Third Day Poster Session, 17 June 2010 - NanoTR-VI

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Poster Session, Thursday, June 17
Theme F686 - N1123
Preparation of Anion Exchange Membrane and Its Characterization by AFM and EFM
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UZeynep ÇolakoluUP P*, Nilay GizliP P, Mustafa DemircioluP
1
PDepartment of Chemical Engineering, Ege University, Bornova, 35100, zmir, Turkey
Abstract-For the selective removal of arsenic species from water, a heterogeneous anion exchange membrane was prepared on
polyethylene backbone containing quaternized immobilized N-methyl-D-glucamine (NMDG). Surface characterization and electrostatic
conductivity of this material were investigated by atomic force microscopy (AFM) and electrostatic force microscopy (EFM). Roughness
values show that materials have no porosity, while positive values of surface skewness (1.398) point to extreme peaks on the membrane
surface and surface kurtosis (2.174) lower than 3.0 to broader height distributions. Characterization of materials by AFM and EFM served
for both optimization of preparation conditions and improvement of material properties.
Safety in drinking water is a challenge by climate change.
Arsenic is important due to high toxicity and its high levels
some cities in Turkey. Main forms of arsenic met in ground
waters are arsenite or arsenate anions. Therefore the
separation by ion exchange comes as the first alternative
method for ground waters. Removal performance of arsenic
must be enhanced for a viable industrial application. The aim
of this study is to produce the anion exchange membranes
and to characterize them by using AFM and EFM. Recent
studies show hopeful results in the name of using anion
exchange membranes for the purification of water sources
from hazardous ions since these membranes have excellent
electrochemical properties [1].
In this study, membranes were prepared by a
heterogeneous method, in which powdered ion exchange
resin of NMDG was combined with polyethylene, pressed
and heated up till 250°C and kept for 10 min. Then the
membrane was subjected to morphological and
electrochemical characterization. The surface structure of
membranes was observed by multimode AFM (RT-SHPM,
NanoMagnetics Instruments). The membrane surfaces were
scanned by aluminium reflex coated silicon probe (Tap
300AI, NanoMagnetics Instruments) having the spring
constant of 40 N/m and the resonance frequency of 300 kHz
in dynamic mode. Scan area and speed were chosen as
2
10x10 μmP Pand 5 μ/s, respectively.
The roughness parameters such as root mean square
roughness (RMS), mean roughness (Ra), average mean
height (Hav), surface skewness (Ssk) and surface kurtosis
(Sku) were obtained by using built-in software SPM 1.16.13.
It’s found that surface skewness was positive 1.398 which is
also numerically greater than 1.0 indicates that it has extreme
peaks on the surface [2]. Surface Kurtosis was found as
2.174 which is lower than 3.0, so the membrane shows
broader height distributions [3]. Imaging by EFM, another
AFM technique, is used to characterize materials for
electrical properties. In this technique, a conductive AFM tip
interacts with the sample through long-range Coulombic
forces. These interactions change both oscillation amplitude
and phase of AFM cantilever, which are monitored to create
EFM phase image [4]. In this study, the voltage levels were
chosen as -4V and +4V for forward and backward potentials.
Scan speed of 8μm/s was applied for the samples with the
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area of 30 x 30μmP P.
Figure 1. AFM and EFM Phase views of membranes.
The image at the left in Figure 1 is an AFM image on
which lighter regions show peaks on the sample surface, on
EFM image (to the right) lighter regions represent
conductive areas. Various properties were observed by
changing the parameters such as area scanned, scan speed,
applied voltage, head lift, rising and falling time in order to
determine the optimum conditions for measurement. As a
result, before delving into experimental tests and
performance studies requiring large amount of material and
laborious tasks in a separation process, characterization of
materials by AFM and EFM during preparation phase of
them helps both to screen the alternatives and to optimize the
preparation conditions for the development of novel
selective materials and the improvement of their properties.
*Corresponding author: HTzeynepcolakoglu@hotmail.comT
[1] Punita V. Vyas, B.G. Shah, G.S. Trivedi, P. Ray, S.K.
Adhikary, R. Rangarajan, Characterization of heterogeneous anionexchange
membrane, Journal of Membrane Science 187 (2001)
[2] J. F. Jørgensen, L. L. Madsen, J. Garnaes, K. Carneiro, K.
Schaumburg, Calibration, drift elimination and molecular structure
analysis, JVST B, 12(3), 1698-1701 (1994)
[3] J. F. Jørgensen, N. Schmeisser, J. Garnaes, L. L. Madsen, K.
Schaumburg, L. Hansen, P. Sommer-Larsen. (1994) Dynamics
and structure of selfassembled organic molecules at the solidliquid
interface, Journal of Surface & Coating Technology 67, pp.
201-11
[4] F. M. Serry, K. Kjoller, J. T. Thornton, R. J. Tench, and D.
Cook. Electric Force Microscopy, Surface Potential Imaging, and
Surface Electric Modification with the Atomic Force Microscope
(AFM).
6th Nanoscience and Nanotechnology Conference, zmir, 2010 674