Enhanced mercury adsorption in activated carbons from biomass materials and waste tires

Agricultural residues and waste tires constitute an important source of precursors for activated carbon production. Activated carbons offer a potential tool for mercury emissions control. In this work, pine and oak wood, olive seed and tire wastes have been used for the preparation of activated carbons, in order to be examined for their mercury removal capacity. In the case of activated carbons produced from pine/oak woods and tire wastes, a two stage physical activation procedure was applied. Activated carbons derived from olive seeds were prepared by chemical activation using KOH. Pore structure of the samples was characterized by N₂ and CO₂ adsorption, while TPD-IR experiments were performed in order to determine surface oxygen groups. Hg° adsorption experiments were realized in a bench-scale adsorption unit consisting of a fixed-bed reactor. The influence of activation technique and conditions on the resulted activated carbon properties was examined. The effects of pore structure and surface chemistry of activated carbons were also investigated. Activated carbons produced from olive seeds with chemical activation possessed the highest BET surface area with well-developed micropore structure, and the highest Hg° adsorptive capacity. Oxygen surface functional groups (mainly lactones) seem to be involved in Hg° adsorption mechanism.     

微波辐射烟杆CO_2活化制取活性炭及孔结构表征

以烟杆为原料,CO2为活化剂,采用微波辐射法制备了活性炭。采用正交实验研究了CO2流量、活化时间和微波功率对活性炭得率和吸附性能的影响,得到了最佳工艺条件。该工艺将常规加热方法的炭化和活化简化为一个过程,产品的碘吸附值超过了国家一级品标准,所需要加热时间仅为传统法的1/10,同时测定了该活性炭的氮吸附等温线,并通过BET、H-K方程和密度函数理论表征了活性炭的孔结构,结果表明该活性炭为微孔孔型,最后采用电子探针和透射电镜分析了活性炭的微观结构,结果与氮吸附测定的较为一致。     

Coniferous Wood Sawdust-based Activated Carbons as Adsorbents Obtained with the Use of Microwave Radiation

Activated carbons were prepared by physical and direct activation of sawdust pellets coming from coniferous trees, with the use of microwave radiation. The activated carbons obtained were used as adsorbents for the removal of methylene blue (MB) from aqueous solutions. Liquid-phase adsorption experiments were conducted and the maximum adsorption capacity of each activated carbon sample was determined. The effects of activation procedure as well as adsorption tests parameters i.e., temperature, pH, initial methylene blue concentration, and contact time on the sorption capacity of each activated carbon were investigated. The kinetic models for MB adsorption on the activated carbons were also studied. Better fit to the experimental data was obtained with the Langmuir isotherm than Freundlich one, for all samples.     

废活性炭微波加热法再生研究进展

论述了微波加热技术的特点,初步探讨了微波加热再生废活性炭的原理,综述了国内外微波再生废活性炭的研究进展。与传统加热技术相比较,微波加热再生废活性炭具有耗时短、产品质量好、能耗低、污染少等优点,并且微波加热再生废活性炭产品有更发达的孔隙结构,吸附性能较好。影响微波再生废活性炭的因素依次是微波功率、加热时间、活性炭吸附量。展望了微波加热再生废活性炭的发展方向。     

Activated carbon from cherry stones

Fruit stones constitute a significant waste disposal problem for the fruit-processing industry. High-quality activated carbon can be produced from waste cherry stones: the activated carbon is low in impurities and has an adsorption capacity that compares favorably with commercial activated carbons. Activation at 800°C in steam for 2–3 hours, following initial carbonization, produces an activated carbon in about 10% yield (by weight) of the initial cherry stone. The activated carbons produced have surface areas (CO₂ adsorption) as high as 1200 m²/g and CCl₄ numbers of 70–80. Activation in carbon dioxide requires higher temperatures (900°C) and gives a carbon of slightly lower activity. Carbon from the hull, or hard outer portion of the fruit stone, provides essentially all of the adsorption capacity; the inner kernel does not form a microporous material. The hull structure is dominated by 0.4-micron pores which facilitate access to internal microporosity. This structure requires that the carbon be ground to less than 75 micron particles to achieve reasonable adsorption rates.     

