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oink银虫 (著名写手)
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Further increase in the grinding times to 6 (for PAL-6, PAL-8 and PAL- 10 samples), the intensity of the characteristic diffraction peak at 2θ=8.38° (d=10.6 Å  [24] remarkably decreased and the otherpeaks had no obvious change, indicating that the repeated grinding treatment with high intensity would affect the crystal structure of PAL to certain extent and slightly reduced its order–disorder structural degree [26], which was an advantageous property for well-defined adsorbents [27], as validated by the following adsorption results for MB. The intensity of the peak at 2θ=8.38° (d=10.6 Å [24] forPAL-6 was lowest, increased for PAL-8 and decreased for PAL-10. This may be according to following reasons: for PAL-6, the crystal aggregates were dissociated and crystal rods were shortened, thusleading to large degree of destructiveness in crystal structure; for PAL-8, more stressing force acted on the sample, and then crystal structure was further affected. The crystal rods would rearrange due to minimum energy principle, leading to the crystal structure was recovered to a certain extent; whereas for PAL-10, superabundant stressing force operated on the sample, and then crystal structure was affected so serious that it was difficult to be recovered 3.4. Effect of grinding treatment on specific surface area Specific surface area is one of the most crucial physical-chemical properties of an adsorbent as to remove heavy metal ions and dyes. Liu et al. [28] found that the specific surface area of CTA+-REC had significant effect on the removal of anionic dye Congo red, and the similar results were reported by Chen et al. [29]. Thus, the effect of grinding times on specific surface area of PAL was investigated and shown in Table 1. SBET and Smicro of PAL-0 were only 153 and 28 m2/g, respectively. The SBET was greatly enhanced after grinding treatment. The SBET firstly increased to 229 m2/g for PAL-2, and then decreased to 184 m2/g for PAL-6. With further increasing the grinding times to 8, the SBET increased to 213 m2/g and kept constant. Furthermore, the tendency of Sext/SBET ratio versus grinding times was quite the reverse of the SBET and only little change in the value of Sext can be found. For PAL samples with grinding treatment, the Sext/SBET ratio increased until PAL-6 and then decreased with increasing grinding times due to the change in the SBET, indicating grinding treatment had insignificant effect on the Sext. The tendencies in Smicro and the Smicro/SBET ratio with grinding timeswere in linewith the obtained for SBET. Itwas also clearly observed that Smicro increased with the grinding times until PAL-2 and then decreased until PAL-6 and finally increased. The Smicro of PAL with grinding treatment was higher than that initial PAL-0 value. In all, the SBET of grinding treated PAL was obviously higher than that of PAL-0 due to the increase in Smicro. This was attributed to that the rod-like crystals of PAL become shorter after grinding treatment as validated by FESEMimages, which led to the increase inmicroparticles, and then resulted in the increase of Smicro 3.5. Effect of grinding treatment on pore-size distribution The pore size of an adsorbent material exhibits great influence on the adsorption capacity for dyes or metal ions, especially for adsorbates with large and complex molecular structures. In this case, the effect of grinding treatment on pore-size distribution for PAL samples was studied and illustrated in Fig. 4. As shown in the inset of Fig. 4, the first peak at about 3.5 nm for PAL-0, 3.6 nm for PAL-2 and PAL- 4, 3.8 nm for PAL-6, PAL-8 and PAL-10 was ascribed to the mesopores between layers of PAL and furthermore, as pore