Roughness and hydrophobicity studies of nanofiltration membranes using different modes of AFM

被引:246
作者
Boussu, K
Van der Bruggen, B
Volodin, A
Snauwaert, J
Van Haesendonck, C
Vandecasteele, C
机构
[1] Katholieke Univ Leuven, Dept Chem Engn, Lab Appl Phys Chem & Environm Technol, B-3001 Heverlee, Belgium
[2] Katholieke Univ Leuven, Dept Phys & Astron, Lab Solid State Phys & Magnetism, B-3001 Heverlee, Belgium
关键词
nanofiltration; tapping mode AFM; noncontact AFM; phase imaging; contact angle; surface roughness;
D O I
10.1016/j.jcis.2005.01.095
中图分类号
O64 [物理化学(理论化学)、化学物理学];
学科分类号
070304 ; 081704 ;
摘要
Determination of the surface roughness by AFM is crucial to the study of particle fouling in nanofiltration. It is, however, very difficult to compare the different roughness values reported in the literature because of a lack in uniformity in the methods applied to determine surface roughness. AFM is used in both noncontact mode and tapping mode; moreover, the size of the scan area is highly variable. This study compares, for six different nanofiltration membranes (UTC-20, N30F, Desal 51HL, Desal 5DL, NTR7450, NF-PES-10), noncontact mode AFM with tapping mode AFM for several sizes of the scan area. Although the absolute roughness values are different for noncontact AFM and tapping mode AFM, no difference is found between the two modes of AFM in ranking the nanofiltration membranes with respect to their surface roughness. NTR 7450 and NF-PES-10 are the smoothest membranes, while the roughest surface can be found with Desal 51HL and Desal 5DL. UTC-20 and N30F are characterized by an intermediate roughness value. An increase in roughness with increasing scan area is observed for both AFM modes. Larger differences between the roughnesses of the membranes are obtained with tapping mode AFM because of the tapping of the tip on the surface. Phase imaging is an extension of tapping mode AFM, measuring the phase shift between the cantilever oscillation and the oscillation of the piezo driver. This phase shift reflects the interaction between the cantilever and the membrane surface. A comparison with contact angle measurements proves that a small phase shift corresponds to a large contact angle, representing a hydrophobic membrane surface. (c) 2005 Elsevier Inc. All rights reserved.
引用
收藏
页码:632 / 638
页数:7
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