Surface modified granular activated carbon for enhancement of nickel adsorption from aqueous solution

Coal-based granular activated carbon was modified with acetates of sodium, potassium and lithium at concentrations of 10 and 15% and used as adsorbents to explore the adsorption mechanism of nickel ion in aqueous solution. Acetate treatment reduced surface area and pore volume of the activated carbons, but the adsorption amount of Ni(II) on the modified activated carbons (MAC) was greater than that on the virgin activated carbon. The adsorption depended on pH of the solution with an optimum at 4.5 and the adsorbed nickel could be fully desorbed by using 0.05M HCl solution. The maximum adsorption capacity of nickel ion on Li (15 wt%) modified activated carbon was 151.3 mg/g and the adsorption isotherm follows Langmuir, Sips, and Redlich-Peterson isotherm models better than the Freundlich isotherm model. The kinetic data was better fitted by a non-linear form of the pseudo-first order than the pseudo-second order, but the difference between two kinetic models was small.     

微波辐照巴旦杏核壳制备活性炭及其吸附性能研究

以巴旦杏核壳为原料,采用微波辐照法制备活性炭。考察了活化条件对活性炭得率和吸附性能的影响。研究结果表明,在活化剂种类、活化剂用量、微波功率和辐照时间4个因素中,微波辐照时间对活性炭质量指标影响最大,延长时间可以提高其产品的得率和吸附性能。巴旦杏核壳基质活性炭的最佳制备工艺：巴旦杏核壳10g,固液比1：3（g：mL）,磷酸质量分数40％、浸溃24h,微波功率640W、活化时间16min。在此条件下制得的活性炭的亚甲基蓝吸附值为231．5mg/g,活性炭得率为56．8％。二级动力学模型能很好的描述巴旦杏核壳活性炭对亚甲基蓝大分子的吸附动力学过程。吸附符合Freundlich吸附等温线方程。     

活性炭表面热氧化对其吸附二苯并噻吩性能影响

本文主要研究活性炭表面氧化对其吸附二苯并噻吩性能的影响。将活性炭在不同低温下氧化制得表面氧化活性炭，用静态吸附法进行了二苯并噻吩在初始及氧化活性炭上的吸附等温线，应用Langmuir方程对吸附等温线进行拟合，用漫反射红外谱（DRIFTS）表征活性炭表面含氧基团，用Boehm滴定测定活性炭表面官能团含量，讨论了活性炭表面化学性质对其吸附二苯并噻吩的影响。结果表明：活性炭表面酸性含氧基团对二苯并噻吩的吸附有重要影响，酸性含氧基团越多，其吸附量越大。低温气相氧化活性炭提高了活性炭表面酸性含氧基团，提高了其对二苯并噻吩的吸附。氧化温度越高，其表面含氧基团含量越多，其对二苯并噻吩的吸附量也越大。Langmuir吸附等温线可适用于描述二苯并噻吩在活性炭表面上的吸附。     

微波辐射-KOH活化兰炭粉制备活性炭

研究了以兰炭粉为原料,KOH为活化剂,采用微波辐射法制备活性炭的可行性。探讨了微波功率、碱炭质量比和活化时间对活性炭吸附性能的影响。同时采用美国ASAP-2020吸附仪测定了所制备活性炭的N2吸附脱附等温线和孔径分布,采用红外光谱分析了样品的表面官能团。结果表明:微波功率为700 W,碱炭质量比为3,活化时间为15 min工艺条件下制得的活性炭碘吸附值为694.5 mg/g,比表面积为513.62 m2/g,总孔容为0.510 3 cm3/g,平均孔径为3.973 8 nm,该活性炭为中孔型。以兰炭粉为原料,传统加热和微波加热制备的活性炭红外光谱图其峰形基本一致,只是峰强不同。     

Adsorption of lead on activated carbons from olive stones

Studies on the adsorption of lead on activated carbons from aqueous solutions are described. Olive stones have been used as raw material to prepare the activated carbon samples. The porous texture and the chemical nature of the surface of the carbon samples were studied. The adsorption yield as a function of pH, salinity and presence of different cations has been investigated. The results obtained by using these activated carbons have been compared with those corresponding to a commercial activated carbon. All samples show a high adsorption capacity against lead ions.     

石油焦制备活性炭工艺条件的优化及其孔结构表征

以独山子石油焦为原料,以氯化锌为活化剂,采用微波加热方式制备活性炭,通过碘吸附、苯吸附等考察所制活性炭的吸附性能,并对活性炭的制备工艺条件进行筛选和优化。结果表明：微波加热法制备活性炭时,最佳工艺条件是：氯化锌、石油焦、煤沥青的质量比为1．5：7．5：1,微波功率1300W,辐照时间6min。所得样品比表面积1095．7m^2／g,碘吸附值673．7mg／g,苯吸附值781．1mg／g,强度20．3N。通过与电炉法对比发现,微波加热和电加热制备的活性炭孔结构不同,微波法制备的活性炭在比表面积、孔径分布等方面优于电炉法制备的活性炭。     

