Yeap , Swee Pin (2016) Magnetophoresis Of Poly (SODIUM 4-STYRENESULFONATE) Fe3O4 Clusters The Influence of Colloidal Stability. PhD thesis, Universiti Sains Malaysia.
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Abstract
Kajian ini didedikasikan untuk mendedahkan pengaruh kestabilan berkoloid terhadap magnetoforesis zarah-zarah Fe3O4. Pertama sekali, kestabilan berkoloid Fe3O4 terdedah telah berjaya dipertingkatkan selepas permukaanya disalut dengan polimer anionik yang kuat, poli(natrium 4-stirenasulfonat) berberat molekul 70K Da (PSS 70K), melalui teknik pascasalutan diaruh oleh elektrostatik yang dilakukan pada pH ~ 3.50. Peningkatan kestabilan berkoloid yang dicapai oleh kelompok-kelompok PSS 70K/Fe3O4 tersebut sebahagian besarnya disumbangkan daripada tolakan elektrostatik dan tolakan sterik yang masing-masingnya mengatasi tarikan dwikutubdwikutub magnet apabila jarak antara zarah adalah < 97 nm dan < 50 nm. Namun begitu, kajian permisahan magnet menunjukkan bahawa semakin stabil berkoloid Fe3O4 itu, semakin sukar untuk memisahkannya dengan magnet. Dengan mengesani profil magnetoforesis bawah kecerunan medan magnet dengan purata magnitud 40.55 T/m, didapati bahawa Fe3O4 terdedah mencapai 100 % permisahan dalam masa 8 minit; manakala kelompok-kelompok PSS 70K/ Fe3O4 tidak dapat dipisahkan sepenuhya walaupun masa bagi permisahan magnet tersebut dilanjutkan sehingga satu jam. Dalam erti kata yang lain, salutan polimer yang pada mulanya digunakan untuk menstabilkan Fe3O4 itu secara elektrosterik justerunya menjejaskan kebersambutan mereka terhadap magnet. Berlainan daripada Fe3O4 terdedah yang menjalani magnetoforesis secara berkerjasama, didapati bahawa kelompok-kelompok PSS 70K/Fe3O4 mengalami magnetoforesis berdasarkan pemeringkatan mengikut saiz di mana pemisahan magnetnya dikawal oleh kehadiran taburan saiz hidrodinamik di dalam ampaian tersebut. Selain daripada itu, kajian mikroskopik seterusnya mendedahkan perbezaan di antara kedua-dua entiti di mana kelompok-kelompok PSS 70K/Fe3O4 cenderung untuk terhala sesama sendiri menjadi struktur seperti benang; manakala Fe3O4 terdedah cenderung untuk agregat sesama sendiri menjadi struktur fraktal yang berpelbagai dimensi. Pendekatan perhimpunan pengantara elektrostatik yang mudah telah dicadangkan dalam kajian ini untuk menghasilkan kelompokkelompok PSS 70K/Fe3O4 yang berpelbagai saiz (~ 200 nm hingga ~ 700 nm ). Di sini, didapati bahawa kelompok-kelompok PSS 70K/Fe3O4 dengan purata saiz kelompok 459 nm bukan sahaja mempunyai kestabilan berkoloid yang baik, malahan menawarkan kebolehpisahan magnet yang tinggi (> 98 % kecekapan pemisahan dicapai apabila didedahkan kepada kecerunan medan magnet yang sama untuk 5 minit sahaja). Penemuan ini menunjukkan bahawa memanipulasi saiz kelompok bagi kelompok-kelompok PSS 70K/Fe3O4 boleh digunakan sebagai penyelesaian untuk kebimbangan keseimbangan antara peningkatan kestabilan berkoloid dan kebolehpisahan magnet. Dalam bahagian akhir kajian ini, kestabilan berkoloid bagi kelompok-kelompok PSS 70K/Fe3O4 didapati telah merosot selepas penambahan ionion logam (e.g., Ag+, Cu2+, Cr3+, Ca2+, Mg2+). Keputusan menunjukkan bahawa kepekatan kation logam memainkan peranan yang lebih penting daripada kekuatan ion yang lazimnya dipercayai dalam meningkatkan proses pengagregatan tersebut. Di samping itu, dengan kehadiran ion Cu2+, bahan-bahan organic terlarut seperti asid humik dan natrium alginat didapati membentuk kompleks dengan kelompokkelompok PSS 70K/Fe3O4. Pembentukan kompleks ini kemudiannya juga akan mempengaruhi kestabilan berkoloid dan justerusnya kelakuan magnetoforesis kelompok-kelompok PSS 70K/Fe3O4. ________________________________________________________________________________________________________________________ The present work is dedicated to reveal the influence of colloidal stability towards magnetophoresis of Fe3O4 particles. First of all, colloidal stability of bare Fe3O4 was successfully enhanced after surface coating with a strong anionic polymer, poly(sodium 4-styrenesulfonate) of molecular weight 70K Da (PSS 70K), through electrostatic-induced post-coating technique conducted at pH ~3.50. Enhanced colloidal stability attained by the resultant PSS 70K/Fe3O4 clusters is mainly contributed from the electrostatic and the steric repulsion, which overwhelm the magnetic dipole-dipole attraction, when the interparticle distance is < 97 nm and < 50 nm, respectively. However, magnetic separation study showed that the more colloidally stable the Fe3O4 is, the harder it is to be magnetically separated. By carefully tracking on the magnetophoresis profiles under magnetic field gradient of average magnitude 40.55 T/m, it was found that bare Fe3O4 attained ~ 100 % separation within 8 minutes; while there was no complete separation for PSS 70K/Fe3O4 clusters even the magnetic separation time was extended to 1 hour. In another words, the polymer coating that was initially employed to electrosterically stabilize the Fe3O4 in turn compromises their magnetic responsiveness. Unlike the bare Fe3O4 which undergo a typical cooperative magnetophoresis, it was found that the PSS 70K/Fe3O4 clusters experienced a size-fractionation based magnetophoresis in which the magnetic separation was controlled by the presence of distribution of hydrodynamic sizes in the suspension. Besides that, microscopic study further revealed the differences between both entities in which PSS 70K/Fe3O4 clusters tend to self-oriented into thread-like structures; while bare Fe3O4 tend to self-aggregate into fractal structures of various dimensions. A simple electrostatic-mediated assembly approach was proposed in this study to produce PSS 70K/Fe3O4 clusters of various sizes (~200 nm up to ~ 700 nm). Here, it was found that PSS 70K/Fe3O4 clusters of average cluster size 459 nm not only possess good colloidal stability, but also offer high magnetic separability (> 98 % separation efficiency was attained when exposed to the same magnetic field gradient for just 5 minutes). This finding indicates that manipulating the cluster sizes of the PSS 70K/Fe3O4 clusters can be used as the solution for the trade-off concern between enhanced colloidal stability and magnetic separability. In the last part of this study, it was revealed that the colloidal stability of PSS 70K/Fe3O4 clusters being deteriorated after addition of metal ions (e.g., Ag+, Cu2+, Cr3+, Ca2+, Mg2+). Results showed that it is the concentration of the metal cation, instead of the conventionally believed ionic strength, plays a more decisive role in enhancing the aggregation process. In addition, with the presence of Cu2+ ion, dissolve organic matters such as humic acid and sodium alginate was found to form complexes with the PSS 70K/Fe3O4 clusters. This formation of complexes can later on influence the colloidal stability and thus magnetophoresis behavior of the PSS 70K/Fe3O4 clusters.
| Item Type: | Thesis (PhD) |
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| Additional Information: | Full text is available at http://irplus.eng.usm.my:8080/ir_plus/institutionalPublicationPublicView.action?institutionalItemId=2859 |
| Subjects: | T Technology T Technology > TP Chemical Technology > TP155-156 Chemical engineering |
| 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 04:08 |
| Last Modified: | 16 Aug 2018 07:13 |
| URI: | http://eprints.usm.my/id/eprint/40993 |
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