1、.附錄A：英文譯文及原文活性炭和活化海泡石顆粒對NH3和H2S吸附性能研究作者：Molina-Sabio, J.C. Gonz_alez, F. Rodr_guez-Reinoso光鍵詞：A、活性炭 B、黏合 C、吸附 D、多孔性 從空氣中分離氣態化合物應用在很多工業領域。對于這種應用，使用活性粒進行吸附相當普遍，這種顆粒在活化之前與適當的黏合劑混合后制成。然而，使用混合后的活性炭黏土顆粒吸附象氨和硫化氫這樣的極性分子，會影響吸附效果，但是海泡石作為黏合劑加入黏土顆粒后，吸附效果會變的更好。海泡石是一種纖維狀硅酸鹽，分子式是Si12Mg6O30(OH)4(H2O)4,由很多相互平行的纖維管狀物

2、構成1。纖維的尺寸變化范圍廣，但是在很多情況下，長度為10-5000nm,寬度為10-30nm，高度為5-10nm。如果在海泡石遇到水，它通過毛吸現象吸收水分，如果水繼續滲透進去，就會形成松散的海泡石粉末。海泡石在自然界中廣泛的存在，因此它經常作為其他材料一種黏合劑2。本課題主要研究海泡石、活性炭、和二者黏合后的顆粒作為一種吸附劑對廢氣中的氨和硫化氫的吸附性能的研究。實驗中，準備4份活性炭顆粒，其中一份在850°C蒸汽下加熱活化，其他3份加入化學試劑氫氧化鉀進行活化3。我們從實驗樣品的化學式中可以看到樣品的制備過程。因此，C5-3由炭石在500°C溫度下燒成粉末，再加入3m

3、ol/L的氫氧化鉀溶液，然后在85°C下加入大量的酸進行加熱酸化處理。本實驗用到的海泡石原料來自西班牙的Yonclillos,并在實驗的前天晚上在100°C左右做烘干處理。對于吸附劑的后期制備4，是將活化過的活性炭顆粒粉碎到合適的大小，一般不低于100目，然后再與海泡石粉末進行混合處理，在110°C左右進行烘干，樣品制成后其中海泡石的含量約為70%、活性炭含量約為30%。本實驗中氨和硫化氫的吸附條件為：20°C、1個標準大氣壓101.3kpa。這個壓力要比NH3和H2S的飽和蒸汽壓（P0）0.857Mpa、1.773Mpa要低的多。吸附劑的多孔性在前面已

4、經描述過了3、4。所有的活性炭微孔相當的多，但是微孔的不同尺寸決定了吸附劑的吸附量大小。用經過氫氧化鉀活化過的3種活性炭粉末對氮氣進行吸附，在溫度每增加77K情況下，三種活性炭吸附量大小順序為C8-0.5C5-0.5C5-3。經過高溫活化過的活性炭對氮氣的吸附量和C5-0.5接近。另一方面微孔大小的分布還與所用的化學試劑的濃度大小有關系。活性炭C8-0.5的孔隙與二氯甲烷（0.33nm）接近，活性炭C5-0.5孔隙和苯相近，但是與2-2二甲基丁烷相差較大，但是活性炭C5-3孔隙和以上3中有機物都很相似。海泡石與活性炭吸附的不同點在于：（1）海泡石的表面含氧量較大，（2）海泡石的比表面積大，達到

5、191m2/g5，（3）由于海泡石內部含有的纖維管狀微孔的存在，所以它的吸附量要比活性炭要小一些。當NH3和H2S的密度分別為0.61g/cm3、0.78g/cm3,從Dubinin-Radushkevich吸附等溫線上可以得出吸附劑對于NH3和H2S的吸附效果，吸附劑對于N2的吸附容量可以從圖1中看出來，從圖上可以看到吸附曲線的斜率較小。注意到這一點相當重要，多數的吸附劑微孔吸附量與以上3種吸附劑的吸附量相似。樣品C5-3微孔分布相對于其他吸附劑而言更加密集，對于NH3的吸附量要比對H2S的吸附量要低，而對NH3和H2S吸附量都比對N2的吸附量要低。將表面相互吸附作用同特征曲線作比較是一個很

6、好的方式，比如液體，可以繪制吸附曲線進行比較。有一個典型的例子，圖2中包含了活性炭C5-3和S型海泡石的吸附曲線，活性炭表面對于被吸附物的吸附作用能量是吸附劑微孔的作用，與被吸附物的關系不大。因此，活性炭的多孔性是影響NH3和H2S的主要因素，微孔的吸附作用近似在吸附劑內部充人了N2。這與海泡石的性質有關，圖2b顯示出氨與H2S相對于N2而言，前者的吸附能量是很強的，因此表明了具體的相互作用和一些不確定的因素有很大的關系。從圖1中，海泡石的微孔對N2的吸附容量為0.11cm3/g，和對H2S的吸附容量接近。海泡石對于氨的強有力吸附已經有很多人通過實驗驗證過了6，前人的研究表明只要對海泡石表面進

7、行酸化以后，這種作用就會變的很明顯。因此，在對海泡石進行酸化的過程中，適當的增加酸的濃度，對于海泡石對氨的吸附能力就會大大提高。為了驗證這種表面的相互作用隨酸的濃度增加而增加，我們做如下實驗：用不同濃度的硝酸（濃度分別為0.1、0.5、1.0和1.5mol/L）對S型海泡石進行酸化處理，硝酸和海泡石的液固比為0.7ml/g，如圖3所示，酸化結果是對于氨的吸附量大大的增加了，但是在溫度為77K情況下，對于N2吸附量卻相應的減少了，原因是由于海泡石中的Mg2+正離子的結構發生了改變，同時內部的纖維狀管道遭到了阻塞，所以才會出現上述的情況。.在20°C時，活性炭-海泡石顆粒和海泡石、活性炭

8、顆粒對于NH3和H2S的吸附量很接近。當活性炭-海泡石顆粒中海泡石的用量減少時，顆粒的吸附能力也隨之下降了。從實驗結果似乎可以看出，海泡石在其中充當了兩重角色：一是作為黏合劑，一是作為吸附劑。海泡石其中的極性結構對它的吸附容量有很大影響。此外，從吸附等溫線上所獲得的吸附容量與把其中兩種組分分別在等溫線上查到的吸附容量之和是一致的。同時實驗也表明，對于N2的吸附量也是差不多的，由此可以說明海泡石作為一種黏合劑，不會阻止也不會去減少對NH3和H2S的吸附能力。參考文獻：1 Jones BF, Galan E. Sepiolite, Palygorskite. In: Bailey SW, edit

9、or.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 carbonmol

10、ecular 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 activ

11、ated 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 microp

12、orous 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 m

13、any 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 ad

14、sorption 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 fi

15、bres 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

16、 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 i

17、n 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

18、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, knead

19、ed 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

20、 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 a

21、dsorption 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 ca

22、rbon 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

23、 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 b

24、eing 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

25、 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 wide

26、r 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 t

27、o 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

28、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 simi

29、lar 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

30、 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 sugges

31、ted 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

32、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

33、 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

34、 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