Sains Malaysiana 42(6)(2013): 827–836

Fouling of Ultrafiltration Membrane during Adsorption of Long

Chain Fatty Acid in Glycerine Solutions

(Pengotoran Membran Ultraturasan semasa Penjerapan Asid Lemak Rantai

Panjang di dalam Larutan Gliserin)

Abdul Wahab Mohammad*

Department of Chemical and Process Engineering, Faculty of Engineering and Built Environment

Universiti Kebangsaan Malaysia, 43600 UKM Bangi, Selangor D.E. Malaysia

Indok Nurul Hasyimah Mohd Amin

Section of Chemical Engineering Technology, Universiti Kuala Lumpur Malaysian Institute of Chemical & Bioengineering Technology, 78000 Alor Gajah, Melaka, Malaysia

Diserahkan: 2 Ogos 2012/Diterima: 15 Oktober 2012

ABSTRACT

Membrane fouling caused by the adsorption of fatty acids limits the application of membrane technology in oleochemical industry especially for the pretreatment of glycerin-rich solution. The aim of the work presented in this paper was to understand the adsorptive fouling of palm oil based fatty acid on ultrafiltration membranes. The influence of solution pH, molecular weight cut-off (MWCO) and hydrophobicity of the membrane were studied. Oleic acid was used as a foulant, representing the long chain palm oil based fatty acid in glycerol−water solution. The outer membrane exposed to the mixtures for 6 h without pressure. The stirring speed was set at 300 rpm and polyethersulfone (PES) membranes with MWCO of 5, 20 and 25 kDa were used. The adsorptive fouling was determined using the relative flux reduction (RFR) method. It is demonstrated in this study that PES membranes are susceptible to the deposition of fatty acids on the membrane surface and pores. The fouling phenomenon at low pH is more severe than that of high pH due to the attractive force between solutes and the membrane. The PES membranes after adsorption were characterized by contact angle and Fourier transform infrared (FTIR), while the surface was visualized with scanning electron microscopy (SEM).

Keywords: Adsorption; fatty acid; fouling; glycerin; ultrafiltration

ABSTRAK

Pengotoran membran yang disebabkan oleh penjerapan asid lemak telah mengehadkan aplikasi teknologi membran dalam industri oleokimia terutamanya untuk penjernihan larutan kaya gliserin. Tujuan utama kajian ini dijalankan adalah untuk memahami pengotoran terjerap terhadap membran ultraturasan yang disebabkan oleh asid lemak rantai panjang berasaskan minyak kelapa sawit. Kesan beberapa faktor seperti pH, nilai potongan berat molekul (MWCO) dan kimia permukaan membran (sifat hidrofobik) telah dikaji. Asid olik yang mewakili asid lemak rantai panjang berasaskan minyak kelapa sawit telah digunakan sebagai bahan larut. Permukaan membran telah didedahkan kepada larutan selama enam jam tanpa faktor tekanan membran. Kelajuan pengacau telah diatur pada 300 rpm, manakala membran polietersulfon (PES) yang mempunyai nilai MWCO 5, 20 dan 25 kDa telah digunakan. Pengotoran terjerap ini dinilai dengan menggunakan pengurangan fluks relatif (RFR). Melalui kajian ini, didapati asid lemak mudah melekat di atas permukaan membran PES dan juga di dalam liang membran tersebut. Fenomena pengotoran pada pH rendah lebih teruk berbanding pada keadaan pH tinggi yang disebabkan oleh daya tarikan antara bahan larut dan membran. Perubahan struktur pada permukaan membran selepas pengotoran telah dianalisis menggunakan sudut sesentuh, FTIR dan juga SEM.

Kata kunci: Asid lemak; gliserin; pengotoran; penjerapan; ultraturasan

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