Development Of Magnetophoretic Actuation Composite Membranes For Removal Of Humic Acid

Ng , Qi Hwa (2016) Development Of Magnetophoretic Actuation Composite Membranes For Removal Of Humic Acid. PhD thesis, Universiti Sains Malaysia.

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Abstract

Teknologi membran yang digunakan untuk penghasilan air yang bersih telah berkembang sejak beberapa tahun kebelakangan ini, disebabkan oleh reka bentuk padat modul membran, menurunkan penggunaan tenaga, dan kualiti efluen yang diakui. Walau bagaimanapun, pengotoran membran disebabkan oleh pemendapan bahan-bahan kotoran ke atas membran masih menjadi isu kritikal dalam banyak aplikasi proses penapisan air dan adalah merupakan faktor dominan yang menghalang penggunaan membran yang meluas. Oleh itu, kajian ini menyiasat kecekapan penyingkiran asid humik (AH) oleh satu membran komposit penggerakan magnetoforetik untuk mengurangkan kecenderungan pengotoran membran. Pertama, nanopartikel magnetit (NPM) yang terdedah akan difungsionalisasikan untuk meningkatkan kestabilan koloid NPM, serta bagi memastikan pengagihan sekata daripada NPM ke atas permukaan membran. Oleh itu, kepekatan larut air poli(natrium 4-stirena sulfonat) (PSS) yang berbeza telah disalut sekitar permukaan NPM, di mana nisbah molar PSS/NPM yang optimum ditemui pada 6:1. Sebelum salutan MNP yang telah difungsionalisasikan (F-NPM) ke atas permukaan membran, teknik “Quartz Crystal Microbalance with Dissipation” (QCM-D) digunakan untuk menyiasat afiniti interaksi antara F-NPM dengan permukaan spesifik membran. Keputusan QCM-D menunjukkan satu interaksi yang baik antara F-NPM dan membran polietersulfon (PES) di dalam kehadiran polielektrolit PSS dan poli(diallyldimetilammonium klorida) (PDDA). Seterusnya, tahap penggerakan magnetoforetik berdasarkan kehadiran kepekatan F-NPM yang berbeza (contohnya, 100, 1000, dan 2500 ppm) disalut ke atas permukaan membran juga dikaji. Keputusan menunjukkan bahawa prestasi terbaik daripada membran komposit telah diperolehi dengan penyalutan F-NPM 2500 ppm ke atas permukaan membran PSS-PDDA-PES yang telah diubahsuai dengan PSS dan PDDA pada kadar putaran 3000 rpm dan 8 s bagi masa putaran. Selepas itu, pengaruh medium akueus pH-berubah ke arah kestabilan lapisan fungsi magnet-responsif ke atas membran komposit juga dinilai. Berdasarkan analisis, pH operasi terbaik untuk membran komposit ditemui dalam julat pH 2-10. Akhir sekali, membran yang dihasilkan dengan prestasi penapisan yang terbaik tertakluk kepada kajian mekanisma kotoran, dan penilaian prestasi jangkat hayat membran untuk mendedahkan potensi membran komposit dalam penyingkiran AH. Keputusan penapisan menunjukkan satu peralihan mekanisma pengotoran membran, dari liang sekatan piawai kepada pembentukan lapisan kek dalam sepanjang proses penapisan tetapi pengotoran kek telah dikenal pasti sebagai faktor yang paling kritikal yang menyumbang kepada pengotoran membran. Manakala bagi kajian jangkat hayat membran, membran yang beroperasi di bawah medan magnet berayun luar telah menubuhkan keupayaan anti-kotoran membran yang terbaik dengan mengekalkan 96 % daripada fluks permulaan (Jo = 9.44×10-6 m3/m2s) selepas 48 jam penapisan dengan penolakan AH 99.4 ± 0.14 %. Prestasi penapisan yang dipertingkatkan adalah disebabkan oleh penggerakan magnetoforetik F-NPM yang mengurangkan kepekatan polarisasi berhampiran permukaan membran dan seterusnya mengurangkan potensi pengotoran membran. ________________________________________________________________________________________________________________________ Membranes used for potable water production have remarkable progressed over the past few years due to the compact design of the membrane module, lowered energy consumption, and reliable effluent quality. Nevertheless, membrane fouling caused by the deposition of fouling materials on the membrane remains a critical issue in many applications of water filtration processes and is the dominant factor that restricts the widespread application of membranes. Thus, this study investigates the efficiency of humic acid (HA) removal by a magnetophoretic actuation composite membrane through magnetic actuation to reduce the membrane fouling propensity. First, the bare magnetite nanoparticles (MNPs) were functionalized to increase its colloidal stability, to ensure the homogenous distribution of the MNPs on the membrane surface. Thus, different concentration of water-soluble poly(sodium 4-styrene sulfonate) (PSS) were coated around the surface of MNPs, where the optimum PSS/MNPs molar ratio was found at 6:1. Prior to end-capping the functionalized-MNPs (F-MNPs) onto the membrane surface, Quartz Crystal Microbalance with Dissipation (QCM-D) technique is used to investigate the interaction affinity between F-MNPs with a specific surface of a membrane. The QCM-D results demonstrated a good interaction between F-MNPs and polyethersulfone (PES) membrane in the presence of polyelectrolytes PSS and poly(diallyldimethylammonium chloride) (PDDA). Next, the extent of magnetophoretic actuation based on the presence of different concentrations of F-MNPs (e.g., 100, 1000, and 2500 ppm) coated on the membrane surface were also studied. The results shown that the best performance of the magnetophoretic actuation composite membrane was obtained by spin coated the 2500 ppm F-MNPs onto the PSS-PDDA-PES modified membrane surface at the spinning rate of 3000 rpm and 8 s of the spinning time. Subsequently, the influence of pH-fluctuated aqueous mediums toward the stability of the magnetic-responsive functional layer laid on the composite membrane was also being evaluated. Based on the analyses, the best operating pH for the composite membrane were found in the range of pH 2-10. Last but not least, the developed membranes with the best filtration performance were subjected to the fouling mechanisms study, and membrane longevity performance evaluation to reveal the potential of magnetophoretic actuation composite membrane in HA removal. Filtration results indicate a transition of membrane fouling mechanism, from a standard pore blocking to the formation of cake layer throughout the filtration processes but cake fouling was identified as the most critical factor that contributes to the membrane fouling. While for the membrane longevity study, the membrane operated under an external oscillating magnetic field established excellent membrane anti-fouling capability by retaining 96 % of the initial flux (Jo= 9.44×10-6 m3/m2s) after 48 h of filtration with HA rejection of 99.4±0.14 %. The enhanced filtration performance was due to the magnetophoretic actuation motions of F-MNPs that reduces concentration polarization near the top surface of the membrane and consequently reduces the potential for membrane fouling.

Item Type: Thesis (PhD)
Additional Information: Full text is available at http://irplus.eng.usm.my:8080/ir_plus/institutionalPublicationPublicView.action?institutionalItemId=2805
Subjects: T Technology
T Technology > TP Chemical Technology > TP1-1185 Chemical technology
Divisions: Kampus Kejuruteraan (Engineering Campus) > Pusat Pengajian Kejuruteraan Kimia (School of Chemical Engineering) > Thesis
Depositing User: Mr Mohd Jasnizam Mohd Salleh
Date Deposited: 12 Jul 2018 08:01
Last Modified: 15 Aug 2018 04:08
URI: http://eprints.usm.my/id/eprint/41023

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