Magnetophoresis of poly (SODIUM 4-STYRENESULFONATE)Fe3O4 clusters the influence of colloidal stability

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dc.contributor.authorYeap Swee Pin
dc.date.accessioned2021-05-03T04:22:58Z
dc.date.available2021-05-03T04:22:58Z
dc.date.issued2016-06-01
dc.description.abstractThe 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.en_US
dc.identifier.urihttp://hdl.handle.net/123456789/13223
dc.language.isoenen_US
dc.titleMagnetophoresis of poly (SODIUM 4-STYRENESULFONATE)Fe3O4 clusters the influence of colloidal stabilityen_US
dc.typeThesisen_US
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