不同孔结构对活性炭动态吸附高浓度甲苯的影响

研究不同孔结构的活性炭对于高浓度甲苯的吸附性能、吸附行为和吸附位的影响。结果表明,微孔活性炭对甲苯的吸附量随着微孔孔容的增大而增大,0.6~1.2 nm的微孔孔容和甲苯吸附量存在良好的线性正相关。当中孔孔容达到微孔孔容的0.32倍时,微孔利用率达到100%,甲苯首先吸附在微孔中,待微孔吸附饱和,吸附位向中孔转移,中孔不仅起到通道作用,同时也起到吸附作用;当中孔孔容继续增大,增加的中孔容量主要起到吸附作用,最高吸附量达565 mg·g-1,是已有研究的2.5倍。随着吸附温度升高,饱和吸附量减少,表明活性炭吸附甲苯是以物理吸附主。     

孔结构和表面化学性质对活性炭吸附性能的影响

测定了室温下3种活性炭(GAC-C、GAC-P和GAC-T)对CO2、CH4和N2的吸附性能,并对颗粒活性炭孔结构和表面化学性质进行了表征,探讨了孔结构和表面化学性质对活性炭吸附性能的影响。结果表明:由于吸附机理、孔结构、表面含氧官能团和分子极性的差异,CO2、CH4和N2在活性炭上的饱和吸附量和吸附常数的关系为CO2>CH4>N2;CH4和N2的饱和吸附量主要受活性炭微孔孔容的影响,N2和CO2饱和吸附量的差异分别是由0.572～2.0 nm的微孔和0.4～6 nm的孔引起的;CH4吸附常数主要受较大中孔和大孔影响,N2吸附常数与微孔密切相关,大孔对CO2的吸附常数影响最大。     

改性整体式活性炭净化NO

通过KOH改性整体式无烟煤活性炭,制备了NO吸附净化材料。利用SEM、EDS和N2吸附-脱附对活性炭表面形貌特性、元素组成、比表面积及孔径分布等进行表征,并分别考察了KOH溶液浓度、干燥温度、反应空速、反应温度等因素对活性炭净化NO性能的影响。结果表明,活性炭的微孔结构对NO的吸附起主要作用,NO的净化效率随空速的增加而降低,随反应温度升高先升高后降低。经20%KOH溶液改性,30℃干燥的活性炭材料具有较丰富的微孔结构和孔容,在30℃和空速15 000 h-1的反应条件下,材料对NO的净化效率可达到73%左右。     

钙化物在废弃物基活性炭制备过程中的影响

研究了以城市垃圾中3种典型的固体有机废弃物——锯木屑、纸张和塑料的热解产物(分别简称木炭、纸炭和塑料热解物)为原料，水蒸气为活化剂制备废弃物基活性炭时钙化物含量对活化过程、活性炭吸附性能(以碘值表征)及其孔结构的影响。结果表明，钙化物可加快活化反应的速度，且钙化物含量在1.5％时活化反应速度即已不再随钙化物含量的增加而增加；活性炭的吸附性能则随钙化物含量的增加而减少，同时钙化物对活性炭的孔径分布基本无影响，但降低了活性炭的比表面积、微孔孔容及中孔孔容；钙化物的2种前驱体（即CaO和Ca(OH)₂）对活化过程具有相同的催化作用。     

Mn改性活性炭吸附VOCs性能

采用浸渍焙烧法对活性炭进行负载锰(Mn)改性,考察改性活性炭对甲苯、乙酸乙酯及甲苯-乙酸乙酯二元混合气体的吸附性能.研究表明,活性炭浸渍于1.0％高锰酸钾溶液改性后的吸附性能最好.对于单组分VOCs气体,改性后活性炭对甲苯和乙酸乙酯的吸附量较未改性前分别提高了12.7％和16.3％;对于二元混合VOCs气体,改性后活性炭对甲苯及乙酸乙酯的吸附量分别提高了13.1％和22.9％.BET、SEM、FTIR等分析表明,Mn改性活性炭比表面积变大和总孔容增加是改性后吸附量提高的主要原因.     

