Sains Malaysiana 40(3)(2011): 237–244

Atomic Force Microscopy as a Tool for Asymmetric Polymeric Membrane Characterization

(Mikroskop Daya Atom sebagai Alat Pencirian Asimetrik Membran Polimer)

Abdul Wahab Mohammad^*,1, Nidal Hilal², Lim Ying Pei¹, Indok Nurul Hasyimah Mohd Amin¹ & Rafeqah Raslan¹

¹Department of Chemical and Process Engineering

Faculty of Engineering and Built Environment, Universiti Kebangsaan Malaysia, 43600 UKM Bangi, Selangor D.E., Malaysia

²Centre for Water Advanced Technologies and Environmental Research (CWATER)

Multidisciplinary Nanotechnology Centre, College of Engineering, Swansea University, Swansea SA2 8PP, United Kingdom

Diserahkan: 15 Julai 2010 / Diterima: 3 September 2010

ABSTRACT

Atomic force microscopy (AFM) has a wide range of applications and is rapidly growing in research and development. This powerful technique has been used to visualize surfaces both in liquid or gas media. It has been considered as an effective tool to investigate the surface structure for its ability to generate high-resolution 3D images at a subnanometer range without sample pretreatment. In this paper, the use of AFM to characterize the membrane roughness is presented for commercial and self-prepared membranes for specific applications. Surface roughness has been regarded as one of the most important surface properties, and has significant effect in membrane permeability and fouling behaviour. Several scan areas were used to compare surface roughness for different membrane samples. Characterization of the surfaces was achieved by measuring the average roughness (Ra) and root mean square roughness (Rrms) of the membrane. AFM image shows that the membrane surface was composed entirely of peaks and valleys. Surface roughness is substantially greater for commercial available hydrophobic membranes, in contrast to self-prepared membranes. This study also shows that foulants deposited on membrane surface would increase the membrane roughness.

Keywords: Atomic Force Microscopy (AFM); fouling; hydrophobic; membrane roughness

ABSTRAK

Mikroskop Daya Atom (AFM) mempunyai penggunaan yang meluas dan berkembang pesat dalam penyelidikan serta pembangunan. Teknik ini telah digunakan untuk menggambarkan permukaan di udara dan proses berkaitan persekitaran yang berair. Ia merupakan alat yang berkesan untuk menghasilkan imej 3D yang beresolusi tinggi struktur permukaan pada ukuran julat subnanometer tanpa penyediaan awal sampel. Dalam kajian ini, penggunaan Mikroskop Daya Atom untuk menentukan kekasaran membran ditunjukkan untuk membran komersial dan membran yang dihasilkan di makmal dan bagi aplikasi yang khusus. Kekasaran permukaan adalah salah satu ciri permukaan yang penting dan memberi kesan yang signifikan kepada kebolehtelapan air dan sifat kekotoran pada membran. Beberapa kawasan imbasan telah digunakan untuk memperbaiki perbezaan kekasaran permukaan pada sampel yang berlainan. Ciri-ciri permukaan telah diperolehi melalui ukuran purata kekasaran (Ra) dan punca kuasa dua kekasaran membran (Rrms). Imej AFM menunjukkan permukaaan membran terdiri daripada puncak dan lembah. Kekasaran permukaan adalah lebih tinggi bagi membran komersil sedia ada yang hidrofobik, berbeza dengan penghasilan membran sendiri. Kajian ini juga menunjukkan agen kotoran yang terendap pada permukaan membran akan meningkatkan kekasaran membran.

Kata kunci: Hidrofobik; kekasaran membran; kekotoran; Mikroskop Daya Atom (AFM)

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*Pengarang untuk surat-menyurat; e-mail: wahabm@vlsi.eng.ukm.my