Conventional and microwave-heated oxygen pulsing techniques on metal-doped activated carbons

Conventional and microwave-heated oxygen pulsing techniques on metal-doped activated carbons to achieve a controlled meso/micropore structure were investigated. The gas pulsing experiments consisted of repeated cycles. Each cycle consists of an oxidising stage, under O₂/Ar atmosphere and constant temperature, and a burn-off stage, under N₂ atmosphere at variable temperature (heating and cooling). The porosity of the carbons was analysed by nitrogen adsorption at ?196 °C. Two different activated carbons, Cu-doped BPL (BPL-Cu) and ASC, were used as raw materials. The commercial activated carbon ASC showed higher reactivity towards O₂, due to the catalytic effect of the metals (mainly, Cu and Cr) that are on the carbon surface and their better dispersion. After several pulses, ASC underwent a moderate increase in the micropore volume and a significant increase in mesopore volume. BPL-Cu showed a higher increase in microporosity than mesoporosity, giving rise to a meso/micropore volume ratio lower than that of the original BPL-Cu. Oxygen pulsing technique was carried out in a conventional furnace and in a microwave oven. Conventional and microwave-heated oxygen pulsing on ASC yielded similar textural development. However, the time required under microwave heating was remarkably reduced respect to conventional heating (around 2.5 times less), which suggests that microwave-heated oxygen pulsing technique would be an interesting alternative to conventional activation.     

Comparison of textile dyeing effluent adsorption on commercial activated carbon and activated carbon prepared from olive stone by ZnCl2 activation

Adsorption of Remazol Red B on activated carbon prepared from olive stone and commercial activated carbon from aqueous solutions was compared. Different activating agent (ZnCl₂) amounts and adsorbent particle size were studied to optimize adsorbent surface area. The adsorptive property of commercial activated carbon and activated carbon prepared from olive stone were investigated in terms of adsorbent dose, temperature, equilibrium time and pH. Then the obtained results were compared for all parameters, According to the results, the equilibrium time, optimum pH, adsorbent dosage were found 60 min, pH < 3–4 and 1.0 g/50 ml respectively. Lower adsorption capacity for RRB on activated carbon prepared from olive stone was found. The kinetic data for both adsorbents supports pseudo-second order model (r² > 0.99) and intra-particle model (r² > 0.95) but the first order kinetic model did not adequately fit to the experimental values (r² < 0.76). The equilibrium adsorption data were interpreted using Langmuir and Freundlich models. The adsorption of Remazol Red B was better represented by the Langmuir equation. In addition, the thermodynamic parameters, standard free energy (ΔG°), standard enthalpy (ΔH°), standard entropy (ΔS°) of the adsorption process were calculated for both adsorbents. To reveal the adsorptive characteristics of the produced active carbon, surface area measurements were carried out and structural analysis was performed using SEM-EDS.     

Adsorption Equilibrium and Fixed Bed Adsorption of Aniline onto Polymeric Resin and Activated Carbons

The adsorption of aniline on several adsorbents including resin Sepabeads SP206 and activated carbons Jacobi and Norit, has been studied. The influence of temperature in the adsorption capacity was obtained by batch method. Langmuir and Bi-Langmuir were the best models to represent the equilibrium sorption isotherm of aniline in the resin and the activated carbons, respectively. Higher adsorption capacity was obtained for both activated carbons than that for resin, being the maximum adsorption capacity three times higher. Nevertheless, the aniline adsorption capacity onto resin is much more influenced by the temperature.

The dynamic behavior of aniline onto Sepabeads SP206 resin and activated carbon Jacobi was also studied. Breakthroughs and reverse breakthroughs were carried out in a laboratory-scale column to study the adsorbent regeneration. A Linear Driving Force (LDF) model was used to predict the experiments for the two adsorbents. The results demonstrated that Sepabeads SP206 resin can be easily regenerated by using water, while around 50% of aniline remains adsorbed in the activated carbon. Furthermore, after 4 cycles of adsorption-desorption, only around 60% of aniline can be recovered from the activated carbon Jacobi; this behavior can be explained by the aniline that is chemically adsorbed into the activated carbon.     

