外文翻译---活性炭和活化海泡石颗粒对NH3和H2S吸附性能研究.docx

附录A：英文译文及原文活性炭和活化海泡石颗粒对NH3和H2S吸附性能研究作者：Molina-Sabio, J.C. Gonz_alez, F. Rodr_guez-Reinoso光键词：A、活性炭 B、黏合 C、吸附 D、多孔性 从空气中分离气态化合物应用在很多工业领域。对于这种应用，使用活性粒进行吸附相当普遍，这种颗粒在活化之前与适当的黏合剂混合后制成。然而，使用混合后的活性炭黏土颗粒吸附象氨和硫化氢这样的极性分子，会影响吸附效果，但是海泡石作为黏合剂加入黏土颗粒后，吸附效果会变的更好。海泡石是一种纤维状硅酸盐，分子式是Si12Mg6O30(OH)4(H2O)4,由很多相互平行的纤维管状物构成1。纤维的尺寸变化范围广，但是在很多情况下，长度为10-5000nm,宽度为10-30nm，高度为5-10nm。如果在海泡石遇到水，它通过毛吸现象吸收水分，如果水继续渗透进去，就会形成松散的海泡石粉末。海泡石在自然界中广泛的存在，因此它经常作为其他材料一种黏合剂2。本课题主要研究海泡石、活性炭、和二者黏合后的颗粒作为一种吸附剂对废气中的氨和硫化氢的吸附性能的研究。实验中，准备4份活性炭颗粒，其中一份在850C蒸汽下加热活化，其他3份加入化学试剂氢氧化钾进行活化3。我们从实验样品的化学式中可以看到样品的制备过程。因此，C5-3由炭石在500C温度下烧成粉末，再加入3mol/L的氢氧化钾溶液，然后在85C下加入大量的酸进行加热酸化处理。本实验用到的海泡石原料来自西班牙的Yonclillos,并在实验的前天晚上在100C左右做烘干处理。对于吸附剂的后期制备4，是将活化过的活性炭颗粒粉碎到合适的大小，一般不低于100目，然后再与海泡石粉末进行混合处理，在110C左右进行烘干，样品制成后其中海泡石的含量约为70%、活性炭含量约为30%。本实验中氨和硫化氢的吸附条件为：20C、1个标准大气压101.3kpa。这个压力要比NH3和H2S的饱和蒸汽压（P0）0.857Mpa、1.773Mpa要低的多。吸附剂的多孔性在前面已经描述过了3、4。所有的活性炭微孔相当的多，但是微孔的不同尺寸决定了吸附剂的吸附量大小。用经过氢氧化钾活化过的3种活性炭粉末对氮气进行吸附，在温度每增加77K情况下，三种活性炭吸附量大小顺序为C8-0.5C5-0.5C5-3。经过高温活化过的活性炭对氮气的吸附量和C5-0.5接近。另一方面微孔大小的分布还与所用的化学试剂的浓度大小有关系。活性炭C8-0.5的孔隙与二氯甲烷（0.33nm）接近，活性炭C5-0.5孔隙和苯相近，但是与2-2二甲基丁烷相差较大，但是活性炭C5-3孔隙和以上3中有机物都很相似。海泡石与活性炭吸附的不同点在于：（1）海泡石的表面含氧量较大，（2）海泡石的比表面积大，达到191m2/g5，（3）由于海泡石内部含有的纤维管状微孔的存在，所以它的吸附量要比活性炭要小一些。当NH3和H2S的密度分别为0.61g/cm3、0.78g/cm3,从Dubinin-Radushkevich吸附等温线上可以得出吸附剂对于NH3和H2S的吸附效果，吸附剂对于N2的吸附容量可以从图1中看出来，从图上可以看到吸附曲线的斜率较小。注意到这一点相当重要，多数的吸附剂微孔吸附量与以上3种吸附剂的吸附量相似。样品C5-3微孔分布相对于其他吸附剂而言更加密集，对于NH3的吸附量要比对H2S的吸附量要低，而对NH3和H2S吸附量都比对N2的吸附量要低。将表面相互吸附作用同特征曲线作比较是一个很好的方式，比如液体，可以绘制吸附曲线进行比较。有一个典型的例子，图2中包含了活性炭C5-3和S型海泡石的吸附曲线，活性炭表面对于被吸附物的吸附作用能量是吸附剂微孔的作用，与被吸附物的关系不大。因此，活性炭的多孔性是影响NH3和H2S的主要因素，微孔的吸附作用近似在吸附剂内部充人了N2。这与海泡石的性质有关，图2b显示出氨与H2S相对于N2而言，前者的吸附能量是很强的，因此表明了具体的相互作用和一些不确定的因素有很大的关系。从图1中，海泡石的微孔对N2的吸附容量为0.11cm3/g，和对H2S的吸附容量接近。海泡石对于氨的强有力吸附已经有很多人通过实验验证过了6，前人的研究表明只要对海泡石表面进行酸化以后，这种作用就会变的很明显。因此，在对海泡石进行酸化的过程中，适当的增加酸的浓度，对于海泡石对氨的吸附能力就会大大提高。为了验证这种表面的相互作用随酸的浓度增加而增加，我们做如下实验：用不同浓度的硝酸（浓度分别为0.1、0.5、1.0和1.5mol/L）对S型海泡石进行酸化处理，硝酸和海泡石的液固比为0.7ml/g，如图3所示，酸化结果是对于氨的吸附量大大的增加了，但是在温度为77K情况下，对于N2吸附量却相应的减少了，原因是由于海泡石中的Mg2+正离子的结构发生了改变，同时内部的纤维状管道遭到了阻塞，所以才会出现上述的情况。.在20C时，活性炭-海泡石颗粒和海泡石、活性炭颗粒对于NH3和H2S的吸附量很接近。当活性炭-海泡石颗粒中海泡石的用量减少时，颗粒的吸附能力也随之下降了。从实验结果似乎可以看出，海泡石在其中充当了两重角色：一是作为黏合剂，一是作为吸附剂。海泡石其中的极性结构对它的吸附容量有很大影响。此外，从吸附等温线上所获得的吸附容量与把其中两种组分分别在等温线上查到的吸附容量之和是一致的。同时实验也表明，对于N2的吸附量也是差不多的，由此可以说明海泡石作为一种黏合剂，不会阻止也不会去减少对NH3和H2S的吸附能力。参考文献：1 Jones BF, Galan E. Sepiolite, Palygorskite. In: Bailey SW, editor.Hydrous phyllosilicates, vol. 19. Reston: Mineralogical Society ofAmerica; 1988. p. 63274 Chapter 16.2 Murray HH. Applied clay mineralogy today and tomorrow. Clay Miner 1999;34:3949.3 Gonz_alez JC, Sep_ulveda-Escribano A, Molina-Sabio M,Rodrguez-Reinoso F. Micropore size distribution in carbonmolecular sieves by immersion calorimetry. In: McEnaney B, Mays TJ, Rouquerol J, Rodr_guez-Reinoso F, Sing KSW, Unger KK,editors. Characterization of porous solids, vol. IV. Cambridge: The Royal Society of Chemistry; 1997. p. 916.4 Rodr_guez-Reinoso F, Molina-Sabio M, Gonz_alez JC. Preparation of activated carbon-sepiolite pellets. Carbon 2001;39:77185.5 Caturla F, Molina-Sabio M, Rodr_guez-Reinoso F. Adsorptiondesorption of water vapor by natural and heat-treated sepiolite in ambient air. Appl Clay Sci 1999;15:36780.6 Dandy AJ. Zeolitic water content and adsorptive capacity for ammonia of microporous sepiolite. J Chem Soc A 1971:23837.Adsorption of NH3 and H2S on activated carbonand activated carbonsepiolite pellets Molina-Sabio, J.C. Gonz_alez, F. Rodr_guez-Reinoso *Keywords: A. Activated