Effect of pore size distribution

A sv po with a ocxitinuous distribution of pore sizes will yield an increased separation range of solute sizes but a decrease in selectivity as ccnpared to a single pore size si iport (e.g. see Fig. 8). Itiis was theoretically shown by Haller et al. (110) and ty Yau and co-workers (108) using different derivations of K. It was also shown that the deviation frcm a linear calibration curve increases with the width of the pore size distribution. Thus, assumption of a linear calibration curve me introduce gross errors in analytical SEC (108). 

Large disocntinuities in the pore size distributions of the columr-set may result in substantial errors in the calculated molecular weight (113). 

In order to get a linear calibration curve it is also very inportant to select sipport volumes to obtain equal pore volumes from the different stpports (108). nils is equivalent to procuring calibration curves with parallel linear regions in the plot of log M versus VpX A recent r x rt described the p )earance of artificial peaks vdien oolums oonteLining supports of different pore sizes are oonbined (114). However, the noticed effect nay be due to that no ocnpensatlon of support volumes was made for the differences in pore volumes of the two supports. 

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Fig. 26. The effect of pore size distribution spread (standard deviation) on the predicted tensile failure [jrobability distribution for grade H-451 graphite.

Gryglewicz, G., Machnikowski, J., Lorenc-Grabowska, E., Lota, G., and Frackowiak, E. Effect of pore size distribution of coal-based activated carbons on double layer capacitance. Electrochim. Acta. 50, 2005 1197-1206. 

The modelling of gas permeation has been applied by several authors in the qualitative characterisation of porous structures of ceramic membranes [132-138]. Concerning the difficult case of gas transport analysis in microporous membranes, we have to notice the extensive works of A.B. Shelekhin et al. on glass membranes [139,14] as well as those more recent of R.S.A. de Lange et al. on sol-gel derived molecular sieve membranes [137,138]. The influence of errors in measured variables on the reliability of membrane structural parameters have been discussed in [136]. The accuracy of experimental data and the mutual relation between the resistance to gas flow of the separation layer and of the support are the limitations for the application of the permeation method. The interpretation of flux data must be further considered in heterogeneous media due to the effects of pore size distribution and pore connectivity. This can be conveniently done in terms of structure factors [5]. Furthermore the adsorption of gas is often considered as negligible in simple kinetic theories. Application of flow methods should always be critically examined with this in mind. 

Ebie, K., Li, F., and Hagishita, T. (1995). Effect of pore size distribution of activated carbon on the adsorption of humic substances and trace organic compounds. Water... 

This value of x is quite low, and it suggests that a significant fraction of the pores may be much larger than 25 A in radius. The effect of pore size distribution is illustrated later (Examples 4.2, 4.5). 

Some authors believe that the inclined line of impedance at low frequencies comes from the pore size distribution of porous materials [171,182], and a few attempts have been made to consider the effect of pore size distributions (PSD) on the impedance of a porous electrode [171,182], although the PSD must contribute considerably to the distributed characteristics [171,182]. The impedance curve in the Nyquist plot is observed to change with the shape of a pore in the intermediate frequency region, despite its similarity to a cylindrical pore at extremely low or high frequencies. Some authors have reported that the real part of the reduced impedance (the ratio of impedance of a pore to electrolyte resistance in a pore) approached one-third at low frequency, irrespective of the shape of a pore [171,182]. The PSD effect is difQcult to take into account, particularly because of the time-consuming calculations required by this method, while a parametric study is difficult because of too many parameters (sizes of different pores), but some analytical solutions are being used to represent the pore size distribution of a porous electrode [171,182]. 

Perez, J, E.R, Gonzalez, and E.A. Ticianelli, Oxygen electrocatalysis on thin porous coating rotating platinum electrodes. Electrochimica Acta, 1998, 44 pp. 1329-1339 Song, H,-K, H,-Y, Hwang, K.-H. Lee, and L.H, Dao, The effect of pore size distribution on the frequency dispersion of porous electrodes. Electrochimica Acta, 2000. 45 pp. 2241-2257 Srikumar, A, T.G. Stanford, and J.W, Weidner, Linear sweep voltammetry in flooded porous electrodes at low sweep rates. Journal of Electroanalytical Chemistry, 1998. 458 pp. 161-173... 

Grethlein HE. (1985). The effect of pore size distribution on the rate of enzymatic hydrolysis of ceUulosic suhstrutes. Nat Biotechnol, 3(2), 155-160. 

Kaiser R, Kulczyk A, Rich D, Ronald JW, Mmicucci J and Maciver B (2007). Effect of pore size distribution of commercial activated carbon fabrics on the adsorption of CWA simulants from the hquid phase. Industrial Engineering Chemistry Research, 46(19), p. 6126. 

Do, H.D., and Do, D.D., Effect of pore size distribution on the surface diffusivity in activated carbon Hybrid Dubinin-Langmuir isotherm. Adsorption, 1(4), 291-302 (1995). 

Song HK, Jung YH, Lee KH, Dao LH (1999) Electrochemical impedance spectroscopy of porous electrodes the effect of pore size distribution. Electrochim Acta 44(20) 3513-3519... 

Khayet, M., Velazquez, A., and Mengual, J. I. (2004a). Modelling mass transport through a porous partition Effect of pore size distribution. J. Non-Equilib. Thermodyn. 29, 279. 

Phattaranawik, J., Jiraratananon, R., and Fane, A. G. (2003b). Effect of pore size distribution and air flux on mass transport in direct contact membrane distillalion. J. Membr. Sci. 215, 75. 

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