Abstract:
Naturally occurring nanostructured layered materials are receiving increased attention from
researchers in academia and industries owing to their unique characteristic features including
naturally controlled nano-scale particle size, higher surface area, cheap, availability,
biocompatibility etc. Surface modification o f the nanomaterials with various natural and
synthetic materials largely extends their applicability in various fields such as packaging,
coating, water purification, antimicrobial agents, cancer nanotherapy etc. However, the potential
o f nanostructured kaolinite having layered aluminosilicate structure for diversified applications
has largely been unexplored in Bangladesh ahhough it is widely available in the country. In this
doctoral research, we have thoroughly investigated the effect o f the modification o f kaolinite in
terms o f various physio-chemical properties. Here, we have prepared four different types of
composites using different proportions o f kaolinite with starch, choline chloride,
poly(methyimethacrylate), and inorganic salt solutions separately. Firstly, we have successfiilly
fabricated nanocomposite films through incorporating kaolinite into potato starch. Secondly,
self-standing porous composite beads were prepared by modification o f kaolinite with choline
chloride. Thirdly, choline chloride-modified kaolinite was incorporated as fillers for preparing
nanocomposite films using poly(methylmethacrylate) (PMMA) as a matrix. Finally, metal oxides
[c.f. zinc oxide (ZnO), ferric oxide {Fe203)] were anchored onto kaolinite surface via heat
treatment. In order to confirm the successfiil modification o f kaolinite, we employed several
analytical techniques such as attenuated total reflectance infra-red analysis (ATR-IR), x-ray
diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive x-ray
spectroscopy (EDX). Various useful mechanical properties o f the films were investigated widi a
universal testing machine (UTM), whereas, thermogravimetric analysis (TGA) was performed to
investigate the improvement in thermal stability.
We carefully observed that the incorporation o f both virgin and modified kaolinite into natural
and synthetic polymer dramatically improved thermal and mechanical properties o f the films.
These films are expected to find widespread applications in packaging industries. Modification
o f kaolinite with choline chloride led to the development o f a novel self-standing porous
composite bead, which displayed unique fiUration ability for anionic azo dyes (Remazol Red) at
alkaline pH. The dye filtration performance was continuously monitored using a UV-Vis
spectrophotometer. We strongly believe that this advanced material might contribute
significantly in treating effluents from textile indusfries. Lastly, metal oxide-loaded kaolinite
showed significantly improved antibacterial action against selective bacteria (Salmonella
pullorum Escherichia coli. Pseudomonas aeruginosa) and cytotoxic effect against cancer cells
(HeLa and BHK-21). Due to this promising performance, metal oxide-loaded kaolinite might
find potential biomedical applications. In conclusion, we firmly state that this study would open
new doors for the development o f kaolinite-based technology for the advancement o f materials
science.
Description:
This dissertation Submitted in Partial Fulfilment o f the Requirement for the Degree o f Doctor o f Philosophy (Ph.D.) in Applied Chemistry and Chemical Engineering at University of Dhaka, Dhaka-1000, Bangladesh.