Effect of textural property of coconut shell-based activated carbon on desorption activation energy of benzothiophene

In this work, the effect of the textural property of activated carbons on desorption activation energy and adsorption capacity for benzothiophene (BT) was investigated. BET surface areas and the textural parameters of three kinds of the activated carbons, namely SY-6, SY-13 and SY-19, were measured with an ASAP 2010 instrument. The desorption activation energies of BT on the activated carbons were determined by temperature-programmed desorption (TPD). Static adsorption experiments were carried out to determine the isotherms of BT on the activated carbons. The influence of the textural property of the activated carbons on desorption activation energy and the adsorption capacity for BT was discussed. Results showed that the BET surface areas of the activated carbons, SY-6, SY-13 and SY-19 were 1106, 1070 and 689 m²g^-1, respectively, and their average pore diameters were 1.96, 2.58 and 2.16 nm, respectively. The TPD results indicated that the desorption activation energy of BT on the activated carbons, SY-6, SY-19 and SY-13 were 58.84, 53.02 and 42.57 KJ/mol, respectively. The isotherms showed that the amount of BT adsorbed on the activated carbons followed the order of SY-6 > SY-19 > SY-13. The smaller the average pore diameter of the activated carbon, the stronger its adsorption for BT and the higher the activation energy required for BT desorption on its surface. The Freundlich adsorption isotherm model can be properly used to formulate the adsorption behavior of BT on the activated carbons.     

Comparison between microwave and conventional thermal reactivations of spent activated carbon generated from vinyl acetate synthesis

Microwave and traditional thermal reactivations of activated carbon (AC) used as catalyst support in vinyl acetate synthesis have been investigated. Experiments have been carried out by using a single mode microwave device (MW) operating at 2450 MHz and a conventional electric furnace (CF) under steam and CO₂ atmosphere, respectively. The surface properties of the spent AC and the reactivated samples were characterized by means of N₂ adsorption and SEM, and compared the effects of different heating mechanisms and activating agents on the adsorption capacities and pore structures of the reactivated AC. These results indicated that the AC obtained by microwave irradiation showed higher adsorption capacities for iodine, methylene blue (MB) and acetate acid, higher BET surface areas and mesoporosity than those obtained by conventional thermal heating. The reactivated samples activated by steam had a narrower and more extensive microporosity as well as higher BET than those activated by carbon dioxide under the same heating equipment. From the results, it was concluded that microwave heating combined with steam as an activating agent could remarkably increase the reactivating efficiency compared to the traditional thermal heating.     

微波辐射亚麻屑制活性炭的研究

以亚麻屑为原料,采用微波辐射氯化锌法制备活性炭。研究了浸渍时间、氯化锌浓度、微波功率和辐射时间等因素对活性炭吸附性能和得率的影响。确定了用亚麻屑制备活性炭的最佳工艺条件:亚麻屑15g、浸渍时间24h、氯化锌浓度20%、微波功率600W、辐射时间12min。在该工艺条件下制备的活性炭其碘吸附值为1071.3mg/g、亚甲基蓝吸附值165mL/g、得率可达37.1%,均超过了国家标准一级产品的指标,且该工艺所需炭化活化时间为传统方法的1/30。     

竹制活性炭处理酸性染料废水吸附等温线模型的误差分析(英文)

High surface area activated carbons were produced by thermal activation of waste bamboo scaffolding with phosphoric acid.Single component equilibrium dye adsorption was conducted on the carbons produced and compared with a commercially available carbon.Two acid dyes with different molecular sizes,namely Acid Yellow 117(AY117) and Acid Blue 25(AB25),were used to evaluate the adsorption capacity of the produced carbons.It was found that the dye with smaller molecular size,AB 25,was readily adsorbed onto the produced carbon,nearly three times higher than a commercially available carbon,while the larger size dye,AY117,showed little adsorption.The experimental data were analyzed using isotherm equations including Langmuir,Freundlich,Tempkin,Toth,Redlich-Peterson and Sips equations.The equilibrium data were then analyzed using five different non-linear error analysis methods.     

Preparation of activated carbon from Jatropha hull with microwave heating: Optimization using response surface methodology

Preparation of activated carbon has been attempted using steam as the activating agent by microwave heating from Jatropha hull. The response surface methodology (RSM) technique is utilized to optimize the process conditions. The influences of the three major parameters, activation temperature, activation time and steam flow rate on the properties of activated carbon are investigated using analysis of variance (ANOVA), to identify the significant parameters. The optimum conditions for the preparation of activated carbon has been identified to be an activation temperature of 900 °C, activation time of 19 min and steam flow rate of 5 g/min. The optimum conditions resulted in an activated carbon with an iodine number of 988 mg/g and a yield of 16.56% respectively, while the BET surface area evaluated using nitrogen adsorption isotherm correspond to 1350 m²/g, with the pore volume of 1.07 cm³/g. The activated carbon is hetero porous with the micropore volume contributing to 40.8%.