size was in the range of 0 and 8.0 nm, the peak area was in the order of PAL-4>PAL-2> PAL-0>PAL-6>PAL-8>PAL-10, suggesting the mesopore volume had the same sequence except PAL-0 and PAL-4. It was clear from Fig. 4 that another peak at 30 nm for PAL-0 and 28 nm for PAL-2, PAL-4, PAL-6 and PAL-8 and 29 nm for PAL-10 was corresponding to non-structural pores between microparticles of PAL. In addition, the first set of peaks were small and narrow attributed to the inner surface area, while the second set of peaks were large and broad attributed to the outer surface area of PAL. This means that the pores present an irregular size distribution [30,31]. Furthermore, the results suggested that the non-structural pores among microparticles of PAL were dominant and responsible for the large proportion of the pore volume and specific surface area. It can be also seen from Fig. 4 the non-structural pore of PAL-2, PAL-4, PAL-6, PAL-8 and PAL-10 was a little smaller than that of PAL-0. This may be due to that the change of crystal aggregates and the break of rod-like crystals of PAL. The strong compression and shearing action resulting from the stone miller disc led to the rearrangement of crystal bundles and the stack of crystals became compact, which caused a small decrease in nonstructural pores of PAL-2, PAL-4, PAL-6, PAL-8 and PAL-10 and thechange in structure of crystal aggregates. Due to strong shearing forces induced by the stone miller operating on the PAL, crystal aggregates, bundles were dissociated and part of single crystals were shortened. According to the Van der Waals forces and hydrogen bonds, part of dissociated crystal aggregates, bundles and single crystals would rearrange and part of the interstitial spaces between the crystal aggregates would change according to minimum energy principle. Under these conditions, shortened crystals would be more compact. A slight decrease of intensity in the second peak set and the increase of intensity in the first peak set with grinding treatment were observed. Thus there was a slight change in pore volume of PAL after grinding treatment and the extent in change depended on the decreasing extent in the second set of peak and increasing extent in the first set of peak |
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xiaoyingwv
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爱与雨下: 金币+2 2012-10-20 07:10:26
oink: 金币+30, 翻译EPI+1, ★★★★★最佳答案 2012-10-21 15:31:21
爱与雨下: 金币+2 2012-10-20 07:10:26
oink: 金币+30, 翻译EPI+1, ★★★★★最佳答案 2012-10-21 15:31:21
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将样品的研磨次数增加到六次（PAL-6，PAL-8，PAL-10），在2θ=8.38°处的特征峰强度显著减弱，而其他衍射峰强度 没有明显变化，说明高强度的重复研磨能在一定程度上影响PAL的晶型，降低PAL的有序-无序的结构比例，这是较好吸附 剂的优良性质，下面对MB的吸附试验也证实了PAL的这一优良性质。 在2θ=8.38°处的特征峰强度，PAL-6的峰强度最低，PAL-8的峰强度增加了而PAL-10的峰强度降低了。原因可能如下： 对PAL-6而言，聚集的晶体解离，棒状晶体缩短，进而导致晶体结构在很大程度上遭到破坏；对于PAL-8，由于对样品施 加了更大的压力，晶体结构受到了更大的影响。根据最低能量法则，晶体棒会重新排列，从而导致晶体结构在一定程度上 回复。然而对于PAL-10而言，由于对样品施加了过多的压力，严重影响了其晶体结构，这种影响很难回复。 3.4 研磨程度能影响样品的比表面积，比表面积是吸附剂在吸附重金属离子和燃料时的，一个很重要的物理化学性质。 Liu等人发现吸附剂CTA+REC在除刚果红时，其比表面积对吸附效果影响很大，Chen等人也报道过类似的结论。 因此，研磨次数对PAL比表面的的影响效果已测试，结果见表1.PAL-0的比表面积和Smicro分别为153,28平方米每克。研 磨后比表面积显著增强，PAL-2的比表面积首先增加到229平方米每克，PAL-6的比表面积又降低到184平方米每克.研磨次 数增加到8，比表面积增加到213平方米每克并且保持不变。此外，Sext/比表面积的比例随着研磨次数的增加反而降低， 而且Sext的含量很少改变。 研磨PAL样品，直至PAL-6样品Sext/比表面积的比例一直增加，然而由于比表面积的改变，随着研磨次数的增加Sext/比 表面积的值反而降低，说明研磨次数对Sext有较大影响。 Smicro 和 Smicro/比表面积 的值与研磨次数的均符合所得到的比表面积。PAL-2之前Smicro随着研磨次数增加而增加 ，到PAL-6会减少，最后又会增加。 PAL的Smicro随研磨后均高于PAL-0，总之，由于Smicro的增加，研磨过的PAL的比较表面都明显比PAL-0的比表面积高。 FESEM图像证实，这是由于研磨后棒状PAL晶体变短，导致微小粒子增多进而导致Smicro增加。 附注：3.5之前的均已翻译过，部分专业词汇可能翻译不是很准确（例如Smicro; Sext ;），仅供参考 |
2楼2012-10-19 23:00:02
xiaoyingwv
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3楼2012-10-19 23:02:36
爱与雨下: 请勿点击"确认回帖应助" 2012-10-20 07:11:39
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