硝酸改性对不同介孔结构生物质炭铅吸附的影响

在通过成功制备2种不同介孔结构的生物质炭AC-1与AC-2的基础上,研究了硝酸氧化改性对不同介孔结构生物质炭铅吸附特性的影响与等温吸附特性。低温氮吸附测试表明,生物质炭AC-1与AC-2的微孔孔容相近,而介孔孔容相差较大,分别为0.319和0.535 cm3·g-1。改性后AC-2-HNO3的介孔孔容与表面含氧酸官能团含量均高于AC-1-HNO3。吸附数据表明,硝酸改性可增强介孔生物质炭对水中铅的吸附去除能力,特别是改性前吸附量较低的AC-2,由于具有较大的介孔孔容和介孔尺寸,经硝酸改性后对铅的吸附性能与去除率均高于微孔孔容相近的生物质炭AC-1,这表明增大介孔孔容与介孔尺寸不仅有利于在介孔炭上接枝活性吸附位,并可缩短被吸附重金属铅离子到吸附活性点的路径,增大硝酸改性生物质炭活性位点对水中铅离子的捕捉机率,从而增大改性生物质炭对铅的吸附性能。Freundlich模型能很好地描述改性前后4种炭对铅的吸附行为,说明上述生物质炭的吸附位主要是非均匀孔隙或表面。     

活性炭负载I-TiO_2对气体中甲苯的吸附

利用溶胶凝胶-浸渍烧结法制备了碘掺杂二氧化钛修饰的活性炭复合吸附剂。利用XRD、SEM、BET、Boehm滴定、亚甲蓝吸附值等手段研究了活性炭负载前后表面结构与性质。利用动态吸附实验研究了活性炭负载I-TiO_2复合材料(IT/AC)和再生IT/AC对气体中甲苯的吸附。考察了活性炭粒径、气体的流速、吸附床层高度和气体中甲苯的浓度对活性炭吸附性能的影响及甲苯在活性炭固定床上的吸附动力学。结果表明:由于介孔I-TiO_2和活性炭的协同作用,负载适量I-TiO_2对活性炭结构和吸附性能影响较小。活性炭的粒径越小、复合材料的吸附穿透点和饱和吸附量越大;气体的流速和甲苯的初始浓度越大,复合材料的吸附穿透点越小但饱和吸附量越大。YOON-NELSON模型可以预测复合材料吸附甲苯的动力学过程。     

废弃物基活性炭吸附挥发性有机污染物特性的研究

研究了废弃物基活性炭对挥发性有机污染物中的典型组分--甲苯的吸附特性.结果表明,废弃物基活性炭吸附甲苯等温线的类型系优惠型吸附等温线,表明具有良好的吸附能力;同时其吸附甲苯时穿透时间的对数与甲苯入口浓度的对数之间具有良好的线性相关性,即可由吸附高浓度甲苯时的穿透时间估算低浓度时的穿透时间;动态吸附时废弃物基活性炭的中孔对甲苯亦具有一定的吸附性能.     

低温等离子体改性活性炭纤维对不同极性苯系物的吸附

探究了不同改性时间下的活性炭纤维孔结构和表面化学性质的变化,并进一步研究了改性后的活性炭纤维对不同极性苯系物的吸附。通过BET比表面积、Boehm滴定分析、FTIR红外光谱对改性前后的活性炭纤维进行表征。结果表明,功率150 W,改性时间为30、60和90 min时,活性炭纤维烧失率随着改性时间延长而升高,分别达到16.5%、27.8%、45.5%。改性过程中,活性炭纤维比表面积和微孔孔容显著增加,有助于改善活性炭纤维吸附性能。在物理吸附和化学吸附作用下,改性活性炭纤维对邻二甲苯、间二甲苯和对二甲苯吸附性能有所提高,其中,改性90 min活性炭纤维对其吸附量分别增加了0.58、0.55和0.44 mg·mg-1。酸性含氧基团由原来的0.973 mmol·g-1增加到1.675 mmol·g-1,改性后酸性含氧官能团的增加使活性炭纤维表面极性增大,有利于对极性有机物邻、间二甲苯吸附量增加率的提高。     

活性炭纤维吸附含溴甲烷气体的性能

采用动态吸附法在25℃下,测定了3种活性炭纤维(ACF-1、ACF-2和ACF-3)对含溴甲烷气体的吸附性能和回收效果,并对活性炭纤维的孔结构进行表征.探讨了孔结构、溴甲烷浓度、气体流量、循环使用次数等因素对活性炭纤维吸附溴甲烷性能的影响.结果表明,活性炭纤维比表面积大小及0.4～0.8 nm左右的微孔数量决定了其对溴甲烷吸附性能的优劣;气体中溴甲烷的浓度的提高使活性炭纤维对溴甲烷的穿透和饱和吸附量增加,而气体流量的增加则使活性炭纤维对溴甲烷的穿透和饱和吸附量降低,但两者均使穿透和饱和吸附时间缩短;活性炭纤维多次循环使用后,对溴甲烷的吸附容量明显地降低,循环12次后达到稳定吸附,其稳定吸附值为133.5 mg/g.     