carbon; B. Mixing; C. Adsorption; D. PorosityThe removal of gaseous compounds from air is a need in many industrial applications. For this application, it is rather common to use activated carbon pellets produced by extrusion of the arbonised precursor with a suitable binder before activation. However, the use of a mixed activated carbonclay pellet could be convenient for processes involving the adsorption of polar molecules such as ammonia and hydrogen sulphide. In the case of sepiolite the clay could, additionally, act as a binder.Sepiolite is a fibrous silicate, Si12Mg8O30(OH)4 (H2O)4,constituted by microporous channels (0.37 1.06 nm) parallel to the fibre axis 1. The size of the fibres varies widely but in most cases the range is 105000 nm in length,1030 nm in width and 510 nm in thickness. If liquid water is added to sepiolite there is absorption of water by capillarity and, if addition of water is continued, a suspension of sepiolite is formed, with properties very adequate to act as a binder for other materials 2.The objective of this work is to study the possible use of sepiolite, activated carbon and the mixed pellets as adsorbents for ammonia and hydrogen sulphide in gas phase.Four activated carbons were prepared from olive stones, carbon P by thermal activation in steam at 850 _C,and the other three by chemical activation with KOH 3.Nomenclature of samples refers to the preparation condition. Thus, carbon C5-3 has been prepared by carbonising olive stones at 500 _C and mixing this char with KOH with a ratio 3 g KOH/g recursor; heat treatment of the mixture at 850 _C was followed by extensive washing with acidic water. The sepiolite is from Yunclillos, Spain and it was dried at 100 _C overnight.For the preparation of the pellets 4, the activated carbon was crushed to a particle size lower than 100 lm,mixed with an aqueous suspension of sepiolite, kneaded and conformed before drying at 110 _C. The proportion used for pellets ranges from 30% sepiolite, 70% carbon to 7030%.Adsorption of ammonia and hydrogen sulphide (both with a purity higher than 99%) was carried out at 20 _C in a conventional gravimetric adsorption system up to a pressure of 101.3 kPa. This pressure is much lower than saturation pressure (P0) for NH3, 0.857 MPa and H2S,1.773 MPa.The porosity of the adsorbents has been already described 3,4. All activated carbons are microporous but with different volume and micropore size distribution.The volume of micropores determined by adsorption of nitrogen at 77 K increases in the order C8-0.5 C5-0.5 C5-3, the volume for carbon P being similar to carbon C5-0.5. On the other hand, the micropore size distribution was determined by immersion calorimetry in liquids with different molecular dimensions. The microporosity of carbon C8-0.5 is accessible to dichloro methane (0.33 nm) but not to benzene (0.37 nm) or 2,2-dimethylbutane (0.56 nm), all microporosity in carbon C5-0.5 is accessible to benzene but not to 2,2-dimethylbutane and the microporosity of C5-3 is accessible to the three molecules.Sepiolite is an adsorbent differing from activated carbon in: (i) there is a large proportion of oxygen in the surface of sepiolite, (ii) the external surface area is high,191 m2/g 5, (iii) microporosity is homogeneous because of the existence of microporous channels in the interior of the fibres, the volume of micropores being much smaller than in activated carbon.To evaluate the role of microporosity in the adsorption of NH3 