Results from X-ray photoelectron spectroscopy examination further suggested that H2O molecules react with the carbon surface, enhancing the deconvoluted peak area of carbonyl and carboxyl groups. Equilibrium adsorption of toluene indicated that the adsorption capacities increased with an increase in the inlet toluene concentration and a decrease in temperature. The adsorption isotherms were successfully fitted with Freundlich, Langmuir, and Dubinin-Radushkevich equations. Activated carbons derived from agricultural residues appear to be more applicable to adsorb volatile organic compounds at a low concentration and high-temperature environment.     

废棉布制备活性炭影响因素与机理研究

研究了采用磷酸活化法制备废棉布活性炭的工艺条件。研究表明,废棉布活性炭吸附能力随着磷酸浓度、浸渍时间、活化温度和活化时间的增加呈现先增加后减小的趋势。最佳制备条件为:磷酸浓度40%,浸渍时间24 h,活化温度500℃,活化时间30 min。此时制备的废棉布活性炭性能优于商品活性炭。另外,通过对最佳浓度磷酸浸渍的废棉布进行热失重分析,对磷酸活化废棉布制备活性炭机理开展了初步研究,研究表明磷酸活化废棉布制备活性炭过程分为水分蒸发阶段、炭化阶段、过渡阶段、活化阶段和煅烧阶段。     

微波法污水厂污泥制备活性炭的研究

研究了以污水厂污泥为原料、微波辐照下磷酸活化法制备污泥活性炭的工艺条件,探讨了微波功率、辐照时间以及磷酸浓度对活性炭碘值的影响.结果表明,微波功率480 W、辐照时间315 s、磷酸浓度40%～45%的条件下,制备的污泥活性炭碘值为301 mg/g,总孔孔容是0.37 mL/g,平均孔径8.8 nm,比表面积168 m2/g.将该污泥活性炭用于处理TNT红水,吸附效果良好.     

微波法污水厂污泥制备活性炭的研究

研究了以污水厂污泥为原料、微波辐照下磷酸活化法制备污泥活性炭的工艺条件,探讨了微波功率、辐照时间以及磷酸浓度对活性炭碘值的影响.结果表明,微波功率480 W、辐照时间315 s、磷酸浓度40%～45%的条件下,制备的污泥活性炭碘值为301 mg/g,总孔孔容是0.37 mL/g,平均孔径8.8 nm,比表面积168 m2/g.将该污泥活性炭用于处理TNT红水,吸附效果良好.     

磷酸低温活化蔗渣基中孔生物炭及其影响因素

以甘蔗渣为原料,磷酸为活化剂,采用低温活化法制备蔗渣基中孔生物质炭.采用L9(34)4因素3水平正交实验,探讨制备蔗渣基中孔生物质炭的实验方案与工艺条件;分析了浸渍比、烘干时间、活化温度、活化时间在3个不同水平下,对蔗渣基生物质炭碘吸附值、亚甲基蓝吸附值的影响.结果表明,对蔗渣基生物质炭孔结构和得率影响最大的因素是活化温度,影响最小的因素是烘干时间;实验范围内,提高活化温度有利于材料中孔结构的形成;最佳条件下制备的蔗渣基生物质炭其低温氮气等温吸附线有明显的回滞环, BET比表面积和总孔容分别为939 m2/g和1.35 mL/g,中孔占总孔容比例为89%,亚甲基蓝吸附值高达240 mg/g,远高于木质净水用活性炭国家一级标准(135 mg/g),属于典型的中孔炭.