浸渍-碱性微波法载磁活性炭粉对壬基酚的吸附

利用浸渍-碱性微波法制备载磁粉末活性炭,通过等温吸附实验和动力学吸附实验,研究对比了其与原料活性炭、浸渍载铁活性炭对壬基酚的吸附性能。采用氮气吸附仪、FTIR、XRD、国标(GB/T12496.19-1999)邻菲啰啉分光度法及VSM,分别对3种样品进行了物相结构、表面官能团、铁含量及磁性能的分析,并探讨了吸附机理。结果表明,浸渍-碱性微波法载磁活性炭的总孔容及孔隙率均有较大提高;其吸附等温线符合Freundich方程,吸附动力学过程符合准二级动力学方程与孔道内扩散模型,相关系数R2均大于0.900。原活性炭经一定浓度的铁盐溶液浸渍后,铁含量由2%提高到8%。在碱性、N2气氛条件下微波后,铁系物主要存在形式为零价铁和Fe3O4,制得的载磁活性炭饱和磁化强度为1.12 emu/g。     

废活性炭微波再生新工艺的研究

提出用微波加热-二氧化碳活化法再生乙酸乙烯合成用触媒载体废活性炭工艺.采用条件实验法研究了活化时间、二氧化碳流量和微波功率对活性炭碘吸附值,亚甲基蓝吸附值和再生得率的影响,得到微波辐射加热二氧化碳活化再生乙酸乙烯用触媒载体废活性炭的最佳工艺条件为活化时间25 min,二氧化碳流量0.2 L/min,微波功率700 W.在此条件下制得的活性炭碘吸附值为1158.02 mg/g、亚甲基蓝吸附值为240 mg/g、得率为74.19%.并对活性炭进行了比表面积的测定和孔结构的分析,活性炭的比表面积为1308.13 m2/g,总孔容为0.76 mL/g.     

微波活化制备加拿大一枝黄花活性炭及对Cd（Ⅱ）的吸附

以入侵植物加拿大一枝黄花为原料,在400℃氮气保护下,直接碳化90 min后,以KOH为活化剂,微波活化的方法制备了高比表面积微孔活性炭SCAC。结果显示活性炭SCAC的表面面积为1 888 m2/g,总孔容量为0.804 cm3/g,微孔容量为0.741 cm3/g,平均孔径0.567 nm,微孔平均孔径0.488 nm。通过静态吸附实验研究了活性炭添加量、溶液初始浓度、初始pH及吸附时间对SCAC吸附Cd(Ⅱ)的影响,通过动力学方程拟合探讨了活性炭对Cd(Ⅱ)的吸附机理。结果表明,吸附平衡时间、最佳pH及活性炭添加量分别为120 min、pH>7.5及0.05 g/50 mL,活性炭SCAC吸附动力学过程符合准二级方程模型。     

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.     

Physicochemical characteristics of carbonaceous adsorbent for dioxin-like polychlorinated biphenyl adsorption

It has been known that dioxin-like polychlorinated biphenyls (DL-PCBs) are present in almost all types of environments worldwide. Activated carbon treatment has been expected for the removal of DL-PCBs because it is a simple and low-cost removal technology. In the present study, the physicochemical properties of activated carbon were investigated to identify the characteristics of 16 different types of activated carbon on adsorption properties for DL-PCBs. To accomplish this, micropore volume, and pore diameter were calculated by t-plot analysis and the mesopore volume was analyzed by the Barrett-Joyner-Halenda (BJH) method. In addition, the Brunauer-Emmett-Teller (BET) surface area, pH, metal elements, and surface acid functional groups were analyzed. Then, adsorption experiments using DL-PCB in hexane solution were conducted, and the relationship between adsorption and physicochemical properties of activated carbon was investigated. The results showed that activated carbons having a surface area of 700-1200 m² g⁻¹ and micropores with diameters of about 0.7-0.8 nm exhibited high activity for the adsorption of PCBs. The results also clearly showed that the mesopore volume of activated carbon influenced the adsorption rate and the equilibrium adsorption.     