and H2S, the DubininRadushkevich equation has been applied to the adsorption isotherms,using adsorbate densities of 0.61 and 0.78 g/cm3 for NH3 and H2S, respectively. The corresponding values of micropore volume have been plotted in Fig. 1 versus those derived from the adsorption of N2, the slope of the reference line being unity. It is important to note that for most adsorbents the value of micropore volume deduced from the three adsorbates is very similar. Only for the sample with a wider micropore size distribution, C5-3,the volume deduced from the adsorption of ammonia is somewhat lower than for the adsorption of hydrogen sulphide, and both lower than the value measured with nitrogen.A good way to compare the interaction of the adsorbent surface with the different adsorbates is to plot the so-called characteristic curves, where the amount adsorbed, as a liquid, is plotted versus the adsorption potential. As a typical example, Fig. 2 includes the curves for the activated carbon C5-3 and the sepiolite S.For carbon C5-3 (Fig. 2a) one can consider that the three adsorbates fit a single curve, this meaning that the energy of interaction between the carbon surface and the adsorbates is a function of the adsorbent and not the adsorbate. Consequently, the porosity of the carbon is the main factor controlling the adsorption of NH3 and H2S, the micropores being filled in a similar fashion as for nitrogen.This is not the case for sepiolite, Fig. 2b where the adsorption energy is very strong for ammonia as compared with hydrogen sulphide or nitrogen, thus indicating the presence of specific interactions in addition to the non-specific ones. In fact, the volume of micropores for sepiolite deduced from the adsorption of nitrogen,0.11 cm3/g, is similar to the value deduced from H2S,although somewhat lower than the value deduced for NH3, 0.15 cm3/g, as it can be seen in Fig. 1. The special affinity of sepiolite for ammonia has been described by some authors 6, whom suggested the presence of specific interactions with the acid groups of the surface,additional to the typical non-specific interaction in aphysisorption process. Consequently, an acid treatment of sepiolite should increase the number of acid centres and the capacity to adsorb ammonia.In order to see this increased interaction, sepiolite S was treated with acid solutions (HNO3, 0.1, 0.5, 1.0 and 1.5 M) using a 0.7 ml acid/g sepiolite ratio, and then dried in an oven at 110 _C. As shown in Fig. 3, the acid treatment induces an increase in the volume of micropores deduced from the adsorption of ammonia but,at the same time, a decrease in the micropore volume measured by adsorption of N2 at 77 K. This later decrease is possibly due to lixiviation and deposition of Mg2t cations on different sites of the structure, altering or blocking the channels.The adsorption isotherms of NH3 and H2S at 20 _C on carbonsepiolite pellets exhibit a shape very similar to activated carbons and sepiolite. The uptake for pellets is lower than for activated carbon, as a consequence of the lower adsorption capacity of sepiolite.It seems that sepiolite plays a double role in the pellet: as the binder and as adsorbent, the polar character of sepiolite contributing to widen the adsorption applications. Furthermore, the volume of micropores obtained from the adsorption isotherms is coincident with that calculated from the addition of the micropore volumes of the two components in the pellet, as it is the case for t