玉米芯掺杂对污泥基活性炭性能的影响

针对以城市污水厂剩余污泥为原料制备的污泥基活性炭微孔性差、比表面积低的缺陷,将一定比例玉米芯掺杂到污泥中以期改善活性炭性质。通过对活性炭的比表面积、孔结构、碘值、表面官能团测定以及表面电镜分析,探讨了不同比例玉米芯掺杂对活性炭物理化学性质的影响,并以苯酚和硝基苯为目标物,对比考察所制活性炭对有机物的吸附性能。实验结果表明,随着玉米芯掺杂比例的提高,活性炭微孔体积及比表面积明显增大,但活性炭表面官能团种类及数量变化不明显。所制活性炭表面都以酸性基团为主。结果显示苯酚和硝基苯吸附值与活性炭表面酸性基团含量关系密切,因此,玉米芯的掺杂对苯酚和硝基苯的吸附没有明显的促进作用。     

A comparative study of anaerobically digested and undigested sewage sludges in preparation of activated carbons.

Disposal of sewage sludge is an increasingly expensive and environmentally sensitive problem throughout the world. Preparation of activated carbon from sewage sludge offers an attractive re-use alternative to the traditional disposal routes. The objective of this research work was to compare anaerobically digested sewage sludge (DS) and undigested sewage sludge (US) as source materials in the preparation of activated carbons. Prior to the preparation the properties of the two types of sewage sludges were determined and compared. Subsequently the sludge samples were activated with 5 M ZnCl2 solution and thereafter pyrolysed at heating temperature of 650 degrees C for 2 h with the heating rate of 15 degrees C/min under a nitrogen atmosphere. The produced activated carbons were characterised by surface area and porosity analysis, CHN elemental composition and ash contents determination, and aqueous phase phenol adsorption tests. The results indicate that in comparison with the DS, the US had a higher carbon content and lower ash content, and accordingly yielded a better activated carbon with a higher BET surface area, pore volume, carbon content and phenol adsorption capacity.     

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.     

Kinetic, equilibrium isotherm and thermodynamic studies of Cr(VI) adsorption onto low-cost adsorbent developed from peanut shell activated with phosphoric acid

A particular agricultural waste, peanut shell, has been used as precursor for activated carbon production by chemical activation with H₃PO₄. Unoxidized activated carbon was prepared in nitrogen atmosphere which was then heated in air at a desired temperature to get oxidized activated carbon. The prepared carbons were characterized for surface area, surface morphology, and pore volume and utilized for the removal of Cr(VI) from aqueous solution. Batch mode experiments were conducted to study the effects of pH, contact time, particle size, adsorbent dose, initial concentration of adsorbate, and temperature on the adsorption of Cr(VI). Cr(VI) adsorption was significantly dependent on solution pH, and the optimum adsorption was observed at pH 2. Pseudo-first-order, pseudo-second-order, and intraparticle diffusion models were used to analyze the kinetic data obtained at different initial Cr(VI) concentrations. The adsorption kinetic data were described very well by the pseudo-second-order model. Equilibrium isotherm data were analyzed by the Langmuir, Freundlich, and Temkin models. The results showed that the Langmuir adsorption isotherm model fitted the data better in the temperature range studied. The adsorption capacity which was found to increase with temperature showed the endothermic nature of Cr(VI) adsorption. The thermodynamic parameters, such as Gibb’s Free energy change (ΔG°), standard enthalpy change (ΔH°), and standard entropy change (ΔS°) were evaluated.     

Preparation and characterisation of activated carbon from waste tea by physical activation using steam

ABSTRACT

In this study, the feasibility of preparing activated carbon from waste tea by physical activation using steam was investigated. The effects of activation temperature on yield and pore properties of the prepared activated carbon were studied. The yield decreased with increased activation temperature owing to the decomposition of cellulose and hemicellulose. The specific surface area and pore volume of the activated carbon were estimated using the Brunauer–Emmett–Teller method, Langmuir equation, and t-plot method. The specific surface area and micropore volume increased with increases in activation temperature, as additional volatile materials were released. The specific surface area significantly decreased at first but slightly increased with increasing activation time. The maximum specific surface area reached 995 m²/g at an activation temperature of 800 °C with a water flow rate of 0.075 g/min and a constant hold time of 0.5 hr. According to the nitrogen adsorption isotherms, micropores mainly developed when the activation temperature was below 800 °C, and both micropores and mesopores developed when it was above 800 °C. The results showed that activation temperature significantly affected micropore and mesopore volumes, as well as the specific surface area of the activated carbon. Overall, waste tea was found to be an attractive raw material for producing low-cost activated carbon.

Implications: Every year, a large amount of waste tea is generated after extraction. The high carbon content of waste tea showed that it can be used as raw material to produce activated carbon. This study investigated the feasibility of preparing activated carbon from waste tea by physical activation using steam. Temperature and time were found to have clear effects on pore properties. Our proposed method and raw material are more environmentally friendly and involve low cost. Furthermore, this offers a potential solution to the problems of waste tea disposal and low-cost activated carbon production.